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  • phosphorus  (118)
  • biological control
  • Springer  (204)
  • 1995-1999  (203)
  • 1970-1974  (1)
  • 1999  (125)
  • 1995  (78)
  • 1974  (1)
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  • 1995-1999  (203)
  • 1970-1974  (1)
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  • 1
    ISSN: 1570-7458
    Keywords: host suitability ; acceptance ; biological control ; new associations ; Lepidoptera ; Pyralidae ; New World ; Old World ; stemborers ; Braconidae ; larval parasitoids ; Gramineae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present study examined the acceptability and suitability of Old World stemborers (Chilo partellus and C. orichalcociliellus) for the development of New World parasitoids (Apanteles deplanatus and A. minator) and New World stemborers (Diatraea saccharalis and D. grandiosella) for the development of Old World parasitoids (Cotesia sesamiae, C. flavipes and C. chilonis). Results revealed that acceptance and suitability were high in old associations. In new associations, parasitoids accepted about 60% of the new association hosts. In addition, 10 out of 17 new associations were successful. Apanteles species appeared to be more physiologically host specific than Cotesia species. For example, two of four new association hosts were accepted by A. deplanatus and only one (D. saccharalis) was partially suitable for progeny development. Among the Cotesia species, Cotesia flavipes appeared to have a wider host range than the two other species. It attacked all hosts offered and successfully parasitized all but one (D. grandiosella). Diatraea saccharalis was accepted and was a suitable host for the development of all parasitoid species tested, whereas D. grandiosella was unsuitable for the development of four out of five parasitoid species tested. No clear pattern was observed as behavioral acceptance did not always agree with the pattern of physiological suitability. Implications of these findings for importation biological control of stemborers are discussed.
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  • 2
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    Entomologia experimentalis et applicata 74 (1995), S. 219-224 
    ISSN: 1570-7458
    Keywords: Festuca arundinacea ; Festuca rubra subsp ; commutata ; Acremonium coenophialum ; Acremonium typhinum ; Heterorhabditis bacteriophora ; ergot alkaloid ; ergotamine tartrate ; feeding deterrence ; entomopathogenic nematodes ; biological control ; stressors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We evaluated tritrophic level interactions among fungal endophytes (Acremonium spp.) of fescue grasses (Festuca spp.), the root-feeding Japanese beetlePopillia japonica Newman larvae, and the entomopathogenic nematodeHeterorhabditis bacteriophora Poinar. Third-instarP. japonica larvae were introduced into pots containing endophyteinfected or endophyte-free plants of tall fescueFestuca arundinacea Schreber (cultivars Kentucky 31 and Georgia Jesup Improved) and the Chewings fescueFestuca rubra commutata Guad. (cultivars F-93 and Jamestown II). After two weeks, the surviving larvae were recovered, and their susceptibility to nematodes was evaluated in sand columns. Endophytes enhanced the rate of nematode-induced mortality in all cultivars except Georgia Jesup Improved, and increased the proportion of dead larvae with nematodes in all cultivars except Jamestown II. Endophytes in the cultivar Kentucky 31 were associated with improved nematode establishment in the larvae. No effect on nematode reproduction was found. Since endophytes produce biologically active alkaloids, we tested the effects of an ergot alkaloid, ergotamine tartrate, on the feeding behavior and weight ofP. japonica larvae in agar medium. The alkaloid caused feeding deterrence, and reduced the consumption of medium by the larvae, resulting in weight loss. These larvae were more susceptible toH. bacteriophora than the untreated larvae. Unfed ‘starved’ larvae were more susceptible to nematodes than those fed on untreated agar. Our results support the hypothesis that endophyte-induced starvation ofP. japonica would reduce larval vigor, and render them more susceptible to entomopathogenic nematodes.
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  • 3
    ISSN: 1570-7458
    Keywords: biological control ; Thripidae ; Frankliniella occidentalis ; Phytoseiidae ; Amblyseius ; diapause ; drought tolerance ; predation ; oviposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In spring and summer, two groups of natural enemies are successfully used for biological control of western flower thrips,Frankliniella occidentalis (Pergande) in greenhouses: phytoseiid mites (Amblyseius cucumeris (Oudemans) and, to a lesser extent,A. barkeri (Hughes)) and anthocorid bugs (Orius spp.). During winter, however, these predators often fail to control the pest. One likely cause for failure is the predators' tendency to enter diapause under short day conditions. In addition, eggs of predatory mites are generally susceptible to low humidity conditions, which often arise in greenhouses when outside temperatures drop below zero, or at bright, hot days in summer. In search for a thrips predator that is not hampered by these conditions, five subtropical phytoseiid species were selected which were known to feed on thrips:A. hibisci (Chant),A. degenerans Berlese,A. limonicus s.s. Garman and McGregor,A. scutalis (Athias-Henriot) andA. tularensis (Congdon). These species were compared toA. cucumeris andA. barkeri, with respect to the following features: (1) predation and oviposition rate with youngF. occidentalis larvae as prey, (2) oviposition rate on a diet of sweet pepper pollen, (3) drought tolerance spectrum of eggs, and (4) incidence of reproductive diapause under short day conditions. The results showed thatA. limonicus exhibited the highest predation and oviposition rates on a diet of thrips larvae. Moreover,A. limonicus females showed total absence of diapause under the conditions tested. A major disadvantage of this species was, however, that its eggs were most sensitive to low air humidity conditions. Least sensitive to low air humidity were eggs ofA. degenerans andA. hibisci. Females ofA. degenerans andA. hibisci also showed total absence of diapause, and intermediate rates of predation and oviposition, on both thrips larvae and pollen. In conclusion, we argue thatA. degenerans andA. hibisci are the most promising candidates for biological control ofF. occidentalis under conditions of low humidity and short day length. The success of these candidates remains to be shown in greenhouse experiments.
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  • 4
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    Entomologia experimentalis et applicata 91 (1999), S. 327-336 
    ISSN: 1570-7458
    Keywords: biological control ; in vitro rearing ; rearing techniques ; host selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An artificial host egg was developed as a first attempt to improve the techniques for in vitro rearing of Trichogramma galloi Zucchi and T. pretiosum Riley (Hymenoptera, Trichogrammatidae). Plastic membranes (polyethylene, polypropylene and polystyrene) of different thickness were tested for their usefulness in manufacturing artificial eggs, using a thermal system to produce semi-spherical cupules on the plastic surface. These artificial eggs were filled with larval hemolymph of Helicoverpa zea (Boddie) (Lepidoptera, Noctuidae), and the optimal size of the artificial egg and density of females/artificial egg for the highest host acceptance (percentage of artificial eggs with at least one parasitoid egg) as well as the ideal level of parasitism (eggs/artificial egg) were determined. High-density polyethylene 7–8 and 9–10 μm thick resulted in the best acceptance and level of parasitization for both parasitoid species. Six females per artificial egg resulted in the best rate of parasitization for these parasitoids, although these data were not different when using 4 or 5 females of T. galloi. The size, shape and surface texture of the artificial eggs were found to provide enough cues to elicit parasitization behavior in Trichogramma females, since no chemical stimulus was provided.
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  • 5
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    Entomologia experimentalis et applicata 76 (1995), S. 203-209 
    ISSN: 1570-7458
    Keywords: oviposition deterrence ; herbivory ; insect-plant interactions ; biological control ; Apionidae ; Mimosaceae ; Mimosa pigra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The oviposition and feeding preferences ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore ofMimosa pigra L. (Mimosaceae), were studied in relation to conspecific damage to its hostplant. Adults ofC. aculeatum cease ovipositing in inflorescences when the egg load reaches a number consistent with the larval carrying capacity of the inflorescence. The basis for this oviposition deterrence was examined by offering inflorescences damaged by adult feeding alone, larval feeding alone and a combination of adult feeding and oviposition. Adults preferred to oviposit on inflorescences which are not damaged by either adult feeding, larval feeding, or oviposition. No evidence for the existence of an oviposition deterring pheromone (ODP) was found. I suggest that the ability of a single host inflorescence to support the development of many larvae causes selection for the use of these oviposition deterring cues which can convey more quantitative information about the level of previous infestation than can ODPs. Adults fed a similar amount on damaged compared to undamaged inflorescences. These results assisted in the design of host range testing trials and allows predictions to be made about the effectiveness of this insect as a biological control agent.
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  • 6
    ISSN: 1570-7458
    Keywords: Trichogramma spp. ; Helicoverpa armigera ; Chrysoperla carnea ; Portugal ; parasitism ; biological control ; non-target species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Parasitism of two host species by five Trichogramma species (Hymenoptera, Trichogrammatidae) was studied in the laboratory. The host species were: i) the bollworm Helicoverpa armigera Hübner (Lepidoptera, Noctuidae), an important pest of many crops in the tropics and subtropics, and ii) one of its natural enemies, the lacewing Chrysoperla carnea Stephens (Neuroptera, Chrysopidae), a predator often used as a biological control agent. The proportion of H. armigera eggs parasitized from the total number of parasitized hosts differed between Trichogramma species. The average number of parasitized eggs per female in 24 h by Trichogramma pintoi and T. bourarachae was 10 of H. armigera and about 0.5 of C. carnea. For the other three Trichogramma species (T. cordubensis, T. evanescens and T. turkestanica) these averages varied from 6 to 11 H. armigera eggs and from 3 to 4 C. carnea eggs. Total adult offspring production, contacts with hosts, secondary clutch size and sex-ratio of each Trichogramma species were determined as well. The results show that sympatric Trichogramma may parasitize target and non-target species in different proportions. If this difference corresponds to the field situation, simple laboratory tests could be performed to select not only efficient biogical control agents, but also species which are the least detrimental to non-target hosts.
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  • 7
    ISSN: 1570-7458
    Keywords: host feeding ; host paralysis ; oviposition ; pre-oviposition phase ; Hypothenemus hampei ; Scolytidae ; biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of the density of the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae) on reproductive and host-feeding behaviours of the parasitoid Cephalonomia stephanoderis (Hymenoptera: Bethylidae) was evaluated under laboratory conditions. The number of hosts used for oviposition was density-dependent at low host density. Beyond a density of six hosts/day, the oviposition rate reached a maximum of 1.2 eggs/day due to egg limitation. Cephalonomia stephanoderis females responded to increasing host availability with a linear increase in host feeding. Overall, parasitoids killed more coffee berry borers by feeding and paralysis than by parasitism. At low host density, the pre-oviposition phase was extended, oogenesis was delayed, more males were produced, and host feeding occasionally occurred concurrently with oviposition. We suggest that the efficacy of C. stephanoderis as a biological control agent depends on seasonal variations in host density. Inoculative vs inundative releases in coffee plantations are discussed in relation to the abundance of the coffee berry borer during the fructification and interharvest periods.
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  • 8
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    Entomologia experimentalis et applicata 76 (1995), S. 121-131 
    ISSN: 1570-7458
    Keywords: Aphis gossypii ; life history ; cucumber ; temperature ; partial resistance ; biological control ; Aphidius colemani
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Life table data forAphis gossypii Glover (Homoptera: Aphididae), an important pest in glasshouse cucumber crops, were studied at 20, 25 and 30°C on two cucumber cultivars (Cucumis sativus L.) in controlled climate cabinets. The development time on the cucumber cv. ‘Sporu’ ranged from 4.8 days at 20°C to 3.2 days at 30°C. Immature mortality was approximately 20% and did not differ between temperatures. Most mortality occurred during the first instar. Reproduction periods did not differ among temperatures, but at 25 and 30°C more nymphs were produced (65.9 and 69.8 nymphs/♀, respectively) than at 20°C (59,9 nymphs/♀) because of a higher daily reproduction. Intrinsic rate of increase was greatest at 25°C (r m =0.556 day−1). At 20 and 30°C the intrinsic rate of increase was 0.426 and 0.510, respectively. On cv. ‘Aramon’, the development time ofA. gossypii was approximately 20% longer at all temperatures. Immature mortality did not differ between the two cultivars. The intrinsic rate of increase on cv. ‘Aramon’ was 15% smaller than on cv. ‘Sporu’. The use of cucumber cultivars partially resistant to aphids is discussed in relation to biological control of cotton aphid in glasshouses. Development time and immature mortality on leaves of the middle and upper leaf layer of glasshouse grown cucumber plants (cv. ‘Aramon’) were comparable to development in the controlled climate cabinets. On the lower leaves immature mortality was much higher (approximately 82%) than on leaves of the middle (24.0%) and upper leaf layer (24.5%). Reproduction was less on the lower leaf layer (45.9, 70.5 and 70.1 nymphs/♀ on leaves of the lower, middle and upper leaf layer, respectively). Aphids, successfully parasitized byAphidius colemani Viereck (Hymenoptera: Braconidae) only reproduced when they were parasitized after the third instar. Fecundity was 0.1 to 0.9 and 10.5 to 13.3 nymphs/♀ for aphids parasitized in the fourth instar or as adults, respectively. Reproduction of aphids that were stung but survived the attack was lower than for aphids not stung. Average longevity of these aphids was equal to the longevity of aphids not stung byA. colemani.
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  • 9
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    Entomologia experimentalis et applicata 77 (1995), S. 11-15 
    ISSN: 1570-7458
    Keywords: mushrooms ; Lycoriella solani ; Steinernema spp. ; entomopathogenic nematodes ; bioassays ; biological control ; dose response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory bioassays were done to assess the susceptibility of larvae of the mushroom sciarid flyLycoriella solani Winnertz (Diptera; Sciaridae) to 16 isolates comprising five species of the entomopathogenic nematode,Steinernema (Nematoda; Steinernematidae). Each isolate was tested by challenging sciarid larvae with single nematodes. Six isolates were also tested in dose-response experiments. Variations in nematode infectivity occurred (p〈0.001) at both inter- and intraspecific levels.Steinernema feltiae (Filipjev) was the most virulent species: two isolates, Nemasys (LD50=1.5–3.9) and Sus 94 (1.8–3.9) were superior to the rest.Steinernema kraussei (Steiner) was the least infectious nematode tested as its infection probability never exceeded 0.10. In addition, lethal dose50 values for this species ranged from 9.0–62.6 and two isolates failed consistently to infect any hosts.
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  • 10
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    Entomologia experimentalis et applicata 77 (1995), S. 239-250 
    ISSN: 1570-7458
    Keywords: diamondback moth ; Lepidoptera ; Plutellidae ; Steinernema ; Heterorhabditis ; relative humidity ; biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the ability of entomopathogenic nematodes to infect diamondback moth (DBM),Plutella xylostella (L.) (Lepidoptera: Plutellidae) on a leaf surface. In a leaf disk assay, mortality of late stage DBM larvae ranged from 〈7% caused bySteinernema kushidai Mamiya to 〉95% caused byS. carpocapsae (Weiser) All strain. LC50 values forS. carpocapsae, S. riobravis Cabanillas, Poinar & Raulston, andHeterorhabditis bacteriophora Poinar NC1 strain were 14.6, 15.4, and 65.4 nematodes/larva, respectively.S. carpocapsae, S. riobravis, andH. bacteriophora caused 29%, 33%, and 14% mortality of DBM pupae, respectively. DBM mortality caused byS. carpocapsae on radish declined at low (〈76%) to moderate (76–90%) RH, because nematode survival and infectivity declined at low (〈76%) to moderate (76–90%) RH. However, DBM mortality caused byS. riobravis did not decline with RH.S. riobravis survival declined with RH, but infectivity did not. Overall, nematode survival and infectivity to DBM larvae were lower forS. riobravis than forS. carpocapsae. In addition, DBM mortality was higher on radish plants (pubescent leaves) than on cabbage plants (glaborous leaves).
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  • 11
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    Entomologia experimentalis et applicata 91 (1999), S. 449-457 
    ISSN: 1570-7458
    Keywords: Schizaphis graminum ; Aphelinus asychis ; aphid ; parasitoid ; natural enemy ; biological control ; greenbug ; host selection ; plant volatile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Aphelinus asychis (Walker) can be valuable as a biocontrol agent of the aphid, Schizaphis graminum (Rondani), a major pest on grain crops in the United States. This study reports the wind tunnel, and olfactometric responses of this parasitoid to the host (aphid), plant (sorghum), and host-plant complex (aphid-infested sorghum). In addition, the parasitoids' response to malathion-treated plants is also presented. The goal of the present study was to test the hypothesis that volatiles associated with the host attract natural enemies, as reported in cases of many hymenopterous parasitoids, and also to learn about the effects of insecticides on these parasitoids. In wind tunnel studies, these parasitoids moved upwind in the direction of the host-infested plant. There was no direct flight observed, however, these parasitoids were observed to hop and jump, and sometimes walk to their host. In the olfactometer experiments, we found that A. asychis is attracted to host-plant complex. The parasitoids' response to malathion in the olfactometer suggested that a malathion formulation when applied to plants can lure these beneficials, thus providing new insight into the ongoing task of integrating chemical and biological control of insect pests.
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  • 12
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    Entomologia experimentalis et applicata 93 (1999), S. 267-273 
    ISSN: 1570-7458
    Keywords: Macrolophus caliginosus ; mirid bug ; life table ; longevity ; fecundity ; development time ; mortality ; sex ratio ; oviposition period ; intrinsic rate of increase ; spider mite ; Tetranychus urticae ; tomato ; biological control ; glasshouse pests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The life table characteristics of the polyphagous mirid Macrolophus caliginosus Wagner (Heteroptera: Miridae) preying on various stages of Tetranychus urticae Koch (Acari: Tetranychidae) with tomato as host plant were described at 22 °C. The following average parameters were obtained: Female longevity: 28.7 days; fecundity: 0.7 eggs/female/day; egg mortality: 2.6%; pre-oviposition period: 5.5 days; oviposition period: 18.1 days; post-oviposition period: 3.2 days; juvenile development time: 26.8 days; juvenile mortality: 34.9%; and sex ratio (♀/(♀+♂): 0.46. Life table parameters were estimated as net reproduction rate (R 0): 6.15; intrinsic rate of increase (r m): 0.031 day−1; finite rate of increase (λ): 1.032; mean generation time (T c): 58.17 days; and doubling time (T 2) 22.2 days. The parameters obtained were in accordance with those reported for M. caliginosus fed on another mite species (T. turkestani Ugarov & Nikolski (Acari: Tetranychidae)). However, compared to the performance of M. caliginosus fed on common glasshouse insect pests, a diet consisting of only mites appeared to be inferior. However, being a voracious predator, M. caliginosus may be a valuable addition to existing methods of mite control.
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  • 13
    ISSN: 1570-7458
    Keywords: biological control ; greenhouse crops ; sweet pepper ; western flower thrips ; Frankliniella occidentalis ; predatory mites ; Amblyseius barkeri ; Amblyseius cucumeris ; diapause ; genetic variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Europe and North America the western flower thrips,Frankliniella occidentalis, is an important pest in various greenhouse crops, such as sweet pepper and cucumber. Two species of predatory mite are commercially applied for biological control of this pest:Amblyseius cucumeris andA. barkeri. Thrips control is generally successful from March onwards. During winter, however, thrips control by these predatory mites is less effective. An important reason for this is that the commercially applied strains of both mite species enter reproductive diapause under short-day photoperiods, whereas the western flower thrips does not enter diapause. In this paper we report on selection experiments for non-diapause in strains of both mite species, aimed at obtaining predators that do not enter diapause under light- and temperature conditions prevailing in winter. Additional experiments were done to estimate the potential of the selected lines as control agents ofF. occidentalis. Selection for non-diapause proved highly successful in both predatory mite species. In a New Zealand strain ofA. cucumeris diapause incidence decreased from 41% to 0% in about ten generations; in a Dutch strain ofA. barkeri diapause incidence decreased from 67% to 0% in about six generations. Furthermore, selection for non-diapause had no influence on predator performance, measured as predation rate and oviposition rate on a diet of first instar thirps larvae. Rates of predation and oviposition were the same for selected and unselected lines in both species; rates of predation and oviposition were higher forA. cucumeris than forA. barkeri. After 18 months under non-diapause conditions, no less than 92% of a sample of the selected non-diapause line ofA. cucumeris did not enter diapause when tested under diapause-inducing conditions. This indicates that ‘non-diapause’ is a stable trait in these predatory mites. Finally, a small-scale greenhouse experiment in a sweet pepper crop showed that the selected non-diapause line ofA. cucumeris established successfully under diapause-inducing short-day conditions.
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  • 14
    ISSN: 1570-7458
    Keywords: biological control ; food web interactions ; volatiles ; Phytoseiidae ; predatory bugs ; thrips ; predator-predator interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Arthropods use odours associated with the presence of their food, enemies and competitors when searching for patches. Responses to these odours therefore determine the spatial distribution of animals, and are decisive for the occurrence and strength of interactions among species. Therefore, a logical first step in studying food web interactions is the analysis of behaviour of individuals that are searching for patches of food. We followed this approach when studying interactions in an artificial food web occurring on greenhouse cucumber in the Netherlands. In an earlier paper we found that one of the predators of the food web, the predatory mite Phytoseiulus persimilis Athias-Henriot, used to control spider mites, discriminates between odours from plants with spider mites, Tetranychus urticae Koch, and plants with spider mites plus conspecific predators. The odours used for discrimination are produced by adult prey in response to the presence of predators, and probably serve as an alarm pheromone to warn related spider mites. Other predator species may also trigger production of this alarm pheromone, which P. persimilis could use in turn to avoid plants with heterospecific predators. We therefore studied the response of the latter to odours from plants with spider mites and 3 other predator species, i.e. the generalist predatory bug Orius laevigatus (Fieber), the polyphagous thrips Frankliniella occidentalis and the spider-mite predator Neoseiulus californicus (McGregor). Both olfactometer and greenhouse release experiments yielded no evidence that P. persimilis avoids plants with any of the 3 heterospecific predators. This suggests that these predators do not elicit production of alarm pheromones in spider mites, and we argue that this is caused by a lack of coevolutionary history. The consequences of the lack of avoidance of heterospecific predators for interactions in food webs and biological control are discussed.
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  • 15
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    Entomologia experimentalis et applicata 93 (1999), S. 51-61 
    ISSN: 1570-7458
    Keywords: Metarhizium anisopliae ; Atta sexdens rubropilosa ; leaf-cutting ants ; biological control ; social homeostasis ; entomopathogenic fungus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is growing interest in the use of entomopathogenic organisms to control leaf-cutting ants (Hymenoptera: Formicidae: Attini). However, the way leaf-cutting ants react as a colony to biohazards is poorly understood. We investigated the effects of Metarhizium anisopliae (Metschnikoff) (Deuteromycotina: Hyphomycetes) applied to the foraging arenas of mini-nests (queenless sub-colonies) of the leaf-cutting ant Atta sexdens rubropilosa (Forel). Dry spores were applied either alone or mixed with citrus powder, at 0.5 g or 0.05 g per mini-nest. The spores were removed four days after application, and all dead ants removed every three days. Ant numbers near the Metarhizium increased as the ants attempted to clean up the biohazard. The ants attempted to place the spores in piles, which they then covered over with other material. They were able to deal with the low doses in this way, but the high doses overwhelmed them. All treated mini-nests suffered increased ant mortality during the first ten days after application. This mortality was particularly high in the media worker caste which had played the major role in attempting to clean up the spores. Foraging activity decreased, as did the health of the fungus gardens. The mini-nests exposed to the low dose of spores mixed with citrus powder then recovered fully. The health of the other treated mini-nests declined gradually until around 26 days after application, when they began deteriorating sharply. However, the decline of these mini-nests after day 26 was not due directly to the pathogenic action of the Metarhizium, nor to the initial ant mortality it had caused. The results suggest that the social stress caused by even such a short-lived Metarhizium epizootic was sufficient to cause the decline and ultimate death of the mini-nests. This has important implications for the control of leaf-cutting ants. It also demonstrates how important the social homeostasis of the colony is to leaf-cutting ants.
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  • 16
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    Entomologia experimentalis et applicata 90 (1999), S. 103-107 
    ISSN: 1570-7458
    Keywords: learning ; Orius majusculus (Reuter) ; Heteroptera ; Anthocoridae ; predator ; biological control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 17
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    Entomologia experimentalis et applicata 90 (1999), S. 183-189 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; Aphelinidae ; Platygasteridae ; Hemiptera ; Aleyrodidae ; whiteflies ; Bemisia ; Amitus bennetti ; parasitoid ; biological control ; life history ; instar preference ; oviposition behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Amitus bennetti Viggiani & Evans (Hymenoptera: Platygasteridae) is a recently described parasitoid of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae). Behaviour and life history of the parasitoid are described. The first nymphal instar of B. argentifolii is preferred by the parasitoid, but the 1st through 4th instar may be parasitised. Females first investigate hosts with their antennae, then walk over the host, and eventually step with their front legs on the leaf and insert their ovipositor inside the host facing away from the host, while the hind legs are still on the host. The time from encounter to oviposition (=latency to oviposition) is shortest on the 1st instar. Oviposition duration (mean=39 s) comprises 50% of the handling time. Development time from egg to adult decreases from 72 days at 15 °C to 42 days at 20 °C to 28 days at 25 °C. We estimate that 400 degree days is required for development, with a development threshold of 10 °C. Adult longevity in the absence of hosts was 29, 26 and 19 days and with hosts present 8, 8 and 5 days at 15, 20 and 25 °C, respectively. Amitus bennetti is proovigenic and oviposits most eggs shortly after adult emergence. During the first day of their adult lives females laid 1, 31 and 49 eggs at 15, 20 and 25 °C, respectively. Compared with other parasitoid species, the development time of A. bennetti is very long, and the implications of this for management of B. argentifolii are discussed.
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  • 18
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    Entomologia experimentalis et applicata 75 (1995), S. 135-143 
    ISSN: 1570-7458
    Keywords: Trichogramma minutum ; Trichogramma brassicae ; Trichogramma nr.sibiricum ; egg parasitoid ; host range ; biological control ; forest pests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a laboratory study, we determined the potential of threeTrichogramma (Hymenoptera: Trichogrammatidae) species,T. brassicae Bezdenko,T. minutum Riley andT. nr.sibiricum Sorokina, for biological control against six species of forest lepidopteran pests, black army cutworm, hemlock looper, eastern spruce budworm, western spruce budworm, white-marked tussock moth, and gypsy moth. Females of each parasitoid species were offered eggs from each of the six host species. Parasitization and the effect of the host species on the emerging progeny were examined and recorded.Trichogramma minutum had the broadest host range and successfully parasitized four host species out of the six offered.Trichogramma nr.sibiricum had the narrowest host range and parasitized only two species of hosts. Of the six host species, black army cutworm was the most preferred by all threeTrichogramma species; white-marked tussock moth and gypsy moth were not parasitized by any parasitoids. There was a positive correlation between the size of female offspring and their corresponding egg complement in all three parasitoid species. The developmental time of parasitoids from egg to adult was influenced by both the parasitoid and host species. Our results suggest thatT. minutum has the greatest potential for biological control against various forest lepidopteran pests and that the black army cutworm may be the best target candidate for further study.
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  • 19
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    Entomologia experimentalis et applicata 75 (1995), S. 151-157 
    ISSN: 1570-7458
    Keywords: evaluation of parasitoids ; biological control ; Aphis gossypii ; Braconidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four aphidiine parasitoid species (Hymenoptera: Braconidae) were evaluated with respect to their potential to controlAphis gossypii Glover (Homoptera: Aphididae) in glasshouse cucumbers. In a laboratory experiment thirty cotton aphids were offered to individual females for two hours.Aphidius matricariae Haliday parasitized less than six percent of the aphids and was ruled out as potential biological control agent.Ephedrus cerasicola Starý andLysiphlebus testaceipes Cresson parasitized 23 and 26 percent of the aphids, respectively.Aphidius colemani Viereck parasitized 72 to 80 percent of the aphids. With the latter three species, experiments were performed in small glasshouses with cucumbers (Cucumis sativus L. cv. ‘Aramon’). As in the laboratory testA. colemani performed best; significantly more colonies were found and parasitization rates in the colonies were higher byA. colemani than byE. cerasicola andL. testaceipes. Because of the good correspondence between laboratory and glasshouse experiments, it is suggested that bad performance of an aphid parasitoid species in a simple laboratory trial might be sufficient evidence to disregard this species for further tests.
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  • 20
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    Entomologia experimentalis et applicata 93 (1999), S. 77-86 
    ISSN: 1570-7458
    Keywords: Acari ; behaviour ; biological control ; Gerbera jamesonii ; herbivore induced synomones ; infochemicals ; indirect defence ; Phytoseiidae ; semiochemicals ; terpenoids ; Tetranychus urticae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Jasmonic acid (JA) is a plant hormone that is involved in the induction of plant defence in response to herbivore attack. We studied the effect of exposure of gerbera leaves to JA on indirect plant defence, i.e. attraction of natural enemies of herbivores. Treatment of gerbera leaves with JA or feeding damage by the herbivorous spider mite Tetranychus urticae, both induced the production of a complex odour blend that attracts the predatory mite Phytoseiulus persimilis. This phytoseiid predator is a very effective biological control agent of the spider mite T. urticae. Comparison of headspace composition of gerbera leaves exposed to either JA or T. urticae revealed a large degree of resemblance, but some quantitative and qualitative differences were recorded. The major chemical group in both treatments is formed by the terpenoids which quantitatively comprised up to 80% of the total odour blend. These terpenoids included (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-β-ocimene and linalool that are known to attract P. persimilis. Aldehydes, alcohols, esters and ketones, together with nitrogenous compounds formed the remaining constituents of the odour blend. The induction of predator attractants in plants by JA may be applied in biological control programs, which is discussed in this paper.
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  • 21
    ISSN: 1570-7458
    Keywords: host suitability ; host acceptance ; host-parasitoid ; host switching ; biological control ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two parasitoids,Pteromalus cerealellae (Ashmead) andAnisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), were compared for their ability to parasitize two important internally-developing insect pests of stored maize (Zea mays L.). Parasitism byP. cerealellae was greater on Angoumois grain moth,Sitotroga cerealella (Olivier), than on maize weevil,Sitophilus zeamais Motschulsky, in no-choice experiments.Anisopteromalus calandrae parasitized more maize weevils than didP. cerealellae. The former parasitoid parasitized only a few Angoumois grain moths successfully in maize, but parasitized many in wheat if the hosts were younger than 3 weeks old. Thus, both host age and type of grain affect suitability for parasitism. The effects of parental host (species on which the female developed) and experimental host (species exposed to parasitism) on parasitism rate ofP. cerealellae were tested in a host-switching experiment. Parasitism by parasitoids reared on maize weevils was 23% lower than that of parasitoids reared on Angoumois grain moth. This effect was independent of which host the filial generation of parasitoids was tested on. However, the experimental host species had a much greater effect on parasitoid fecundity than the parental host species. Female progeny had smaller body sizes when emerging from maize weevil than from Angoumois grain moth, which may explain the parental host effect on fecundity. There was also a slight intergenerational effect of host species on parasitoid body size.
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  • 22
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    Entomologia experimentalis et applicata 76 (1995), S. 195-201 
    ISSN: 1570-7458
    Keywords: herbivory ; insect-plant interactions ; biological control ; Apionidae ; Mimosaceae ; Mimosa pigra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The oviposition behaviour ofCoelocephalapion aculeatum Fall (Coleoptera: Apionidae), a host specific florivore exploiting an ephemeral resource, was studied in relation to host development. Immature inflorescences of its host, the weedMimosa pigra L. (Mimosaceae), were categorised into 5 developmental stages ranging from first appearance to one day before opening. The duration, weight, percent abortion, and nitrogen content of each stage were measured. Oviposition preferences ofC. aculeatum for all inflorescence stages were determined in multiple choice trials. Newly hatched, larvae were transferred into inflorescences of each stage to determine larval survival as a function of stage. Numbers of eggs laid into inflorescences generally correlated with larval survival except that oviposition was greater in stage 4 inflorescences than expected from the larval survival. Numbers of eggs laid into inflorescences generally correlated with their carrying capacity except that adults avoided stage 5 inflorescences in which larval survival was low. The evolution of oviposition preferences ofC. aculeatum appears to have been influenced by two opposing selective forces. The need to complete development before the inflorescence deteriorated would have selected for oviposition in young inflorescences. The greater availability of food and lower probability of abortion offered by older inflorescences would have selected for oviposition in these. The net outcome of these pressures has resulted in the observed oviposition strategy.
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  • 23
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    Journal of applied electrochemistry 29 (1999), S. 1171-1176 
    ISSN: 1572-8838
    Keywords: alloys ; cyclic voltammetry ; electrodeposition ; electroless deposition ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy deposition from a sulphate bath, containing sodium hypophosphite as reducer, was investigated. To increase the plating rate, the deposition parameters were optimized. The effect of process parameters (T, pH and [Zn2+]) on the plating rate and deposit composition was examined and it was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition. As a consequence, the percentage of zinc in the electroless Ni–Zn–P alloys never reaches high values. Using cyclic voltammetry the electrodeposition mechanism of Ni–Zn–P alloys was investigated. It was observed that the zinc deposition inhibits the nickel discharge and, as a consequence, its catalytic activity on hypophosphite oxidation. It was also found that increase in temperature or pH leads to the deposition of nickel rich alloys.
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  • 24
    ISSN: 1572-8854
    Keywords: Octahedral ; phosphorus ; chloride
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    Topics: Geosciences , Physics
    Notes: Abstract The title compound [P(tpp)Cl2]+Cl− crystallizes in the space group P21/n witha=10.701(2),b=24.860(2),c=14.799(2), β=94.24(2)°,Z=4. The phosphorus atom has an octahedral coordination geometry formed by the four nitrogen atoms (Np) of the porphyrinato group and the two chloride ions. The average phosphorus-chloride distance is 2.150(1) Å, with phosphorus situated 0.006 Å below the porphyrin ring.
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  • 25
    ISSN: 1572-8838
    Keywords: alloys ; electroless ; microstructure ; morphology ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy coatings were obtained on an iron substrate from a sulfate bath at various pH values. The effects of changes in bath pH on alloy composition, morphology, microstructure and corrosion resistance were studied. Scanning electron microscopy was performed to observe the morphological change of the deposits with bath pH. Coating crystallinity was investigated by grazing incidence asymmetric Bragg X-ray diffraction and transmission electron microscopy. A transition from an amorphous to polycrystalline structure was observed on increasing the bath alkalinity, and thus decreasing the phosphorus content of the alloys. A single crystalline phase corresponding to face-centred-cubic nickel was identified in the alloys obtained from a strong alkaline solution. An increase in zinc percentage up to 23% in the deposits does not change the f.c.c. nickel crystalline structure. Corrosion potential and polarization resistance measurements indicated that the corrosion resistance of electroless Ni–Zn–P alloys depends strongly on the microstructure and chemical composition. The deposits obtained at pH 9.0–9.5 and with 11.4–12.5% zinc and 11.8–11.2% phosphorous exhibited the best corrosion resistance.
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  • 26
    ISSN: 1432-0789
    Keywords: Key words Phosphorus dynamics ; Olsen ; phosphorus ; Soil phosphorus fractions ; Manure ; Soybean-wheat rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (Pi) and organic P (P0) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha–1 applied to both soybean and wheat) in the absence and presence of 16 t ha–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg–1 was 17.9 kg ha–1 of fertilizer P in unmanured plots and 5.6 kg ha–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO3-extractable Pi (NaHCO3-Pi) and NaHCO3-extractable P0 (NaHCO3-P0)], moderately labile [NaOH-extractable Pi (NaOH-Pi) and NaOH-extractable P0 (NaOH-P0)] and stable [HCl-extractable P (HCl-P) and H2SO4/H2O2-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO3-Pi and -P0 and NaOH-Pi, and -P0 fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO3-Pi, NaOH-Pi and NaOH-P0 fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P.
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  • 27
    ISSN: 1436-5073
    Keywords: aluminium oxide ; phosphorus ; XRF ; RBS ; FTIR
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Phosphorus-doped aluminium oxide thin films were deposited in a flow-type ALE reactor from AlCl3, H2O and from either P2O5 or trimethyl-phosphate. Structural information of the films was obtained from Fourier transform infrared (FTIR) spectra. Rutherford backscattering spectroscopy (RBS) was used to quantitatively determine the composition of the films. The P/Al intensity ratios calculated from X-ray fluorescence (XRF) results were in a linear relation with the P/Al concentration ratios calculated from RBS results. For comparison, the intensity ratios of the phosphorus peak (P=O) at about 1250 cm−1 and the aluminium peak (Al-O) at about 950 cm−1 were determined from the IR absorption spectra. The calibration of FTIR peak intensities was done by plotting the intensity ratios of phosphorus and aluminium peaks against the P/Al concentration ratios measured by RBS. FTIR gave also a linear calibration curve with RBS but the method is less suitable for routine analysis of P/Al ratio than XRF.
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  • 28
    ISSN: 1573-0417
    Keywords: diatoms ; eutrophication ; lake management ; paleolimnology ; British Columbia ; lakes ; phosphorus ; training sets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Eighteen lakes were added to a published training set of 46 British Columbia (BC) lakes in order to expand the original range of total phosphorus (TP) concentrations. Canonical correspondence analysis (CCA) was used to analyze the relationship between diatom assemblages and environmental variables. Specific conductivity and [TP] each explained significant (P≤0.05) directions of variance in the distribution of the diatoms. The relationship between diatom assemblages and [TP] was sufficiently strong to warrant the development of a weighted-averaging (WA) regression and calibration model that can be used to infer past trophic status from fossil diatom assemblages. The relationship between observed and inferred [TP] was not improved by the addition of more eutrophic lakes, however the [TP] range and the number of taxa used in the transfer function are now superior to the original model. Diatom species assemblages changed very little in lakes with TP concentrations greater than 85 µg 1−1, so we document the development of a model containing lakes with TP≤85 µg 1−1. The updated model uses 59 training lakes and covers a range of species optima from 6 to 41.9 µg 1−1 TP, and a total of 150 diatom taxa. The updated inference model provided a more realistic reconstruction of the anthropogenic history of a highly eutrophic BC lake. The model can now be used to infer past nutrient conditions in other BC lakes in order to assess changes in trophic status.
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  • 29
    ISSN: 1573-0417
    Keywords: carbon isotopes ; diatoms ; lake management ; nitrogen isotopes ; phosphorus ; radium-226 ; sediments ; trophic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.
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  • 30
    ISSN: 1573-0417
    Keywords: diatoms ; Everglades ; phosphorus ; wetland ; calibration ; multivariate ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781 μg g-1, and was not found to be correlated with the other geochemical variables. Canonical correspondence analysis (CCA) was used to examine which environmental variables correlated most closely with the distributions in diatom taxa. Canonical correspondence analysis with forward selection, constrained and partial CCA, and Monte Carlo permutation tests of significance show the most significant changes in diatom assemblages along the P gradient (p 〈 0.01), with additional species differences correlated with soil C, N, Ca, and BSi. Weighted-averaging (WA) regression and calibration models of diatom assemblages to P and BSi were developed. The diatom-based inference model for soil [P] had a high apparent r2 (0.86) with RMSEboot = 218 μg g-1. Indicator diatom species identified by assessing species WA optima and WA tolerance to [P], such as Nitzschia amphibia and N. palea for high [P] (~1300-1400 μ g-1) and Achnanthes minutissima var. scotica and Mastogloia smithii for low [P] (~400-600 μg g-1), may be useful as monitoring tools for eutrophication in WCA-2A as well as other areas of the Everglades. Diatom assemblages analyzed by cluster analysis were related to location within WCA-2A, and dominant taxa within clusters are discussed in relation to the geochemical variables measured as well as hydrology and pH. Diversity of diatom assemblages and a ‘Disturbance Index’ based on diatom data are discussed in relation to the historically P-limited Everglades ecosystem. Diatom assemblages should be very useful for reconstructions of [P] through time in the Florida Everglades, provided diatoms are well preserved in soil cores.
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  • 31
    ISSN: 1573-0832
    Keywords: biological control ; compatible solutes ; Epicoccum nigrum ; polyols ; solid substrate fermentation ; water activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Epicoccum nigrum conidia were produced by solid fermentation on wheat grains (cv. Rendeveaux and Brigadier) at different water activities (aw). Conidial production was highest at high aw(0.996) than at reduced aw (0.98). However, conidial production at reduced aw was improved when the aw of the substrate was adjusted with a mixture of glycerol and water. Maximum levels ofconidiation were 7–11 × 106 conidia g−1 grain. The aw of the solid substrate affected the pattern of accumulation of compatible solutes in the conidia. Mannitol was the main polyol in all conidialtypes. However, the amounts of mannitol were higher in conidia produced at high aw. At reduced aw the conidia of E. nigrum accumulated moreglycerol, which is more efficient in the osmorregulation proccess than mannitol. Arabitol accumulated in low amounts, specifically in conidia produced at the lower aw, on cv. Rendeveaux but not on cv. Brigadier. Trehalose was detected in higher amounts in cv. Rendeveaux than in cv. Brigadier, andthe amounts were higher in conidia produced at high aw. A significant amount of endogenous solutes was detected in the washing liquid used for the separation of the conidia.
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  • 32
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    Nutrient cycling in agroecosystems 41 (1995), S. 167-178 
    ISSN: 1573-0867
    Keywords: phosphorus ; workshop ; environment ; review
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A workshop was held in 1990 in Muscle Shoals, Alabama to discuss current and future research on phosphorus in agriculture. Twenty four presentations were given in areas ranging from basic to applied research. For five of the research areas presented at the workshop, this paper presents a literature review, a review of presentations at the workshop, and a discussion of future research ideas.
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  • 33
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    Nutrient cycling in agroecosystems 43 (1995), S. 109-115 
    ISSN: 1573-0867
    Keywords: phosphorus ; European network ; maintenance fertilization ; fixation capacity ; comparison of methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract After three years of a research network project on mineral phosphorus fertilization including five experimental fields located in Europe the first results are discussed. Crop response was very significant to TSP application in the alluvial calcareous polder soil of Netherlands, and in the brown silty acid soil of Scotland, both having a low level of P availability and a high fixation capacity. In the alluvial sandy loam on chalk in England, a response was observed to the first fertilization level equal to the previous crop export of phosphorus. In the brown sandy-silty soil on sand in Germany the highest rate of TSP led to a response in the third year. No effect on the final yields was observed in the brown silt loam of Belgium characterised by a textural B horizon with a high P fixation capacity. The critical values for phosphorus fertilization are discussed as the amount of P needed to maintain a target value of soil phosphorus. Concerning the supply of the different soils, no balance was reached in the Dutch and Scottish soils, a steady state was reached in the English soil with the return of the previous crop removal and the critical value for P was lower than the return of the previous crop export in the German and Belgian soils. According to the eight methods of P determination compared in the network, the P contents in the plow layer were raised in the soils of Netherlands, England and Scotland. They remained at the same level or fluctuated depending on the soil testing methods in Germany and in Belgium. High correlations exist between the different methods used in routine analysis, except for the calcium cloride and calcium acetate lactate method. Annual fluctuations in the soil P were detected at different depths depending on analytical methods and need further research.
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  • 34
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    Nutrient cycling in agroecosystems 43 (1995), S. 131-136 
    ISSN: 1573-0867
    Keywords: phosphorus ; titanium ; fertilizer efficiency ; plant nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To study the titanium effect on P nutrition, a greenhouse experiment withCapsicum annuum L., cv. Bunejo plants growing under differential P fertilization was conducted. All the plants were grown under identical conditions and they only differred in the P fertilization and in Ti supply. Plant biomass production of the Ti-untreated plants was affected by the diminution of the P-feed, but the plants growing under the lowest P supply did not showed any deficiency symptom during the crop cycle. All the Ti-treated plots showed a significative increase of the plant biomass against their corresponding untreated references. The biomass enhancement was mainly caused by the increase of the fruit yield with an absolute enhancement of 62% in the plants growing under the lowest P feed, and of 45% in the plants with a complete P support.
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  • 35
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    Nutrient cycling in agroecosystems 43 (1995), S. 209-215 
    ISSN: 1573-0867
    Keywords: phosphorus ; saturation ; inventory ; leaching ; eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The last three decades, pig breeding has evolved towards a specialised, large scaled, land independent bio-industry in the province of West-Flanders. Subsequently, in certain regions, very high amounts of liquid pig manure are produced each year. This pig slurry is used as a fertilizer at a rate which very often exceeds normal agricultural practices. Because of the nonequilibrium between the phosphorus crop requirements and the P-inputs, phosphates accumulate in the soil. However, the phosphate sorption capacity of a soil is limited. Once the sorption capacity is exceeded, phosphates will start leaching through the soil profile. Since, during winter, in these areas, the groundwater table is situated at a depth of less than 1.0 m, phosphate breakthrough might take place. In the sandy loam soil region (± 1000 km2) of the province, an inventory of the P status of the soil was made. The region was sampled according to a regular grid with 2 km intervals. At random, some sample points were only 500 m apart. This resulted in a total of 296 samplings. In view of fertilizer recommendations, lactate extractable P of the plough layer (0-30 cm) was determined. A maximum value of 101 mg P 100 g−1 of air dry soil, a minimum value of 6 mg P 100 g−1 and a median value of 31 mg P 100 g−1 were found, indicating that for half of the spots monitored, the P status of the soil is high to very high. An oxalate extraction was done to investigate the phosphate saturation of the soil profile (0-90 cm). Based on a critical phosphate saturation degree of 30%, more than half of the soil profiles are phosphate saturated. Phosphate leaching at a rate higher than 0.1 mg ortho-P 1−1 at a depth of 90 cm can be expected. Therefore, a restriction of the P fertilization should be highly recommended. The geostatistical processing of the data using block kriging resulted in a spatial continuous estimate of the phosphate saturation degree. A good agreement was found between the pig density and the phosphate saturation degree of the soil profile.
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  • 36
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    Nutrient cycling in agroecosystems 45 (1995), S. 221-233 
    ISSN: 1573-0867
    Keywords: fertilizer recovery ; modelling ; nitrogen ; nutrient efficiency ; nutrient surplus ; phosphorus ; Poland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Research on nutrient losses from agricultural systems should try to relate these losses to farm characteristics. This was done for private farms in two districts in Poland. Using data from a farm survey, nutrient surpluses and Nutrient Use Efficiency (NUE, defined as the ratio of outgoing and incoming nutrients) were calculated for nitrogen and phosphorus. Both nutrient surplus and NUE are relatively high. A model was developed to estimate surpluses and NUE from farm characteristics like location, farm size, fertilizer application level, animal density, grass production and sugar beet or potato area. The results of the model are satisfying for nutrient surplus (R2=0.9) and nitrogen NUE (R2=0.4). Estimation of phosphorus NUE was not satisfactory. High surpluses are associated with high fertilizer applications, high animal density and high grass production while an increasing share of sugar beets leads to lower surpluses. A high nitrogen NUE is associated with low fertilizer applications, low animal density and little grass production, and with a high sugar beet area share. Results suggest that, with exception of sugar beet, fertilizer recovery in Poland is very low. Sugar beet, however, combines high fertilizer applications with low surpluses and high NUE. The outcome of the model can be used in the design of environmental policies. The paper ends with some remarks on the type of measures that can be taken, and the effects these will have on private farms in Poland.
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  • 37
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    Nutrient cycling in agroecosystems 44 (1995), S. 1-8 
    ISSN: 1573-0867
    Keywords: aerobic incubation ; cation-anion-exchange resin ; phosphorus ; resin beads ; resin membranes ; suspension incubation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Six Portuguese soils of varying P sorption capacity were incubated aerobically at 30° C without and with added P in order to give 0.1.mg P L−1 in the soil solution. Two methods of measuring extractable P were compared: (i) mixed-bed cation-anion-resin beads in bags and (ii) a simpler method with anion-resin membrane only. The bag method extracted about twice and 1.5 times as much as the strip method, respectively, without and with added P. The relationships were much closer after one extraction for 2 hours (r = 0.982, p 〈 0.01) instead of the cumulative extraction of 24 hours (r = 0.635,p 〉 0.05.). P recovery after incubation was inversely related to some soil properties as organic matter, buffer capacity, selective dissolution Al forms (Alox and Ald) and P sorption. It is suggested that the simpler resin membrane method is more adequate to assess P for many studies of P reaction with soil. A simpler incubation method was tried, consisting of incubation as a soil suspension in water at a high temperature (50° C). The results suggested that this method gave similar results to aerobic incubation, with the advantage that there was no need to measure the required and final water contents of incubated soil.
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  • 38
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    Nutrient cycling in agroecosystems 55 (1999), S. 7-14 
    ISSN: 1573-0867
    Keywords: fertiliser formulation ; nutrients ; phosphorus ; relative humidity ; soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 °C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 °C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
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  • 39
    ISSN: 1573-0867
    Keywords: dairy systems ; feeds ; fertilizers ; phosphorus ; P surplus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inputs of phosphorus (P) above requirements for production on dairy farms lead to surplus P with increased risk of P transfer in land run-off to surface waters causing eutrophication. The impact of reducing surplus P inputs in purchased feeds and fertilizers on milk and forage production was investigated in a comparison of three dairy farm systems on chalkland soils in southern England over a 3-year period. In accordance with current commercial practice, no attempt was made to regulate P inputs in system 1, which accumulated an average annual surplus of 23 kg P ha-1. Progressive reductions in purchased feed and/or fertilizer inputs into systems 2 and 3 decreased surplus P to 17 and 3 kg ha-1, respectively, without apparently limiting either milk or herbage dry matter production. The estimated reduction in faecal P output from system 3 cows fed a low P diet compared to system 1 cows fed a high P diet was 26%. Milk P concentrations significantly (P 〈0.001) increased in systems 2 and 3 which included maize in the diet. Output of P in milk and meat products, as a proportion of the total dietary P inputs, increased from 28% in system 1 to 36% in system 3. Surplus P was greatest in continuous maize fields receiving both dairy manure and starter P fertilizer. Withholding P fertilizer in system 3 did not reduce P offtake in cut herbage on soils of moderate P fertility. Total annual losses of P in storm run-off and leaching were no greater than annual inputs of P from the atmosphere (0.5 kg ha-1). The results indicate there is scope to reduce surplus P on commercial dairy farms without sacrificing production targets at least in the short term. Purchased feeds are the largest of the P inputs on intensive dairy farms, yet these are rarely quantified on commercial holdings.
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  • 40
    ISSN: 1573-0867
    Keywords: leaching ; phosphorus ; poultry litter ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine P loadings, added through poultry litter, sufficient to cause downward movement of P from the cultivated layer of a sandy soil, six rates of poultry litter were applied annually for four years to a site in central England. (total loading 0 – 1119 kg P ha-1). A single extra plot also received an extra 1000 kg ha-1 as triple superphosphate (TSP; total loading 2119 kg P ha-1) and three other treatments received 200 – 800 kg ha-1 P as TSP only. Annual soil sampling in 30-cm increments to 1.5-m depth provided information on P build-up in the topsoil and P movement to depth. There were strong linear trends between P balance (P applied – P removed in crops) and total P, Olsen bicarbonate extractable P and water-soluble P in the topsoil. Phosphorus from TSP and poultry litter fell on the same regression lines, suggesting that both would be equally effective as fertilizer sources. We calculated that 100 kg ha-1 surplus total P would increase the Olsen extractable P content by c. 6 mg kg-1 and the water-soluble P by c. 5 mg kg-1. Thus, relatively large amounts of P would need to be applied to raise soil P status. We found some evidence of P movement into the soil layers immediately below cultivation depth. However, neither soil sampling nor soil solution extracted through Teflon water samplers showed evidence of movement into the deep subsoil (1 m) despite large P loadings.
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  • 41
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    Nutrient cycling in agroecosystems 54 (1999), S. 259-266 
    ISSN: 1573-0867
    Keywords: bahiagrass ; manure ; pasture fertilization ; phosphorus ; phosphorus cycling ; Spodosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations have traditionally been based upon clipping studies. Inclusion of P from manure, not originally considered when P recommendations were developed for pastures, may minimize the need for P fertilization without reducing bahiagrass production or P uptake. The objective of this research was to determine if manure contributes greatly to the P crop nutrient requirement. A 2-year field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried manure ha-1 with 0, 17, 34, 51, and 68 kg inorganic P ha-1 from triple superphosphate to evaluate bahiagrass yield, root distribution, and P uptake response on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). Because air-dried manure was used in the field study, a greenhouse study was employed to confirm that there were no differences in bahiagrass yield or P uptake from either air-dried or fresh cattle (Bos spp.) manure sources. There were no manure or manure by P interaction effects on yield or P uptake of bahiagrass indicating that manure source did not effect grass production in the greenhouse. In the field study, bahiagrass roots were distributed into the Bh horizon, and the Bh horizon had at least four times more Mehlich-1 extractable P than that of the Ap horizon. This horizon was most likely acting as a main source for P-uptake by the grass. This observation was further confirmed by no yield response to levels of inorganic P application in 1989. A linear-response-and-plateau (R2=0.196) relationship with a critical point of 15.4 kg P ha-1 was found in 1990. Bahiagrass yield and P uptake were not dependent on P fertilization, either from manure or inorganic P, due to the availability of P from the Bh horizon.
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  • 42
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    Nutrient cycling in agroecosystems 45 (1995), S. 193-197 
    ISSN: 1573-0867
    Keywords: cation activity ; phosphorus ; potassium chloride ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The electrolyte concentration of the soil solution affects the availability of some nutrients in the soil, especially of P, but it is not know at what salt concentration the reactions start to be significantly affected and their magnitude. This study was carried out to evaluate the effect of rates of potassium chloride (KCl) on some soil parameters that determine supplying of P, K, Ca, Mg, and Al in an unlimed acid soil. Increasing rates of KCl (from zero up to 2000 mg K kg−1) were applied to soil samples fertilized with 360 mg P kg−1. Solution (Cli) and exchangeable (Csi) forms of P, Ca, Mg, K, and Al were determined in the treated soil samples after 30-days of incubation; cation activity in solution and their selectivity coefficients were then calculated. Addition of KCl at rates equal to or above 500 mg K kg−1 caused a large relative increase on P in the soil solution (Pli) but a small and insignificant increase on the absolute value of Pli. All forms of soil K increased with increases on K applied, and buffer power for K varied according to the range of soil K. At all KCl rates, K displaced Ca, Mg, and Al from the solid phase to the soil solution, but had no effect on the extractable values. The relative preference of cations for the adsorption sites increased with increase on cation valency, and only those selectivity coefficients involving K were affected by K applied.
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  • 43
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    Integrated pest management reviews 4 (1999), S. 127-143 
    ISSN: 1572-9745
    Keywords: wheat ; stored-grain ; integrated pest management ; aeration ; biological control ; grain sampling ; insect monitoring ; modeling ; area-wide IPM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Management of stored-grain insect pests by farmers or elevator managers should be based upon a knowledge of the grain storage environment and the ecology of insect pests. Grain storage facilities and practices, geographical location, government policies, and marketing demands for grain quality are discussed as factors influencing stored-grain insect pest management decisions in the United States. Typical practices include a small number of grain samples designed to provide grain quality information for segregation, blending and marketing. This low sampling rate results in subjective evaluation and inconsistent penalties for insect-related quality factors. Information on the efficacy of insect pest management practices in the United States, mainly for farm-stored wheat, is discussed, and stored-grain integrated pest management (IPM) is compared to field-crop IPM. The transition from traditional stored-grain insect pest control to IPM will require greater emphasis on sampling to estimate insect densities, the development of sound economic thresholds and decision-making strategies, more selective use of pesticides, and greater use of nonchemical methods such as aeration. New developments in insect monitoring, predictive computer models, grain cooling by aeration, biological control, and fumigation are reviewed, their potential for improving insect pest management is discussed, and future research needs are examined.
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  • 44
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    Integrated pest management reviews 1 (1995), S. 15-29 
    ISSN: 1572-9745
    Keywords: biological control ; calcium ; chemical control ; covered crops ; cultural measures ; decision support system ; epidemiology ; fertilization ; forecasting ; fungicide resistance ; grey mould ; heating ; integrated disease management ; light filtration ; nutrition ; plant hormones ; sanitation ; sporulation ; Trichoderma ; ventilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Botrytis cinerea is an ubiquitous pathogen which causes severe losses in many fruit, vegetable and ornamental crops. The pathogen infects leaves, stems, flowers and fruits. The complexity of diseases caused by B. cinerea in greenhouses makes this pathogen one of the most important diseases of vegetable crops in greenhouse in many countries. In general, epidemics occur in cool and humid conditions, which favour infection and may also predispose the host to become susceptible. High relative humidity in the greenhouse and free moisture on plant surfaces are considered the most important environmental factors which influence infection by B. cinerea. In this review we specify the factors affecting the development of diseases incited by B. cinerea and discuss different approaches for its suppression. Chemical and non-chemical controls are outlined and their integration is discussed. Finally, achievements, gaps in knowledge, and future needs are indicated. The most common means for disease management is by application of chemical fungicides. Both spraying of fungicides and application of fungicides directly to sporulating wounds is practiced. However, high activity of several fungicides is being lost, at least in part, due to the development of resistance. As fungicides still remain an important tool for control of epidemics caused by B. cinerea, it is important to monitor populations of the pathogen for their resistance towards potential fungicides. Cultural measures can be a powerful means to suppress plant diseases in greenhouses where the value of crops is high and the farmers make considerable efforts during long cropping seasons. Such measures are usually aimed at altering the microclimate in the canopy and around susceptible plant organs, prevention of inoculum entrance into the greenhouse and its build up, and, rendering the host plants less susceptible to diseases. Calcium loading of plant tissues and alteration of nitrogen fertilization reduce susceptibility to Botrytis. Cultivars resistant to B. cinerea are not available. Another alternative methods to control B. cinerea is by means of biological control agents. At least one preparation is already available in the market and in many cases it was as effective as the conventional fungicides. A decision support system was recently developed for integration of chemical and biological controls. Adaquate suppression of B. cinerea diseases in greenhouse crops is an attainable goal. In our opinion this goal can be reached by considering the ecology of the pathosystem in its broader sense and by integration of all possible control measures. This implies optimization of plant nutrition, microlimate and control (cultural, biological, physiological and, if necessary, chemical) measures. Moreover, Botrytis management must be incorporated in a more holistic system that is compatible with insect control, crop production systems and profitability of the crop.
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  • 45
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    Integrated pest management reviews 4 (1999), S. 21-37 
    ISSN: 1572-9745
    Keywords: carrot weevil ; IPM ; Anaphes spp. ; biological control ; ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The carrot weevil, Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae) is a major pest of carrots in northeastern North America. The females oviposit in the leaf petiole and the developing larvae make tunnels in the carrot roots. Exclusive reliance on chemical control and the poor control obtained, prompted, in the early 1980s, research on the ecology and physiology of the pest and its natural enemies. Carrot weevil females start their oviposition by 147±9 DD7°C but they oviposit only in carrots past the 4 true-leaf-stage. As a result, oviposition is delayed, and damage reduced, in late-sown carrots. Monitoring carrot weevil adults in the spring with either carrot root sections or wooden plate traps enables growers to apply control treatments only if the population density justifies it. Egg parasitoids of the genus Anaphes (Hymenoptera: Mymaridae) are the most important natural enemies and they account, in untreated plots, for up to 80% mortality. Their effectiveness could be improved by managing field borders to establish secondary host species. An IPM programme was developed in the 1980s based on the research results obtained and, through regular monitoring, has achieved a substantial decrease in pesticide use.
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  • 46
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    Integrated pest management reviews 4 (1999), S. 39-52 
    ISSN: 1572-9745
    Keywords: Scapteriscus ; Neocurtilla ; Gryllotalpa ; biological control ; turf ; pastures ; vegetables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There are at least 70 species of mole crickets (Orthoptera: Gryllotalpidae). Some are rare, others are innocuous, and a few are important pests. These soil-dwelling pests damage underground parts of a long list of cultivated plants. Although tillage and flooding are used successfully in some situations to bring these pests to the soil surface and expose them to vertebrate and other predators, chemical pesticides are widely used against them. Knowledge of their life history is used to time application of chemical treatments to save money, but is not used as widely as it might be. Classical biological control has been used against immigrant mole crickets in Hawaii, Puerto Rico, and the southern USA. In Florida, three Scapteriscus species from South America cause major damage to pastures and turf and are targets of a classical biological control program. Population levels of two of the pest species have been reduced substantially in Florida by establishment of a tachinid fly (Ormia depleta) and a steinernematid nematode (Steinernema scapterisci) from South America. The nematode also functions as a biopesticide. Managers of pastures and turf in Florida have thus far derived benefit from these classical biological control agents without understanding their function: use of chemicals is reduced when mole cricket populations are lower due to action of these organisms. Future enhancement of the action of O. depleta and of a sphecid wasp (Larra bicolor, which also was introduced from South America) probably will demand deliberate planting of nectar sources for adults of these biological control agents, and the advantage will be to managers who adopt such a strategy. Chemical pesticide use is strongly promoted by a large chemical industry, whereas biopesticidal use has thus far been little promoted and sales have been few. Even managers who do not change their simple strategy of pesticide use in response to damage by mole crickets, and have no knowledge of the differing life cycles of the three Scapteriscus species or of the presence and action of the classical biological control agents, will derive benefit as these biological control agents (and a predatory beetle which has not yet been released) increase their distribution.
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  • 47
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    Integrated pest management reviews 4 (1999), S. 97-126 
    ISSN: 1572-9745
    Keywords: agriculture ; biological control ; campaign ; chemosterilent ; commensal ; control methods ; economics ; environmental and cultural methods ; horticulture ; India ; pest management ; pre- and post-harvest crop losses ; poultry farms ; rodent ; rodenticide ; South Asia ; trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Eighteen species of rodents are pests in agriculture, horticulture, forestry, animal and human dwellings and rural and urban storage facilities in India. Their habitat, distribution, abundance and economic significance varies in different crops, seasons and geographical regions of the country. Of these, Bandicota bengalensis is the most predominant and widespread pest of agriculture in wet and irrigated soils and has also established in houses and godowns in metropolitan cities like Bombay, Delhi and Calcutta. In dryland agriculture Tatera indica and Meriones hurrianae are the predominant rodent pests. Some species like Rattus meltada, Mus musculus and M. booduga occur in both wet and dry lands. Species like R. nitidus in north-eastern hill region and Gerbillus gleadowi in the Indian desert are important locally. The common commensal pests are Rattus rattus and M. musculus throughout the country including the islands. R. rattus along with squirrels Funambulus palmarum and F. tristriatus are serious pests of plantation crops such as coconut and oil palm in the southern peninsula. F. pennanti is abundant in orchards and gardens in the north and central plains and sub-mountain regions. Analysis of the information available on the damage and economic losses caused by rodents in rice, wheat, sugarcane, maize, pearl millet, sorghum, oil seed, legume and vegetable crop fields, horticulture and forestry, poultry farms, and rural and urban dwellings and storage facilities clearly shows that chronic damage ranging from 2% to 15% persists throughout the country and severe damage, sometimes even up to 100% loss of the field crop, is not rare. Several traditional and modern approaches and methods of rodent control are being used. The existing knowledge of the environmental, cultural, biological, mechanical and chemical methods of rodent control in India is reviewed. Considerable variations exist in the susceptibility of the pest species to different methods, particularly to rodenticides and trapping, their field applicability, efficacy and economics in different crops, seasons and geographical regions, behavioural responses of the pest species to these methods in different ecological conditions and their adoption by farmers in different regions of India. Environmental and cultural techniques, such as clean cultivation, proper soil tillage and crop scheduling, barriers, repellents and proofing which may reduce rodent harbourage, food sources and immigration have long lasting effects but are seldom adopted. However, their significance in relation to normal agricultural practices, intensification and diversification are discussed. Rodenticides, which provide an immediate solution to the rodent problem, form the major component of rodent control strategies in India. Poison baiting of rodents with zinc phosphide and burrow fumigation with aluminium phosphide are common in agricultural fields and recently Racumin (coumatetralyl) and bromadiolone have been introduced for the control of both agricultural and commensal rodent pests in India. Methods and timings of campaigns and successes and problems in implementation of rodent control are also reviewed.
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  • 48
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    Integrated pest management reviews 4 (1999), S. 307-312 
    ISSN: 1572-9745
    Keywords: microbial control ; biological control ; biopesticide ; mycopesticide ; Metarhizium ; Beauveria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microbial control agents generally kill insects more slowly than chemical pesticides, and fast-moving migratory pests may not at first sight appear to offer the most promising targets for microbial control. Operators responsible for control may need to have recourse to chemical control agents. Nevertheless, there are many occasions when pests breed and feed outside the crop and a microbial control agent can be used. Similarly, immature stages may cause little damage and early treatment in the crop can avoid damage. Microbial control agents are particularly likely to be favoured if the pest breeds in a conservation area, and if a publicly-accountable agency is responsible for control. Other key points of importance are the IPM context, in particular detection, planning and forecasting of outbreaks and the role of natural enemies. With these points in mind, we identify several locust and grasshopper systems where microbial control is becoming established; additionally, Sunn pest of wheat and Armyworm are identified as promising situations forbreak microbials.
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  • 49
    ISSN: 1573-1561
    Keywords: Kairomone ; biological control ; cabbage ; wheat ; Diuraphis noxia ; Brevicoryne brassicae ; olfactometer ; infochemical ; preference ; host plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiidae) is a parasitoid of several aphid species, including the Russian wheat aphid (RWA),Diuraphis noxia (Mordvilko), and the cabbage aphid (CA).Brevicoryne brassicae (L.). The response of matedD. rapae females to odors from wheat, cabbage, and plant-host complexes was investigated using a four-choice olfactometer. Experienced parasitoids, but not inexperienced females, responded positively to odors of the wheat-RWA complex in a no-choice test. In choice tests, experienced parasitoids did not respond to odors of uninfested cabbage and wheat leaves, but did respond positively to aphid-infested plants and to aphids alone. The response ofD. rapae to the cabbage-CA complex and to CA alone was significantly greater than to the wheat-RWA complex and RWA alone, suggesting an innate odor preference for crucifer-feeding aphids.
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  • 50
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    Journal of chemical ecology 25 (1999), S. 1555-1565 
    ISSN: 1573-1561
    Keywords: Yeasts ; Botrytis cinerea ; apple ; volatiles ; gray mold ; biological control ; fungal interaction ; acetate esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The fungus, Botrytis cinerea, causes decay in apples in postharvest storage. Conidia of B. cinerea on polycarbonate membranes were incubated on filter paper disks saturated with water or suspensions of yeasts (2 × 106 CFU/filter) and then exposed for 24 hr at 22°C to 0–16 μl of ethyl, butyl, or hexyl acetates injected into the headspaces of 500-cc glass jars. Germination of conidia was increased by exposure to 4–16 μl of ethyl acetate compared to the no-ester controls. Conidia were stimulated to germinate by 4 μl of butyl acetate and 8 μl of hexyl acetate, but greater volumes were toxic to germination. The yeasts Cryptococcus laurentii and Sporobolomyces roseus were more effective at reducing the stimulatory effect than Saccharomyces cerevisiae. Acetate esters also stimulated germination of conidia on polycarbonate membranes on apples inside jars. Cryptococcus laurentii or S. roseus suppressed this effect more than S. cerevisiae. Germination of conidia on a membrane on water inside a 3.9-liter jar containing an apple was 2.5-fold greater than the no-apple control. Butyl acetate increased Botrytis infection of apple wounds. Butyl and hexyl acetate were detected by GLC in the headspace of Golden Delicious apples. Results indicated that some acetate esters produced by apple stimulated germination of B. cinerea conidia, and this effect was suppressed by yeasts.
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  • 51
    ISSN: 1871-4528
    Keywords: bioassay ; biological control ; blackleg ; green crop harvesting ; haulm killing ; skin damage ; wound protection ; Solanum tuberosum L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Green crop lifting (GCL) for haulm killing was developed in The Netherlands and offers ideal conditions for controlling the blackleg pathogenErwinia carotovora subsp.atroseptica (Eca) by antagonists. Based on the use of mini-tubers or young tubers from field crops, two bioassays for wound protection were developed. GCL was simulated by artificially skinning or wounding tubers, inoculating the damaged skin with Eca, treating with antagonists and incubating in either potting compost or outside in field soil. Mainly fluorescent pseudomonads, pre-screened for in vitro antagonistic activity on agar and high soft rot reducing ability on tuber slices, were tested in the mini-tuber bioassay. Strains giving the highest degree of wound protection were further tested individually and in combination under field conditions in the young tuber bioassay. One individual strain and two combinations, resulting in reduction of contamination levels on skinned surfaces of 85% and between 60% and 70%, respectively, show good potential for biological control of blackleg.
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  • 52
    ISSN: 1573-5125
    Keywords: denitrification ; nature restoration ; nitrogen ; phosphorus ; riparian areas ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Denmark, as in many other European countries, the diffuse losses of nitrogen (N) and phosphorus (P) from the rural landscape are the major causes of surface water eutrophication and groundwater pollution. The export of total N and total P from the Gjern river basin amounted to 18.2 kg ha−1 and 0.63 kg P ha−1 during June 1994 to May 1995. Diffuse losses of N and P from agricultural areas were the main nutrient source in the river basin contributing 76% and 51%, respectively, of the total export. Investigations of nutrient cycling in the Gjern river basin have revealed the importance of permanent nutrient sinks (denitrification and overbank sedimentation) and temporary nutrient storage in watercourses. Temporary retention of N and P in the watercourses thus amounted to 7.2–16.1 g N m−2 yr−1 and 3.7–8.3 g P m−2 yr−1 during low-flow periods. Deposition of P on temporarily flooded riparian areas amounted from 0.16 to 6.50 g P m−2 during single irrigation and overbank flood events, whereas denitrification of nitrate amounted on average to 7.96 kg N yr−1 per running metre watercourse in a minerotrophic fen and 1.53 kg N yr−1 per linear metre watercourse in a wet meadow. On average, annual retention of N and P in 18 Danish shallow lakes amounted to 32.5 g N m−2 yr−1 and 0.30 g P m−2 yr−1, respectively, during the period 1989–1995. The results indicate that permanent nutrient sinks and temporary nutrient storage in river systems represent an important component of river basin nutrient budgets. Model estimates of the natural retention potential of the Gjern river basin revealed an increase from 38.8 to 81.4 tonnes yr−1 and that P-retention increased from −0.80 to 0.90 tonnes yr−1 following restoration of the water courses, riparian areas and a shallow lake. Catchment management measures such as nature restoration at the river basin scale can thus help to combat diffuse nutrient pollution.
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    Aquatic ecology 29 (1995), S. 245-255 
    ISSN: 1573-5125
    Keywords: phosphorus ; sediments ; estuary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Great Ouse estuary in southern England is a macrotidal estuary with rather coarse sediment. Two intertidal sites were sampled five times over the year at low tide. The sediments are suboxic, organic poor (approximately 1.5% organic carbon). They are composed mainly of detrital quartz and feldspar with some calcite. At both sites the total phosphorus in the sediments ranges from 0.03 – 0.12% dry weight and total iron from 0.42–1.22% dry weight. Of the total phosphorus 20% is organic and 80% is inorganic of which 10% is water extractable. Total iron and phosphorus correlate well and the ratio of iron:phosphorus is 8.4 which is similar to that found when phosphorus is adsorbed by iron oxyhydroxides, suggesting that iron oxyhydroxides are an important substrate for phosphorus sorption in these sediments. Fluxes of phosphorus from the sediment to the overlying water, measured in cores incubated in the laboratory, are low and show no seasonality. The sodium concentration in the porewaters at both sites is variable suggesting that there is movement of water through the sediment to depths of at least 20 cm. This is borne out by variable phosphorus, iron and phosphorus concentrations in the porewaters and ill defined redox zones in the sediments.
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  • 54
    ISSN: 1573-5052
    Keywords: mineralization ; nitrogen ; phosphorus ; salinity ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant zonation patterns across New England salt marshes have been investigated for years, but how nutrient availability differs between zones has received little attention. We investigated how N availability, P availability, and plant N status varied across Juncus gerardii, Spartina patens, and mixed forb zones of a Northern New England high salt marsh. We also investigated relationships between several edaphic factors and community production and diversity across the high marsh. P availability, soil salinity, and soil moisture were higher in the mixed forb zone than in the two graminoid zones. NH+ 4-N availability was highest in the J. gerardii zone, but NO− 3-N availability and mid season net N mineralization rates did not vary among zones. Plant tissue N concentrations were highest in the mixed forb zone and lowest in the S. patens zone, reflecting plant physiologies more so than soil N availability. Community production was highest in the J. gerardii zone and was positively correlated with N availability and negatively correlated with soil moisture. Plant species diversity was highest in the mixed forb zone and was positively correlated with P availability and soil salinity. Thus, nutrient availability, plant N status, and plant species diversity varied across zones of this high marsh. Further investigation is needed to ascertain if soil nutrient availability influences or is a result of the production and diversity differences that exist between vegetation zones of New England high salt marshes.
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  • 55
    ISSN: 1573-1464
    Keywords: Adelges tsugae ; biological control ; Diapterobates humeralis ; hemlock ; Japan ; natural enemies ; Picea spp. ; population dynamics ; predators ; Pseudoscymnus tsugae ; Tsuga spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hemlock woolly adelgid, Adelges tsugae Annand (Homoptera: Adelgidae), is native to Japan where it is an innocuous inhabitant of Tsuga diversifolia Masters and T. sieboldii Carriere throughout their natural growing areas. Native adelgid populations are regulated by host resistance and natural enemies, in particular the oribatid mite, Diapterobates humeralis (Hermann) and the coccinellid beetle, Pseudoscymnus tsugae Sasaji and McClure. Invading populations of A. tsugae in western North America on T. heterophylla Sargent and T. mertensiana Carriere are mainly regulated by host resistance. However, invading populations in eastern North America attain damaging levels on T. canadensis (L.) Carriere and T. caroliniana Engelmann and are regulated mainly by weather and negative density-dependent feedback mechanisms related to host deterioration. Although A. tsugae is only passively dispersed by wind, birds, forest-dwelling mammals and humans, it is spreading at an alarming rate and is sufficiently cold hardy to threaten the existence of the two eastern hemlock species throughout their natural ranges. The current hope for suppressing invading populations of hemlock woolly adelgid in eastern North America lies with the exotic predator, P. tsugae. Extensive laboratory studies of the biology and predatory ability of P. tsugae revealed that it feeds on all life stages of its prey, that its multivoltine life cycle is well synchronized with that of the adelgid, and that it has great potential for biological control. We have reared and released nearly 130,000 adults of P. tsugae in forests in Connecticut, New Jersey and Virginia during the past four years. P. tsugae has reproduced, dispersed, overwintered and reduced densities of hemlock woolly adelgid by 47–88% in only five months on release branches at these sites. Current studies are investigating the long-term ability of P. tsugae to regulate invading populations of A. tsugae in eastern North America.
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  • 56
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    Biological invasions 1 (1999), S. 301-311 
    ISSN: 1573-1464
    Keywords: Alliaria petiolata ; biological control ; garlic mustard ; invasions ; Lythrum salicaria ; monitoring ; Phragmites australis ; purple loosestrife
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The invasion of non-indigenous plants is considered one of the primary threats to rare and endangered species as well as to the integrity and function of North American ecosystems. However, many of the suspected negative ecosystem impacts are based on anecdotal evidence. For example, there is almost unanimous agreement among natural resource managers of the detrimental ecological impacts of species such as Lythrum salicaria (purple loosestrife), Phragmites australis (common reed) and Alliaria petiolata (garlic mustard) but convincing documentation is scarce. Experimental and theoretical ecology predicts large ecosystem impacts of the most widespread invasive species. However, it is difficult to prioritize control of species that occur at intermediate densities. Long-term monitoring before and during the invasion as well as before, during and after any control attempts can provide valuable ecological information. In particular, it is important to understand how changes in the abundance of species influence ecosystem properties and processes which, in turn, will help guide management decisions. Ideally, this monitoring has to go beyond 'simple’ impacts on plant communities, involve cross-disciplinary teams of scientists and should incorporate many different taxa and their interactions. Monitoring design and data collection should be sophisticated enough to allow statistically sound data analysis. The available information will be paramount in (1) developing new political and scientific guidelines in invasive species management, (2) helping resolve potential conflicts of interest and (3) helping change public attitudes regarding growth, sale, and control of non-indigenous species.
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  • 57
    ISSN: 1573-1464
    Keywords: biological control ; biological invasions ; colonization ; Galerucella calmariensis ; Galerucella pusilla ; population ; establishment ; release size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Introductions of biological control organisms offer a unique opportunity to experimentally study the process of invasion by exotic species. I used two chrysomelid beetles, Galerucella calmariensis and Galerucella pusilla, which are currently being introduced into North America for the biological control of purple loosestrife (Lythrum salicaria), to determine how the initial size of a release affects the probability that the introduced population grows and persists. I released both species into stands of their host plant at 36 sites scattered throughout central New York State using four release sizes: 20, 60, 180, and 540. I returned to these sites over the next 3 years to census the populations. For both species, the probability of population establishment increased with release size. Population growth rates also depended positively on release size. The implication from these results is that the demographic factors whose influence depends on population size or density such as demographic stochasticity, Allee effects, and genetics play important roles in the establishment of invading populations. A second set of releases was used to determine if it was at all possible for a single gravid female to found a population. Out of twenty individual females released, one female (a G. calmariensis) founded a population that persisted until the end of the study (3 generations).
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  • 58
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    Aquatic ecology 33 (1999), S. 55-64 
    ISSN: 1573-5125
    Keywords: estuaries ; nitrogen ; oxygen depletion ; phosphorus ; regression model ; vertical mixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e. 〈15% of saturation) by more than 50%.
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  • 59
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    European journal of plant pathology 105 (1999), S. 61-76 
    ISSN: 1573-8469
    Keywords: core sampling ; foliar nutrient concentrations ; minirhizotrons ; nitrogen ; phosphorus ; potassium ; Rhizolab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potato-cyst nematodes (Globodera pallida) cause severe yield losses in potato. Plants infected with potato-cyst nematodes generally have reduced concentrations of nitrogen, phosphorus and potassium in the foliage. This study investigated whether reduced growth of nematode-infected potato is caused by nutrient limitation. Experiments in the field and in containers showed that phosphorus concentration correlated best with total crop biomass at early stages of growth. The role of phosphorus in nematode damage was further investigated in the field and in the Wageningen Rhizolab. The experimental field was infested with potato-cyst nematodes and two levels of nematode density were established by fumigation with a nematicide. Prior applications of calcium carbonate resulted in pHKCl levels of 4.8 and 6.1. Two levels of phosphorus fertiliser were applied: either 0 or 225 kg P ha−1. In the Wageningen Rhizolab, soil of both pH levels from the field was used after treatment with 1 MRad gamma irradiation to kill the nematodes. Subsequently, half of the soil was inoculated with cysts to give a nematode density of 30 viable juveniles per gram of soil. In the field, nine weeks after planting, the total crop biomass ranged from 107 g m−2 for the treatment with nematodes at pHKCl 6.1 without phosphorus fertiliser to 289 g m−2 for the fumigated treatment at pHKCl 4.8 with phosphorus fertiliser. The differences in total biomass for the various treatments were explained by differences in foliar phosphorus concentration. Nematodes induced or aggravated P deficiency and reduced total biomass. This was not the only damage mechanism as at high, non-limiting levels of foliar phosphorus concentration, nematodes still reduced total biomass. In the Wageningen Rhizolab, directly after planting, the number of roots visible against minirhizotrons was reduced by nematodes. However, the increase of root number in the nematode treatment continued longer than in the control, until root number was higher than that of the control. The compensary root growth of the nematode treatment was restricted to the top 30 cm and nematodes reduced rooting depth. High soil pH reduced growth, mainly by reducing the availability of phosphate. Both nematodes and high soil pH reduced nutrient uptake per unit root length. Our results lead us to suggest an interaction between nematodes and soil pH, with nematode damage being higher at pHKCl 6.1 than at pHKCl 4.8.
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  • 60
    ISSN: 1573-8469
    Keywords: biological control ; Botrytis allii ; Botrytis cinerea ; leaf wetness ; onion ; plant debris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Saprophytic antagonists were evaluated for suppression of sporulation ofBotrytis allii andB. cinerea on artificially killed segments of onion leaves that were pre-inoculated with the pathogens. During incubation of the antagonisttreated leaf segments in moist chambers, periods of leaf wetness and leaf dryness were alternated to simulate conditions in the field. Interruption of humid conditions with dry periods had a differential effect on antagonists.Alternaria alternata, Chaetomium globosum, Ulocladium atrum andU. chartarum suppressed sporulation ofB. allii almost completely under continuously wet conditions, and when the leaf wetness periods were interrupted with drying periods of 9h imposed 16, 40, and 64 h after the antagonists were applied. When leaf wetness was interrupted 16 h after antagonist application, the number of conidia ofB. allii produced cm−2 leaf surface after eight days was under the detection limit of 5.2 × 103 conidia on leaves treated with these antagonists compared to 3.7 × 105 conidia on leaves that were not treated. On the other hand,Gliocladium roseum, G. catenulatum andSesquicillium candelabrum, all highly efficient under continuously wet conditions, were of low to moderate efficiency when leaf wetness periods had been interrupted 16 h after application of the antagonists. The antagonists showed the same differentiation and sensitivity to interrupted wetness periods when tested withB. cinerea.
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  • 61
    ISSN: 1573-8469
    Keywords: biological control ; immunofluorescence colony-staining ; inoculum delivery ; inoculum density ; rockwool bioassay ; strain specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Pseudomonas fluorescens-mediated induction of systemic resistance in radish against fusarium wilt (Fusarium oxysporum f. sp.raphani) was studied in a newly developed bioassay using a rockwool system. In this bioassay the pathogen and bacterium were confirmed to be confined to spatially separate locations on the plant root, throughout the experiment. Pathogen inoculum obtained by mixing peat with microconidia and subsequent incubation for four days at 22 °C, yielded a better percentage of diseased plants than a microconidial suspension drench, an injection of a microconidial suspension into the hypocotyl, or a talcum inoculum.Pseudomonas fluorescens strain WCS374 applied in talcum or peat, but not as a suspension drench, induced systemic resistance. A minimal initial bacterial inoculum density of ≥105 CFU WCS374 root−1 was required to significantly reduce the percentage diseased plants. At least one day was necessary between bacterization of strain WCS374 in talcum on the root tips and inoculation of the pathogen in peat on the root base, for an optimal induction of systemic resistance. Strain WCS374 induced systemic resistance in six radish cultivars differing in their susceptibility toF. oxysporum f. sp.raphani. Significant suppression of disease by bacterial treatments was generally observed when disease incidence in the control treatment, depending on pathogen inoculum density, ranged between approximately 40 to 80%. Strains WCS374 and WCS417 ofPseudomonas fluorescens induced systemic resistance against fusarium wilt, whereasP. putida WCS358 did not. This suggests that the induction of systemic resistance byPseudomonas spp. is dependent on strain-specific traits.
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  • 62
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    European journal of plant pathology 101 (1995), S. 665-672 
    ISSN: 1573-8469
    Keywords: biological control ; seeds ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Isolates of different endophytic bacteria were recovered from surface-disinfected seeds obtained from commercial companies, plants in the field and tissue culture. The bacteria were isolated from seeds after stringent surfacedisinfection.Pseudomonas fluorescens (isolate no. 14) from bean inhibited growth of all fungi tested and was fluorescent on King B medium.Bacillus cereus fromSinapis (isolate no. 65) inhibited growth ofRhizoctonia solani, Pythium ultimum andSclerotium rolfsii and also exhibited chitinase activity.Bacillus subtilis from onion tissue culture (isolate no. 72) inhibitedR. solani andP. ultimum growth.B. cereus from cauliflower (isolate no. 78) inhibited growth ofR. solani. B. pumilus from sunflower (isolate no. 85) inhibited growth ofR. solani andS. rolfsii. B. cereus (isolate no. 65) was introduced into cotton, and by using radioactive labelling we found that it was present for 16 days in the root-stem junction. It is most likely that these bacteria were still found 72 days after their introduction in the root and stem, at levels of 2.8·105 and 5·104 cfu g−1 fresh weight, respectively, when selective medium was used. There was no difference between control and treated plants in their height or in the fresh weight of roots, stems and leaves. When cotton seedlings were inoculated withB. cereus (isolate no. 65),B. subtilis (isolate no. 72) orB. pumilus (isolate no. 85), disease incidence caused byRhizoctonia solani was reduced in the greenhouse by 51%, 46% and 56%, respectively. In bean seedlings inoculated withB. subtilis (isolate no. 72),B. cereus (isolate no. 78) orB. pumilus (isolate no. 65), disease incidence caused bySclerotium rolfsii was reduced by 72%, 79% and 26%, respectively, as compared to control. In both cotton and bean seedlings, these endophytes reduced the disease index more than 50%. These results indicate that endophytic bacteria can survive inside cotton plants and are efficient agents for biological control against plant pathogens under greenhouse conditions.
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  • 63
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    Hydrobiologia 297 (1995), S. 1-9 
    ISSN: 1573-5117
    Keywords: phosphorus ; nutrient deficiency ; phosphate ; phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mesocosms (1.3 m3) in a eutrophic reservoir were treated with NH4Cl (160 µmol l−1), KH2PO4 (10 µmol l−1) or nothing (control) and sampled after 8 days to determine how P dynamics are related to relative P deficiency. Photosynthetic rate and chlorophyll data suggested P deficiency in ammonium and control mesocosms and no P deficiency with phosphate additions. Biologically available P (BAP) and the ratio of BAP to soluble reactive P (SRP) decreased as P deficiency increased. Log of short-term uptake as a function of log of phosphate concentration exhibited an approximate linear increase in control and N mesocosms; substrate dependent uptake kinetics showed no saturation up to 500 µmol l−1 phosphate. Uptake was independent of phosphate concentration (saturated) in samples from the 10 µmol l−1 P enriched mesocosm. This suggests that P uptake may not saturate at ecologically realistic values in short term experiments under P deficient conditions. Particle associated phosphatase activity was greatest in the 0.2–3 µm size-fraction in all mesocosms, but total activity varied little with P deficiency.
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  • 64
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    Hydrobiologia 300-301 (1995), S. 391-398 
    ISSN: 1573-5117
    Keywords: phytoplankton ; phosphorus ; 31P-NMR ; in situ sample fixation ; maximum entropy method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new fixation method was developed for the Nuclear Magnetic Resonance (NMR) study of natural phytoplankton samples collected in situ. To test NMR reliability, a Chlorella continuous culture was used in a phosphorus deficiency recovery experiment. The method was then applied to natural metalimnetic cyanobacterial plankton. The maximum Entropy Method was used to enhance the generally poor signal to noise ratio resulting from the low amount of available material and NMR sensitivity. Suggestions are made on how to improve reliability.
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  • 65
    ISSN: 1573-5117
    Keywords: reservoirs ; phosphorus ; sediments ; exchanges ; euthrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Les échanges de phosphore au niveau de l'interface eau-sédiment couplés á la distribution temporelle de divers éléments chimiques et biologiques ont été étudiés dans divers réservoirs de niveaux trophiques différents, au Maroc et en France. Nos résultats mettent clairement en évidence une influence directe de l'environnement physico-chimique, de la nature géologique des bassins versants et de l'état trophique du lac sur la dynamique du phosphore au sein de cette interface. De plus, il apparait que dans le lac hypereutrophe de Villerest (Roanne, France), le phosphore est majoritairement complexé au fer alors que dans les retenues marocaines, ce sont les complexes phosphore-calcium qui prédominent. Nous préconisons un contrôle drastique des apports en phosphore á travers l'installation et la multiplication d'unités de déphosphatation afin d'éviter d'une part, la prolifération massive de la Cyanobactérie Microcystis aeruginosa á Villetest (Aleya et al., 1994) et d'autre part la dissociation des complexes phhosphore-calcium au sein des retenues marocaines avec libération de phosphore biodisponible.
    Notes: Abstract Phosphorus exchange at the sediment-water interface coupled with several parameters were assessed in several reservoirs with geologically different catchment basins and different trophic status in Morocco and France. The results showed that these exchanges were regulated by a combination of factors: physical chemical variability of the environment, the geological composition of catchment basins and the trophic status of the lake. In the hypereutrophic Villerest, iron-bound phosphorus is the major form of phosphorus trapped by the sediment whereas, in Moroccan reservoirs, calcium-bound phosphorus prevailed. We suggest that a drastic control of phosphorus inputs into the waters must be done through a large program of dephosphatization of tributaries to avoid Microcystis aeruginosa bloom formation in Villerest (Aleya et al., 1993) and calcium-bound phosphorus dissociation in Moroccan reservoirs with upward release of bioavailable phosphorus.
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  • 66
    ISSN: 1573-5117
    Keywords: phosphorus ; chemical fractionation ; synthetic P compounds ; minerals ; sediments ; eutrophic lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphorus (P) reactivity and bioavailability in lake sediments may be determined by different forms of P and their distribution. Reactive and nonreactive P pools in two shallow subtropical lake sediments (Lake Apopka and Lake Okeechobee) were determined by sequential chemical extraction using 1 M NH4Cl (pH 7.0), 0.1 M NaOH, and 0.5 M HCl, reportedly representing loosely-bound P, Fe- and Al-bound P, and Ca- and Mg-bound P respectively. The sequential P fractionation was tested using pure P compounds and selected P minerals. The scheme effectively separated Fe- and Al-P from Ca-P fractions in an FePO4-AlPO4-Ca3(PO4)2 mixture. Readily available P, defined as the sum of water-soluble P and NH4Cl-extractable P, in the unconsolidated gyttja (UCG) layer (surface 0–30 cm) of Lake Apopka sediments accounted for 10.1 to 23.7% of total P (TP). This sediment P fraction constitutes a large reservoir which may act as a source of P to the overlying water. In subsurface marl layers (134–148 cm depth) of Lake Apopka, NH4Cl-P constituted 〈I% of TP whereas Ca-Mg-bound P and highly resistant P (residual P) accounted for 35 and 64% of TP respectively. Results suggest that 1 M NH4Cl (pH 7.0) and 0.5 M HCl, reported to dissolve carbonate-bound P and Ca-Mg-bound P, respectively, may not be extracting distinct pools of P. Lake Okeechobee mud sediments had low concentrations of readily available P (2% of TP) and were dominated by Ca-Mg-bound P (HCl-P≥58% of TP). Sediments in the littoral and peat areas of Lake Okeechobee, however, had high concentrations of readily available P (9.7 and 17.4% of TP respectively); hence, these sediments may play an important role in internal P cycling. The NaOH-P (Fe-Al-P) concentrations for Lake Okeechobee sediments were strongly correlated with amorphous and poorly-crystalline Fe (p〈 0.01), suggesting that some P reactions in these sediments may be sensitive to changes in physico-chemical conditions such as redox potential and sediment resuspension.
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  • 67
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    Hydrobiologia 302 (1995), S. 179-188 
    ISSN: 1573-5117
    Keywords: river ; diatom ; index ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The performance of five types of benthic diatom index (four quantitative methods and a zoning system) to evaluate water quality was tested in rivers in England and Scotland. Significant correlations were observed between the four quantitative indices examined. In the case of SPI (Specific Pollution sensitivity Index) and GDI (Generic Diatom Index), over 80% of the variation in GDI was explained by a bivariate regression on SPI. Samples taken from six sites at four different times of year showed no significant influence of season on any of the indices. The zoning system led to a similar assessment of organic pollution as the SPI and GDI indices , but it was sometimes difficult to determine the zone. This method showed no obvious advantages over the quantitative indices. The high correlation between values for indices based on species and those on genera suggests that for routine monitoring, recognition to the generic level is adequate.
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  • 68
    ISSN: 1573-5117
    Keywords: Bangladesh ; deepwater rice ; flood ; nitrogen ; phosphorus ; biomass ; damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Measurements of the biomass of deepwater rice plants at sites on the three major floodplains in Bangladesh (Ganges, Jamuna, Meghna) with and without fertilizer treatment were made from shortly before the arrival of flood water (June) until it was receding (mid-October). There was usually an approximately linear increase in biomass per unit area with time until September, but subsequently there were marked differences in response, ranging from a continued steady increase to a sharp drop. Difference in the flood pattern were an important factor influencing changes in biomass and productivity. Net productivity (biomass change) measured at different stages in growth ranged from - 73 to + 220 kg ha-1 d-1 in unfertilized fields and from - 141 to + 430 kg ha-1 d-1 in fertilized fields, with mean values of + 130 in unfertilized and + 160 kg ha-1 d-1 in fertilized fields. However,grain yield reflected the increased biomass in only one of four experiments.
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  • 69
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    Hydrobiologia 295 (1995), S. 311-321 
    ISSN: 1573-5117
    Keywords: mangrove forest ; nitrogen ; nutrient budgets ; phosphorus ; shrimp pond effluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Preliminary estimates of the ratio of mangrove forest: shrimp pond area necessary to remove nutrients from shrimp pond effluent are made using budgets of nitrogen and phosphorus output for semi-intensive and intensive shrimp ponds combined with estimates of total net primary production in Rhizophora-dominated mangrove forests in tropical coastal areas. If effluent is delivered directly to mangrove forest plots, it is estimated that, depending on shrimp pond management, between 2 and 22 hectares of forest are required to filter the nitrogen and phosphorus loads from effluent produced by a 1 hectare pond. While such ratios may apply to small scale, integrated shrimp aquaculture — mangrove forestry farming systems, the variability in mangrove hydrodynamics makes it difficult to apply such ratios at a regional scale. Before mangroves can be used to strip shrimp pond effluent more research is required on the effects that high ammonia and particulate organic matter loads in pond effluent have on nutrient transformations in mangrove sediments and on forest growth.
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  • 70
    ISSN: 1573-5117
    Keywords: Deep lake ; eutrophication ; restoration ; mathematical modeling ; phosphorus ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper demonstrates how mathematical modeling can contribute to improve understanding of lake behavior. Since the 60's Lake Bourget, one of the largest in France, had been suffering from eutrophication which was checked in 1980 by the diversion of the main sewers entering the lake. A research program was implemented between 1987 and 1990, including an on-site sampling campaign conducted concurrently with thermal and biogeochemical modeling of lake behavior. The model helped provide a better understanding of the ecosystem, displaying some processes hitherto misunderstood: (1) Winter overturn does not reach the bottom of the water column when the weather is mild. This leads to a incomplete reoxygenation of the hypolimnion and to redox conditions inducing the release of orthophosphate from the sediment, (2) Grazing by herbivorous zooplankton is getting more important in the control of spring algal growth as eutrophication of the lake regresses, (3) Settling of particulate phosphorus seems a complex and very important process in Lake Bourget, showing high sedimentation rates for particulate mineral phosphorus.
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  • 71
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soilwater and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    Biogeochemistry 46 (1999), S. 179-202 
    ISSN: 1573-515X
    Keywords: carbon dioxide ; grazing ; nitrogen fixation ; nitrogen limitation ; phosphorus ; shade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The widespread occurrence ofN limitation to net primary production (NPP) and other ecosystem processes, despite the ubiquitous occurrence ofN-fixing symbioses, remains a significant puzzle in terrestrial ecology. We describe a simple simulation model for an ecosystem containing a generic nonfixer and a symbioticN fixer, based on: (1) a higher cost forN acquisition byN fixers than nonfixers; (2) growth of fixers and fixation ofN only when lowN availability limits the growth of nonfixers, and other resources are available; and (3) losses of fixedN from the system only when the quantity of availableN exceeds plant and microbial demands. Despite the disadvantages faced by theN fixer under these conditions,N fixation and loss adjustN availability close to the availability of other resources, and biomass and NPP in this simple model can be substantially but only transientlyN limited. We then modify the model by adding: (1) losses ofN in forms other than excess availableN (e.g., dissolved organicN, trace gases produced by nitrification); and (2) constraints to the growth and activity ofN fixers imposed by differential effects of shading,P limitation, and grazing. The combination of these processes is sufficient to describe an open system, with input from both precipitation andN fixation, that is nevertheless stronglyN-limited at equilibrium. This model is useful for exploring causes and consequences of constraints toN fixation, and hence ofN limitation, and we believe it will also be useful for evaluating howN fixation and limitation interact with elevatedCO 2 and other components of global enviromental change.
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  • 73
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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  • 74
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    European journal of plant pathology 105 (1999), S. 123-137 
    ISSN: 1573-8469
    Keywords: Aureobasidium pullulans ; biological control ; Cryptococcus albidus ; grey mould ; Trichoderma harzianum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The efficacy of Trichoderma harzianum T39 and the yeasts Aureobasidium pullulans and Cryptococcus albidus against Botrytis cinerea in cucumber and tomato was compared with chemical control. Four experiments were conducted in cucumber grown under different climatic conditions in The Netherlands, and two experiments were done in tomato both in the Netherlands and in Israel. T. harzianum and A. pullulans showed the most consistent control of B. cinerea, reducing stem lesions and death of plants by 40–100% in most cases. Control of stem lesions and subsequent wilting was generally better than control of symptoms on fruits. In some cases, the biocontrol agents were more effective than the broad-spectrum fungicide tolylfluanid and the selective fungicide iprodione. The climatic conditions did not strongly influence the efficacy of the biocontrol agents, but regression analysis showed that high temperature during the day and high vapour pressure deficit during the night reduced biocontrol efficacy. From the results, prospects for biocontrol of B. cinerea in greenhouse vegetables appear good under a range of conditions.
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  • 75
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    European journal of plant pathology 105 (1999), S. 95-101 
    ISSN: 1573-8469
    Keywords: bacteria ; biological control ; Chryseobacterium ; Flavobacterium ; grey mold ; Pseudomonas ; strawberries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Most potential fungal antagonists have been identified only after exhaustive non-selective screening. Bacteria antagonistic to Botrytis cinerea were selected using a simple method based on techniques developed for trace enrichment studies, where a crude cell wall preparation from B. cinerea was used as a selective substrate and bacteria were isolated based on growth on cell wall agar media. Most of the 52 bacterial isolates that were obtained from the surface of ‘organically grown’ strawberry fruit and could grow on B. cinerea wall media in culture showed some ability to inhibit the growth of the fungus. Potato dextrose agar seeded with B. cinerea spores (104 ml−1) were challenged with each of these bacterial isolates at concentrations of 109 and 106 colony forming units ml−1. Eleven of the 52 isolates initially recovered, subsequently demonstrated strong antagonism in vitro and were selected for additional screening tests on strawberry fruit. All 11 isolates reduced grey mold rot incidence on fruit in storage. Three of the best isolates were tested in limited field trials, and also reduced grey mold rot on fruit under field conditions.
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  • 76
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    European journal of plant pathology 101 (1995), S. 251-259 
    ISSN: 1573-8469
    Keywords: antagonism ; biological control ; Botrytis cinerea ; Botrytis squamosa ; Gliocladium roseum ; onion leaf spot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In this study, the hypothesis was tested that removal of substrate for sporulation ofBotrytis spp. may lead to a retardation of an epidemic if the majority of the inoculum is produced inside the treated crop. Suppression of sporulation ofBotrytis spp. could be an attractive option for biological control ofBotrytis leaf spot in onions. In a field experiment, necrotic leaf tissue was removed to simulate the effect of a biocontrol agent. By this means, the amount of substrate on whichBotrytis spp. sporulates was reduced. In the experiment, the spore load above the onion plots was significantly reduced and the epidemic of onion leaf spot was retarded. At the end of the growing season, the number of leaf lesions in the green leaf area was lower in plots with substrate removal than in control plots (0.6 and 1.1 cm−2, respectively). The results demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop. Thus, suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists.
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  • 77
    ISSN: 1573-8469
    Keywords: in vitro interactions ; biological control ; rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fusarium wilt diseases, caused by the fungus Fusarium oxysporum, lead to significant yield losses of crops. One strategy to control fusarium wilt is the use of antagonistic, root-colonizing Pseudomonas spp. It has been demonstrated that different strains of these bacteria suppress disease by different mechanisms. Therefore, application of a mixture of these biocontrol strains, and thus of several suppressive mechanisms, may represent a viable control strategy. A prerequisite for biocontrol by combinations of biocontrol agents can be the compatibility of the co-inoculated micro-organisms. Hence, compatibility between several Pseudomonas spp. strains, that have the ability to suppress fusarium wilt of radish, was tested in vitro on KB agar plates. Growth of P. fluorescens strain RS111 was strongly inhibited by Pseudomonas spp. strains RE8, RS13, RS56 and RS158, whereas a mutant of strain RS111 (RS111-a) was insensitive to inhibition by these strains. Strains RS111 and RS111-a only slightly inhibited some other strains. Suppression of fusarium wilt of radish in a potting soil bioassay by the incompatible combination of RE8 and RS111 was comparable to the effects of the single strains. However, disease suppression by the compatible combination of RE8 and RS111-a was significantly better as compared to the single strains. In contrast, the incompatible combination of RS56 with RS111 resulted in enhanced disease suppression as compared to the single strains. Increased disease suppression by combinations of RS13 or RS158 with RS111 or RS111-a was not observed. This indicates that specific interactions between biocontrol strains influence disease suppression by combinations of these strains.
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  • 78
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    Evolutionary ecology 9 (1995), S. 633-661 
    ISSN: 1573-8477
    Keywords: co-evolution ; parasitoid ; population dynamics ; refuge ; biological control ; population stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the theoretical consequences of character evolution for the population dynamics of a host—parasitoid interaction, assuming a monophagous parasitoid. In the purely ecological model it is assumed that hosts can escape parasitism by being in absolute refuges. A striking property of this model is a threshold effect in control of the host by the parasitoid, when host density dependence is weak. The approximate criteria for the parasitoid to regulate the host to low densities are (1) that the parasitoid's maximum population growth rate should exceed the host's and (2) that the maximum growth rate of the host in the refuge should be less than unity. We then use this ecological framework as a basis for a model which considers evolutionary changes in quantitative characters influencing the size of the absolute refuge. For each species, an increase in its refuge-determining character comes at a cost to maximum population growth rate. We show that refuge evolution can substantially alter the population dynamics of the purely ecological model, resulting in a number of emergent and sometimes counter-intuitive properties. In general, when the host has a high carrying capacity, systems are polarized either with low or minor refuge and ‘top-down’ control of the host by the parasitoid or with a refuge and ‘bottom-up’ control of the host by a combination of its own density dependence and the parasitoid. A particularly tantalizing result is that co-evolutionary dynamics can modify ecologically unstable systems into ones which are either stable or quasi-stable (with bouts of unstable dynamics, punctuating long-term periods of quasi-stable behaviour). We present five quantitative criteria which must all be met for the parasitoid to be the agent responsible for control of the host at a co-evolutionary equilibrium. The apparent stringency of this full set of requirements supports the empirically-based suggestion that monophagous parasitoid-driven systems should be less common in nature than those driven by multiple forms of density dependence. Further, we apply our theory to the question of whether exploiters may ‘harvest’ their victims at maximum sustainable yields and to the evolutionary stability of biological control. Finally, we present a series of testable predictions of our theory and methods useful for testing them.
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  • 79
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    Wetlands ecology and management 7 (1999), S. 165-175 
    ISSN: 1572-9834
    Keywords: flow ; loading ; models ; phosphorus ; removal limits ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphorus concentrations exported from wetlands are explored via data and a first order model. The graph of outlet concentration versus areal phosphorus loading is used to display these data and the model. For a given wetland, data and models show that P concentrations show an ‘S’ curve response to increasing P loadings. The lower plateau is the background concentration and the upper plateau is the inlet concentration. The position of the ascending limb between the two plateaus is positioned differently for different wetlands. Phosphorus (P) removal in wetlands is often typified by a stable decreasing gradient of P concentrations from inlet to outlet, and an accompanying stable decreasing gradient in P assimilation. Limits to removal are inherent in the physical, chemical and biological processes. A lower outlet concentration limit exists because of the P cycle in the un-impacted wetland. The loading at which the outlet concentration departs from background, the lower knee in the loading curve, varies from wetland to wetland. An upper outlet concentration limit is imposed by the source concentration for extremely high inflows. The first order mass balance equation interpolates between these limits. The model gives further insights about performance within an overall envelope. The water carrying capacity of the wetland precludes flows in excess of the hydraulic conveyance capacity, thus limiting the possible P loadings to the system. Conversely, extremely low hydraulic loadings cause the wetland to be dominated by atmospheric additions and losses. The central tendency of inter-system data in the North American Database is shown to be inadequate to draw generalized conclusions about ecosystem processes in an individual wetland. The proposed ‘one gram rule’ of Richardson, et al. (1997) is shown to be an over-simplification.
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  • 80
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    Plant and soil 168-169 (1995), S. 313-317 
    ISSN: 1573-5036
    Keywords: growth ; internal cycling ; partitioning ; phosphorus ; 32P ; Sitka spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The availability of phosphorus in many UK forest soils limits growth of Sitka spruce (Picea sitchensis (Bong.) Carr.). Efficient cycling of P within such systems is therefore necessary for sustained tree growth. Internal cycling of P is an important component of the overall P cycle in forests and the current work aims to quantify the impact of P nutrition on internal cycling and seasonal growth of Sitka spruce. Two-year old seedlings of Sitka spruce were grown in sand culture in the glasshouse for one year. Two treatments were imposed in which trees received either a complete nutrient solution from which P was excluded (-P) or one in which P was applied as labelled 32P (+P). Internal cycling of P was measured directly in plants which had received no P and by difference in those which received 32P. The contrasting P treatments produced an eight-fold difference in P content and a three-fold difference in tree growth between May and October. Root:shoot ratios increased during the growing season from 0.29 to 0.38 and from 0.29 to 0.52 in +P and-P treatments, respectively. In both treatments P was translocated from old shoots to support new shoot growth. P supply did not affect the amount of P remobilised but there was evidence that the rate of remobilisation may have been affected. The partition of remobilised P was affected by current P supply and differed from the partition of current P uptake. Results are compared to those from studies of growth and internal cycling of nitrogen in Sitka spruce.
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  • 81
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    Plant and soil 176 (1995), S. 95-100 
    ISSN: 1573-5036
    Keywords: isotopically exchangeable ; lupin ; phosphorus ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract White lupin (Lupinus albus L. var. Ultra) and soybean (Glycine max L. var. Elgin) were grown in an acidic soil low an available phosphorus (P) to investigate their different capacities to acquire soil phosphorus. Experiments done in the controlled environment of a biotron were supplemented with four separate greenhouse experiments. Lupin and soybean were grown in monoculture and intercropped on a soil with low available P that was labeled with carrier-free 32P as phosphate. Lupin had significantly lower values of specific activity of 32P and higher values of isotopically exchangeable P than soybean in all cases. The results show that lupin utilizes soil P from a normally non-labile pool of soil P that is not utilized by soybean.
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  • 82
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    Plant and soil 176 (1995), S. 161-169 
    ISSN: 1573-5036
    Keywords: Casuarina cunninghamiana ; Frankia ; nitrogen fixation ; nodulation ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A study was conducted to investigate the effects of phosphorus on nodule formation and function in the Casuarina-Frankia symbiosis. The effects of P on growth and survival of Frankia in the rhizosphere was assessed by examing Frankia growth and survival in flasks of basal nutrient solution. There was no growth in the nutrient solution during the experimental period. However, the viability of Frankia in the nutrient solution without P supply was half that of the initial level, whereas, with P supply, there was only a minor decline during the first week. In a growth pouch experiment, supplying P increased plant and nodule growth, irrespective of P status of the inoculant Frankia culture. There were no effects of P status on any growth or nodulation parameters measured when the inoculants had been standardized on the basis of viability. In a split root experiment, Frankia inoculation and application of P together or separately did not cause any significant difference. This suggests that growth and nodulation respond only to total P supply. Increasing P from 0.1 to 10 μM significantly increased plant growth but not N concentrations. Both nitrogen-fixation and nitrate supported growth were strongly increased as P increased from 0.1 to 1.0 μM. This study indicates that P deficiency limits the growth of host plants more severely than nitrogen fixation processes and P deficiency on nodulation and symbiotic nitrogen fixation in Casuarina cunninghamiana operated indirectly via reducing host plant growth.
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  • 83
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    Plant and soil 176 (1995), S. 171-181 
    ISSN: 1573-5036
    Keywords: aluminium ; iron ; phosphorus ; relative growth rate ; relative uptake rate ; steady state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relative uptake rates of N, P, K, S, Ca, Mg, Fe, Mn, Zn, Cu, and Al were estimated in beech seedlings pot cultured in the field in six acid soils (treatments). The relative uptake rates were compared with the relative growth rates. The relative uptake rates of N, K and Ca agreed well with the growth rates of the seedlings irrespective of widely differing soil conditions (acid sand-clayey till, pH 4–6). The relative uptake rates of P, Fe, and Al differed from that predicted by the growth rate. The uptake rates of Fe and Al were highest at the lowest growth rates, and the P uptake rate was lower than the growth rate in these treatments. Thus the P availability probably limited growth in an eluvial (E) horizon of a podzol, and possibly in the illuvial (B) horizon of a podzol and in an acid clayey till (Dystric Cambisol). Low P uptake was associated with a tendency towards higher relative root growth rates. In terms of the concept of steady state nutrition the high relative root growth rate in some treatments may be interpreted as an acclimation to low P supply. The P limitation seemed to be related to interactions among Fe, Al and organic compounds of the soil solution.
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  • 84
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    Plant and soil 177 (1995), S. 219-223 
    ISSN: 1573-5036
    Keywords: biological control ; compost ; Cucumis sativus ; Pythium aphanidermatum ; suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Composts prepared from mixtures of bagasse + filter mud (BF) and bagasse + vinasses + filter mud (BVF) were evaluated for suppressiveness to Pythium aphanidermatum in climatic chamber experiments. Twenty five-g samples of BF and BVF composts in plastic pots (130 mL) were infested with 1,000 oospores of P. aphanidermatum produced on oat meal agar. After 1, 15, 30 and 45 days, survival of the fungus was estimated by measuring inoculum density. Disease incidence was appraised on cucumber (Cucumis sativus) “Vert Long Anglais” seedlings raised on the composts. Propagules of P. aphanidermatum surviving in the compost after 24 hr was estimated at 22 and 18 cfu g−1 dry wt. potting mix, for BF and BVF, respectively. This population decreased significantly to 6–7 cfu g−1 of compost for the 15–45-d incubation treatment. Seedling mortality was not observed in uninfested controls. In uninfested treatments, 40 and 67% of seedlings died for the 1-d incubation treatment in BVF and BF, respectively; no mortality was recorded thereafter. Heat treatment of the composts revealed that the suppressive effect was biological in nature. Quantitative reduction of micro-organisms occurred in pasteurized composts (55°C for 2 h), compared to the populations in unheated controls. However the greatest decrease was observed for fungal populations. The main fungal species observed in unheated, suppressive composts were Aspergillus sp., Geotrichum sp. and a non-sporulating Pythium. The last two species disappeared in pasteurized, conducive composts.
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  • 85
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    Plant and soil 209 (1999), S. 283-295 
    ISSN: 1573-5036
    Keywords: leaf emergence ; phosphorus ; photosynthesis ; tillering ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus (P) deficiency limits the yield of wheat, particularly by reducing the number of ears per unit of area because of a poor tiller emergence. The objectives of this work were to (i) determine whether tiller emergence under low phosphorus availability is a function of the availability of assimilates for growth or a direct result of low P availability, (ii) attempt to establish a quantitative relation between an index of the availability of P in the plant and the effects of P deficiency on tiller emergence, and (iii) to provide a better understanding of the mechanisms involved in tiller emergence in field-grown wheat. Wheat (Triticum aestivum L., cv. INTA Oasis), was grown in the field under drip irrigation on a typic Argiudol, low in P (5.5 μg P g-1 soil Bray & Kurtz I) in Balcarce, Argentina. Treatments consisted of the combination of three levels of P fertilization 0, 60 and 200 kg P2O5 ha-1, and two levels of assimilate availability, a control (non-shaded) and 65% of reduction in incident irradiance from seedling emergence until the end of tillering (shaded). Phosphorus treatments significantly modified the pattern of growth and development of the plants. Shading reduced the growth and concentration of water-soluble carbohydrates in leaves and stems. Leaf photosynthetic rate at saturating irradiance was reduced by P deficiency, but was not affected by shading. At shoot P concentrations less than 4.2 g P kg-1 the heterogeneity in the plant population increased with respect to the number of plants bearing a certain tiller. At a shoot P concentration of 1.7 g P kg-1 tillering ceased completely. Phosphorus deficiency directly altered the normal pattern of tiller emergence by slowing the emergence of leaves on the main stem (i.e. increasing the phyllochron), and by reducing the maximum rate of tiller emergence for each tiller.
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  • 86
    ISSN: 1573-5036
    Keywords: ectomycorrhizae ; Eucalyptus regnans ; forest burns ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to compare the effects on the growth of Eucalyptus regnans seedlings of unheated soil and soil heated to different extents (as indicated by soil colour–bright red or black) in burnt logging coupes, and to separate the effects of heating of the soil on direct nutrient availability and on morphotypes and effectiveness of ectomycorrhizae. Burnt soils were collected from three logging coupes burnt 2, 14 and 25 months previously and unbumt soil from adjacent regrowth forests. Compared to unburnt soil, the early seedling growth was stimulated in black burnt soil from all coupes (burnt 2, 14 and 25 months previously). Seedling growth was generally poor in red burnt soil, especially in soil collected 2 months after burning. However, the concentration of extractable P was extremely high in red burnt soil, especially in soil collected 2 months after burning. In black burnt soil, extractable P was increased in soil 2 months after burning, but not in the soils collected 14 or 25 months after burning. However, both total P content and concentration in seedlings were increased in all collections of black burnt soil. Frequency of ectomycorrhizae was high in seedlings grown in all black burnt soils, but the mycorrhizal mantles were poorly developed in seedlings in black burnt soil collected 2 months after burning. Seedlings were also ectomycorrhizal in red burnt soil, except in soil collected 2 months after burning. Fine root inocula from seedlings grown in black burnt soils collected 14 and 25 months after burning significantly stimulated both seedling growth and P uptake compared with the uninoculated control, whereas the fine root inocula from the seedlings grown in all the other soils did not. These results suggest that, in black burnt soil, both direct nutritional changes and changes in the ectomycorrhizae may contribute to seedling growth promotion after regeneration burns. The generally poor seedling growth in red burnt soils is likely to have been due to N deficiency as the seedlings in these soils were yellow-green and the tissue concentrations of N were significantly lower than in other treatments.
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  • 87
    ISSN: 1573-5036
    Keywords: acid-subsoils ; aluminium ; phosphorus ; root growth ; velvet bean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Previous laboratory experiments showed that velvet bean Mucuna pruriens is moderately tolerant to the presence of Al (up to 185 µM) in the root environment, but that it only develops a shallow root system in acid soils. Field experiments showed that Mucuna can tolerate acid subsoil conditions in a homogeneous root environment, but avoids subsoil if topsoil is present. Subsequent split-root experiments with a recirculating nutrient solution showed that this subsoil avoidance may be based on an Al avoidance mechanism in the root system. This Al avoidance mechanism, however, was not evident when phosphorus (P) supply to the whole plant was adequate. We thus hypothesized that surface application of P may help to overcome Al avoidance in the subsoil. In a field experiment on an ultisol in Lampung (Indonesia), only a moderate increase in aboveground biomass production was found for a wide range of P application rates, although the soil was low in available P, and the P adsorption isotherm was very steep. An increased P status of the topsoil and an increased P concentration in the aboveground biomass (from 50 to 75 mmol kg-1) had no effect on root development in the subsoil.
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  • 88
    ISSN: 1573-5036
    Keywords: Arachis hypogaea ; Aspergillus flavus ; biological control ; geocarposphere ; rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Selected bacterial strains isolated from the region of peanut pod development (geocarposphere) and two additional bacterial strains were screened as potential biological control agents against Aspergillus flavus invasion and subsequent aflatoxin contamination of peanut in laboratory, greenhouse, and field trials. All 17 geocarposphere strains tested delayed invasion of young roots and reduced colonization by the fungus in a root-radicle assay used as a rapid laboratory prescreen. In a greenhouse study, seven bacterial strains significantly reduced pod colonization by A. flavus compared to the control. In a field trial, conducted similarly to the greenhouse assay, pods sampled at mid-peg from plants seed-treated with suspensions of either 91A-539 or 91A-550 were not colonized by A. flavus, and the incidence of pods invaded from plants treated with either 91A-539 or 91A-599 was consistently lower than nonbacterized plants at each of five sampling dates. At harvest, 8 geocarposphere bacterial strains significantly lowered the percentage of pods colonized (〉 51%) compared to the control. Levels of seed colonization ranged from 1.3% to 45% and did not appear related to aflatoxin concentrations in the kernels.
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    Plant and soil 176 (1995), S. 101-105 
    ISSN: 1573-5036
    Keywords: arbuscular mycorrhiza ; “criollo” ; growth ; inoculation ; maize ; mycorrhizal ; native ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We tested the effect of two single species inocula and a mixed inoculum of the native population of arbuscular mycorrhizal (AM) fungi on the growth response of “criollo” maize (Zea mays L.). To determine the inocula that produced the highest response on maize growth, we conducted a greenhouse experiment at 3 levels of P fertilization (0, 40 and 80 kg ha−1). Inoculation with Glomus mosseae (Nicolson and Gerdemann) Gerd. and Trappe (LMSS) produced the greatest shoot growth rates at the two lowest P fertilization levels. Inoculation with Acaulospora bireticulata Rothwell and Trappe (ABRT) and the native population (NP) resulted in similar shoot growth rates at all P levels. These rates were higher than the non-mycorrhizal control rate at the lowest P level but lower than the control at the highest P level. Also, ABRT and NP had significantly lower shoot growth rates than the inoculation treatment with G. mosseae at all P levels. The non-mycorrhizal control had the lowest growth rate at the lowest P level but its growth rate increased linearly with increased P fertilization. Inoculation with G. mosseae and A. bireticulata produced similar colonization rates which were lower than the native population colonization rate. There was no correlation between colonization and shoot growth rates.
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  • 90
    ISSN: 1573-5036
    Keywords: biological control ; eggplant ; rhizosphere ; Talaromyces flavus ; Verticillium dahliae ; Verticillium wilt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Quantitative aspects of the interaction between the antagonist Talaromyces flavus, the pathogen Verticillium dahliae and eggplant roots, were studied. When eggplant roots were inoculated with T. flavus, prior to the infection with the pathogen, the population density of T. flavus on V. dahliae-infected roots was at least 3 times higher than on healthy uninfected roots, and the proliferation of T. flavus on diseased eggplant roots was related to the severity of wilt symptoms, in the two levels of application of T. flavus studied. However, in all classes of disease severity tested (disease index, 0–3), the population density of T. Flavus on eggplant roots treated with 106 ascospores g−1 rooting mixture was significantly (p=0.05) higher than with 105 ascospores g−1. In roots treated with 105 and 106 T. flavus ascospores g−1 rooting mixture, the population density of V. dahliae was reduced by 51% and 69%, respectively. When testing the relationships between the population density of V. dahliae in the roots and disease severity, no significant (p=0.05) difference was found between disease indexes 2 and 3. However, the density of V. dahliae on roots of plants with disease index 1 was significantly (p=0.05) lower than disease indexes 2 and 3. The positive relationship between the inoculum concentration of V. dahliae and the population density of T. flavus developed on eggplant roots was significant (p=0.001), linear, and highly correlated (r=0.945) on a logarithmic scale. In addition, the analysis of these data revealed a significant (p=0.05), high, negative and linear correlation (r=−0.985) between the log concentration of V. dahliae inoculum and the disease reduction achieved by T. flavus.
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  • 91
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    Plant and soil 176 (1995), S. 255-262 
    ISSN: 1573-5036
    Keywords: carbon ; cocksfoot grass ; mineralisation ; nitrogen ; phosphorus ; radiata pine ; sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Radiata pine (Pinus radiata) and cocksfoot grass (Dactylis glomerata) were grown in small pots containing grassland soils collected from seven sites in the South Island montane zone. After one year the overall mean dry matter yield of pine exceeded that of grass by a factor of 2.6, and uptake of all nutrients by pine was substantially greater. Mean soil pH was 0.3 units lower after pine growth than after grass. Organic carbon (C), total nitrogen (N), and organic phosphorus (P) levels were 15–19% lower after pine, while total P was 7% lower. Despite greater nutrient uptake by pine, mean mineralisable N and sulphate sulphur (S) levels in the soil were 500% and 200% higher respectively after pine growth than after grass. Inorganic and Bray-2 P levels were 10% and 20% higher respectively. Grass obtained almost all of its P from the inorganic pool, while pine obtained P from both inorganic and organic pools, though mostly from the latter. It is concluded that the differences observed in C, N, and P concentrations in soil indicate higher rates of mineralisation of soil organic matter in the presence of radiata pine than in the presence of cocksfoot grass. Possible implications for pastoral hill land use in New Zealand are discussed. It is suggested that pines incorporated into farming systems either on a rotational basis, or in wide-spaced agroforestry regimes, may be able to increase the rate of mineralisation of organic P, and also of N and S, and increase their availability to pasture species.
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  • 92
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    Plant and soil 176 (1995), S. 317-324 
    ISSN: 1573-5036
    Keywords: chelate ; copper ; deficiency ; genotypic differences ; iron ; manganese ; phosphorus ; Triticum ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ten Triticum aestivum and two Triticum turgidum conv. durum genotypes differing in Zn efficiency were grown in chelate-buffered nutrient solution at Zn supplies ranging from deficient to sufficient (free Zn activities from 2 to 200 pM, pZn from 11.7 to 9.7). Correlation between the rate of Zn uptake and the Zn efficiency ranking was poor. Uptake of Zn by all genotypes increased linearly with an increase in solution Zn activities, with a slight saturation apparent at 200 pM. Relative amounts of Zn and Fe transported to shoots increased with duration of growth and at higher supply of Zn. With an increase in solution Zn activities, uptake rates of Fe, Mn and Cu dropped in Zn-efficient genotypes and increased in Zn-inefficient ones. While shoot concentrations of Fe did not differ between Zn-efficient and inefficient genotypes at ≥10 pM Zn activity, root Fe concentrations were around 3-fold higher in Zn-efficient genotypes at 2 pM Zn activity. All genotypes accumulated high amounts of P in shoots after 22 d of growth at deficient Zn supply. It is concluded that nutrient interactions, especially at deficient Zn supply, may be influential in determining the level of Zn efficiency of wheat genotypes.
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  • 93
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    Plant and soil 168-169 (1995), S. 243-248 
    ISSN: 1573-5036
    Keywords: carbohydrate ; ectomycorrhiza ; ergosterol ; extramatrical mycelium ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient uptake by forest trees is largely dependent on their associated ectomycorrhizal fungi. The presence of extramatrical mycelium produced by ectomycorrhizal fungi allows trees to exploit a larger soil volume. In this paper the effects of macronutrients on the production of extramatrical mycelium are reviewed. It is concluded that elevated levels of nitrogen and, to some extent, phosphorus strongly inhibit the development of extramatrical mycelium. A deficiency of phosphorus, on the other hand, stimulates ectomycorrhizal development. Low levels of phosphorus may offset the negative influence of nitrogen, indicating that the nitrogen effect is indirect. No other macronutrients have been shown to affect extramatrical mycelium significantly, however, very few studies have been made. To explain reduced ectomycorrhizal development under conditions of high N availability, it has been suggested that the host would allocate less carbohydrate to the mycobiont under such conditions owing to a greater demand for carbon by growing shoots. In the present paper an alternative explanation is suggested: The fungus is forced to take up all available nitrogen and must therefore consume the available carbohydrate in order to assimilate it. The surplus of carbohydrates after nitrogen assimilation can then be used to produce fungal mycelium and fruit bodies. However, the total allocation of host carbohydrate to the mycorrhizal fungus is not reduced at elevated levels of N supply. In contrast with previous theories, the present one proposes that it is the fungus, rather than the host which adjusts its carbon allocation patterns to the N supply.
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  • 94
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    Plant and soil 175 (1995), S. 31-44 
    ISSN: 1573-5036
    Keywords: lime ; nitrogen ; phosphorus ; radiata pine ; soil acidity ; stem deformity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plantations of radiata pine (P. radiata D.Don) on soils previously under legume based pastures have a high incidence of stem deformity compared with forest soils. A comparison of soil properties and tree nutrition of 5 to 7 year-old radiata pine on former pastures in the first part of the study showed that stem deformity was strongly correlated with mineralisation of soil N and in particular with nitrification. Other soil properties that have changed as a result of pasture improvement, e.g. pH, available P and Mn, were only partially correlated with stem deformity. In the second part of the study, the role of N availability and other soil properties in the expression of deformity was further investigated in a separate field experiment on soils formerly under native eucalypt forest, tobacco cropping, and improved pasture. Young radiata pine plantings were treated with lime, phosphorus, and nitrogen applied as urea and sodium nitrate. Liming increased soil pH by around 1.5 units, raised exchangeable Ca2+ and decreased available Mn. Soil mineral N content was only marginally affected by liming. Superphosphate increased soil available P and raised levels of P in foliage. Changes in soil pH, availability of P, Mn, and B did not affect growth or stem deformity at any of the sites. In contrast, application of N fertilisers at 200 and 600 kg N ha-1 increased mineral N content and stimulated nitrification, particularly at the forest site. The high rate of N fertiliser increased basal area at the forest site by 45%, but also raised the level of stem deformity from 12% to 56%. At the tobacco and pasture sites, this treatment did not increase growth and did not significantly raise stem deformity above the already high basic level of deformity (63%). Implications of stem deformity in young plantations of radiata pine on potential utilisation later in the rotation are discussed.
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  • 95
    ISSN: 1573-5036
    Keywords: deficiency ; drought ; field experiment ; irrigation ; phosphorus ; Picea abies ; wood ash
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Increased atmospheric deposition of N might eventually lead to P deficiency. The relation between needle P concentration and acid phosphatase activity in the humus layer was studied during 1990–93 in a Norway spruce stand where the water and N and P supplies had been experimentally manipulated since 1988. Treatments included control (C), yearly application of ammonium sulphate (NS), N-free fertilizer (V), granulated wood ash (A), irrigation (I), drought (D) and water plus nutrients in an “optimum” combination (IF). We found indications of a feed-back mechanism for P, where low concentrations in the needles were associated with increased acid phosphatase activity in the humus layer. Acid phosphatase estimations made during moist soil conditions were much more informative than those made during dry conditions. We further argue that a site-specific “base-line” exists for acid phosphatase activity in the soil, mainly originating from enzymes immobilized in the field, but active in the assay. Increased phosphatase activity, above the base line, was generally found in the A, I and NS treatments, but in some cases also in C. Although P and N concentrations were significantly higher in the IF treatment as compared to the C and the D treatments, the P as fraction of N was 0.10 and thus balanced in all cases. In the A and I treatment P:N was around 0.09, while it was only 0.07 in the NS treatment, mainly due to high N concentrations. The latter treatment thus created an imbalanced situation where P additions most likely would have increased tree growth.
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  • 96
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    Plant and soil 177 (1995), S. 73-83 
    ISSN: 1573-5036
    Keywords: acid sulphate soils ; iron ; Oryza sativa L. ; phosphorus ; temperature ; Vietnam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Climatic and soil factors are limiting rice growth in many countries. In Vietnam, a steep gradient of temperature is observed from the North to the South, and acid sulphate soils are frequently devoted to rice production. We have therefore attempted to understand how temperature affects rice growth in these problem soils, by comparison with rice grown in nutrient solution. Two varieties of rice, IR64 and X2, were cultivated in phytotrons at 19/21°C and 28/32°C (day/night) for 56 days, after 3 weeks preculture in optimal conditions. Two soils from the Mekong Delta were tested. Parallel with the growing experiments, these two soils were incubated in order to monitor redox potential (E h ), pH, soluble Al and Fe, soluble, and available P. Tillering retardation at 20°C compared to 30°C was similar in nutrient solutions and in soils. The effect of temperature on increasing plant biomass was more marked in solutions than in soils. The P concentrations in roots and shoots were higher at 20°C than at 30°C, to such an extent that detrimental effect was suspected in plants grown in solution at the lowest temperature. The translocation of Fe from roots to shoots was stimulated upon rising temperature, both in solutions and in soils. This led to plant death on the most acid soil at 30°C. Indeed, the accumulation of Fe in plants grown on soils was enhanced by the release of Fe2+ due to reduction of Fe(III)-oxihydroxides. Severe reducing conditions were created at 30°C: redox potential (E h ) dropped rapidly down to about 0 V. At 20°C, E h did not drop below about 0.2 V, which is a value well in the range of Fe(III)/Fe(II) buffering. Parallel to E h drop, pH increased up to about 6–6.5 at 30°C, which prevented plants from Al toxicity, even in the most acid soil. Phosphate behavior was obviously related to Fe-dynamics: more reducing conditions at 30°C have resulted in enhancement of available P, especially in the most acid soil.
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  • 97
    ISSN: 1573-5036
    Keywords: carbon dioxide ; fertilising effect ; greenhouse effect ; N-deposition ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A model of the interacting global carbon and nitrogen cycles (CQUESTN) is developed to explore the possible history of C-sequestration into the terrestrial biosphere in response to the global increases (past and possible future) in atmospheric CO2 concentration, temperature and N-deposition. The model is based on published estimates of pre-industrial C and N pools and fluxes into vegetation, litter and soil compartments. It was found necessary to assign low estimates of N pools and fluxes to be compatible with the more firmly established C-cycle data. Net primary production was made responsive to phytomass N level, and to CO2 and temperature deviation from preindustrial values with sensitivities covering the ranges in the literature. Biological N-fixation could be made either unresponsive to soil C:N ratio, or could act to tend to restore the preindustrial C:N of humus with different N-fixation intensities. As for all such simulation models, uncertainties in both data and functional relationships render it more useful for qualitative evaluation than for quantitative prediction. With the N-fixation response turned off, the historic CO2 increase led to standard-model sequestration into terrestrial ecosystems in 1995AD of 1.8 Gt C yr−1. With N-fixation restoring humus C:N strongly, C sequestration was 3 Gt yr−1 in 1995. In both cases C:N of phytomass and litter increased with time and these increases were plausible when compared with experimental data on CO2 effects. The temperature increase also caused net C sequestration in the model biosphere because decrease in soil organic matter was more than offset by the increase in phytomass deriving from the extra N mineralised. For temperature increase to reduce system C pool size, the biosphere “leakiness” to N would have to increase substantially with temperature. Assuming a constant N-loss coefficient, the historic temperature increase alone caused standard-model net C sequestration to be about 0.6 Gt C in 1995. Given the disparity of plant and microbial C:N, the modelled impact of anthropogenic N-deposition on C-sequestration depends substantially on whether the deposited N is initially taken up by plants or by soil microorganisms. Assuming the latter, standard-model net sequestration in 1995 was 0.2 Gt C in 1995 from the N-deposition effect alone. Combining the effects of the historic courses of CO2, temperature and N-deposition, the standard-model gave C-sequestration of 3.5 Gt in 1995. This involved an assumed weak response of biological N-fixation to the increased carbon status of the ecosystem. For N-fixation to track ecosystem C-fixation in the long term however, more phosphorus must enter the biological cycle. New experimental evidence shows that plants in elevated CO2 have the capacity to mobilize more phosphorus from so-called “unavailable” sources using mechanisms involving exudation of organic acids and phosphatases.
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  • 98
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    Plant and soil 187 (1995), S. 277-288 
    ISSN: 1573-5036
    Keywords: carbon isotopes ; carbon storage ; elevated CO2 ; phosphorus ; rhizodeposition ; root exudation ; soil organic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Atmospheric CO2 concentrations can influence ecosystem carbon storage through net primary production (NPP), soil carbon storage, or both. In assessing the potential for carbon storage in terrestrial ecosystems under elevated CO2, both NPP and processing of soil organic matter (SOM), as well as the multiple links between them, must be examined. Within this context, both the quantity and quality of carbon flux from roots to soil are important, since roots produce specialized compounds that enhance nutrient acquisition (affecting NPP), and since the flux of organic compounds from roots to soil fuels soil microbial activity (affecting processing of SOM). From the perspective of root physiology, a technique is described which uses genetically engineered bacteria to detect the distribution and amount of flux of particular compounds from single roots to non-sterile soils. Other experiments from several labs are noted which explore effects of elevated CO2 on root acid phosphatase, phosphomonoesterase, and citrate production, all associated with phosphorus nutrition. From a soil perspective, effects of elevated CO2 on the processing of SOM developed under a C4 grassland but planted with C3 California grassland species were examined under low (unamended) and high (amended with 20 g m−2 NPK) nutrients; measurements of soil atmosphere δ13C combined with soil respiration rates show that during vegetative growth in February, elevated CO2 decreased respiration of carbon from C4 SOM in high nutrient soils but not in unamended soils. This emphasis on the impacts of carbon loss from roots on both NPP and SOM processing will be essential to understanding terrestrial ecosystem carbon storage under changing atmospheric CO2 concentrations.
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  • 99
    ISSN: 1573-5036
    Keywords: fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
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  • 100
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    Plant and soil 212 (1999), S. 173-181 
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphatase activity ; phosphorus ; protease activity ; soil microbial biomass ; substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Estimating in situ N and P status of the soil microbiota is complicated because microbiological features reflect potentials rather than field conditions. Complementary microbiological assays were, therefore, combined to evaluate the N and P requirement of the microbiota in seven agricultural, grassland and forest topsoils of the Bornhöved Lake district as follows: (i) the sensitivity of the substrate-induced respiration (SIR) to supplemental addition of N and P was monitored during microbial growth and (ii) soil protease and phosphatase activities were analysed and related to soil mass and microbial biomass content. Nitrogen addition increased the maximal SIR rate in all except one soil indicating that the growth of organisms is restricted by this element when easily degradable C source is present. Supplemental N (and in some cases also P) retarded the respiratory response within the first 24 h which suggests microbial sensitivity and/or greater anabolic efficiency. With additional N the maximal SIR rate was most strongly enhanced in topsoils of the beech forest and the dystric alder forest. Thus, the microbial growth in these soils that were below litter horizons seems to be mostly restricted by N. Supplemental P positively affected respiratory response of soils under monoculture, wet grassland and dystric alder forest. In the dystric alder forest soil, high rates of alkaline and unbuffered phosphatase activity were observed when activity was related to either soil mass or microbial biomass content. The data of proteolytic and phospholytic enzymes are discussed with reference to nutrient deficiency and microbial strategy for N and P adsorption.
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