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  • Articles  (190)
  • Articles: DFG German National Licenses  (190)
  • Engineering  (77)
  • phosphorus  (31)
  • Solanum tuberosum L.  (29)
  • 15N  (20)
  • biological control  (20)
  • crystal structure
  • 2015-2019
  • 1995-1999  (190)
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  • 1995  (190)
  • Geosciences  (99)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (96)
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  • Articles  (190)
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  • Articles: DFG German National Licenses  (190)
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  • 2015-2019
  • 1995-1999  (190)
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  • 1
    ISSN: 1572-8854
    Keywords: Tautomerism ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystals consisting of two distinct chemical entities, tautomers of each other, in exact 1∶1 ratio, have been obtained and their structure determined by X-ray analysis. The crystals of C9H11N3·C9H11N3 are monoclinic,P21/c,a=15.674(3),b=17.085(3),c=13.758(3)Å, β=90.78(2)°,Z=8. There are two hydroxylamine and two aminonitrone molecules in the asymmetric unit. Hydrogen bonds connect those molecules into chiral layers. Layers of opposite chirality alternate andthe crystal is centrosymmetric as a whole. Within those layers chains of tautomers joined by very strong O−H... O and strong N−H... N bonds can be recognized. Proton transfer along those chains with simultaneous rearrangement of π-bonds within the molecules would result in interconversion of tautomers and would affect chirality of the layer.
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  • 2
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    Journal of chemical crystallography 25 (1995), S. 57-62 
    ISSN: 1572-8854
    Keywords: phase diagram ; buffered chloroaluminate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The phase diagram of the buffered neutral aluminum chloride + 1-ethyl-3-methyl-1H-imidazolium chloride + sodium chloride (AlCl3-EMIC-NaCl) ternary melt system can be represented by a binary phase diagram composed of (EMI)AlCl4 and NaAlCl4. In the binary phase diagram, the salts are liquid at, or near, room temperature for a wide range of compositions. At the 1∶1 composition, the congruently melting compound (EMI)(Na)(AlCl4)2 with m.p.=36.7°C is formed. Crystals of this mixed organic-inorganic salt were grown for single crystal x-ray diffraction analysis. The compound crystalizes in the space group $$P\bar 1$$ with lattice parametersa=10.321(1) Å,b=10.895(3) Å,c=9.284(4) Å, α=98.31(2)°, β=100.83(4)°, γ=101.95(3)°. Data collected at −120°C gave final residuals ofR=0.037 andR w=0.045 using 2713 observed reflections. The packing diagram reveals Na+ ion zig-zag chains running along thea-axis with each Na+ surrounded by four AlCl 4 − units, reminiscent of NaAlCl4. The AlCl 4 − ions form a distorted square planar coordination sphere around Na+ at an average Na−Al distance of 3.76(4) Å. Using a sodium ionic radius of 1.16 Å, a new AlCl 4 − ionic radius of 2.60 Å is calculated. This radius is 0.21 Å shorter than the reported thermodynamic radius.
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  • 3
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    Journal of chemical crystallography 25 (1995), S. 223-226 
    ISSN: 1572-8854
    Keywords: Antifungal alkaloids ; 3-methylsampangine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 3-Methylsampangine, C16H10N2O, crystallizes in the monoclinic space group P21/c witha=7.260(3),b=10.697(5),c=15.342(6) Å, and β=102.69(4). All nonhydrogen atoms of this potent antifungal agent are planar to within 0.082 Å. The title compound exhibits potentin vitro antifungal activity againstC. neoformans, C. albicans andA. fumigatus.
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  • 4
    ISSN: 1572-8854
    Keywords: Octahedral ; phosphorus ; chloride
    Source: Springer Online Journal Archives 1860-2000
    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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  • 5
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    Journal of chemical crystallography 25 (1995), S. 219-222 
    ISSN: 1572-8854
    Keywords: Calcium phosphate ; calcium pyrophosphate ; calcium potassium pyrophosphate ; crystal structure ; layer-type structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of Ca10K4(P2O7)6·9H2O has been determined by single crystal X-ray diffraction. Crystals are hexagonal, space group P63cm witha=11.761(1),c=9.770(1) Å, andZ=1. The structure was refined toR=0.028 andR w=0.037 for 468 reflections withI≥3σ(I). The structure consists of a compact assembly of Ca and P2O7 ions arranged in layers perpendicular to thec-axis in a hexagonal array with relatively large open channels along thec-axis. The K ions and the water molecules are located in these open channels and are disordered.
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  • 6
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    Journal of chemical crystallography 25 (1995), S. 295-298 
    ISSN: 1572-8854
    Keywords: Cage-diol ; crystal structure ; photooxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An unusual photooxidation was noted upon photolytic cage closure of a substituted tricyclo[6.2.1.02.7]undecane-exo, exo-diol. The resultant compound, which may be regarded as a mono-reduced pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione, was characterizedvia X-ray crystallography. This species could be reduced to the tricyclo[6.2.1.02,7]undecane-endo, exo-diol under conditions previously shown to be inert for the parent dione.
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  • 7
    ISSN: 1572-8854
    Keywords: Benzonaphthodioxosuberane ; crystal structure ; radermachol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound (2) C21H16O4 has been determined by an X-ray analysis, by direct methods from diffractometer data and refined by full-matrix least squares. The compound (2) crystallizes in the space group P21/a, with cell parameters:a=36.432(5),b=5.512(3),c=8.269(5) Å, β=108.0(3)°,z=4,D c =1.397 g/cm−3,R=7.8 for 1136 observed reflections. The conformation of the tetracyclic ring system shows a folding of two planar parts of the carbon skeleton about an axis passing thorough C8 and C16 of the seven membered ring C.
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  • 8
    ISSN: 1572-8854
    Keywords: Molecular mechanics ; molecular dynamics ; MNDO ; CMPO ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide, or CMPO was recently determined. The compound crystallizes in the space group P21/c witha=13.446(6),b=22.280(7),c=17.217(7) Å, β=92.07(4)°, andD calc=1.05 g/cm3 forZ=8 @20°C). Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL1 suite of programs. The results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY2,3. In general, the results from the calculations agree fairly well with the parameters from the crystal structure.
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  • 9
    ISSN: 1572-8854
    Keywords: Mercury(II) terpyridine complex ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [Hg(terpy)2](CF3SO3)2·0.5(CH3)2CO crystallizes in the triclinic $$P\bar 1$$ space group witha=14.631(6),b=15.258(4),c=18.785(7) Å, α=69.66(2), β=70.72(1), γ=88.55(1)°. The crystal structure consists of two independent [Hg(terpy)2]2+ cations, four trifluoromethanesulfonate anions and an acetone molecule in the asymmetric unit. Each mercury atom is coordinated by two tridentate terpyridine ligands forming an irregular six-coordination polyhedron. The Hg−N bond lengths range from 2.27(2) to 2.53(2) Å.
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  • 10
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    Journal of chemical crystallography 25 (1995), S. 463-467 
    ISSN: 1572-8854
    Keywords: 1,3-dithiole-4-carboxamides ; resonance effect ; short intramolecular S...O contact ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The two closely related compoundsN,N-dimethyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide1 andN-(p-methoxy-phenyl)-N-methyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide2 have been characterized by X-ray crystal structure determination. Crystal data for1: triclinic, $$P\bar 1$$ ,a=6.767(1),b=12.594(2),c=6.648(1) Å, α=101.38(1), β=93.37(2), γ=79.62(1)°,V=546.2 Å3,Z=2. Crystal data for2: monoclinic, Cc,a=19.836(4),b=6.057(1),c=15.860(3) Å, β=127.61(3)°,V=1509.5Å3,Z=4. The molecular structures of1 and2 show remarkable differences concerning the conformational behavior. These differences are related to the nature of the substituents at the nitrogen atom. The presence of an aromatic system in2 leads to an almost planar arrangement of the α-oxoketene dithioacetal moiety. This effect is accompanied by a short intramolecular S...O contact of 2.648(2) Å. In the absence of an aromatic system, as is the case for compound1, neither a resonance effect along the α-oxoketene dithioacetal fragment nor a short S...O distance is observed.
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  • 11
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    Journal of chemical crystallography 25 (1995), S. 579-582 
    ISSN: 1572-8854
    Keywords: Dibenzo-18-crown-6 ; hetero bimetallic ; crown ether ; crystal structure ; ferric chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Slow evaporation of a solution of ferric chloride and dibenzo-18-crown-6 in 3∶1 CH3CN∶CH3OH produced single crystals of the title complex. This heterobimetallic crown ether complex, [Na(dibenzo-18-crown-6)][FeCl4], crystallizes in the monoclinic space group P2t/n with cell parameters (at 22°C)a=14.608(6),b=10.466(9),c=17.276(9)Å, β=91.47(6)°, andD calc=1.46 g cm−3 for Z=4. The structure consists of discrete ions with the shortest Na ... Cl distance a lengthy contact of 3.56(1)Å. The average Na...O separation is 2.69(3)Å. The [FeCl4]− anion exhibits a distorted tetrahedral geometry with an average Fe−Cl bond length of 2.16(2)Å.
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  • 12
    ISSN: 1572-8854
    Keywords: Amines ; crystal structure ; pentacycloundecane-8,11-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of three compounds formedvia nucleophilic attack of a heterocyclic secondary amine on PCU-8,11-dione, with the concomitant intramolecular attack of one keto oxygen on the carbon of the other ketone, are presented. In all three compounds, the bridging oxygen contains substantial p-character, and the bonds to the “attacking” nitrogen are significantly shorter than would be expected.
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  • 13
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    Journal of chemical crystallography 25 (1995), S. 765-768 
    ISSN: 1572-8854
    Keywords: Sesterterpene ; scalaran ; crystal structure ; marine compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular geometry of a tetracyclic sesterterpene has been determined by X-ray diffraction. The conformation of the aldehyde group as observed in the crystal structure supports the rationalization for the absence of aldehyde proton coupling in the nmr spectra of the compound. Crystal data: C28H42O5, M.W.=458.6; orthorhombic, P212121;a=10.797(2),b=29.270(9),c=8.033(1)Å,V=2538.7Å3,Dx=1.199 g cm−3;R=0.045 for 2287 observed reflections.
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  • 14
    ISSN: 1572-8854
    Keywords: Calixarene ; complex ; crystal structure ; chirality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound was obtained by treatment ofp-tert-butylcalix[4]arene with (+) camphorsulfonyl chloride in triethylamine and toluene. A (1∶2) complex with toluene has been found. Its structure has been determined by X-ray crystallography. Crystals are triclinic with space group P1,a=16.426(3),b=18.553(3),c=13.661(2) Å, α=94.78(2), β=110.76(2), γ=72.83(2)°,V=3720(2) Å3,d c =1.127 g/cm3 Z=2. Refinement based on 10495 observed reflections led to a finalR value of 0.100. The two independent molecules of calixarene in the asymmetric unit are in the cone conformation and the calixarene cavities are empty. The guest molecule occupies the interhost space. The norborane skelton of (+) camphorsulfonyl group is the same as ones found in literature. Only van der Waals interactions exist between the host and the guest molecules.
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  • 15
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    Biology and fertility of soils 19 (1995), S. 36-40 
    ISSN: 1432-0789
    Keywords: Soil nitrogen ; Immobilisation ; Mineralisation ; Nitrification ; Solanum tuberosum L. ; Plant effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Following application of fertiliser-N to the seedbed of potato crops, concentrations of extracted mineral-N were up to 3 times greater than would be anticipated by calculation. The rates at which both NO 3 − -N and NH 4 + -N apparently appeared and disappeared in the soil solution were, at various times, also much greater than could be attributable to any transformations resulting from microbial activity. This suggests that the involvement of other factors in this phenomenon must be considered. The effect of certain physical parameters such as water movement, resulting from capillary action and evaporation from the soil surface, may be implicated. We suggest that soil microbes are not directly involved in the early fate of fertiliser-N, primarily due to C-limitation in arable soils. N dynamics in fertilised potato systems require further studies targeting the relationships between nutrient concentrations in soil solution and mass flow of soil water.
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  • 16
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    Biology and fertility of soils 19 (1995), S. 29-35 
    ISSN: 1432-0789
    Keywords: Ammonium sulphate ; Biomass N ; Clay CO2 ; Gross mineralization ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A sandy loam soil was mixed with three different amounts of quartz sand and incubated with (15NH4)2SO4 (60 μg N g-1 soil) and fresh or anaerobically stored sheep manure (60 μg g-1 soil). The mineralization-immobilization of N and the mineralization of C were studied during 84 days of incubation at 20°C. After 7 days, the amount of unlabelled inorganic N in the manure-treated soils was 6–10 μg N g-1 soil higher than in soils amended with only (15NH4)2SO4. However, due to immobilization of labelled inorganic N, the resulting net mineralization of N from manure was insignificant or slightly negative in the three soil-sand mixtures (100% soil+0% quartz sand; 50% soil+50% quartz sand; 25% soil+75% quartz sand). After 84 days, the cumulative CO2 evolution and the net mineralization of N from the fresh manure were highest in the soil-sand mixutre with the lowest clay content (4% clay); 28% fo the manure C and 18% of the manure N were net mineralized. There was no significant difference between the soil-sand mixtures containing 8% and 16% clay, in which 24% of the manure C and -1% to 4% of the manure N were net mineralized. The higher net mineralization of N in the soil-sand mixture with the lowest clay content was probably caused by a higher remineralization of immobilized N in this soil-sand mixture. Anaerobic storage of the manure reduced the CO2 evolution rates from the manure C in the three soil-sand mixtures during the initial weeks of decomposition. However, there was no effect of storage on net mineralization of N at the end of the incubation period. Hence, there was no apparent relationship between net mineralization of manure N and C.
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  • 17
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    Biology and fertility of soils 19 (1995), S. 49-54 
    ISSN: 1432-0789
    Keywords: N2 fixation ; N supplying potential ; Grain legumes ; Green manuring ; 15N ; Wetland rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Studies were conducted on paddy soils to ascertain N2 fixation, growth, and N supplying ability of some green-manure crops and grain legumes. In a 60-day pot trial, sunhemp (Crotalaria juncia) produced a significantly higher dry matter content and N yield than Sesbania sesban, S. rostrata, cowpeas (Vigna unguiculata), and blackgram (V. mungo), deriving 91% of its N content from the atmosphere. Dry matter production and N yield by the legumes were significantly correlated with the quantity of N2 fixed. In a lowland field study involving sunhemp, blackgram, cowpeas, and mungbean, the former produced the highest stover yield and the stover N content, accumulating 160–250 kg N ha-1 in 60 days, and showed great promise as a biofertilizer for rice. The grain legumes showed good adaptability to rice-based cropping systems and produced a seed yield of 1125–2080 kg ha-1, depending on the location, species, and cultivar. Significant inter- and intraspecific differences in the stover N content were evident among the grain legumes, with blackgram having the highest N (104–155 kg N ha-1). In a trial on sequential cropping, the groundnut (Arachis hypogaea) showed a significantly higher N2 fixation and residual N effect on the succeeding rice crop than cowpeas, blackgram, mungbeans (V. radiata), and pigeonpeas (Cajanus cajan). The growth and N yield of the rice crop were positively correlated with the quantity of N2 fixed by the preceding legume crop.
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  • 18
    ISSN: 1432-0789
    Keywords: Leucaena ; Nodulation ; Nitrogen fixation ; Nitrogen use ; 15N ; Time course
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dynamics of nodulation, N2-fixation and N use in Leucaena leucocephala cv. K28 over time was investigated in a screenhouse at 4, 8, 12 and 16 months after planting (MAP) using the 15N-labelling method. Leucaena had a consistently increasing pattern of nodulation, dry biomass and nitrogen yield. A sharp rise in nodulation was observed between 12 and 16 MAP, whereas for biomass, N accumulation and N2-fixation, and N2-fixation, an upward surge occurred between 4 and 12 months. Nodulation, N accumulation, N2-fixation and biomass yield all peaked at 16 MAP. Along with the steady increase in N2-fixation throughout the 16-month growth period, the % N derived from the atmosphere rose from 17.9% to 61.5%, 70.1% and 74%, equivalent to 191, 1623, 2395 and 3385 mg N2 fixed plant-1 at 4, 8, 12 and 16 MAP, respectively. Nitrogen assimilation from soil and fertilizer decreased inversely to the increase in symbiotic nitrogen fixation with time.
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  • 19
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    Biology and fertility of soils 20 (1995), S. 41-48 
    ISSN: 1432-0789
    Keywords: Added nitrogen interaction ; Ammonia fixation ; 15N ; Immobilization ; Fertilizer-induced solubilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Added N interactions were measured in four soil incubated with 15N-labelled urea or diammonium phosphate. The use of biologically active, γ-irradiated, or reinoculated γ-irradiated samples allowed us to separate added N interactions due to chemical and biological processes, and to distinguish real interactions from apparent effects. Real biologically mediated added N interactions were observed in one soil for both fertilizer sources and in three soils amended with urea. These real interactions increased with the N fertilizer rate, but did not differ significantly between N sources. Fertilizer-induced unlabelled organic N in soil extracts declined during incubation in both sterile and non-sterile samples, but the temporal decline was higher in biologically active soil. Changes in fertilizer-induced unlabelled organic N in the extracts of three soils attributed to biological processes were similar to the measured real biologically mediated added N interactions. The results are consistent with the hypothesis that real biologically mediated added N interactions arise from the mineralization of soil organic N solubilized by alkaline-hydrolysing N fertilizers.
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  • 20
    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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  • 21
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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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  • 22
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    Nutrient cycling in agroecosystems 42 (1995), S. 139-148 
    ISSN: 1573-0867
    Keywords: denitrification ; methods ; 15N ; nitrate ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper attempts to answer the question: is denitrification a major route of N loss from tropical agro-ecosystems? This question turns out to be very difficult to answer due to a severe shortage of data on this process for tropical agro-ecosystems other than rice. Given this lack of data, I approach this question by analyzing data on denitrification and nitrous oxide flux in tropical native forest and pasture soils and attempt to make some conclusions and pose some hypotheses about the significance of denitrification in tropical agricultural soils. I also briefly review methods for measuring denitrification. The data analysis suggests that denitrification in tropical forest soils is strongly influenced by the nature and amount of soil C and N turnover. Studies to examine differences in denitrification in different tropical agricultural systems should focus on the effects of system management on C and N turnover. The data analysis also suggests that, just as in temperate regions, denitrification may not be a significant route of N loss from most tropical agricultural systems. However, field studies are necessary to determine if this is actually the case.
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  • 23
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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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  • 24
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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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  • 25
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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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  • 26
    ISSN: 1573-0867
    Keywords: 15N ; non-nod beans ; quantification of N2 fixation ; reference crops ; simulation technique ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A technique for the application of the15N isotope dilution technique for the quantification of plant associated biological nitrogen fixation (BNF) was tested and applied to quantify the BNF contribution to two genotypes ofPhaseolus vulgaris. The technique makes use of sequential measurements of the15N enrichment of soil mineral N, and the uptake of labelled N by the “N2-fixing” plant, to simulate its uptake of soil N (the “soil to plant simulation” technique). The test was made with two non-N2-fixing crops (non-nodulating beans and wheat) and two bean genotypes (PR 923450 and Puebla 152), at two levels of N fertilizer addition (10 and 40 kg N ha−1), to compare the actual N uptake with that simulated from the soil and crop15N data. The simulation of the soil N uptake by the non-nod bean crop using this “soil to plant simulation” technique underestimated by 20 to 30% the true N uptake, suggesting that the mineral N extracted from soil samples taken from the 0–15cm layer had a higher15N enrichment than that N sampled by the roots of this crop. In the case of the wheat crop the simulation resulted in a much greater underestimation of actual N uptake. In general the results using this technique suggested that BNF inputs to the bean cultivars was higher than would be expected from the nodulation and acetylene reduction data, except for the early PR beans in the 40 kg N ha−1 treatment. In this case the total N and simulated soil N accumulation were well matched suggesting no BNF inputs. An allied technique (the “plant to plant simulation technique”) was proposed where the15N enrichrnent of soil mineral N was simulated from the data for total N and labelled N accumulation taken from sequential harvests of either of the non-N2 -fixing control crops. This was then utilized in combination with the labelled N uptake data of the other crop to simulate its soil N uptake. However, the results using either technique indicated that the wheat and non-nod or nodulating beans exploited pools of N in the soil with completely different15N enrichments probably due to differences in exploitation of the soil N with depth.
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  • 27
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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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  • 28
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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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  • 29
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    Nutrient cycling in agroecosystems 42 (1995), S. 33-41 
    ISSN: 1573-0867
    Keywords: acetylene ; 15N ; nodules ; reference plant ; ureide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The four commonly used methods for measuring biological nitrogen fixation (BNF) in plants are: the total nitrogen difference (TND) method, acetylene reduction assay (ARA) technique, xylem-solute (or ureide production) method and the use of15N labelled compounds. The TND method relies on a control non-N2-fixing plant to estimate the amount of N absorbed by the fixing plant from soil. It is one of the simplest and least expensive methods, but works best under low soil N conditions. The ARA technique measures the rate of acetylene conversion to ethylene by the N2-fixing enzyme, nitrogenase. The ethylene produced can then be converted into N2 fixed, using a conversion ratio, originally recommended as 3. Although the method is inexpensive and highly sensitive, its major disadvantages are, the short-term nature of the assays, the doubtful validity of always using a conversion ratio of 3 and the auto-inhibition of acetylene conversion to ethylene. The ARA technique is therefore not a method of choice for measuring BNF. The xylem-solute technique can be used to measure BNF for those species that produce significant quantities of ureide as product of BNF. Although simple and relatively inexpensive, it is an instantaneous assay and also needs to be calibrated against a known method. The most serious limitation is, that only a small proportion of N2-fixing plants examined are ureide exporters, and the method is therefore not widely applicable. The15N methods, classified into the isotope dilution and A-value methods, appear to be the most accurate, but also the most expensive. They involve labelling soil with15N fertilizer and using a non-N2-fixing reference plant to measure the15N/14N ratio in the soil. The15N isotope dilution approach is both operationally and mathematically simpler than the A-value approach. To limit potential errors in the selection of reference crops, it is recommended to use15N labelled compounds or soil labelling methods that result in the slow release of15N or the slow decline of15N/14N ratio in the soil. Additionally, the use of several reference plants rather than a single one can improve the accuracy of the results.
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  • 30
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    Nutrient cycling in agroecosystems 42 (1995), S. 185-192 
    ISSN: 1573-0867
    Keywords: 15N ; nitrogen ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The use of15N as a tracer in soil/plant research is examined. The limitations of the so-called Ndff approach are discussed to show the need to consider not just the fate of the added label but also the path that was followed and the rate of the transformation. The development of15N isotope dilution techniques to determine gross rates of nitrogen transformation in soil is reviewed with some indications as to the further development of the approach.
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  • 31
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    Nutrient cycling in agroecosystems 42 (1995), S. 109-115 
    ISSN: 1573-0867
    Keywords: Colocasia esculenta var.esculenta ; crop uptake ; 15N ; soil management ; tropical soils ; urea ; Vertisols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Vertisols are an important natural resource, particularly in the developing world, but a greater understanding of their chemical characteristics with special reference to the fate of applied N is needed for their greater sustainable use. The Bejucal clay (Chromic Dystraquerts, very fine, mixed, acid) is an important agricultural soil in North Trinidad and a series of studies were undertaken on it to determine the optimum rate and the best time of application and to quantify the efficiency of applied N using CO(NH2)2-15N and taro, commonly called dasheen locally, (Colocasia esculenta var.esculenta), as a test crop. The optimum rate was found to be 280 kg N ha−1 for corm production from a field experiment, laid out in a randomised incomplete block design. This corresponded to an apparent recovery at 10 per cent when CO(NH2)2 was applied at 14 days after planting (DAP). Generally, a decrease in N uptake with increasing levels and later application times was observed. Another field experiment which employed15N applied at 14, 56, and 112 DAP showed that15N applied at 112 DAP corresponded to the highest15N level in the plant tissue. A green house experiment conducted to determine the efficiency of the use of the applied N showed the highest recovery of approximately 49 per cent at a rate equilavent to 280 kg N ha−1 with efficiencies of 43 and 40 per cent at the 140 and 420 kg N ha−1 of applied N levels, respectively. A single application at 14 DAP resulted in an efficiency of 41 per cent compared to 44 and 47 per cent for the 2 split and 3 split applications, respectively. Split applications increased N uptake but without a corresponding increase in yield. These studies showed that N applied as CO(NH2)2 at 280 kg N ha−1 at 14 DAP is optimum for upland taro production under conditions of the Bejucal clay. Under normal field conditions surface washing may be the most important N loss pathway but when excessive fertilizers are used then the gaseous pathways may also contribute to N losses.
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  • 32
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    Nutrient cycling in agroecosystems 42 (1995), S. 149-158 
    ISSN: 1573-0867
    Keywords: Micrometeorology ; N flux ; livestock waste ; NH3 ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Gaseous ammonia (NH3) transport is an important pathway in the terrestrial N cycle. In the atmosphere NH3 neutralizes airborne acids and is a major factor determining air quality and acid rain deposition patterns. Redeposition of atmospheric NH3 plays an important role in the N balance of natural ecosystems and has been implicated in forest decline, plant species change and eutrophication of surface water. Much of the N in soil-plant animal systems can be lost to the atmosphere, particularly with surface applied livestock waste, or urea and anhydrous ammonia fertilizers. Plants can have a significant impact on NH3 transport because they can both absorb and desorb atmospheric NH3. Under conditions of low soil N or high atmospheric NH3 concentrations, plants absorb NH3. Under conditions of high soil N or low atmospheric NH3 concentrations, plants volatilize NH3. This article discusses methods for evaluating NH3 transport in the filed, the rate of NH3 volatilized from fertilizer application, and the effects of plants on net NH3 transport.
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  • 33
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    Nutrient cycling in agroecosystems 42 (1995), S. 165-174 
    ISSN: 1573-0867
    Keywords: Anabaena ; cropping systems ; fertilizer management ; integrated nitrogen management ; 15N ; nitrogen balance ; Oryza sativa ; urea ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract By the year 2020, an additional 300 million tons of rice are needed annually to meet the demands of a growing population. If our natural resource base is to be preserved, intensification strategies should rely on integrated nutrient management, making full use of biological nitrogen fixation. TheAzolla-Anabaena complex is amongst the most effective systems of fixing nitrogen. In this paper we present evidence from greenhouse studies on the potential ofAzolla to curb the volatilization of NH3 following the application of urea to a mixedAzolla-rice culture, providing a new incentive for developing ways of integratingAzolla in intensive rice cultivation systems. The results of a series of short term greenhouse experiments show that a full cover ofAzolla can significantly reduce losses of applied urea-N from 45 and 50% to 20 and 13% for the 30 and 60 kg N ha−1 treatments, respectively. About one-quarter of the applied N was tied up in theAzolla biomass. The applied N inhibitedAzolla growth as well as the amount of N fixed. Inoculation with smaller quantities ofAzolla allowing for more vigorousAzolla multiplication was equally effective in reducing NH3 volatilization and doubled the amount of15N tied-up byAzolla. The reduction in NH3 volatilization is largely related to the depression byAzolla of the floodwater pH, which in its absence may reach values between 9 and 10 as a result of algal activity. Early rice growth responded positively to urea as well as the large quantities of appliedAzolla and increased the yield potential of the crop. Smaller quantities ofAzolla alone were not effective in this regard. The conservation of fertilizer N byAzolla, particularly when it fully covered the water, was reflected in a synergistic effect on rice dry matter production, amounting to 9% at the 30 kg N rate and 16% at the 60 kg N rate. In all likelihood this interaction is attributable to the higher efficiency of the applied N. The benefits ofAzolla in conserving basal urea-N even in small quantities (200-500 kg fresh material ha−1), outweighed competition for the applied N and may be as important as its BNF. The most promising integratedAzolla/rice management systems emerging from our studies should be given further attention under field conditions.
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  • 34
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    Nutrient cycling in agroecosystems 42 (1995), S. 205-214 
    ISSN: 1573-0867
    Keywords: Colocasia esculenta ; fertilizer efficiency ; fertilizer management ; 15N ; urea transformations ; volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Urea has become the most important N carrier in many parts of the world and its reaction when added to soil is unique in many ways. Two field experiments were therefore undertaken using15N to investigate the uptake efficiency of the added urea-15N which was banded in Experiment I and broadcast in Experiment II. In both experiments the uptake efficiencies were not affected by N-rate and cropping system (Exp. I) or crop residue management (Exp. II) and averaged 17.4 and 16.9% respectively. These low values were supported by evidences of high losses; high pH increases following urea application (volatilization), downward movement of N (leaching), and cycles of waterlogged and well drained conditions in the soil (de-nitrification). Evidence of leaching at least down to 30 cm in the profile was observed in the first experiment where urea was banded but not in experiment II where it was broadcast. The proportion of N in the crop that was derived from added urea (%Ndff) was 57.7% and 36.4% in experiments I and II respectively, suggesting that band application resulted in a higher proportion of the added N in the root zone compared to that for broadcast application. The results indicate the need to investigate other management strategies, such as higher application frequencies and placement closer to the root zone, in order to improve the uptake efficiency of added urea-N in upland rainfed dasheen.
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  • 35
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    Nutrient cycling in agroecosystems 40 (1995), S. 41-48 
    ISSN: 1573-0867
    Keywords: Arachis hypogaea ; intercropping ; maize ; N2 fixation ; N-transfer ; 15N ; Vigna radiata ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Grain legumes are used widely in intercropping systems. However, quantitative and comparative data available as to their N2 fixation and N beneficial effect on the companion crop in intercropping systems are scarce. Hence, studies were conducted to ascertain the above when cowpea (Vigna unguiculata L.), mungbean (Vigna radiata L.) and groundnut (Arachis hypogaea L.) were intercropped with maize. The study was15N-aided and made outdoors in basins (30 L) filled with 38 kg of soil.15N labelling was effected by incorporating15N-tagged plant material or applying15N-labelled fertilizer along with sucrose to stabilize15N enrichment in the soil during the experimental period. Intercropped groundnut fixed the highest amount of nitrogen from the atmosphere (i.e. 552 mg plant−1), deriving 85% of its N from the atmosphere. Intercropped cowpea and mungbean fixed 161 and 197 mg N plant−1, obtaining 81% and 78% of their N content from the atmosphere, respectively. The proportion of N derived by maize from the associated legume varied from 7-11% for mungbean, 11–20% for cowpea and 12–26% for groundnut which amounted to about 19–22, 29–45 and 33–60 mg N maize plant−1, respectively. The high nitrogen fixation potential of groundnut in dual stands and its relatively low harvest index for N have apparently contributed to greater N-benefical effect on the associated crop.
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  • 36
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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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  • 37
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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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  • 38
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    Potato research 38 (1995), S. 345-351 
    ISSN: 1871-4528
    Keywords: disease screening ; progeny test ; Fusarium coeruleum ; Fusarium sulphureum ; Gibberella pulicaris ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field-grown tubers of 22 progenies ofSolanum tuberosum L. generated in a crossing programme involving seven parents differing in resistance toFusarium coeruleum Lib. ex Sacc. andF. sulphureum Schlect. (=F. sambucinum Fuckel, teleomorphGibberella pulicaris (Fr.) Sacc.) were wound-inoculated with a cornmeal + sand culture of each pathogen. Parental genotypes were also included. The mean lesion size of each progeny was compared in 2 years of tests, as well as with published data on glasshouse-grown tubers. ForF. coeruleum there was a high correlation between years as well as with the glasshouse data, but no such correlations were apparent withG. pulicaris. Furthermore, parental and GCA values, as well as progeny means and mid-parent scores, also correlated highly forF. coeruleum but not forG. pulicaris. Glasshouse-grown tubers of 11 wildSolanum spp. were also inoculated with both pathogens. Some resistance to one or other, or both, was apparent, particularly inS. chacoense.
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    Potato research 38 (1995), S. 363-370 
    ISSN: 1871-4528
    Keywords: wart disease ; inoculation ; Solanum tuberosum L. ; Synchytrium endobioticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sprouts of cvs Arran Chief, Pentland Kappa and Golden Wonder were inoculated with fresh wart tissue using the Glynne-Lemmerzahl (GL) method and results of tests carried out using five different incubation regimes were compared. When tubers of Arran Chief and Pentland Kappa were incubated uncovered in the light. rotting of sprouts was reduced and there was more extensive development of summer sporangia. Similar results were obtained on a range of cultivars when inoculations were done using summer or winter spores. Winter spores, which germinate freely in distilled water, can readily be extracted from dried rotted wart tissue to provide a reliable and continuous supply of inoculum. At the Scottish Agricultural Science Agency, wart susceptibility testing using the GL method has been done with winter spores since 1987.
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  • 40
    ISSN: 1871-4528
    Keywords: potato ; cyst nematodes ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Accessions of tuber-bearingSolanum spp. related toS. tuberosum subsp.tuberosum were obtained from the German-Dutch collection (Braunschweig, Germany) and the Inter-regional potato collection (Sturgeon Bay, USA). They were screened for resistance toG. rostochiensis Rol andG. pallida Pa2/3. Among 1567 clones from 52 accessions, 135 clones (23 accessions) were resistant toG. rostochiensis. They mainly representedS. andigena, gourlayi, spegazzinii andvernei. Among 1689 clones (74 accessions), 105 clones (32 accessions) were resistant toG. pallida. They representedS. gourlayi, spegazzinii, sparsipilum andvernei. About 25 clones were resistant to both species.
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  • 41
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; reducing sugars ; sucrose ; ascorbic acid ; citric acid ; nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pot and field experiments were carried out to test fertilizer treatments on the behaviour of potato tubers stores at 4°C and ≥90% relative humidity for 6 months. Weight losses (separated into water and dry matter) were enhanced after N and K fertilization and decreased by increasing P supply. Glucose and fructose contents were reduced at harvest by high N-fertilizer rates compared to no or low fertilization, but throughout storage reducing sugar accumulation was increased, sucrose reduction was decreased and ascorbic acid was increased. K fertilization affected the chemical composition of the tubers somewhat similar to that of nitrogen fertilization. High initial nitrate content of the tubers seemed to be increased and low nitrate values were decreased during storage. The tubers from pot experiments showed similar changes but of greater magnitude.
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  • 42
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; diploid interspecific hybrids ; Solanum spp., chipping ability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The reducing sugar content and chip colour were studied in diploid potatoes bred for superior table and chipping quality. The reducing sugar content in the tubers of 119 diploid clones was estimated before and after cold storage (4–6°C) in the years 1987–1991, and reducing sugar and chip colour were determined in 1990 and 1991 for 36 clones. Thirty two clones had a significantly lower reducing sugar content after cold storage than cv. Mila. The year of evaluation, storage temperature and genotype significantly affected the reducing sugar content.
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  • 43
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Virusresistenzzüchtung ; Nematodenresistenzzüchtung ; Selektionsverfahren ; Sämlingsselektion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zusammenfassung Beschrieben wird ein Verfahren zur gleichzeitigen Selektion von Kartoffelsämlingen auf extreme Y-Virus- und Nematodenresistenz. Pikierte Kartoffelsämlinge werden dazu künstlich mit Y-Virus infiziert, getopfte Pflanzen massivem Befall durch den Gelben Kartoffelnematoden ausgesetzt und nur visuell befallsfreie Genotypen weitergeführt. Die Sämlingsselektion führte zu einer Verdoppelung kombiniert resistenter Kartoffelgenotypen in der Resistenzprüfung. Einsatzgebiet war die Auslese von Zuchteltern.
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  • 44
    ISSN: 1871-4528
    Keywords: potato ; solt rot ; blackleg ; early selection ; Solanum tuberosum L. ; Solanum brevidens Phil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Eleven clones obtained from a cross between cv. Katahdin and fusion products betweenSolanum tuberosum and the non tuber-bearing speciesS. brevidens, were backcrossed again withS. tuberosum (clone AR80-127-5). Small tubers harvested from 583 seedlings of these second backcross (BC2) populations were screened for tuber tissue resistance toErwinia carotovora subsp.atroseptica under aerobic conditions. After multiplication in the field. BC2 clones again were screened for soft rot resistance under aerobic as well as anaerobic conditions. In general, the resistance of the BC2 populations was reduced in comparison with the BC1. Variation for resistance was found within the BC2 populations, but there was no correlation between the results of the three tests performed. Four BC2 populations were also screenned for resistance to blackleg in the field. Significant differences were found between populations for mean percentage of diseased plants, but these differences could not be explained by the resistance of the parental clones.
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  • 45
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    Potato research 38 (1995), S. 119-123 
    ISSN: 1871-4528
    Keywords: fry colour ; dry matter content ; tuber size ; ion and solute accumulation ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of salinity and water dificit on the quality of tubers for processing was investigated. Total tuber yield was not affected by the treatments, while the percentage of non-marketable tubers was significantly reduced by high salinity (ECi=6dS m−1) and by water reduction. Accumulation of dry matter in the tubers was increased by all the treatments, that of proline by salinity only and the content of reducing sugars was increased only by water deficit. The colour of the french fries was similar in tubers from the various treatments.
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  • 46
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    Potato research 38 (1995), S. 143-150 
    ISSN: 1871-4528
    Keywords: reproduction ; distribution ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato plants of cvs Element and Mirka were artificially infected withV. dahliae in two greenhouse experiments. Leaf blade, petiole, aerial stem, subterranean stem, stolon and root mass were separately harvested both when the canopy was still green and at maturity. After 4 weeks incubation, the plant tissue was air-dried and the numbers of microsclerotia per mg tissue and per plant were determined. The highest numbers of microsclerotia were observed in the haulm when harvest took place at maturity. Cultivar Element yielded significantly more microsclerotia in the haulm than cv. Mirka, whilst there were no cultivar differences in the microsclerotial production on subterranean parts. The petiole and the aerial stem contributed most to the total microsclerotial production, whereas roots were much more important for formation of microsclerotia than stolons.
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  • 47
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; seed production ; variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Multiplication factors and progeny yield variation in crops from minitubers of five weight classes (ranging from 0.13–0.25 g to 2.00–3.99 g) and conventional seed tubers were studied in field experiments in three years. Multiplication factors were calculated as the number and weight of progeny tubers produced per planted tuber or per unit planted tuber weight. They were lower for the lighter minitubers when calculated per tuber and higher when calculated per weight. Yield variation was described by coefficients of variation for the number and weight of progeny tubers produced. Variation over individual plants of a crop was higher in stands from the lighter minitubers. Variation over plots within a field was sometimes higher for the lighter minitubers, but variation over years was similar for all minituber classes. Variation over plots in progeny tuber weight was higher for minitubers than for conventional tubers.
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  • 48
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    Potato research 38 (1995), S. 251-256 
    ISSN: 1871-4528
    Keywords: storage ; energy usage ; store temperature ; store management ; weight loss ; power consumption ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of various storage parameters on the power usage and tuber weight loss for a fully refrigerated potato store were investigated. A computer model validated by detailed monitoring of potato stores was used for the calculations. The store parameters considered were: storage temperature, store relative humidity, local ambient conditions, store capacity or loading factor, half cooling time and the infiltration rate or air tightness of the store. The investigation showed that the power consumption was most affected by the storage temperature and the infiltration rate of the store, and that weight loss was most affected by the half cooling time.
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  • 49
    ISSN: 1871-4528
    Keywords: wart disease ; susceptibility ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A comparison of reactions of potato cultivars toS. endobioticum indicated that the degree of susceptibility observed in laboratory tests correlated well with the reaction of cultivars in field tests. Some cultivars found to be less resistant (Resistance Grade 2) in laboratory tests produced winter spores in the field test, and 10% of those derived from cv. Ausonia germinated in distilled water. Compost from the field plot was estimated to contain 14–18 apparently viable spores/g. and this resulted in 100% infection of the highly susceptible cv. Arran Chief. The implications of these findings for descheduling sites previously scheduled due to wart infestation are discussed.
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  • 50
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    Potato research 38 (1995), S. 307-317 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; leaf transpiration ; stomatal resistance ; Mediterranean environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of furrow and drip irrigation giving 0, 33, 66, 100 and 133% of the maximum evapotranspiration (ETM) was studied on leaf transpiration, stomatal resistance, tuber growth, yield and yield response of cv. Spunta. The research was carried out in Sicily in 1988 and 1989 on early potato crops grown during the winter/spring cycle. Increased water supply increased leaf transpiration, plant fresh weight, tuber growth rate, yield and earliness, and decreased stomatal resistance and tuber dry weight. A higher yield response was obtained at the lower water regimes (ETM of 33 and 66%). There were no significant differences between the two methods of irrigation.
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  • 51
    ISSN: 1871-4528
    Keywords: genetic variation ; resistance screening ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Various methods of screening for resistance to root-knot nematodes were compared and evaluated. Seedling populations ofSolanum spp., grown in clay pots and plastic tubes with silver sand and inoculated with juveniles ofMeloidogyne chitwoodi andM. hapla, showed large differences in the number of egg masses on roots 7 weeks after inoculation. The differences were reproducible when re-testing was done with cuttings and plants from tubers. No resistance toMeloidogyne spp. was observed with ten potato cultivars when grown in clay pots, plastic tobes or closed containers. Plants from tubers in growth pouches developed a large two-dimensional root system, and after inoculation with juveniles the infection process could be observed over 8 weeks. A method of infecting potato tuber tissue withMeloidogyne is described, using tuber slices in Petri dishes as a potential screening test for tuber resistance.
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  • 52
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Virusresistenzzüchtung ; Sämlingsselektion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zusammenfassung Studien an 7328 Kartoffelsämlingen und 179 Zuchtstämmen genetisch geeigneter Populationen konzentrierten sich auf die Erarbeitung eines Inokulations- und Selektionsverfahrens. Die Virusinokulation kann mit der Spritzpistole erfolgen, muß aber an getopften Kartoffelsämlingen vorgenommen werden. In Kombination mit der Serodiagnose in den ersten 3 Klongenerationen erzielte ein darauf aufgebautes Selektionsverfahren in der Resistenzprüfung 88.2% Zuchtstämme mit Überempfindlichkeitsresistenz gegen potato virus S gegen nur 55.6% ohne Sämlingsinfektion und Serodiagnose in nur einer Klongeneration.
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  • 53
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; Virusresistenzzüchtung ; Selektionsverfahren ; Sämlingsselektion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Zusammenfassung Zur Auslese auf extreme Y-Virusresistenz kann auch an Kartoffelsämlingen in Hydrostaukultur die künstliche Infektion Anwendung finden. Die Virusinokulation mittels Spritzpistole muß allerdings an Sämlingen in der Aussaatschale und vor der Anzucht in Hydrostaukultur erfolgen. Intensive Bestandeskontrolle. Pflanzguttestung der ersten Klongenerationen und konsequentes Verwerfen Y-Virusbefallener Zuchtstämme sicherten, daß sämlingsinfiziertes Zuchtmaterial im Neuzuchtgarten keine gefährliche Virusinfektionquelle darstellte und ohne räumliche. Trennung gemeinsam mit dem übrigen Zuchtgartenmaterial angebaut werden konnte.
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  • 54
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    Potato research 38 (1995), S. 31-37 
    ISSN: 1871-4528
    Keywords: LAI ; Solanum tuberosum L. ; Phytophthora infestans ; precision ; disease severity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method for assessing the leaf area of potato plants was based on the number of leaves coinciding with imaginary vertical lines descending from a horizontal grid of points above the plant or crop canopy. Leaves seen through each vertically aligned pair of holes in a perforated double table, covering the midpoint of the exposed area, were counted and moved aside one by one, until the ground was seen. For both green and diseased surfaces the leaf area, or its horizontal component, was calculated as the product of sum of records and the grid cell size. Tested against a destructive method, the technique worked equally well for healthy and diseased leaf area of potato plants infected byPhytophthora infestans. The theoretic estimate of the standard error for a single measurement was derived as the geometric mean of the leaf area and the grid cell size. The method is also suitable forLAI of crop stands.
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  • 55
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; NPK nutrition ; tuber weight losses ; chemical composition changes ; vitamin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Empirical mathematical models are described for calculating the effects of varying supplies of nitrogen, phosphorus and potassium on pot and field grown tubers. Through optimization and simulation, potato tuber fresh and dry weight losses and chemical composition changes (ascorbic acid, citric acid, glucose, fructose, sucrose, nitrate) are calculated over a 6-month period of storage at 4°C. The effects of variation in single nutrients as well as of increasing N fertilization on storage are calculated. Calculations giving the maximum vitamin C content at harvest and after storage indicate the nutrient supply required.
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  • 56
    ISSN: 1871-4528
    Keywords: potato ; blackleg ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soft rot caused by Erwinia carotovora ssp. atroseptica is a major disease of stored potatoes. Since varietal resistance can contribute to control, the work reported was designed to find new sources of resistance among related tuber-bearing Solanum spp. True seeds were imported from two international collections and families were screened for resistance to tuber soft rot. Forty-eight resistant clones were found in 21 out of 100 accessions. These clones will be used in breeding programmes at the diploid or tetraploid level.
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  • 57
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    Potato research 38 (1995), S. 151-157 
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In four pot experiments, potato plants of cv. Element were artificially infected withV. dahliae. At an early and a late harvest haulms were killed chemically, by burning or by various other treatments, including cutting them into pieces of different lengths and keeping the debris on the soil surface or covering with soil. After 4 weeks the plant material was air-dried and the number of microsclerotia per mg was determined. At the early harvest, in two experiments, the chemical treatment yielded more microsclerotia than the cutting treatments. Covering colonised haulm tissue with non-sterilised soil was effective in inhibiting microsclerotia formation. Shorter haulm pieces led to fewer microsclerotia at the later harvest if the material was kept on the soil surface. The variation in microsclerotial yield and in treatment effects among the different experiments was large.
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  • 58
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    Potato research 38 (1995), S. 179-186 
    ISSN: 1871-4528
    Keywords: Heat stress ; Leaf bud cutting ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In pot culture experiments over 2 consecutive years, 20 potato genotypes of varying heat tolerance were grown under long day conditions and heat stressed by being exposed to high (38 °C/21 °C mean day/night) temperature. The percent increase in mean internode length of heat stressed plants over those grown at normal temperatue (25°C/16°C day/night) was correlated with the percent tuber dry matter yield of the heat stressed plants (r=0.618, P=0.01). In the same 20 genotypes, grown under short day conditions at normal temperature, the fraction of leaf bud cuttings exposed to high night temperature (23°C) that produced tuber initials correlated with the percentage increase in internode elongation in stem cuttings exposed to 25°C compared with those exposed to 15°C (r=0.680. P=0.01). Thus the relative changes in internode elongation are related to thermal tolerance, and it is suggested that this can be used as a selection criterion for heat tolerance.
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  • 59
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    Potato research 38 (1995), S. 231-239 
    ISSN: 1871-4528
    Keywords: adenylate energy charge ; fermentation ; lipid peroxidation ; posthypoxia ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato tubers kept under hypoxia (1%) showed improved viability in comparison to anoxia, which was associated with the maintenance of intermediate adenylate energy charge values (A.E.C.=0.6) and stable adenylate pools at 50% of the initial levels. Re-admission of oxygen to the tuber resulted in an almost full recovery of adenylate energy charge and total adenylates after up to 3 days of hypoxic pretreatment. Tubers exhibited a mixed fermentation. The high lactate, ethanol and acetaldehyde levels proved to be non toxic. Ethanol was degraded to acetaldehyde during re-aeration. Posthypoxic lipid peroxidation was indicated by malondialdehyde and ethane formation. Both products occurred with a temporary delay and in lower amounts compared to post-anoxia. Ethylene release was also considerably smaller. Severe hypoxia and posthypoxia postponed tissue death compared to anoxia. Survival was correlated with an improved energy supply which stabilized membranes.
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  • 60
    ISSN: 1871-4528
    Keywords: Solanum tuberosum L. ; propagules ; tissue culture ; plastic trays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A greenhouse minituber production system involving low inputs of in vitro potato plantlets and propagation media is described, in vitro plantlets of six potato cultivars were sectioned into nodal cuttings and separately planted into moist peat based growing medium in shallow plastic trays. Cultivar differences were evident with respect to node viability, shoot regrowth and minituber yields. Nodal viability for shoot regrowth varied between 80–100%. Maximum shoot heights were recorded with whole in vitro plantlets (WIP) and the terminal Node-5 cluster. All cuttings produced minitubers. The terminal Node-5 cutting and WIP produced significantly larger minitubers 〉3.0 g as compared to single node cuttings. Greater numbers of minitubers were produced by the cvs Norchip, Red Pontiac and Conestoga as compared to cvs Eramosa. G8610-4PY and Shepody. Total numbers of minitubers were 3 to 5 times higher from each in vitro plantlet that was sectioned into nodal cuttings as compared with intact WIP: the yield ratios depended on cultivar.
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  • 61
    ISSN: 1871-4528
    Keywords: PLRV source ; test plant ; PLRV isolate ; vector efficiency ; Myzus persicae ; Macrosiphum euphorbiae ; Aulacorthum solani ; Aphis gossypii ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Macrosiphum euphorbiae, collected in the field from potato plants infected with potato leafroll virus (PLRV), transmitted the virus to fewer potato plants in a field trial than did laboratory-rearedMyzus persicae. In the laboratory,M. persicae was the only efficient vector of PLRV fromPhysalis floridana seedlings, potato sprouts or excised leaves toP. floridana. Two clones ofM. euphorbiae and one clone ofAulacorthum solani transmitted PLRV from infected potato plants toNicotiana clevelandii as effeciently asM. persicae but a clone ofAphis gossypii was an inefficient PLRV vector. An isolate of PLRV, whichM. persicae transmitted inefficiently from potato toN. clevelandii, was also transmitted inefficiently byM. euphorbiae andA. solani.
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  • 62
    ISSN: 1871-4528
    Keywords: Rapid multiplication ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Potato plants of cvs Eersteling and Bintje were grown from stem cuttings and induced to form aerial tubers for use as seed. Spraying the plants with gibberellic acid in concentrations of 10, 25 and 50 mg/l to induce stolon formation in the leaf axils led to a decrease in the number of tubers formed per plant. Multiple harvesting of the largest tubers from plants treated with gibberellic acid or not, approximately doubled the number of tubers formed but halved their individual weight compared with only one harvest at plant senescence. After a storage period of about 1 year, with their vigour declining, the aerial tubers were planted in the field. Aerial seed tubers taken from multiple harvests during the previous year produced the same number of tubers as plants grown from above-ground tubers harvested at plant senescence only, but the tuber yields declined with earlier harvesting when small (5–13 mm) aerial tubers were used, compared to larger (14–19 mm) tubers.
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  • 63
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    Potato research 38 (1995), S. 171-178 
    ISSN: 1871-4528
    Keywords: zoospore ; Phytophthora infestans ; resistance components ; area under disease progress curve ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The nature and extent of field resistance to late blight, and the effect of plant age and inoculum level on resistance components and host attributes, were studied on the Indian potato cultivars Kufri Chandramukhi, Kufri Jyoti, Kufri Badshah and Kufri Sherpa. Latent period, infection efficiency, colonization rate and sporulation were found to operate in cvs Kufri Jyoti, and Kufri Badshah. Based on component analysis cv. Kufri Jyoti was similar to or sometimes more resistant than Kufri Badshah. No correlation was observed between any of the host attributes and resistance to late blight, except that the erect canopy of Kufri Badshah was associated with its slow blighting rate. At high inoculum, colonization rate and total sporulation were increased but infection efficiency was decreased.
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  • 64
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    European journal of plant pathology 101 (1995), S. 519-525 
    ISSN: 1573-8469
    Keywords: biocontrol ; Clavibacter michiganensis subsp.sepedonicus ; ELISA ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bacterial strains with potential for biological control of bacterial ring rot of potato caused byClavibacter michiganensis subsp.sepedonicus were isolated from the surface of potato tubers. Eighty-eight potential biocontrol candidates, selected on the basis ofin vitro antibiosis toC. m. sepedonicus, produced inhibition zones with radii ranging from 0.5 to 16 mm on test plates. All antagonistic isolates were screened in the greenhouse for biocontrol activity on micropropagated potato plantlets root-inoculated withC. m. sepedonicus. Eight strains consistently prevented infection of plantlets but there was no significant correlation between the width of the inhibition zone in thein vitro assay and ring rot suppression in the plant bioassay. Three strains that showed a high level of biological control potential were identified as a saprophytic enteric bacterium (strain 7G), anArthrobacter sp. (strain 16C), and a soil coryneform bacterium (strain 18A). These were tested in a field plot by co-inoculating cut seed potato tubers withC. m. sepedonicus and antagonists. Strains 7G and 18A significantly increased plant stand whereas 16C decreased disease incidence. The relative number of ostensibly ring rot-free progeny tubers was generally greater when antagonists were present.
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  • 65
    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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  • 66
    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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  • 67
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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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  • 68
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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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  • 69
    ISSN: 1573-5036
    Keywords: 13C ; forests ; 15N ; nitrogen saturation ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Preliminary attempts to make retrospective studies of N balances and water stress in forest fertilization experiments by analyzing changes in the abundances of 15N and 13C, respectively, are discussed. Most evidence is from the Swedish Forest Optimum Nutrition Experiments, which have been running for two decades. Annual additions of N have been given either alone or in combination with other elements, notably P and K, every third year. Processes leading to loss of N, e.g. volatilization of ammonia, nitrification followed by leaching or denitrification, and denitrification alone, discriminate against the heavy isotope 15N. A correlation was found between fractional losses of added N and the change in δ15N (‰) during 19 years in current needles in a Scots pine forest, irrespective of source of N. Isotope effects were larger on urea than on ammonium nitrate plots (2 as compared to 9 δ15N (‰)) because of ammonia volatilization and higher rates of nitrification. They developed gradually over time, which opens possibilities to analyse the development of N saturation. However, the analysis may be confounded by shifts in 15N abundance of fertilizer N. In another trial, N isotope effects could be seen in both plants and soils 10 years after the last fertilization; they were smaller in soils because of a large pretreatment memory effect, but we expect them to persist there for decades. The enzyme RuBisCo discriminates strongly against the heavy isotope 13C during photosynthesis, but this effect becomes less expressed as stomata close because of water stress. The supply of N may also affect the δ13C (‰) via effects on rates of photosynthesis, and the source of N may have an influence directly via non-RubisCo carboxylations, and indirectly via effects on water use efficiency. In a trial with Norway spruce, the effect of N fertilization on the δ13C (‰) of current needles was strongly correlated with production and weakly so with foliar biomass a dry year, but not a wet year. This suggested that these variations are primarily related to induced differences in the balance between supply and demand for water. Hence, studies of {au13}C abundance can disentangle the role of water as such from its effects on mineralization of N and flow of N.
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  • 70
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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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  • 71
    ISSN: 1573-5036
    Keywords: Acacia raddiana ; Acacia senegal ; Acacia seyal ; Faidherbia albida ; isotope dilution ; 15N ; nitrogen fixation ; Parkia biglobosa reference tree ; Tamarindus indica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted in a greenhouse using the 15N isotope dilution method and two reference plants, Parkia biglobosa and Tamarindus indica to estimate nitrogen fixed in four Acacia species: A raddiana, A. senegal, A. seyal and Faidherbia albida (synonym Acacia albida). For the reference plants, the 15N enrichments in leaves, stems and roots were similar. With the fixing plants, leaves and stems had similar 15N enrichments; they were higher than the 15N enrichment of roots. The amounts of nitrogen fixed at 5 months after planting were similar using either reference plant. Estimates of the percentage of N derived from fixation (%Ndfa) for the above ground parts, in contrast to %Ndfa in roots, were similar to those for the whole plant. However, none of the individual plant parts estimated accurately total N fixed in the whole plant, and excluding the roots resulted in at least 30% underestimation of the amounts of N fixed. Between species, differences in N2 fixation were observed, both for %Ndfa and total N fixed. For %Ndfa, the best were A. seyal (average, 63%) and A. raddiana (average, 62%), being at least twice the %Ndfa in A. senegal and F. albida. Because of its very high N content, A. seyal was clearly the best in total N fixed, fixing 1.62 g N plant−1 compared to an average of 0.48 g N plant−1 for the other Acacia species. Our results show the wide variability existing between Acacia species in terms of both %Ndfa and total N fixed: A. seyal was classified as having a high N2 fixing potential (NFP) while the other Acacia species had a low NFP.
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  • 72
    ISSN: 1573-5036
    Keywords: ammonium ; animal manure ; injection ; 15N ; N utilization ; ryegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of incorporating cattle slurry in soil, either by mixing or by simulated injection into a hollow in soil, on the ryegrass uptake of total N and 15NH4 +-N was determined in three soils of different texture. The N accumulation in Italian ryegrass (Lolium multiflorum L.) from slurry N and from an equivalent amount of NH4 +-N in (15NH4) SO4 (control) was measured during 6 months of growth in pots. After this period the total recovery of labelled N in the top soil plus herbage was similar in the slurry and the control treatments. This indicated that gaseous losses from slurry NH4 +-N were insignificant. Consequently, the availability of slurry N to plants was mainly influenced by the mineralization-immobilization processes. The apparent utilization of slurry NH4 +-N mixed into soil was 7%, 14% and 24% lower than the utilization of (NH4)2SO4-N in a sand soil, a sandy loam soil and a loam soil, respectively. Thus, the net immobilization of N due to slurry application increased with increasing soil clay content, whereas the recovery in plants of 15N-labelled NH4 +-N from slurry was similar on the three soils. A parallel incubation experiment showed that the immobilization of slurry N occurred within the first week after slurry application. The incorporation of slurry N by simulated injection increased the plant uptake of both total and labelled N compared to mixing the slurry into the soil. The apparent utilization of injected slurry NH4 +-N was 7% higher, 8% lower and 4% higher than the utilization of (NH4)2SO4-N in the sand, the sandy loam and the loam soil, respectively. It is concluded that the spatial distribution of slurry in soil influenced the net mineralization of N to the same degree as did the soil type.
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  • 73
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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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  • 74
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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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  • 75
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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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  • 76
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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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  • 77
    ISSN: 1573-5036
    Keywords: Helianthus annuus L. ; 15N ; nitrogen supply ; redistribution ; remobilization ; seed N ; sunflower ; total N ; vegetative organs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A glasshouse study was made of the distribution of 15N among vegetative organs of sunflower and its later remobilization and redistribution to seeds, as influenced by the developmental stage at which 15N was provided, and by the N status of the plants. Plants of Hysun 30 sunflower were grown in sand culture and provided with K15NO3 for a 3-day period at: (a) 3 days before the end of floret initiation; (b) 3 days before anthesis; (c) the start of anthesis; (d) full anthesis; and (e) 8 days after full anthesis. The plants were grown on a range of N supply rates, from severely deficient to more than adequate for maximum growth. Nitrogen-15 was distributed to all parts of the plant at the end of the 15N uptake periods. With the exception of the most N-stressed plants, subsequent remobilization of 15N from roots, stems and leaves occurred irrespective of the time the 15N was taken up. However, the percentage redistribution to seeds of 15N taken up at the end of floret initiation was less than for 15N taken up at anthesis. Remobilization of 15N from leaves and roots was higher (70%) for 15N taken up during and after anthesis than for 15N taken up at the end of floret initiation (45%), except for plants grown on the lowest N supply. By contrast, remobilization of 15N from the stem was lower for 15N taken up after full anthesis (40%) than before or during anthesis (〉70%). The proportion of 15N remobilized from the top third of the stem was less than that from the bottom third, and decreased with increasing plant N status. Nitrogen-15 taken up over the 3-day supply periods during anthesis contributed from 2 to 11% of the total seed N at maturity; the contribution to seeds was greatest for plants grown on the highest N supply. Nitrogen taken up just before and during anthesis contributed most of the N accumulated in mature seeds of plants grown on an adequate N supply, but N taken up between the end of floret initiation and just before anthesis, or after full anthesis seemed to make an equally important contribution to mature seeds as N taken up during anthesis for plants grown on a very low N supply. It was concluded that the development of florets and seeds of sunflower is supported by N taken up by the plant between the end of floret initiation and anthesis, and by N redistributed from vegetative organs. Unless soil N is so low as to impair early growth, split applications of N fertilizer would be best made just before the end of floret initiation (‘star stage’) and just before anthesis.
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  • 78
    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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  • 79
    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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  • 80
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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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  • 81
    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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  • 82
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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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  • 83
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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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  • 84
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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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  • 85
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    Plant and soil 173 (1995), S. 205-210 
    ISSN: 1573-5036
    Keywords: citrus ; N mobilization ; N translocation ; 15N ; reserves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The mobilization of N from reserve organs (leaves, roots, branches and trunk) to developing new organs was studied at different moments of the growth cycle. Three-year-old Valencia Late orange trees (Citrus sinensis (L.) Osbeck) were grown individually outdoors in 150 L containers filled with siliceous sand. Trees were irrigated with a nutrient solution labelled with potassium nitrate with an enrichment of 4 atom 15N % excess during a complete growth cycle. At the following year, plants were irrigated with unlabelled nutrient solution, and harvested throughout the growth cycle (flowering, fruit set, second flush, third flush, and dormancy). Total N and 15N analyses were carried out in the different organs of the plants. The highest amounts of N were found in leaves and roots (33–42% and 30–38%, respectively). Distribution of 15N was similar to that obtained for total N (42 and 39% of total 15N in leaves and roots, respectively) as is expected after a long period of labelling. Old leaves were the main reserve organs, contributing a 40–50% of the total N exported. Roots and aerial woody tissues exported between 30–35% and 15–25% of total reserve N, respectively. N exported by old leaves was approximately 57% of the N accumulated during the preceding year, while roots translocated 40% and trunk plus branches 35%. More than 70% of N accumulated in new organs during spring came from N stored in old organs.
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  • 86
    ISSN: 1573-5036
    Keywords: decomposition ; isotope dilution ; 15N ; mineralization ; nodulation ; N use efficiency ; residue management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Alley cropping is being widely tested in the tropics for its potential to sustain adequate food production with low agricultural inputs, while conserving the resource base. Fast growth and N yield of most trees used as hedgerows in alley cropping is due greatly to their ability to fix N2 symbiotically with Rhizobium. Measurements of biological N2 fixation (BNF) in alley cropping systems show that some tree species such as Leucaena leucocephala, Gliricidia sepium and Acacia mangium can derive between 100 and 300 kg N ha-1 yr−1 from atmospheric N2, while species such as Faidherbia albida and Acacia senegal might fix less than 20 kg N ha-1 yr-1. Other tree species such as Senna siamea and S. spectabilis are also used in alley cropping, although they do not nodulate and therefore do not fix N2. The long-term evaluation of the potential or actual amounts of N2 fixed in trees however, poses problems that are associated with their perennial nature and massive size, the great difficulty in obtaining representative samples and applying reliable methodologies for measuring N2 fixed. Strategies for obtaining representative samples (as against the whole tree or destructive plant sampling), the application of 15N procedures and the selection criteria for appropriate reference plants have been discussed. Little is known about the effect of environmental factors and management practices such as tree cutting or pruning and residue management on BNF and eventually their N contribution in alley cropping. Data using the 15N labelling techniques have indicated that up to 50% or more of the tree's N may be below ground after pruning. In this case, quantification of N2 fixed that disregards roots, nodules and crowns would result in serious errors and the amount of N2 fixed may be largely underestimated. Large quantities of N are harvested with hedgerow prunings (〉300 kg N ha-1 yr-1) but N contribution to crops is commonly in the range of 40–70 kg N ha-1 season. This represents about 30% of N applied as prunings; however, N recoveries as low as 5–10% have been reported. The low N recovery in maize (Zea mays) is partly caused by lack of synchronization between the hedgerow trees N release and the associated food crop N demand. The N not taken up by the associated crop can be immobilized in soil organic matter or assimilated by the hedgerow trees and thus remain in the system. This N can also be lost from the system through denitrification, volatilization or is leached beyond the rooting zone. Below ground contribution (from root turnover and nodule decay) to an associated food crop in alley cropping is estimated at about 25–102 kg N ha-1 season-1. Timing and severity of pruning may allow for some management of underground transfer of fixed N2 to associated crops. However many aspects of root dynamics in alley cropping systems are poorly understood. Current research projects based on 15N labelling techniques or 15N natural abundance measurements are outlined. These would lead to estimates of N2 fixation and N saving resulting from the management of N2 fixation in alley cropping systems.
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  • 87
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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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  • 88
    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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  • 89
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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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  • 90
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    Plant and soil 177 (1995), S. 111-126 
    ISSN: 1573-5036
    Keywords: added nitrogen interactions ; Aeschynomene afraspera ; cowpea ; groundnut ; 15N ; nitrogen recovery ; Sesbania rostrata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two field experiments were conducted on farmers' fields in Northeast Thailand to examine the potential of several green manure and short-duration grain legume species as pre-rice green manures. The performance of species mixtures was also investigated. Experiments were conducted under rainfed conditions both with and without recommended applications of lime, P and K fertilizers. 15N-isotope methods were used to estimate N2-fixation in the legumes and N supplied by the legume residues to a following rice crop. When provided with lime, P and K fertilizer, all legumes grew well and fixed 65–85% of their N, amounting to 59–102 kg N ha-1 wihin 90 days. The short-duration groundnut and a mixed Sesbania rostrata and multi-purpose cowpea treatment produced over 4 tonnes ha-1 residue dry weight which contained 135–150 kg N ha-1. In addition groundnut yielded almost 2 tonnes ha-1 of grain, whilst the intercrop yielded 1 t ha-1 of fresh pods of MCP, only 35% less than the sole MCP which only produced 41 kg N ha-1 in its stover. Rice dry weight increases of over 50% were found after several of the legume treatments, and 15N-based estimates indicated up to 18 kg N ha-1 was directly supplied by the legume stover to the rice. Without fertilizer application residue yields of the S. rostrata + multi-purpose cowpea mixed crop were poor (580 kg ha-1) and N2-fixation contributed only 57% of the N accumulated (20 kg N ha-1 fixed). The application of P and K fertilizers was found to approximately double residue yields with the combined addition of lime more than doubling these yields again, resulting in 88% of the legume N derived from N2-fixation (84 kg N ha-1). The following rice recovered 9–17% of the added legume N and the yield response in rice reflected the differences in legume yield. Application of P,K and lime resulted in a fivefold increase in the amount of legume N recovered by rice, indicating the importance of alleviating nutrient deficiencies through fertilizer application if green manures are to be used successfully in Northeast Thailand.
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  • 91
    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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  • 92
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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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  • 93
    ISSN: 1573-5095
    Keywords: aluminumsulfate ; phosphorus ; vesicular-arbuscular mycorrhizal fungi ; Leucaena leucocephala ; reforestation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of 3 species of vesicular-arbuscular mycorrhizal (VAM) fungi on the growth of Leucaena leucocephala (Lam.) De Wit. in a phosphorus-deficient and aluminumsulfate (AIS)-treated medium was investigated in a screenhouse experiment. Plant height, root length, nodulation, phosphorus uptake and nitrogen fixation were used as indices of plant performance. While there were significant differences among mycorrhizal plants with respect to these indices, they outperformed their non-mycorrhizal counterparts in all respects except in nitrogen content. Of the 3 mycorrhizal species studied, Glomus etunicatum (Becker and Gerd) was the most efficient, followed by Glomus fasciculatum (Thaxter) Gerd and Trappe, and finally, Gigaspora margarita (Becker and Hall). Both aluminumsulfate and mycorrhizal treatments increased shoot dry weight.
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  • 94
    ISSN: 1573-515X
    Keywords: budget ; carbon ; mass balance ; Narragansett Bay ; nitrogen ; nutrients ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Narragansett Bay is a relatively well-mixed, high salinity coastal embayment and estuary complex in southern New England (USA). Much of the shoreline is urban and the watershed is densely developed. We have combined our data on C, N, and P inputs to this system, on C, N, and P accumulation in the sediments, and on denitrification with extensive work by others to develop approximate annual mass balances for these elements. The results show that primary production within the bay is the major source of organic carbon (4 times greater than other sources), that land drainage and upstream sewage and fertilizer are the major sources of N, and that landward flowing bottom water from offshore may be a major source of dissolved inorganic phosphorus. Most of the nutrients entering the bay arrive in dissolved inorganic form, though DON is a significant component of the N carried by the rivers. About 40% of the DIN in the rivers is in the form of ammonia. Sedimentation rates are low in most of Narragansett Bay, and it appears that less than 20% of the total annual input of each of these elements is retained within the system. A very small amount of C, N, and P is removed in fisheries landings, denitrification in the sediments removes perhaps 10–25% of the N input, and most of the carbon fixed in the system is respired within it. Stoichiometric calculations suggest that some 10–20% of the organic matter formed in the bay is exported to offshore and that Narragansett Bay is an autotrophic system. Most of the N and P that enters the bay is, however, exported to offshore waters in dissolved inorganic form. This assessment of the overall biogeochemical behavior of C, N, and P in the bay is consistent with more rigorously constrained mass balances obtained using large living models or mesocosms of the bay at the Marine Ecosystem Research Laboratory (MERL).
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  • 95
    ISSN: 1573-0867
    Keywords: model ; pasture ; phosphorus ; RPR ; reactive phosphate rock ; Sechura phosphate rock ; SPR ; superphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A national series of rates × forms of phosphate fertilizer trials has provided a large amount of data on patterns of response of pasture production and soil P tests to forms, rates and frequencies of P fertilizer application over time. A simple mechanistic model of P in pastoral systems has been developed in an attempt to account for the observed patterns. The model considers active P in the soil to be in one of two compartments: undissolved fertilizer P (PF) and a pool of labile, plant-available P (PA). P dissolving from PF enters PA, and P is lost from PA by immobilisation in the soil and by net removal above ground through non-recycled uptake by plants. Both these transfers are taken to follow first order kinetics, with rate constants designated K1 and K2 respectively. Pasture dry matter (DM) production in any year is related to the mid-year value of PA by the diminishing-returns Mitscherlich equation, with nil pasture yield being associated with nil PA. Data from different sites with the same design were combined to give generalised response patterns with which to assess the model. Only the control treatment and treatments receiving triple superphosphate (TSP) and Sechura phosphate rock (SPR) were considered. With a value for K1 corresponding to almost immediate dissolution, the model accounted well for the Olsen soil P test patterns from TSP when K2 corresponded to an annual loss of 16.3% of P in PA and a factor of 10 was used to convert Olsen P to kg P/ha in PA. Pasture DM yield response curves to rates of TSP in individual years were well accounted for when the mid-year value of PA required for 90% relative yield was taken as 130 kg P/ha. The model also accounted well for the difference between response patterns to annual and triennial TSP applications for both soil P tests and DM production. The declines in soil P tests and DM production which occurred in nil P controls were less than model predictions: this could be due to unfertilised pasture making more use of P from greater soil depth or less available forms. Olsen P tests with the higher rates of SPR were always lower than model predictions using a value for K1 derived from chemical measurement of SPR dissolution rates in the trials. However, DM yields from SPR were generally close to model predictions. These divergent results support independent data suggesting that available soil P from reactive phosphate rocks (RPRs) is underestimated by the Olsen P test. The relative success of this simple compartmental model in accounting for generalised response patterns in such a large body of data suggests that it could be a useful starting point for a dynamic P fertilizer recommendation model.
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  • 96
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    Nutrient cycling in agroecosystems 41 (1995), S. 49-57 
    ISSN: 1573-0867
    Keywords: Cameroon ; fertility ; phosphorus ; site characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fertility capability of surface (0–20 cm) soils was evaluated at six sites in the North-West Cameroon highlands. Two main soil groups, designated as Classes A and B, were identified based on elevation. The Class A soils from low elevations (600–1178 m) had higher Ca, Mg, K, pH, sorbed less P and were lower in organic carbon and sesquioxides than the highland (〉 1200 m) soils. Soil acidity (Al saturation 〉 30%) and high P sorption appeared to be the most limiting factors to crop production especially on the Class B soils where the Standard P Requirement exceeded 500 mg kg−1. Phosphorus sorption data were best described by the Freundlich equation. Amorphous aluminium was the most important determinant of solution P concentration (r = 0.85,p 〈 0.001) followed by soil organic carbon, (r = 0.80,p 〈 0.001) at high P rates. Nitrogen deficiency symptoms of maize were pronounced on the Class B soils. Consequently, crop growth and yield were lower on Class B than on Class A soils despite the high organic carbon in B. We hypothesize that the supply of high quality organic material (high in N and low in lignin and polyphenols) at site B through agroforestry and related cropping systems, would improve the fertility of the soil and crop yield.
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  • 97
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    Nutrient cycling in agroecosystems 42 (1995), S. 117-121 
    ISSN: 1573-0867
    Keywords: Cochliobolus miyabeanus ; rice brown leaf spot ; phosphorus ; disease-fertilizer interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Studies have been undertaken in a 1000 ha area of irrigated rice (Oryzica sativa) at Caroni (1975) Limited to determine the effect of the fertilizer programme on the incidence of important diseases. Over a period of three years higher levels of brown leaf spot (Cochliobolus miyabeanus) on rice varieties Oryzica 1 and Oryzica 5 on three different soil types were associated with increasing levels of leaf P, from a low of 0.149% of dry matter (DM) to a high of 0.396% DM. On the Washington silty clay loam series (Inceptisol) brown leaf spot incidence was lowest when leaf P was between 0.135% and 0.149% of DM. However, disease incidence was higher when leaf P levels fell to 0.133% of DM or rose above 0.149%, under conditions where N was more than adequate. The moderate levels of the disease experienced over the period had no effect on yield, as grain infection was minimal. The results support the conclusion that the incidence of brown leaf spot on irrigated rice at Caroni is influenced by sub-optimal levels paticularly of P. Careful monitoring and managememt of P nutrition is seen as an important part in the overall strategy for controlling the disease.
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  • 98
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    Irrigation and drainage systems 9 (1995), S. 259-277 
    ISSN: 1573-0654
    Keywords: drainage ; controlled drainage ; DRAINMOD ; water table management ; model ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The design and management of drainage systems should consider impacts on drainage water quality and receiving streams, as well as on agricultural productivity. Two simulation models that are being developed to predict these impacts are briefly described. DRAINMOD-N uses hydrologic predictions by DRAINMOD, including daily soil water fluxes, in numerical solutions to the advective-dispersive-reactive (ADR) equation to describe movement and fate of NO3-N in shallow water table soils. DRAINMOD- CREAMS links DRAINMOD hydrology with submodels in CREAMS to predict effects of drainage treatment and controlled drainage losses of sediment and agricultural chemicals via surface runoff. The models were applied to analyze effects of drainage intensity on a Portsmouth sandy loam in eastern North Carolina. Depending on surface depressional storage, agricultural production objectives could be satisfied with drain spacings of 40 m or less. Predicted effects of drainage design and management on NO3-N losses were substantial. Increasing drain spacing from 20 m to 40 m reduced predicted NO3-N losses by over 45% for both good and poor surface drainage. Controlled drainage further decreases NO3-N losses. For example, predicted average annual NO3-N losses for a 30 m spacing were reduced 50% by controlled drainage. Splitting the application of nitrogen fertilizer, so that 100 kg/ha is applied at planting and 50 kg/ha is applied 37 days later, reduced average predicted NO3-N losses but by only 5 to 6%. This practice was more effective in years when heavy rainfall occurred directly after planting. In contrast to effects on NO3-N losses, reducing drainage intensity by increasing drain spacing or use of controlled drainage increased predicted losses of sediment and phosphorus (P). These losses were small for relatively flat conditions (0.2% slope), but may be large for even moderate slopes. For example, predicted sediment losses for a 2% slope exceeded 8000 kg/ha for a poorly drained condition (drain spacing of 100 m), but were reduced to 2100 kg/ha for a 20 m spacing. Agricultural production and water quality goals are sometimes in conflict. Our results indicate that simulation modeling can be used to examine the benefits of alternative designs and management strategies, from both production and environmental points-of-view. The utility of this methodology places additional emphasis on the need for field experiments to test the validity of the models over a range of soil, site and climatological conditions.
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  • 99
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    New forests 10 (1995), S. 207-223 
    ISSN: 1573-5095
    Keywords: Fertilization ; foliar analysis ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of thinning and refertilization on growth of Pinus radiata in three experiments planted at 11 960 stems ha−1 were examined. Responses to thinning and refertilization were obtained at 3 or 5 years after planting despite heavy applications of fertilizer at establishment. During the 3 years following retreatment, trees which had been thinned to 2990 stems ha−1 had twice the sectional area increments of unthinned trees, while up to a 3-fold increase in increment was obtained on trees which had been thinned and refertilized. Responses to nitrogen were obtained in all experiments. Response to phosphate was dependent upon soil type and prior treatment. Foliar analyses do not appear to be reliable for predicting responses to fertilization applied in combination with thinning.
    Type of Medium: Electronic Resource
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  • 100
    ISSN: 1573-5087
    Keywords: 2-Chloroethyltrimethyl ammonium chloride ; gibberellin A3 ; Solanum tuberosum L. ; tuberization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cuttings of potato shoots treated with the plant growth retardant 2-chloroethyltrimethyl ammonium chloride (CCC) form tubers earlier and have less biologically-active gibberellin (GA)-like substances in the roots than control cuttings. The major GA-like substance in roots of potato cuttings was identified as GA3 by gas-chromatography-mass spectrometry (GC-MS). The content of GA3 in roots of control cuttings, estimated by GC-MS-selected ion monitoring (SIM) using [17, 17-2H]GA3 as a quantitative internal standard, was 38.8 ng per g fresh weight (fw), and in roots of CCC-treated cuttings, in which tuberization was promoted, was 0.6 ng per g fw. Gibberellin A1, GA8 and GA20 were also indicated as minor components of roots from both control and CCC-treated cuttings. The comparatively high GA3 content in roots of control cuttings might be the ‘root factor’ responsible for delaying tuberization in potato.
    Type of Medium: Electronic Resource
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