ALBERT

Notes: The gene gdhA from Escherichia coli, that encodes a NADPH-dependent glutamate dehydrogenase (GDH), directs a novel pathway in transgenic plants that allows an increase in ammonium assimilation. Glufosinate leads to plant death by the irreversible inhibition of glutamate synthetase (GS) leading to a disruption of subsequent GS-related processes resulting in elevated ammonium and disruption of photorespiration. Therefore, it was speculated that the gdhA-transformed plants may exhibit a novel mechanism of resistance to glufosinate by altered activity of the GDH-directed pathway(s) and subsequently related processes. Studies were conducted in the greenhouse to evaluate the resistance of tobacco plants containing the gdhA gene to glufosinate. Five tobacco genotype lines were investigated including a non-transformed control line, a positive control line and three transformed lines with levels of increasing GDH activity directed by the gdhA gene. Plants transformed with the gdhA gene expressed up to six times increased level of resistance (GR50) to glufosinate compared with the non-transformed control, which is 100 times less resistant than plants transformed with the bar gene. The GDH activity among lines was highly correlated (r2 = 0.9903) with the level of herbicide resistance. Thus, the use of the E. coli gdhA gene in plant transformations can provide an additional mechanism for resistance to glufosinate.

Notes: The joint action of binary mixtures of the amino acid biosynthesis-inhibiting herbicides glyphosate, glufosinate-ammonium, metsulfuron-methyl and imazapyr was assessed in pot experiments applying the Additive Dose Model (ADM). Plants of Sinapis arvensis or S. alba were sprayed with seven doses of the herbicides alone and binary fixed-ratio mixtures of the four herbicides. In total, 73 binary mixtures were studied in six separate experiments. Mixtures of glyphosate and glufosinate-ammonium were less phytotoxic than predicted by ADM whether commercial formulations or technical grade products were applied. In contrast, mixtures of glyphosate and metsulfuron-methyl, glyphosate and imazapyr, glufosinate-ammonium and metsulfuron-methyl, glufosinate-ammonium and imazapyr, and metsulfuron-methyl and imazapyr either followed ADM or were synergistic. Synergism was observed most frequently for mixtures of glyphosate or glufosinate-ammonium with metsulfuron-methyl. Synergism was also more pronounced for commercial formulations of glyphosate and glufosinate-ammonium than for the corresponding technical grade formulations, implying that synergism was caused by the presence of the formulation constituents of the commercial glyphosate and glufosinate-ammonium formulations in the spray solution.

Notes: Experiments evaluated the effect of glyphosate rate and Anoda cristata density, on crop and weed biomass and weed seed production in wide (70 cm) and narrow rows (35 cm) glyphosate-resistant soyabean (Glycine max). Soyabean density was higher at 35 cm row spacing as an increase in planting rate in narrow-row soyabean is recommended for producers in Argentina. Soyabean biomass at growth stage V4 (four nodes on the main stem with fully developed leaves beginning with the unifoliate leaves) was higher when grown on narrow than in wide-rows but was not affected by the presence of A. cristata. At growth stage R5 (seed initiation – seed 3 mm long in a pod at one of the four uppermost nodes on the main stem, with a fully developed leaf and full canopy development), crop biomass was greater in narrow rows compared with wide rows with 12 plants m−2 of A. cristata. In narrow-row soyabean, a single application of a reduced rate of glyphosate maintained soyabean biomass at R5 and provided excellent weed control regardless of weed density. In wide-row soyabean control was reduced at the high weed density. Regardless of row spacing, A. cristata biomass and seed production were severely reduced by half of the recommended dose rate of glyphosate but the relationship between biomass and seed production was not altered. Glyphosate rates as low as 67.5 g a.e. ha−1 in narrow rows or 540 g a.e. ha−1 in wide rows provided excellent control of A. cristata. To minimize glyphosate use, planting narrow-row soyabean are effective where A. cristata density is low.

Notes: Although adult Rumex obtusifolius are problematic weeds, their seedlings are poor competitors against Lolium perenne, particularly in established swards. We investigated the possibility of using this weakness to augment control of R. obtusifolius seedlings with combinations of Gastrophysa viridula (Coleoptera: Chrysomelidae) and the rust fungus Uromyces rumicis. Rumex obtusifolius seedlings were grown in competition with L. perenne sown at different rates and times after R. obtusifolius: they competed successfully with L. perenne when sown 21 days before the grass. Sowing both species at the same time resulted in a dominant grass sward, with R. obtusifolius becoming dominant when sown 42 days prior to L. perenne. Grass sowing rate had no effect on R. obtusifolius growth or biomass. A second experiment investigated how competition from L. perenne sown 21 days after R. obtusifolius combined with damage from G. viridula and/or U. rumicis (applied at either the 3–4- or 10–13-leaf stage, or at both stages) affected the growth and final biomass of R. obtusifolius. Beetle grazing at the latter leaf stage was the only treatment that reduced R. obtusifolius biomass, although rust infection at the earlier application led to an increase in shoot and root weight. The results are discussed in terms of the potential for use of these agents in the field.

Notes: Weed beet populations growing in each crop of the arable rotation could be a relay for the gene flow from adjacent transgenic herbicide-resistant sugarbeet. In this study, weed beet growth and reproduction were assessed under several conditions which could be found in the rotation: various weed beet densities (ranging from 1 to 120 plants m−2) and various crops (winter wheat, spring barley, spring pea, sugarbeet, maize, ryegrass). Measurements were carried out both on life-cycle dynamics (bolting time, time to flowering onset, dynamics of flower opening) and on other quantitative data (survival rate, bolting rate and pollen, flower and seed production). Increasing weed beet density resulted in decreases in bolting rate and flower and seed production per plant. In cereals, weed beet establishment and reproduction were strongly reduced, compared with bare ground as a control situation. In pea, there was no effect on establishment, but the early harvest limited seed set. In the other crops, flower and seed production were reduced to a lesser extent. Parameters of the fitted equations on the bolting and flowering progress were modified by the weed beet density and by the crop. Our data may be used in a model predicting weed beet demographic evolution according to cropping system, and in assessing gene flow.

Notes: Amaranthus hybridus L. populations (A, B and C) obtained from escapes in Massac County and Pope County fields in southern Illinois, USA were subjected to greenhouse and laboratory experiments to measure multiple resistance to triazine and acetolactate synthase (ALS)-inhibiting herbicides and cross-resistance between sulfonylurea and imidazolinone herbicides. Phytotoxicity responses of the three populations revealed that only population B exhibited multiple resistances to triazine and ALS-inhibiting herbicides. This population was 〉167-, 〉152- and 〉189-fold resistant to atrazine, imazamox and thifensulfuron, respectively, at the whole plant level compared with the susceptible population. Population A was only resistant to triazines and population C was only resistant to ALS-inhibiting herbicides. Results from in vivo ALS enzyme and chlorophyll fluorescence assays confirmed these findings and indicated that an altered site-of-action mediated resistance to both triazine and ALS-inhibiting herbicides. Gene sequencing revealed that a glycine for serine substitution at residue 264 of the D1 protein, and a leucine for tryptophan substitution at residue 574 of ALS were the causes of resistance for the three populations.

Notes: Low temperatures may inhibit dormancy break in seeds of winter annuals, therefore it was hypothesized that seeds of Capsella bursa-pastoris and Descurainia sophia that mature at high latitudes in late summer–early autumn would not germinate until they had been exposed to high summer temperatures. Consequently, germination would be delayed until the second autumn. Most freshly matured seeds of both species collected in August and September in southern Sweden were dormant. After 3 weeks of burial at simulated August (20/10°C) and September (15/6°C) temperatures, 28 and 27%, respectively, of the C. bursa-pastoris and 56 and 59%, respectively, of the D. sophia seeds germinated in light at 15/6°C. In contrast, in germination phenology studies conducted in Sweden, only a few seeds of either species germinated during the first autumn following dispersal. However, there was a peak of germination of both species the following spring, demonstrating that dormancy was lost during exposure to the low habitat temperatures between late summer and early autumn and spring. Nearly 100% of the seeds of both species subjected to simulated annual seasonal temperature changes were viable after 30.5 months of burial. In the burial study, exhumed seeds of C. bursa-pastoris were capable of germinating to 98–100% in light at the simulated spring–autumn temperature regime (15/6°C) in both spring and autumn, while those of D. sophia did so only in autumn. In early spring, however, seeds of D. sophia germinated to 17–50% at 15/6°C. Thus, most seeds of these two annual weeds that mature in late summer do not germinate in the first autumn, but they may do so the following spring or in some subsequent autumn or spring.

Notes: The invasive ability of Cynodon dactylon is dependent on self dispersal and on cultivation practices. Tillage can seriously change patch biomass and spatial structure, spreading vegetative propagules of the weed. The objectives of this study were: (i) to quantify the effect on non-inversion tillage on dispersal, establishment and colonization of C. dactylon and (ii) to propose a simple model considering soil cultivation effects and light availability on spatial growth of weed patches. Two experiments were carried out, exploring different soils and environmental conditions. Spatial distribution of vegetative units differed when tillage was conducted with different non-inversion implements and could be described by simple functions. A minimum patch biomass seems necessary before vegetative structures are vulnerable to movement by cultivation. Only a small proportion of the biomass dispersed from original patches was able to establish. However, simulation showed that the area colonized by C. dactylon mostly increased by means of tillage dispersal, both with and without crop competition, in one growing cycle. It appears sensible to consider changing cultivation practices to reduce weed dispersal and to use crop competition for light to create unsuitable habitats limiting weed colonization.

Notes: This paper considers the relationships between the dispersal of seeds and the distribution pattern of an annual weed. A comparative study of seed dispersal by combine harvesters, with and without a straw chopper attached, was established using Lolium rigidum, a common weed in Mediterranean cereal crops. Seed dispersal distance was quantified and the relationships between dispersal and fine-scale seedling distribution evaluated. Primary dispersal of L. rigidum seeds occurs in a very limited space around the parent plants, but the density of seed is low because most seeds do not fall from spikes spontaneously. In contrast, many seeds are spread by combine harvesters. In this study the maximum dispersal exceeded 18 m from established stands in cereal fields, although the modal distance was close to the origin. In addition, the action of the combine harvesters tended to accumulate L. rigidum seeds predominantly under the straw swath, with some lateral movement. This action could explain the fine-scale banded pattern of L. rigidum in cereal fields. Although the treatment of straw by the standard and straw chopper combines differed, the resultant seed distribution showed few differences.

Notes: Striga hermonthica is a major biotic constraint to sorghum production in Nigeria, sometimes causing total yield loss. Recommendations for Striga management often include the use of cultural and agronomic practices, herbicides and host plant resistance when available. The use of biological control has not been commercialized. Fusarium oxysporum (isolate PSM 197)-based mycoherbicide was used in combination with selected sorghums (the Striga-resistant cultivar Samsorg 40, and the Striga tolerant landrace Yar'ruruka) as an Integrated Striga Management strategy (ISM) in on-farm trials in the Sudano-Sahelian savanna of Nigeria. Crop stands were significantly (P = 0.05) higher in ISM compared with non-ISM plots on which the mycoherbicide was not applied. Similarly, ISM plots had significantly (P = 0.05) lower Striga counts than non-ISM plots. Striga emergence was reduced by ISM by around 95%. Sorghum yields were 49.6% higher where integrated management was used. Cost benefit analysis of the ISM package shows that use of the mycoherbicide increased the profitability of sorghum production on Striga-infested soils. Farmers’ preferences monitored during and after the trials highlighted the need for careful selection and integration of control components into an ISM package.

Notes: An accession of Camelina microcarpa suspected to be resistant to sulfonylurea herbicides was identified in Oregon in 1998 field experiments. Greenhouse research confirmed that the putative resistant biotype was resistant to chlorsulfuron and metsulfuron on a whole plant level. Compared with the resistant (R) biotype, the susceptible (S) biotype was 1000 and 10 000-fold more sensitive to metsulfuron and chlorsulfuron respectively. The R biotype was also resistant to other sulfonylurea, sulfonylaminocarbonyl-triazolinone, imidazolinone and triazolopyrimidine herbicides. An in vivo enzyme assay indicated that acetolactate synthase (ALS) from the R plants required 111 times more chlorsulfuron to inhibit activity by 50% compared with the amount required to have a similar effect on ALS from S plants. Analysis of the nucleotide and amino acid sequences demonstrated that a single-point mutation from G to T in the als1 gene conferred the change from the amino acid tryptophan to leucine at position 572 in the resistant biotype. This research confirmed that ALS inhibitor resistance in an Oregon accession of C. microcarpa is based on an altered target site conferred by a single-point mutation.

Notes: As one of the worst invasive weeds in the world, Mikania micrantha H. B. K. spread to southern China after 1910 but without any natural enemies. Since the 1980s it has started to spread and invade widely. The weed has caused significant damage to many ecosystems in Guangdong province in recent years. This paper reviews the research in China on this weed, including its description, history of introduction together with information from morphological and physiological studies. The distribution of this invasive plant in China has been mapped and is presented together with damage being caused and analyses of soil types infested. The measures taken by the Chinese government for prevention and elimination are also discussed. Chinese scientists are now looking for effective biocontrol options to deal with this deleterious plant. Several native insects, mites and fungi have been reported to be able to control the reproduction of this weed in China, but no natural control has been achieved. Cuscuta sp., a native autoecious vine has recently been shown to suppress the growth of M. micrantha. Three major causes for the massive spread of this weed in southern China are presented together with recommendations for future control activities.

Notes: Categorical variables such as water table status are often predicted using the indicator kriging (IK) formalism. However, this method is known to suffer from important limitations that are most frequently solved by ad hoc solutions and approximations. Recently, the Bayesian Maximum Entropy (BME) approach has proved its ability to predict categorical variables efficiently and in a flexible way. In this paper, we apply this approach to the Ooypolder data set for the prediction of the water table classes from a sample data set. BME is compared with IK using global as well as local criteria. The inconsistencies of the IK predictor are emphasized and it is shown how BME permits avoiding them.

Notes: Organotin compounds (OTC) are deposited from the atmosphere into terrestrial ecosystems and can accumulate in soils. We studied the adsorption and desorption of methyltin and butyltin compounds in organic and mineral soils in batch experiments. The adsorption and desorption isotherms for all species and soils were linear over the concentration range of 10–100 ng Sn ml−1. The strength of OTC adsorption correlated well with the carbon content and cation exchange capacity of the soil and was in the order mono- 〉 di- 〉 tri-substituted OTCs and butyltin 〉 methyltin compounds. The OTC adsorption coefficients were much larger in organic soils (Kd 〉 104) than in mineral soils. The adsorption and desorption showed a pronounced hysteresis. Trimethyltin adsorption was partly reversible in all soils (desorption 2–12% of the adsorbed amounts). Dimethyltin, tributyltin and dibutyltin exhibited reversible adsorption only in mineral soils (desorption 4–33% of the adsorbed amounts). Mono-substituted OTCs adsorbed almost irreversibly in all soils (desorption 〈 1% of adsorbed amounts). Trimethyltin was more mobile and more bioavailable in soils than other OTCs. It might therefore be leached from soils and accumulate in aquatic ecosystems. The other OTCs are scarcely mobile and are strongly retained in soils.

Notes: A transfer-function method is proposed to determine transport parameters from solute breakthrough data. The method is based on the assumptions that a linear process governs the transport of solute through soil and that the soil is homogeneous. It needs breakthrough data at two different vertical locations from a pulse input of solute to the soil. The method predicts the response by convoluting the input with the transfer function in the time domain.Solute breakthrough data were measured in unsaturated soil columns by time-domain reflectometry (TDR). An experimental soil column was placed over a supporting column filled with sandy soil. A constant hanging water table, maintained in the lower column, created suction in the upper column and maintained unsaturated conditions. A solution of calcium chloride (CaCl2) was spread over the soil in the upper column during steady flow of water in the column. Resident concentrations of solute in terms of electrical conductivity were measured at two depths by TDR sensors.We analysed breakthrough curves of CaCl2 in 81 experiments to determine the transport parameters in coarse sand, sandy loam soil and clay loam soil by the transfer-function method. The transport parameters obtained were compared with those determined by the widely used deterministic equilibrium model of the CXTFIT program. The transfer-function method provided a better fit between the measured and estimated breakthrough curves in almost all cases and resulted in stable values of the parameters. The method is robust against small errors in measurements. It is a mathematically sound and efficient method for analysing breakthrough data.

Notes: Lime, gypsum and various gypsum-like by-products have long been applied to soil surfaces as ameliorants of soil acidity and aluminium and manganese toxicity. We examined changes in chemical and mineralogical properties at two different depths in two acid soils one year after the application of gypsum, phosphogypsum + dolomitic residue, red gypsum + dolomitic residue, sugar foam, and sugar foam + mined gypsum. All treatments were found to increase the proportion of Ca2+ and decrease those of Al3+ and Mn2+ in the exchange complex of the surface and subsurface horizons, thus reducing its effective Al and Mn saturation. However, the mined gypsum treatment resulted in losses of Mg2+ from the Ap horizon of the soils, and the sugar foam treatment was not so effective with the AB horizons as the other treatments. The combined application of both gypsum-like by-products and the dolomitic residue proved the most effective choice with a view to reducing the effective Al and Mn saturation of the exchange complex in the Ap and AB horizons. In addition, both treatments reduced Mg2+ losses at both depths. Finally, all treatments resulted in the formation and retention on mineral and organic surfaces of a large fraction of the Al3+ released by exchange with Ca2+ as Al polymers. This is quite consistent with the observed changes in the CuCl2-, oxalate- and DTPA-extractable Al contents as well as by SEM and EDS analyses. Based on these results, the use of the appropriate mixtures of these by-products is an effective alternative to that of mined gypsum and lime to alleviate soil acidity and reduce toxic concentrations of Al3+ and Mn2+ in agricultural acid soils.

Notes: One mechanism in the restoration of severely degraded soil by vegetation might be the movement of dissolved organic carbon (DOC) to macropore and aggregate surfaces. We propose that this lowers the soil wetting rate and subsequently its slaking resistance by creating a partially hydrophobic surface. In this study, we determined how wetting and drying (w/d) cycles redistribute DOC to soil surfaces, and how DOC affects hydrophobicity where it accumulates, in relation to the soil surface area to volume ratio and to different types of vegetation planted to restore a severely degraded soil. Repacked soil cores that simulate different soil aggregate sizes were tested. The results showed that w/d cycles increase surface DOC concentration through a depletion of DOC in the interior of the soil. Correspondingly, w/d cycles enhanced hydrophobicity, measured as a water repellency index, R, from 1.5–2.3 to 3.6–7.6, the values affected significantly by the type of vegetation. This index (R) did not change for a control soil with no vegetation. The link between the amount of DOC and water repellency was weak (coefficient of determination r2 = 0.06–0.26), indicating that DOC quality was probably more important than its quantity. Although increasing the core size resulted in a greater accumulation of DOC on the drying surface of the core, the impact of this on water repellency was minimal. Incubation caused a decrease in the amount of DOC, but had minimal influence on water repellency. This work improves the understanding of changes in soil wetting and soil stabilization under processes of natural weathering and vegetation restoration.

Notes: This paper describes the conditions for dispersion and flocculation of clays, and the impact of this process on soils of contrasting textures cropped with rice. Clay seems to be translocated down the profiles and along a topographic sequence. The clays are mixed kaolinite–smectite. The cation exchange capacity of these clays exceeds 20 cmolc kg−1. Both the proportion of smectite and clay content increase with increasing depth and from the top to the lower part of the sequence. The pH ranges from 5 to 8. The aluminium oxide content is small. The soil solutions collected during the rainy season were analysed for Fe2+ and major cations. We calculated the sodium adsorption ratios (SAR) taking into account Fe2+ and compared them with the critical coagulation concentration (CCC) found in a previous study. The Fe2+ contributed to a decrease in the SAR of cropped soils. The comparison between SAR, total electrolyte concentrations and CCC values showed that the dispersible clays are likely (i) to disperse in the abandoned and non-saline fields, (ii) to flocculate in the saline and uncropped soils as a result of the large salt content and in the cropped soils because of either large salt or Fe2+ content, and (iii) to disperse in the flood water and at the surfaces of abandoned fields under rain. No evidence for ferrolysis was found. The observed contrasting textures and clay mineralogy can be explained by clay translocation controlled by salinity and rice farming.

Notes: Our aim was to study the effects of C (as glucose and artificial rhizodeposits) on S immobilization, in relation to microbial biomass-S and soil arylsulphatase (ARS) activity, in contrasting soils (a calcareous and an acid brown soil). The glucose-C and artificial rhizodeposit-C with or without cysteine were added at six rates (0, 100, 200, 400, 600 and 800 mg kg−1 soil) to the two soils and then incubated with Na235SO4 for 1 week prior to analysis. The percentages of 35S immobilized increased when C as glucose and rhizodeposit (without cysteine) were added to both soils. With cysteine-containing rhizodeposit, the percentages of 35S immobilized remained relatively stable (23.5% to 29.9%) in the calcareous soil, but decreased in the acid brown soil (52.7% to 31.5%). For both soils, cysteine-containing rhizodeposit additions showed no significant correlation between immobilized-35S and microbial biomass-35S, suggesting that microorganisms immobilized cysteine-S preferentially instead of 35S from the tracer (Na235SO4). In the calcareous soil, a positive and significant correlation was found between ARS activity and microbial biomass-35S (r = 0.85, P 〈 0.05) when glucose was added. We also saw this correlation in the acid brown soil when rhizodeposit-C without cysteine was added (r = 0.90, P 〈 0.05). Accordingly, the results showed the presence of extracellular arylsulphatase activity of 48.7 mg p-nitrophenol kg−1 soil hour−1 in the calcareous soil and of 27.0 mg p-nitrophenol kg−1 soil hour−1 in the acid brown soil.

Notes: Soils of the urban area of Sevilla have been scarcely studied, especially concerning their concentrations of potentially toxic metals. A previous paper has shown that moderate pollution exists in soils from some public green areas of the city, and a common pattern was found in the distribution of the concentrations of some particular metals. The present paper is aimed at (i) determining possible seasonal changes in the measured concentrations; (ii) checking possible effects of the observed pollution on plant metal contents, and (iii) finding possible relations between metals by statistical techniques.Samples of 35 soils from the urban area of Sevilla were studied. Comparison with previous data shows that samples from a depth of 0–20 cm are representative of the measured soil properties for the city. We show that in most cases differences in the EDTA- and aqua regia-extractable metal contents between autumn 2000 and summer 2001 are not significant. Only Zn shows significant decreases (P 〈 0.05), probably because it is more mobile than the other metals studied. Electrical conductivity and pH also show significant changes related to leaching of soluble salts. We found a strong association between ‘urban’ metals (as defined in the literature) and organic matter, as shown by factor analysis, whereas ‘non-urban’ metals could be related to clay and carbonate contents, perhaps coming from the soil parent materials. The behaviour of the urban metals means that organic matter contributes to their accumulation, either by retention of the incoming metals from the atmosphere, dust or various human activities, or from addition of organic amendments that might provide significant amounts of such metals. Although concentrations of Cu, Pb and Zn at several sites exceeded the limits established elsewhere as acceptable in residential areas, the values in the grass were less than those considered as normal in the literature. This implies that fairly large concentrations in the soil do not necessarily make metals more available.

Notes: The adsorption of phosphate by soil minerals controls availability of P to plants, but the chemical environments of adsorbed phosphate are poorly known. We used 31P MAS NMR to study the adsorption of phosphate on to boehmite (γ-AlOOH) and γ-Al2O3 with large surface areas. The solid phases were reacted in 0.1 m phosphate solutions at pH from 3 to 11 and in solutions with pH 5 at concentrations from 10−1 m to 10−4 m. The spectra suggested three different phosphate environments: (i) orthophosphate precipitated from the residual solution after vacuum filtering, (ii) surface-adsorbed phosphate in inner-sphere complexes, and (iii) Al-phosphate precipitates on the surfaces of the minerals. The chemical shifts of both the inner-sphere complexes and surface precipitates became progressively less shielded with increasing pH and decreasing concentration of phosphate solution. For the inner-sphere complexes, we interpret these changes to be the result of decreasing phosphate protonation combined with rapid proton exchange among phosphate tetrahedra with different numbers of protons, which causes peak averaging. The chemical shifts of 31P of the Al-phosphate precipitates were more negative than those of the surface phosphates at a given pH and solution concentration, probably because of a larger number of P–O–Al linkages per tetrahedron. The observed trend of decreasing shielding is probably due to the decreasing average number of P–O–Al linkages per tetrahedron combined with decreasing protonation and an increasing number of K+ next-nearest neighbours. Even at small concentrations of phosphate solution, a significant amount of Al-phosphate precipitate was present.

Notes: Interactions with dissolved organic matter (DOM) are generally believed to play a crucial role in the translocation of Al and Fe in acid sandy soils. Binding of Al and Fe to DOM affects their mobility in soils by altering sorption equilibria of charged sites on solid soil material, inducing precipitation of organo-metallic complexes and preventing the formation of inorganic Al and Fe phases. The relative importance of the different processes, especially with respect to the translocation of Al, Fe and organic matter in podzols, remains unresolved. We determined the effect of the presence of solid soil material from the eluvial (AhE and AE, respectively) horizons of a Fimic Anthrosol and a Haplic Podzol on the metal-to-organic carbon (M/C) ratio in solution and the formation of dissolved organic Al and Fe complexes. Furthermore, we assessed the resulting influence on the mobilization of Al, Fe and DOM. Even under considerable metal loading, the M/C ratios and ‘free’ metal fractions in solution remained low and relatively constant, due to an apparent buffering by the solid phase and the formation of organo-metal complexes in solution. The M/C ratios remained so low that significant precipitation of organo-metal complexes due to saturation with metals was not found. The apparent buffering by the solid phase can be explained by a strong release of organic matter from solid soil material and adsorption of non-complexed Al and Fe on solid organic matter upon metal addition. Adsorption of organo-metal complexes most likely played only a minor role. The observations confirm the expected mobilization of Al, Fe and DOM in eluvial horizons and seem to indicate that even under fluctuating input of Al, Fe and DOM the soil solution will have a constant composition with respect to M/C ratios and percentage of Al and Fe present in dissolved organo-metal complexes.

Notes: Freezing and thawing influence many physical, chemical and biological processes in soils, including the production of trace gases. We studied the effects of freezing and thawing on three soils, one sandy, one silty and one loamy, on the emissions of N2O and CO2. We also studied the effect of varying the water content, expressed as the percentage of the water-filled pore space (WFPS). Emissions of N2O during thawing decreased in the order 64% 〉 55% 〉 42% WFPS, which suggests that the retardation of the denitrification was more pronounced than the acceleration of the nitrification with increasing oxygen concentration in the soil. However, emissions of N2O at 76% WFPS were less than at 55% WFPS, which might be caused by an increased ratio of N2/N2O in the very moist conditions. The emission of CO2 was related to the soil water, with the smallest emissions at 76% WFPS and largest at 42% WFPS. The emissions of CO2 during thawing exceeded the initial CO2 emissions before the soils were frozen, which suggests that the supply of nutrients was increased by freezing. Differences in soil texture had no marked effect on the N2O emissions during thawing. The duration of freezing, however, did affect the emissions from all three soils. Freezing the soil for less than 1 day had negligible effects, but freezing for longer caused concomitant increases in emissions. Evidently the duration of freezing and soil water content have important effects on the emission of N2O, whereas the effects of texture in the range we studied were small.

Notes: Classical chemical fractionation of soil sulphur (S) into HI-reducible S and carbon-bonded S does not separate S in soil into fractions that have differing mineralization potentials. Other techniques are needed to separate organic S into more labile and less labile fractions of biological significance, irrespective of their bonding relations. We have sequentially fractionated soil S and carbon (C) into their ionic forms released onto ion-exchange resins and organic S and C extracted in alkali of increasing concentration. We evaluated the technique on pasture and arable soils that had received various fertilizer and cultivation treatments. Total S and C were greater in the soil of the fertilized pasture than in that of the unfertilized pastures. Continuous arable cropping decreased total soil S and C, whereas restoration to pasture caused an accumulation.Resin, 0.1 m NaOH, 1 m NaOH and residual fractions accounted for between 1–13%, 49–69%, 4–16% and 19–38% of total soil S and between 5–6%, 38–48%, 5–7% and 46–53% of total soil C, respectively. Among different S and C fractions, the size of the 0.1 m NaOH and residual fractions changed more with the change in land use and management. The 0.1 m NaOH fraction had a narrower C:S ratio (50–75:1) than did the residual fraction (96–141:1). The significant degree of change in these two fractions, caused by differences in land management, indicates that they may be useful indicators of change in ‘soil quality’.

Notes: Loss of phosphorus (P) from agriculture contributes to the eutrophication of surface waters. We have assessed the magnitude and controls of P leaching and the risk of colloid-facilitated transport of P from sandy soils in Münster. Concentrations of soluble reactive P in drainage water and groundwater were monitored from 0.9 to 35 m depth. Total P concentrations, P saturation, and P sorption isotherms of soil samples were determined. Concentrations of dispersible soil P and colloidal P in drainage water and groundwater were investigated. The concentrations of soluble reactive P in drainage water and groundwater were close to background concentrations (〈 20 µg P l−1). Median concentrations in excess of 100 µg P l−1 were found down to 5.6 m depth at one of four research sites and in the lower part of the aquifer. Experimentally determined equilibrium concentrations and the degree of P saturation were good predictors of P concentrations of drainage water. Large concentrations of dispersible P were released from soil with large concentrations of oxalate-extractable P and addition of P induced further dispersion. Colloidal P was transported in a P-rich subsoil when there was a large flow of water and after nitrate had been flushed from the soil profile and total solute concentrations were small. We conclude that the concentration of soluble reactive P in drainage water is controlled by rapid adsorption in the sandy soils. Subsurface transport of dissolved P contributes substantially to the loss of P from the soils we investigated. Accumulation of P in soils increases the risk of colloid-facilitated leaching of P.

Notes: The partitioning of chemical elements between the solid and solution phases in soil is fundamental in understanding processes such as leaching and bioavailability. Here I present a model in which the partitioning of Cd, Al and carbon in both mineral and organic soils can be simulated in the pH range 2–8. A two-phase additivity approach simulates ion adsorption by the soils using a hydrous ferric oxide and humic type surface. A model for the partitioning of soil humic matter has also been developed in which the NICA–Donnan model calculates humic surface charge. Other key processes represented include mineral solubilization and solution speciation.Methods for deriving model input parameters either from analytical data or by parameter optimization were used. Acid ammonium-oxalate-extractable Fe was used to estimate the amount of hydrous ferric oxide, and reactive humic substances were estimated by a scaled down version of the International Humic Substances Society method for the extraction of humic and fulvic acid. For initial calculation the 0.1 m HCl-extractable Al was used to estimate reactive Al. Optimization of reactive Al improved the fit of both the total dissolved Al data and the adsorbed Cd. The model for the solid–solution partitioning of humic substances could simulate reasonably well the release of carbon in the pH range 4–8 for both the organic and mineral soils.

Notes: Overland flow resulting from an excess of rain over infiltration is an essential component of many models of runoff and erosion from fields or catchments. The spatially variable infiltration (SVI) model and a set of associated equations relating depth of runoff and maximum rate of ‘effective’ runoff (as used in the GUEST erosion model) to storm depth, depth-averaged intensity of rainfall, average maximum infiltration capacity and an additional amount of initial infiltration were validated and tested on back-sloping bench terraces in volcanic upland West Java, Indonesia. Data used were runoff rate and depth from 31 small (1.0–8.2 m2) bounded plots representing sections of terrace beds or risers and from six larger (53–231 m2) terrace units with hydrologically defined boundaries. Modelled runoff rates using rainfall intensity data corresponded well with observed patterns and the storm-based equations were used successfully to model runoff depths and maximum effective runoff rates for individual events. Resulting values for maximum average infiltration rate (Im) varied between 18 and 443 mm hour−1 and reflected effects of vegetation or mulch cover and soil compaction. We conclude that the SVI model and the derived equations provide a robust and accurate method for predicting runoff at the investigated scale.

Notes: Spin counting on solid-state 13C cross-polarization (CP) nuclear magnetic resonance (NMR) spectra of two humic fractions isolated from tropical lowland soils showed that only 32–81% of potential 13C NMR signal was detected. The observability of 13C NMR signal (Cobs) was higher in the mobile humic acid (MHA) than in the calcium humate (CaHA) fraction, and increased with increasing intensity of irrigated rice cropping. NMR observability appeared to be related to the nature of the organic carbon, with phenol- and methoxyl-rich samples having the higher values of Cobs. The Bloch decay (BD) technique provided more quantitatively reliable 13C NMR spectra, as evidenced by values of Cobs in the range 91–100% for seven of the eight humic fractions studied. The BD spectra contained considerably more aryl and carbonyl signal, and less O–alkyl and alkyl signal, with the greatest differences between CP and BD spectra observed for the samples with low Cobs(CP). The causes of low CP observability were investigated using the spectral editing technique RESTORE ( REstoration of Spectra via TCH and T One Rho (T1ρH) Editing). Rapid T1ρH relaxation was found to be primarily responsible for the under-representation of carbonyl carbon, whereas inefficient cross-polarization was primarily responsible for the under-representation of aryl carbon in CP spectra. Proton NMR relaxation rates T1H and T1ρH were found to correlate with other NMR properties and also with cropping management. Non-uniform rates of T1H relaxation in two of the CaHA fractions enabled the generation of proton spin relaxation editing subspectra.

Notes: Potential risks for human health and adverse effects on soil quality caused by accumulation of cadmium (Cd) in soil at concentrations around or exceeding current European Union (EU) permitted limits have long been recognized. We have assessed availability and partitioning of Cd in a Mediterranean calcareous soil under four management regimes. Cadmium was added as a single pulse of CdSO4 at the maximum Cd concentration established by the EU for sludge-amended agricultural soils and concentrations exceeding the mandatory limits. Soils were treated with 0, 3, 10 and 50 mg Cd kg−1 soil, incubated moist and analysed at selected times up to 600 days. Cadmium availability and distribution in soil were studied by neutral electrolyte and sequential extractions. During the incubation, the availability of Cd was not strictly dependent on the amount of metal added as the exchangeable fractions were similar shortly after the additions of Cd regardless of its initial concentration. Sequential extractions showed that for concentrations of 3 and 10 mg Cd kg−1 soil Cd was evenly distributed among the soil phases, and its mobility was reduced mainly by adsorption on carbonates. At Cd concentrations exceeding 10 mg Cd kg−1 soil a residual fraction appeared, perhaps from precipitation of Cd. Most of the Cd was associated with carbonates; land management and organic matter content had no major effects on the Cd distribution among different soil phases. The extraction protocols were effective for studying the fate of Cd in this calcareous soil as almost all of the Cd added was recovered. However, the introduction of a preliminary step with buffered NH4NO3 improved the determination of the most labile pools. Availability of Cd in calcareous soils estimated with reference methods appeared to be very small even when its total concentration far exceeded the current EU limits.

Notes: The direct application of Sokoto phosphate rock to restore phosphorus in the savanna soil of Nigeria has not been very successful. The dissolution of Sokoto phosphate rock was investigated in three electrolyte solutions – 0.01 m CaCl2, NaCl and KCl – at pH range 3.5–7.0 under laboratory conditions to provide solubility and kinetic data that are required to develop guidelines for direct application in the field. The phosphate rock dissolved in the salt solutions in the order KCl 〉 NaCl 〉 CaCl2. Particle size and ionic strength had no significant effect on the dissolution. The standard free energy of reaction ΔG°R in an acidic solution with no basic cations was −38 kJ mol−1. If Ca2+ ions were in the acidic solution, then ΔG°R increased to 210 kJ mol−1, 170 kJ mol−1 for Na+ ions, and 107 kJ mol−1 for K+ ions in the solution. The theoretical solubility constant (Ks) calculated from the relation ΔG° = −RT ln Ks gave Ks = 106.7 in an acidic solution without basic cations, but decreased to 10−36.8 with Ca2+ ions in solution, 10−29.8 with Na+ ions, and 10−18.8 with K+ ions in solution. At pH ≥ 5.5, the dissolution was more constrained by Ca2+ ions or basic cations in solution than by availability of protons. The kinetics of the dissolution reaction was best described by a power function: Ct = atb, where Ct is the amount of P released from the rock phosphate at time t, and a and b are fitting parameters. An Elovich and a parabolic diffusion expression equally gave satisfactory fits to the dissolution data, suggesting that the rate of dissolution was limited by a combination of film- and intra-particle diffusion. To utilize this rock phosphate as an effective source of P, management practices that increase Ca sinks and the supply of protons to the soil are necessary. In the savanna, increasing the soil's organic matter greatly enhances cation exchange capacity and availability of protons. The practice should provide adequate sinks for Ca2+ and the acidic environment required for the release of P from rock phosphate.

Notes: In many parts of Europe there has been a net decline in the use of forage legumes since the 1980s, despite the reputed value of legumes for low-input livestock production systems. The political environment within which livestock farming in much of Europe operates (Common Agricultural Policy) is shifting the balance of economic advantage towards legumes and away from high usage of inorganic fertilizer. This has already been found for legume and grass–legume silages when compared with grass silages with a potential economic gain for farmers averaging 137 € ha−1, corresponding to an annual benefit for the European livestock farming sector of as much as € 1300 million.Recent literature has shown that legume-based grazing systems have the ability to reduce environmental problems by increasing the efficiency of N use and by avoiding a high transient surplus of soil mineral N. From the perspective of livestock nutrition, when forage legumes contain moderate levels of secondary compounds, such as condensed tannins and flavonoids, they offer considerable advantages including increased efficiency of N utilization within the digestive tract, reduced incidence of bloat hazard and higher resilience to parasites.Nevertheless, these benefits are partially counterbalanced in both temperate and Mediterranean regions by difficulties in establishment, maintenance and management under grazing. To gain knowledge on mixed grass–legume pastures, further research is required on: (i) the development of sustainable systems of livestock production which can maintain sward persistence and agricultural production under environmental stress; (ii) increasing knowledge of soil–plant–animal relations for a wide range of leguminous species, and under different soil types and climatic situations; and (iii) the benefits for consumers of food produced from low-input livestock production systems.

Notes: A pre-existing mechanistic model of grass growth, developed to simulate grass production in the UK, was extended to include a variety of grass–legume mixtures and used to predict comparative yields across a range of sites in northern Europe, using experimental data from a series of experiments at fifteen sites. Specifically, predictions were made of the comparative yields of grass (Lolium perenne L.), white clover (Trifolium repens L.), red clover (T. pratense L.), lucerne (Medicago sativa L.), lotus (Lotus corniculatus L.) and galega (Galega orientalis Lam.). The results indicated that the model could generate simulated differences in yields between forage crops, which accorded with observed rankings. However, the predictions were more accurate for total yields than individual cuts, for a country than for an individual site, and for monocultures than for grass–legume mixtures. Nevertheless, the results appeared sufficiently robust to be used to prepare forecasts of yield productivity in different agro-climatic zones in northern Europe. Using estimates of the production costs and economic values for the forages, it was also possible to assess their comparative profitability.The study indicated that red clover, whether grown singly or in a mixture with grass economically outperformed all silage systems based on pure grass swards, even those receiving 400 kg N ha−1. White clover and lucerne were also consistently more profitable than grass-based systems, receiving 200 kg N ha−1. In relative terms, lucerne appeared to be more profitable in the south and east of the region, while white clover outperformed lucerne in the north and west. In the north and east of the region, there was some evidence that galega might also hold promise as a silage crop, but lotus was not found to be viable under north European environmental conditions.

Notes: In 1998, seeds of four cultivated native perennial grasses, Bromus inermis (B), Clinelymus nutans (C), Elymus nutans (E) and Agropyron cristatum (A), were sown as mixtures with different seed rates in three combinations (B + C, B + E + A and B + E + C + A) in a field study in the north-eastern part of the Qinghai-Tibetan Plateau, China. A grazing experiment was conducted in 2000 to investigate the performance of these grass mixtures at leaf, plant and sward scales under different grazing intensities (GI). Four GIs, expressed as the proportion of herbage consumed by Tibetan lambs in relation to the available biomass (IP), were applied in the summer: no grazing, and 0·30, 0·50 and 0·70 of IP. Tiller numbers of the grasses increased and leaf photosynthetic rate, sward leaf area index (LAI) and herbage mass declined with increase in GI. No effect of GI on specific leaf area was observed. Interactions between GI and grass mixtures on the dynamics of species composition, swards’ LAI and herbage mass were found. Large fluctuations in species composition with different GIs showed the poor species compatibility and sward persistence of these grass mixtures under high GI by sheep.

Notes: A field study was conducted to test the responses of Leymus chinensis to long-term grazing disturbance on a native grassland in the Songnen plain, north-eastern China. Six grazing intensities were examined using thirty random sample plots in each. Components of biomass, and shoot and tiller densities of L. chinensis decreased significantly (P 〈 0·05) with increased grazing intensity, especially at the extremely high grazing intensity. Conversely, the proportion of the total biomass as rhizomes increased considerably with increased grazing intensity, and peaked on the extremely high grazing treatment (at 0·91 of the total biomass). Shoot and tiller densities, and the proportion of the total biomass as rhizomes were strongly negatively correlated with soil organic matter content and soil moisture content and negatively correlated with soil pH and soil bulk density along the grazing gradient, indicating that the responses of L. chinensis to the canopy removal by long-term grazing are likely to have influenced changes in the soil.

Notes: Annual ryegrass (Lolium multiflorum Lam.) is a primary forage resource for livestock producers throughout the south-eastern USA during the winter-growing season. It is important for livestock producers to begin grazing annual ryegrass as early as possible and any management practices maximizing early season production could be beneficial. To assess the impact of seeding rate on subsequent yield, yield distribution, quality, seedling density, and end-of-season plant and tiller density, a 2-year study was initiated at four locations in Louisiana. Three annual ryegrass cultivars, varying in seed size, were established at four seeding rates based on pure live seed (PLS) rates of 400, 800, 1200 and 1600 PLS m−2. There was no advantage in total yield from increasing seeding rates beyond 800 PLS m−2. However, first-harvest yields increased from 360 to 930 kg dry matter (DM) ha−1 as seeding rate increased from 400 to 1600 PLS m−2. Crude protein and neutral-detergent fibre concentrations, and in vitro DM digestibility, were not affected by seeding rate. Seedling density and end-of-season plant numbers increased as seeding rate increased. However, stems per plant decreased as seeding rate increased, indicating compensatory tillering for the reduced plant numbers observed at the lower seeding rates. These results indicate first-harvest yield can be increased by planting at higher seeding rates but total yields are not increased.

Notes: Wild oat (Avena fatua) is an annual cool-season species that grows in areas with a Mediterranean climate and has potential as a forage source in Jordan. A field experiment was conducted during the growing seasons of 1999–2000 and 2000–2001 under sub-humid Mediterranean conditions at Samta in the Ajloun Mountains, Jordan. Data on seasonal herbage mass, morphology and chemical composition of wild oat were collected at 60, 80, 100, 120 and 140 days after emergence.Plant height increased rapidly beyond 100 days after emergence. The increase in herbage mass of dry matter was gradual and peaked at 140 days after emergence. The lowest concentration of crude fibre was at 60 and 80 days after emergence, with a range of 201–263 g kg−1 DM. Crude fibre concentrations (610–630 g kg−1 DM) peaked at 140 days after emergence (maturity). In contrast to concentrations of crude fibre, concentrations of crude protein decreased gradually with age. The calcium and phosphorus concentrations were sufficient to meet the maintenance requirements of ewes.

Notes: A small-plot field experiment on grazed hill country pastures in the North Island of New Zealand was conducted to examine the productivity and compositional characteristics of swards in response to variation in pasture species diversity. The balanced incomplete factorial design incorporated variation in location, slope, soil fertility and combinations of eight plant functional groups (C4 grasses, annual grasses, annual legumes, perennial C3 grasses, perennial legumes, perennial forbs, ryegrass and browntop). Net herbage accumulation and botanical composition were measured at 18 months (spring) and 24 months (autumn) after oversowing following application of a systemic herbicide. Analysis of variance indicated a significant positive relationship between the number of functional groups sown and herbage accumulation of the sown species in spring, but not with total herbage accumulation. Regression analysis showed that herbage accumulation was also affected by the identity of the functional groups. However, the statistical models indicated that pasture productivity was most strongly influenced by site factors. There was a significant negative relationship between both the number and herbage accumulation of unsown species and the number of functional groups sown, indicating a positive relationship between diversity and resistance to invasion by unsown species. A comparison of the vegetation between the plots before and after oversowing showed that those more diverse prior to sowing returned to their initial composition more rapidly, evidence that diverse vegetation was more resilient in the face of disturbance.

Notes: The history of the European Grassland Federation (EGF) from its founding in 1963 to 2003 is described. The origins and constitution are described together with its membership. How the structure and functions of the EGF have changed in 40 years are outlined and the management and financial arrangements of the EGF explained. The background to Grass and Forage Science becoming the official journal of the EGF in 1996 is described. The developments that have take place in the content and size of the General Meetings and Symposia, and in their publication as Proceedings, are highlighted. The links to other organizations in grassland research and the future direction of the EGF are explored.

Notes: Based on experimental data gathered in a research project on nitrogen fluxes in intensive dairy farming in Northern Germany, an analysis of fossil energy input and energy efficiency in forage production from permanent grassland and maize for silage was conducted. Field experiments comprised different defoliation systems and different rates of mineral N fertilizer and slurry application. Each change from grazing to cutting in grassland systems reduced the energy efficiency. Energy efficiency consistently decreased with increasing rates of mineral N application. In the production of maize for silage, maximum energy efficiency was obtained with an application of 50 kg N ha−1 from slurry only. Net energy yields of maize for silage were much higher than that of grassland when compared at the same level of fossil energy and nitrogen fertilizer input. Considering both nitrate-leaching losses and a necessary minimum quantity of grass herbage in a well-balanced ration, it is suggested that a high proportion of maize for silage in combination with N-unfertilized grass/clover swards used in a mixed cutting/grazing system represents a good trade-off between the leaching of nitrates and energy efficiency.

Notes: Variations in climate are widely recognized as central factors governing the competitive balance in mixed-species plant communities. In agricultural systems, highly variable patterns of crop yield reduction as a function of weed density have been documented across sites and among years at the same site for several crop–weed combinations. This variation is typically attributed to contrasting environmental conditions. Despite broad acknowledgement of their importance, experimental and temporal limitations have constrained the investigation and systematic understanding of environmental controls on the dynamics of competition. For several well-studied crop–weed associations, aggregating historical data from similar competition experiments provides an opportunity to explore interference relationships over an array of conditions. In this study, 19 site-years of maize –Abutilon theophrasti (velvetleaf) data were compiled and the weather characterized (i.e. average ambient temperature and moisture regime) for discrete portions of each growing season. These features were then related to patterns of maize yield loss from A. theophrasti interference at high weed densities. Results of this analysis suggest that temperatures following establishment, together with the presence or absence of water stress during the maize crop's exponential growth phase, account for over 60% of the observed variation in relative yield loss.

Notes: Two experiments were conducted in 14 spring barley cultivars to investigate if crop tolerance to post-emergence weed harrowing is related to morphological traits that reflect competitiveness. The experiments were carried out in organically grown fields where low weed densities and biomass production were assumed to be without significant influence on crop growth. The experiments showed that different cultivars responded differently to post-emergence weed harrowing in terms of yield reduction. Taller and higher yielding cultivars with high leaf area index (LAI) tended to be less tolerant to post-emergence weed harrowing than shorter and lower yielding cultivars with low LAI. This conclusion, however, is only valid for 13 of 14 cultivars because one very tall cultivar was tolerant to harrowing. Although the tallest and highest yielding cultivars were damaged the most, they remained the highest yielding cultivars after weed harrowing. This study is the first attempt to relate competitiveness of cereal cultivars to tolerance to harrowing, and it is thought provoking that competitiveness and tolerance is found to be counterproductive.

Notes: The economic benefits of using site-specific weed management (SSWM) are related to the proportion of the field that is weed-infested, the number of weed patches and the spatial resolution of sampling and spraying technologies. In this paper we simulate different combinations of these factors using parameter values obtained for Avena sterilis ssp. ludoviciana growing in Spanish winter barley crops. The profitability of SSWM systems increased as the proportion of the field infested by this weed decreased and when patch distribution was more concentrated. Under most of the conditions tested, positive net returns for SSWM were obtained when the weed-infested area was smaller than 30%. The highest net return occurred using a 12 m × 12 m mapping and spraying resolution. The critical parameter that determined the economic viability of patch mapping and spraying resolution was the technology costs. The site specific strategy was economically superior to the standard strategy (overall herbicide application) in most cases. However, the differential between the two strategies decreased when the number of patches and the resolution of mapping and spraying increased, such that the highest net returns were obtained with a single patch covering 14% of the field and using a 12-m mapping and spraying resolution; whereas the worst net returns were obtained for all patch numbers when 64% of the field was infested and a 3-m mapping and spraying resolution was used.

Notes: Phomopsis amaranthicola, a bioherbicide agent for Amaranthus spp., was tested in vitro for its compatibility with commercial formulations of 16 adjuvants, 24 herbicides, nine fungicides and four insecticides at 2X, 1X (highest labelled product dose rate), 0.75X, 0.5X and 0.25X concentrations. These chemicals were tested for their effects on spore germination. Selected herbicides and fungicides at 1X were also tested for their influence on colony growth and sporulation. All tested compounds were finally categorized in compatibility classes regarding germination, mycelial growth and sporulation such as low, medium and high compatibility. High compatibility in terms of germination and fungal colony growth was only observed with the herbicide bentazone. Many of the adjuvants tested were highly compatible in the germination studies. Most fungicides and insecticides had medium and low compatibility with P. amaranthicola. Effects of pesticides on spore germination did not fully correspond with their effects on colony growth. Thus, it is possible to integrate the use of P. amaranthicola with some herbicides, fungicides, insecticides and adjuvants but not others. A case-by-case selection of application methods, such as tank-mix or sequential application, along with proper timing of applications of the fungus and the chemical agents will be necessary.

Notes: Orobanche crenata (broomrape) is a root parasite that represents the major constraint for pea (Pisum sativum) cultivation in the Mediterranean area and the Middle East. The efficacy of available control methods is minimal and breeding for O. crenata resistance is considered the most promising strategy of control. Only moderate levels of incomplete resistance are available in pea germplasm. In order to identify and map the quantitative trait loci (QTL) controlling the trait, 115 F2 plants derived from the cross between a susceptible and a resistant parent were analysed using isozymes, random amplified polymorphic DNA and sequence tagged site markers. F2-derived F3 lines were studied for O. crenata resistance under field conditions. The linkage map was constructed with MAPMAKER V2.0. Of 217 markers, 120 could be mapped into 21 linkage groups. Linkage groups consisted of 13 to two marker loci covering 1770 cM. The mean inter-marker distance was 17.64 cM. Simple interval mapping (SIM) and composite interval mapping (CIM) were performed using QTL Cartographer. The CIM approach using five cofactors was clearly the most efficient way to locate putative QTL. Two QTL for O. crenata resistance (Ocp1 and Ocp2), explaining only a moderate portion of the observed variation (9.6% and 11.4% respectively), were detected.

Notes: As a first step in the development of a mycoherbicide for biological control of Cirsium arvense indigenous fungal pathogens that had been isolated from diseased hosts were tested both singly and in combination on potted plants under environmental conditions. Disease symptoms (necroses, chloroses and macerations) and parameters of growth and development were evaluated to determine the potential for weed control. During 1998, Phoma destructiva, Phoma hedericola, a Mycelia sterilia and Puccinia punctiformis were inoculated singly. With the exception of the obligate biotroph P. punctiformis (local infections), the single inoculations reduced the measured parameters. A combined inoculum of P. punctiformis and Ph. hedericola was less effective than Ph. hedericola alone. In 1999, Ph. hedericola, Ph. destructiva, Ph. nebulosa and the Mycelia sterila were applied both singly and as a combined inoculum. Of all the tested inocula, the mixture of four pathogens had the greatest potential for biocontrol, significantly reducing reproductive capacity of the plants. These results demonstrate the importance of taking advantage of synergisms in developing a mycoherbicide.

Notes: The present study was conducted to evaluate the recovery potential of non-target plants affected by two airborne herbicides. Sunflower at the two-leaf stage was used as a test plant and exposed for 24 h in a wind tunnel to a range of concentrations of airborne bromoxynil-octanoate and metribuzin. Quantum yield (φPSII) of exposed leaves and of the second leaf pair developed after exposure was determined at a particular time up to 16 days following exposure. Maximum depression in quantum yield of exposed leaves from which a complete recovery occurred within 16 days was 63% for bromoxynil-octanoate and 60% for metribuzin respectively. The corresponding maximum concentrations were 1.310 and 0.390 μg m−3 respectively. The second leaf pair was also affected and showed a similar recovery potential. From the results it can be concluded that the significance of airborne bromoxynil-octanoate and metribuzin must not be overestimated, as sunflower and non-target plants with a similar sensitivity are likely to recover from air concentrations of both herbicides reported under field conditions.

Notes: Three field experiments were carried out in organically grown winter wheat in Denmark. The treatments were sowing time (normal or late sowing) and false seedbed, row width (12 and 24 cm) and weed control method [untreated; mechanical weed control (weed harrowing at 12 cm supplemented with inter-row hoeing at 24 cm); and herbicide weed control]. Weed biomass in midsummer was greatest on plots sown at the normal sowing time (compared with delayed sowing) and was reduced by mechanical or chemical weed control (compared with untreated plots). Row width alone had no influence on weed biomass, but in the experiment with high weed pressure, the more intensive mechanical weed control used at a row width of 24 cm reduced weed biomass. Normal sowing time tended to give higher yields, but this was only statistically significant in one of the three experiments. Wide rows gave a yield decrease in the experiment with low weed pressure. The effect of weed control on yield was dependent on the weed pressure. At low weed pressure, mechanical weed control caused a yield decrease compared with untreated or herbicide treated. At intermediate weed levels there were no differences, whereas at high weed pressure, mechanical weed control and herbicide treatment caused a yield increase compared with untreated. False seedbeds were shown to contribute to a decrease in the soil seed reserve.

Notes: Five soil samples were taken from each of five fields with different crop management histories. Three of the fields were in an arable rotation, the fourth field was temporary grassland, and the final field was under permanent grass. Of the three arable fields, two had been cropped with winter wheat in three of the preceding 6 years, and the third had last been cropped with winter wheat once only, 6 years previously. With one exception, the winter wheat had been sprayed with the herbicide isoproturon. The rate of isoproturon degradation in laboratory incubations was strongly related to the previous management practices. In the five soils from the field that had been treated most regularly with isoproturon in recent years, 〈2.5% of the initial dose remained after 14 days, indicating considerable enhancement of degradation. In the soils from the field with two applications of the herbicide in the past 6 years, residues after 27 days varied from 5% to 37% of the amount applied. In soils from the other three sites, residue levels were less variable, and were inversely related to microbial biomass. In studies with selected soils from the field that had received three applications of isoproturon in the previous 6 years, kinetics of degradation were not first-order but were indicative of microbial adaptation, and the average time to 50% loss of the herbicide (DT50) was 7.5 days. In selected soils from the field that had received just one application of isoproturon, degradation followed first-order kinetics, indicative of cometabolism. Pre-incubation of isoproturon in soil from the five fields led to significant enhancement of degradation only in the samples from the two fields that had a recent history of isoproturon application.

Notes: Crenate broomrape (Orobanche crenata) is a major constraint for legume cultivation in Mediterranean agriculture. Field trials, pot and in vitro experiments demonstrated that resistance to O. crenata is present in chickpea and wild species of Cicer. The resistance is the result of the combination of several mechanisms, including low induction of parasite seed germination and in some accessions, either a darkening at the infection site on the host root that prevents establishment, or a reduced development of established parasite tubercles.

Notes: A feeding trial was conducted to evaluate the potential of replacing fish meal with co-extruded wet tuna viscera and corn meal in diets for juvenile white shrimp Litopenaeus vannamei. Five practical diets were formulated to contain 30% crude protein and 16.6 kJ g−1. The feeding experiment was carried out in a recirculating seawater system with fifteen 25-L tanks with 15 shrimp per tank. Each dietary treatment was fed in triplicate in a completely randomized design for 41 days. Percent weight gain (WG%), survival (S%) and feed conversion ratio (FCR) were calculated, comparisons of these parameters showed no statistical differences (P〉0.05) among treatments. The shrimp almost tripled their weight during the feeding trial. Under the experimental conditions S%, WG% and FCR were either improved or were not significantly influenced by the replacement of fish meal with double co-extruded viscera+corn, except for a slight increase in feed consumption without affecting FCR. Hence, this product can be included by up to 40% in practical shrimp diets without any detrimental effects.

Notes: In an effort to optimize the efficiency of high-density incubation of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus eggs, the per cent hatch of eggs treated with four disinfectants (3% hydrogen peroxide, 1% polyvinylpyrrolidone iodine, 0.1% sodium hypochlorite and a 0.005% antibiotic solution – penicillin/streptomycin) was compared in both species. The per cent hatch of eggs of each species was greatest after a 24 h treatment with the antibiotic solution. The hatching success of eggs treated within the different disinfectant treatments depended upon the embryonic developmental stage in both species. The sodium hypochlorite treatment had the lowest % coverage of colony growth after disinfected haddock eggs were plated onto sterile agar media, highest survival rates to the end of the embryonic period, but the lowest per cent hatch.

Notes: Experiments were carried out to investigate the growth and haematological parameters in juvenile rockfish, Sebastes schlegeli, exposed to sub-chronic dietary cadmium (Cd) (0, 0.5, 5, 25, and 125 mg kg−1) for 60 days. The daily growth rates of weight and length of the rockfish were significantly different from control, and a significant inverse relationship was observed between weight gain and the exposure concentration of dietary Cd at 25 and 125 mg kg−1 (P〈0.05). Glucose in serum was also increased significantly (P〈0.05). The concentration of total protein in serum was significantly lower than control at 5, 25, and 125 mg kg−1. No differences were observed in serum calcium concentration. The magnesium concentration in serum was increased significantly with dietary Cd concentration.

Notes: Bioactive additives in food to improve growth, development and reproductive success of crustaceans have received little attention. In the present study, the effects of carotenoid and vitamin A injections were characterized and correlated to the ontogenic development of oocytes in female Cherax quadricarinatus reproducers. During an acclimation period, 250 C. quadricarinatus females were fed a basal diet devoid of carotenoids and retinoids. Four treatments were administered by injection: retinol palmitate (RP), β-carotene, astaxanthin and vegetable oil as the control treatment. Before the experiment, total gonadic mass of organisms was obtained to determine the gonadosomatic index. Histological techniques were used to evaluate the effects of the different treatments during the primary vitellogenic phase. Retinol palmitate had the greatest inductive effect on the primary vitellogenic phase and on indicators of ontogenic oocyte development. The bioactive and molecular foundations of the action of carotenoids and retinoids that actively participate during the process of nuclear signalling and differentiation of the oocyte are discussed, considering these compounds as essential nutritional additives during gonadic maturation.

Notes: A genome scan, searching for quantitative trait loci (QTL) for the traits cold tolerance and body weight in tilapia, was performed on a cross between a (Oreochromis niloticus×Sarotherodon galilaeus) male and a (O. mossambicus×O. aureus) female. Fifty-four microsatellites and 23 amplified fragment length polymorphism (AFLP) primer combinations were genotyped and tested for marker–trait associations. Sex-specific linkage maps were constructed from this data. Twenty-three point-wise significant marker–trait associations were found in the genome scan, and putative QTL were subsequently tested in another (On×Sg) × (Om×Oa) family. None of the putative QTL from the first experiment were significant in the second experiment. However, one microsatellite, UNH130, found to be associated to weight in the first experiment, was found to be strongly associated to cold tolerance in the second experiment. Since QTL for cold tolerance and body weight were recently found on the linkage group containing UNH130 (linkage group 23) in another study, this linkage group was investigated more closely using interval mapping. The results provide indications, but not conclusive evidence, of a QTL for cold tolerance on linkage group 23.

Notes: A monitoring program for the prevalence and intensity of sea lice infestations of wild and escaped farmed salmon has been underway on the Magaguadavic River since 1992. Fish are screened in a fish ladder trap located in freshwater a short distance above the head of tide. No trends with time were evident in observed sea lice burdens, and in all years the majority of salmon, both wild and escapees, had no or low levels of infestation with sea lice. In the spring of 2002, 23 landlocked salmon moving to sea from the Magaguadavic River were acoustically tagged. Two fish returned to the river after a brief period of residence in Passamaquoddy Bay, with significant dermal damage from sea lice. These fish were tracked to areas close to commercial salmon farms.

Notes: Genetic variability within salmon louse, Lepeophtheirus salmonis (Caligidae: Copepoda), populations parasitizing farmed and wild Scottish Atlantic salmon (Salmo salar) was investigated using analysis of randomly amplified polymorphic DNA (RAPD) fragments. Seven individual decamer primers were used to analyse samples of salmon lice collected from 15 different locations in Scotland. The polymerase chain reaction products were separated using agarose gel electrophoresis and the resulting band patterns were analysed using a semi-automated analytical scoring system. Dendrograms were produced using the unweighted pair-group average (UPGMA) method using Dice similarity values. The summary dendrogram of the analysis of all RAPD bands showed two separate clusters of salmon lice, the larger being sub-divided into a further two sections. The collections of lice occupying each of these sub-divisions, however, were a mix of sites, which did not exhibit a structured geographical pattern.

Notes: SLICE™ (active ingredient 0.2% emamectin benzoate (EMB)), a feed premix developed by Schering-Plough Animal Health for the control of sea lice on cultured salmonids, is registered for use in several countries and is being prescribed on an emergency basis in Canada and the United States. The concentration of EMB in feed administered to farmed salmon ranges from 1 to 25 μg g−1. To determine the acute toxicity of the compound to juvenile and adult American lobster (Homarus americanus), commercial salmon feed was coated with SLICE™ at a range of concentrations and provided to the animals for 7 d in the laboratory. The LC50 is estimated to be 644 μg g−1 (95% CI=428, 1275) for adult lobsters and 〉589 μg g−1 for stage V and VI juvenile lobsters. The consumption of medicated pellets by adult lobsters decreased significantly with increasing concentration of EMB. Adult lobsters that died during the study had a significantly greater concentration of emamectin B1a in their muscle tissue than those that survived. These results support the conclusion that salmon feed medicated with EMB at the concentrations used by the aquaculture industry is unlikely to pose an acute lethal threat to adult and small juvenile American lobsters.

Notes: This study examines the relative density of sea lice, Lepeophtheirus salmonis (Krøyer), larvae in the inter-tidal areas of Loch Torridon, a fjordic sea loch in Western Scotland and the site of several commercial salmon farms. Samples of planktonic sea lice were collected in each spring from 1999 to 2003 near the mouth of the River Shieldaig, where sea trout have been shown to congregate in the first few days after going to sea, and from 2001 to 2003 near the mouth of the River Balgy.No larval sea lice were found near the mouth of the River Shieldaig in spring 2000 or 2002, when gravid female sea lice were absent on local fish farms. The same finding was observed in 2002 at the mouth of the River Balgy.In springs of 1999, 2001 and 2003, peak densities of larval sea lice of 33, 94 and 143 m−3, respectively, were observed at the mouth of the river Shieldaig. At the mouth of the River Balgy, peak densities of 74 and 78 lice m−3 were observed in 2001 and 2003 respectively. At the time these samples were collected, the two local salmon farms were in the second year of their production cycle and gravid female sea lice were present.Samples of larval sea lice were also obtained year round, at approximately weekly intervals, from a 50-m transect at the mouth of the River Shieldaig, from March 2001 to June 2003, and compared with frequencies of gravid female sea lice on the two local salmon farms. High levels were found in the winter. No planktonic sea lice were found in this transect when gravid females were not present on the local fish farms.

Notes: Risk analysis provides a logical strategy for the identification of hazards in an area of concern leading to their management. This approach has rarely been used for research studies on the possible links between salmon lice in fish farms and variations in wild salmonid populations. Although correlation has been found between some data sets, a series of international meetings of experts has not been able to establish cause–effect relationships between lice on farms and the current low level of salmonid stocks in Europe and eastern Canada. Research in this area is currently in progress in western Canada. Views on the meaning of the correlations found have become highly polarized in both the scientific and non-scientific communities, with the same data often being interpreted in different ways. Farm lice levels are being managed by industry codes and by official strategies in Europe, but these programmes have not so far resulted in associated benefit to the size of wild salmonid stocks. The large array of factors that cause variations in both the size of fish stocks and the level of fish diseases is frequently overlooked. Using a risk analysis approach, the key contributory factors may be identified and appropriate remedial management actions designed to meet achievable objectives. Regular assessment of the effectiveness of the measures introduced would then be possible.

Notes: Most lice infestations on salmon farmed in the North Atlantic are attributed to Caligus elongatus and Lepeophtheirus salmonis. This study reports findings from time-series analysis conducted on observations of the lesser-studied C. elongatus, in four farms on the west coast of Scotland over the period 1996–2000. Least-squares and Poisson regression techniques were applied to one individual site and to the aggregated data of four sites. Models were fitted and tested for goodness of fit using appropriate statistical methods. Findings indicate that infestation levels are highly seasonal with rapidly increasing numbers after week 22 of the year followed by a steady decline from week 40. Abundance is much lower in the second year of the production cycle than the first. Neither of the models indicated that treatment application has a significant effect on C. elongatus infestations.

Notes: Within the State of Maine, only a portion of the farm sites experience sea lice (Lepeophtheirus salmonis) infections on an annual basis. There has been concern about the further spread of lice by farming activities to unaffected areas despite routine disinfection of equipment with sodium hypochlorite or iodophors. We examined the effects of Povidone-iodine, sodium hypochlorite and desiccation on egg strings of L. salmonis and the potential of these methods for preventing hatching of nauplii or development to the copepodid stage. L. salmonis egg strings were exposed to one of eight treatments: 200 ppm of sodium hypochlorite or Povidone-iodine solutions for 1 min, 500 ppm of either disinfectant for one minute or 10 min, or desiccation for either 4 or 24 h. The egg strings were then incubated and the hatched copepods were kept for 6 days in filtered natural seawater at 32 ppt salinity at 12°C. Desiccation for 4 or 24 h were the only methods that prevented L. salmonis nauplii from hatching or developing to the infective copepodid stage. Common disinfection procedures against pathogenic bacteria and virus were not found to be effective against L. salmonis eggs.

Notes: Proper monitoring of all stages of sea lice is imperative to ensure the strategic timing of treatments. Although sea lice receive close attention and management for production purposes, there are no regulations for the reporting of lice burdens on salmon farms in Atlantic Canada, nor are there officially standardized protocols for conducting sea lice counts in the field. The purpose of this study was to complete a survey of Atlantic salmon farms in the Bay of Fundy, NB, Canada. The survey addressed many aspects of sea lice monitoring and control, including methods for sea lice sampling at the site, types of treatments administered for control of sea lice and management practices and decisions regarding the control of sea lice. A total of 83 surveys were completed from July to December 2002. Twelve of the 60 respondents owned and/or operated more than one site and completed a survey for each of their sites at the time of the interview. The position of individuals surveyed included 48 site managers (representing 63 sites), three site owners (representing 11 sites), eight individuals who were both owner and manager (representing nine sites) and one site veterinarian (representing one site). Surveys were completed on 30 sites from the Limekiln Bay and surrounding areas, 23 sites from Grand Manan Island, 18 sites from Deer Island, six sites from Campobello Island and six sites from Passamaquoddy Bay. Fish farmers, in concert with their veterinarians, generally perform intensive monitoring and control practices. However, there is a continued reliance on emamectin benzoate (SLICE®) for sea lice control on Atlantic salmon farms in the Bay of Fundy, which raises concerns regarding the potential for sea lice to develop resistance to the drug.

Notes: Bottom soil samples were collected from 35 ponds in the vicinity of Samutprakarn, Thailand. Ponds ranged in age from 3 to 39 years and had been used continuously for production of tilapia. Liming materials had been applied in large amounts, and bottom soils of all ponds had pH above 7, low exchange acidity, and free carbonate. Pond soils often contained between 1% and 2% total sulphur, suggesting that they were potential acid–sulphate soils. However, acidity from sulphide oxidation was not expressed because carbonate in the soil neutralized it. Concentrations of total carbon seldom exceeded 4% and the average for organic carbon was 1.90%. The correlations between pond age and both total carbon and organic carbon concentration were weak (r=0.34 and 0.36 respectively). Concentrations of nitrogen in bottom soils did not differ with pond age and ranged from 0.1% to 0.3% with an average of 0.19%. The average ratio of concentrations of carbon and nitrogen was 11. Acid-extractable phosphorus concentrations averaged 217 mg kg−1, but the phosphorus adsorption capacity averaged 768 mg kg−1 suggesting that soils still have considerable reserve capacity to adsorb phosphorus. Ponds can be used annually for semi-intensive production of tilapia, and presumably other species, for many years without serious deterioration of bottom soil quality.

Notes: The present study investigated motility, acrosome reaction, fertility and cryobiological parameters of the semen of the sterlet, Acipenser ruthenus L. Sperm motility persisted for about 4 min in water, and the main swimming type was the linear motion. Motility was prolonged at osmolalities of 12.5 mosmol kg−1 and in the presence of magnesium ions, while calcium had no effect. Also a pH in the range of 7.0–9.0 had no effect on ` motility. At osmolalities of 25–50 mosmol kg−1 the sperm motility was partly inhibited, at osmolalities of 100 mosmol kg−1, completely and irreversibly. In 50 mosmol kg−1 solutions with 2.5–5 mM L−1 KCl the motility inhibition was total, but reversible. The acrosome reaction was not induced by one of the described solutions, but the percentage of spermatozoa with reacted acrosomes was low (〈20%) and highly variable in all experiments. The optimal extender base for cryopreservation was a solution consisting of 50 mM L−1 NaCl, 5 mM L−1 KCl, 10 mM L−1 Tris (pH 8.5). From the tested cryoprotectants only dimethylsulphoxide (DMSO) and methanol provided sufficient cryoprotection. After freezing and thawing, the motility rates and swimming velocities were higher with DMSO than with methanol. However, the fertility was very significantly reduced with DMSO (10.3±0.5%) while with methanol fertilization rates in a similar range (32.7±4.4%) as with fresh semen (33.90±0.8%) could be obtained. Optimal freezing conditions for sterlet semen were in the vapour of liquid nitrogen 3–5 cm (−95°C to −85°C) above its surface, the optimal thawing conditions at 25°C for 30 s. The acrosome reaction was not induced by these cryopreservation protocols.

Notes: Effect of season and diet on muscle composition were evaluated in farmed Atlantic cod (Gadus morhua L.), fed varying levels of macro-nutrients, and kept at two different light regimes during 1 year grow-out in sea-cages. The cod were fed seven different diets varying in protein, lipid and starch, in a mixture design. The diets spanned 4–20% starch, 8–26% lipid and 36–66% protein. Each dietary regime was subjected to two different light regimes: continuous light (24 h), or natural light (August 2001 to June 2002). Fish subjected to natural light started to mature in December/January and spawning was more or less completed during March/April. No maturation was registered in the continuous light groups at this point. No variation was found in muscle dry matter, protein or lipid concentration as a consequence of the dietary or light regime variations, except for the groups spawning in March. Glycogen varied from 1 to 6.5 mg g−1 wet weight, without any correlation to the present dietary variations. At the June 2002 sampling all groups given a natural light regime showed almost twice the concentration of muscle glycogen compared with fish subjected to continuous light. Such clear results were not measured at the December or March samplings. Increased dietary lipid resulted in lowered muscle vitamin E concentration. A strong covariation between muscle vitamins C and E was found at all samplings, and these showed a negative correlation towards eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), and the ratio n-3/n-6 in muscle. The highest dietary vitamin E resulted in the lowest muscle vitamin C concentrations. All dietary lipid added was identical and of marine origin; in addition, the wheat added as a starch source summed up parts of the dietary lipid fraction, resulting in slightly decreased sum of polyenes in the diets holding the highest levels of wheat. The lean cod muscle consists almost solely of membrane lipids. These were, however, highly influenced by the dietary lipid composition, especially as concerned the different monoenes. Two of the diets showed tendencies to increased thiobarbituric acid-reactive substances (TBARS). This was not reflected in the muscle concentrations of vitamins E or C, and did not result in any changes in muscle TBARS values at any of the samplings, except for the fish spawning in March. The water-soluble fraction of the muscle protein, pH range from 4.5 to 6, did show a difference in structure when comparing our experimental cod to wild cod. We could also identify a differential pattern between some of the experimental groups. The method used to identify this was, however, not quantitative, and further studies are needed. Taste panel evaluation and shear force measurements after final sampling in June concluded with minor differences between muscles from the different diet groups, except for fish given one diet with relatively high protein, intermediate lipid and low starch levels. Fish kept at continuous light was described as less firm (texture) compared with fish kept at natural light, explained partly by the different size of these two categories of fish. In conclusion, both diet and season (spawning or not) did influence several of the measured muscle parameters.

Notes: The free-living nematode Panagrellus redivivus was mass produced on a solid culture medium enriched with sunflower oil or fish oil by means of a new technology. Nematodes with different fatty acid compositions were obtained. A 7-day experiment was performed in order to compare the lipid enriched nematodes with Artemia as live food for first feeding common carp (Cyprinus carpio L.) larvae. Larvae fed nematodes doubled their body mass and had a mean survival rate higher than 80%. No significant differences could be observed between the two groups fed nematodes. Fish larvae fed with Artemia showed almost no mortality and had a final body mass five times higher than larvae fed nematodes. It is concluded that mass produced nematodes are a promising food source for first feeding common carp larvae. However, further research is needed on the development of improved culture media to increase the nutritional value of P. redivivus.

Notes: This study was designed to investigate growth performance in two sturgeon hybrids reared in two quadrangular floating cages moored in an artificial pond, representing the first experience of sturgeon culture performed at Southern Mediterranean latitudes. The research was carried out from December 2000 to July 2001 and tested the growth performance, feeding parameters and biometric relationships.The sturgeons were randomly collected from the cages on a monthly basis, and total length, standard length (SL) and wet weight (WW) were recorded. The specific daily growth rate (SGRW) as somatic WW, food conversion ratio and condition factor (CF) were calculated. Biometric relationships, as linear regression, were also calculated on SL and WW data.Both hybrids grew slowly from December to April, but faster during the warm months. The growth performance of the two hybrids seems to be influenced by variability of the environmental conditions and, for both fish groups, there was a strong correlation between water temperature and SGRW at temperatures below 25 °C. The CF (constantly below 1) was similar for both hybrids. The regression analysis for WW and SL calculated for the entire period showed a positive allometry for both hybrids, indicating that the fishes grew in weight at a greater rate than required to maintain constant body proportion.

Notes: Considerable size variation emerges at an early stage among redclaw (Cherax quadricarinatus) juveniles. In order to explore whether juveniles from different size fractions of the same population differ in their growth potential, they were reared individually, in the absence of social effects. In the first experiment, post-release siblings were reared for 5 weeks and then categorized into three size fractions: small, med-sized and large. Subsequently, juveniles of each size fraction (n=24, 18, and 18, respectively) were reared in individual cells for 46 days and their moult increments and moult intervals were compared. In addition, the growth indices of the med- and large-sized juveniles were compared with those of juveniles from other broods that were similar in age and size but belonged to a different size fraction, in order to separate the effect of absolute size from that of size rank. In a second experiment, juveniles from the small-, med- and large-size fractions (n=21) of a commercial nursery-reared population were individually reared for 14 weeks and their growth indices were compared. Survival of individuals from the small-size fraction was low, particularly in the first experiment, and increased with fraction size. However, small-sized juveniles did not show reduced growth potential and even grew at a faster rate than large-sized juveniles. The results indicate that social interactions plays an important role in the development of size variation, and that small juveniles have the potential to grow rapidly when reared in individual compartments. Overall, the size rank was a poor predictor of growth potential.

Notes: The influence of a constant magnetic field with an intensity ranging from 0.4 to 0.6 T (Tesla) was determined on physicochemical parameters of water and on rearing of larvae of the European sheatfish Silurus glanis L. larvae. In the experiment, feeding brood of European sheatfish was reared in two groups. One was kept in tanks supplied with magnetically treated water. The second group was kept in tanks supplied with water without treatment with a magnetic field (control). The fish tanks were supplied with circulating river water. Rearing was conducted for 15 days at an initial stocking density for both groups of 8 fish per litre. The mean fish mass obtained was 0.46 g, and in the control group – 0.78 g (P〈0.05). Stocking mortality was 19.1% in the tanks with a constant magnetic field, and 13.5% in the control group. No changes were observed in water phosphate, ammonium, organic compounds or chloride concentrations.

Notes: Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso-N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35%), corn (29%), wheat (20%), wheat bran (10%), fish oil (3%), diamol (2%) and premix (1%). Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20% and 40% of dry matter of duckweed, in a dry and fresh form, was performed. Diets of treatments 1 and 2 included 20% and 40% of duckweed, respectively, in a dry form. In treatments 3 and 4, tilapia received formulated diets 4 and 5 in addition to 20% and 40% fresh duckweed providing the same amount of dry matter and protein as in control. The specific growth rates (SGRs) of tilapia were 1.51±0.07, 1.38±0.03, 1.31±0.06, 1.44±0.02 and 1.33±0.05, in control and treatments 1–4. There was no significant difference between SGR for the control diet and the diet with 20% fresh duckweed, while the other treatment groups had significantly lower SGR. All the treatment diets provide good values for feed conversion ratios (FCRs) and protein efficiency ratio (PER). Dry matter of diets ranged from 61.8% in treatment 4 to 85.2% in control. All the diets have high PD (88.4–93.9%) and high-energy digestibility (78.1–90.7%). Dry matter of duckweed were 66.8, 63.3, 45.8 and 28.3 in treatments 1 to 4 respectively. Protein values were 78.4, 79.9, 77.6 and 75.9, while ED values were 59.8, 60.9, 64.5 and 58.4 in treatments 1 to 4 respectively. Analysis of body composition shows that tilapia fed diets with duckweed contain significantly (P〈0.05) higher phosphorus and protein content and significantly (P〈0.05) lower lipid content. In contrast, tilapia fed control diet had a significant higher (P〈0.05) dry matter content and lower ash content.

Notes: Genetic diversity of the Nile tilapia Oreochromis niloticus collected from the river Nile (Cairo, Assuit and Qena) and two Delta lakes (Burullus and Manzalla) in Egypt was examined by the analysis of randomly amplified polymorphic DNA (RAPD). Of 25 primers examined,21 primers produced 230 RAPD bands. The percentage of polymorphic bands in Manzalla (29.4%) and Burullus (24%) populations was low compared with Assuit (30.54%), Cairo (33.5%) and Qena (44.84%) populations. The highest percentage of polymorphic bands was observed in the Qena population,suggesting a greater potential for use in breeding programs. The molecular phylogenetic tree constructed by unweighted pair-group method of analysis shows Manzalla and Burullus populations strongly linked and separate from the Assuit and Cairo populations, with Qena population as outgroup. The data serve as a baseline analysis of the current genetic diversity found among O. niloticus populations in Egypt.

Notes: Coho salmon Oncorhynchus kisutch (Walbaum), held at 15°C were tested for their susceptibility to toxins of proteolytic and nonproteolytic Clostridium botulinum types A, B, C1, C2, D, E, F, and G administered by the oral and intraperitoneal (i.p.) routes. By the oral route, the fish were most susceptibile to type E neurotoxin, which was lethal at a dose equivalent to 90 mouse intraperitoneal minimum lethal doses (MLDs). The oral lethal dose increased to 2000 MLD for nonproteolytic and proteolytic type F neurotoxins, but the toxin types A, B, and C1 were not lethal to fish at 2000 MLD and type D was not lethal at 20 000 MLD (highest titre tested). The fish were not susceptible to 200 MLD (the highest titres tested) of type G neurotoxin or C2 cytotoxin. By the i.p. route, all of the toxins except type G were lethal to coho salmon. Type E neurotoxin was the most toxic at a level of one-half the mouse MLD. Coho salmon held at temperatures ranging from 1 to 20°C were sensitive to type E neurotoxin by both the oral and i.p. routes. As the temperature decreased the fish became more resistant to type E neurotoxin by the oral route, but the i.p. dose remained one-half the mouse MLD at all temperatures.

Notes: Data on reproductive traits in a cultured population of brown trout (Salmo trutta L.) in southern Chile were collected over three consecutive reproductive seasons: 1999, 2000 and 2001, corresponding to the first (at 3 years), second and third spawnings in females. Data were collected from individual females (n=238, 273 and 169 respectively). The reproductive season lasted mainly from June to August. The peak (July) tended to increase with each season (55.46%, 62.27% and 80.81% of total spawning fish respectively). Female body weight (470.8±102.5, 735.0±150 and 1263.9±263.4 g), total fecundity (1182±344, 1904±595 and 2744±605) and egg diameter (4.64±0.11, 4.67±0.27 and 5.24±0.12 mm) increased significantly (P〈0.01) over successive reproductive seasons, particularly between the second and third spawnings. Relative fecundity, on the other hand, decreased significantly with each season (3577±471, 2591±900 and 2181±360). Following analysis of the variables over the three seasons, the correlation pattern of female body weight with total fecundity (r=0.91, n=458; P〈0.001) and relative fecundity (r=−034, n=451; P〈0.001) proved similar to that described in other salmonid females. Fertilization rate and survival to the eyed egg stage were also positively correlated (r=0.73, n=453; P〈0.001). The systematically high values obtained for these latter variables over the seasons evaluated (consistently above 90%) are clearly greater than those we registered in other species of salmonids bred in Chile under similar conditions and suggest highly efficient biological variables that determine the gamete fertilization of this species. The brown trout is, therefore, an interesting potential aquaculture resource in Chile.

Notes: Nine isonitrogenous (35% crude protein approximately) and isocaloric (18.37 kJ g−1) experimental diets (RLL20–BCFL40) were formulated with either raw or treated (inoculated with fish intestinal bacteria) Leucaena leucocephala leaf meal at 20%, 30% and 40% levels replacing other ingredients partially from a fish meal based reference diet (RD). Two specific strains of fish intestinal bacteria, Bacillus subtilis (isolated from Cyprinus carpio) and B. circulans (isolated from Oreochromis mossambicus) having extracellular cellulolytic and amylolytic activities, were used to inoculate Leucaena leaf meal for 15 days at 37°C. The crude fibre, cellulose and hemicellulose contents and the antinutritional factors, tannin, phytic acid and mimosine in the leaf meal decreased due to inoculation. However, free amino acids and fatty acids increased in the treated leaf meal. The response of rohu, Labeo rohita, fingerlings fed the experimental diets for 80 days was compared with fish fed a RD. Both the inclusion level and type of Leucaena leaf meal in diets significantly affected the growth performance of rohu. Fish fed diets containing inoculated Leucaena leaf meal performed better in comparison with those with the RD. On the basis of growth response, feed conversion ratio, protein efficiency ratio and apparent net protein utilization, diet formulated with 30%Leucaena leaf meal inoculated with B. circulans resulted in the best performance of rohu fingerlings followed by diet with 40%B. subtilis inoculated Leucaena leaf meal. The apparent protein digestibility (APD) was better in fish fed diets containing B. circulans inoculated leaf meal. An increasing level of raw Leucaena leaf meal was associated with a decrease in the carcass protein content of rohu fingerlings. The activity of α-amylase increased with the increasing level of treated leaf meal in diets. Cellulase activity increased with increasing level of inclusion of raw leaf meal, and was comparatively lower in fish fed diets with treated leaf meal. Activities of protease and lipase were higher in fish fed the RD. The results showed that it is possible to incorporate Leucaena leaf meal inoculated with enzyme-producing fish intestinal bacteria in carp diets up to 40% level of inclusion.

Notes: Body movements of cod (Gadus morhua L.) embryos reared from fertilization to hatch at 5.4°C were observed at various stages of development and at six experimental temperatures ranging from 0–10°C. Frequency of cod embryo body movements increased from zero at 42 degree-days post fertilization to maximal at 73–82 degree-days (1 or 2 days prior to hatch). Embryos were most active at 2°C (mean of 5.5 movements per 10 min), with activity declining to less than 1/10 min at 8–10°C. Lengths of hatched cod larvae reared at a series of constant temperatures (from 4–10°C) from fertilization to hatch were greater at lower incubation temperatures. Incubation temperatures of 2–4°C were found to be optimal for incubation of cod eggs.

Notes: Two experiments were conducted with Australian snapper Pagrus auratus (Bloch and Schneider, 1801). The first was aimed at determining the dietary level of astaxanthin that improved skin redness (CIE a*values) of farm-reared snapper. Farmed snapper (ca. 600 g) fed a commercial diet without carotenoids were moved to indoor tanks and fed the same diet supplemented with 0, 36 or 72 mg astaxanthin kg−1 (unesterified form as Carophyll Pink™) for nine weeks. Skin redness (CIE a* values) continued to decrease over time in fish fed the diet without astaxanthin. Snapper fed the diet containing 72 mg astaxanthin kg−1 were significantly more red than fish fed the diet with 36 mg astaxanthin kg−1 three weeks after feeding, but skin redness was similar in both groups of fish after 6 and 9 weeks. The second experiment was designed to investigate the interactive effects of dietary astaxanthin source (unesterified form as Carophyll Pink™ or esterified form as NatuRose™; 60 mg astaxanthin kg−1) and degree of shading (0%, 50% and 95% shading from incident radiation) on skin colour (CIE L*a*b*) and skin and fillet astaxanthin content of farmed snapper (ca. 800 g) held in 1 m3 floating cages. After 116 days, there were no significant interactions between dietary treatment and degree of shading for L*, a* or b* skin colour values or the concentration of astaxanthin in the skin. Negligible amounts of astaxanthin were recovered from fillet samples. The addition of shade covers significantly increased skin lightness (L*), possibly by reducing the effect of melanism in the skin, but there was no difference between the lightness of fish held under either 50% or 95% shade cover (P〉0.05).

Notes: Haddock (Melanogrammus aeglefinus L.) were maintained on either simulated natural (SNP) or advanced, phase-shifted photoperiods (ADV) and reproductive characteristics of female fish were measured throughout two reproductive cycles. By advancing the seasonal photoperiod 8 weeks, relative to ambient conditions, follicle development, peak levels of estradiol and initiation of spawning were all accelerated compared with fish maintained on an SNP. Profiles of steroid synthesis and follicular development were similar between the two groups but the spawning period was protracted by 40 days in the fish maintained on ADV. Ultrasound imaging proved to be an effective and non-invasive tool for accurately assessing ovarian development throughout the reproductive cycle. These results suggest that photoperiod manipulation has significant potential for extending the availability of eggs and larvae for haddock aquaculture.

Notes: The objectives of the study were to investigate the effect of a feeding stimulant on feeding adaptation of gibel carp (Carassius auratus gibelio Bloch) fed diets with replacement of fish meal by meat and bone meal (MBM), and whether or not the juvenile gibel carp could adapt to higher MBM level in the diet. Juvenile and adult gibel carp were tested. Two and one replacement levels were used for juvenile and adult fish respectively. Each group of diets was set as two types with or without a unique rare earth oxide: Y2O3, Yb2O3, La2O3, Sm2O3, Nd2O3 or Gd2O3 (only the first four rare earth oxides were used in adult diets) for four adaptation periods of 3, 7, 14 and 28 days respectively. After mixing, an equal mixture of all six diets for juvenile or four diets for adult was offered in excess for 2 days. During the last 2 days of each experiment, no feed was offered and faeces from each tank were collected. Feeding preference was expressed as relative feed intake of each diet, which was estimated based on the relative concentration of each marker in the faeces.Given some adaptation period, such as 3–28 days, the effects of MBM and squid extract inclusion on the preference to each diet were reduced. After 28 days adaptation, the preferences between groups were not significantly different.

Notes: Open ocean pen aquacultural operations are leaky systems with potential environmental impacts of metabolic excretions products, feed additives, and anti-fouling agents. This study analysed the water–sediment interface along a horizontal transect away from a fish farm, noting variations between water, floc, and sediment properties. The properties examined included nitrogen (N), phosphorus (P), carbon (C), sulphur (S), and trace element content, as well as heterotrophic bacteria populations. C, N, labile P, NH4, Ca, and Zn were elevated in surface sediments at the farm in comparison with sites 100 and 300 m away. The flocs had higher levels of Mg, K, and heterotrophic bacteria than adjacent sediments, indicating the importance of the microbial communities in flocs. The flocs were important in their role as a retention and potential transport mechanism for metals, increasing in concentration of Al, Fe, and Mn with distance from the farm.

Notes: Experiments were designed to determine the effects of temperature and salinity on the virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus. In the temperature experiment, a two-factor design was conducted to evaluate the effects of both pathogen incubation temperature and fish cultivation temperature on pathogen virulence. E. tarda was incubated at 15, 20, 25 and 30±1°C, and the fish (mean weight: 10 g) were reared at 15, 20 and 25±1°C respectively. The fish reared at different temperatures were infected with the E. tarda incubated at different temperatures. The results of a 4-day LD50 test showed that temperature significantly affected the virulence of E. tarda (P〈0.01) and the interaction between the two factors was also significant (P〈0.01). For fish reared at 15°C the virulence of E. tarda was the highest at 25°C of pathogen incubation, followed by 20, 15 and 30°C. When the fish rearing temperature was raised to 20 and 25°C, the virulence of E. tarda incubated at all temperatures increased. Isolation testing demonstrated results similar to those of LD50. The higher rearing temperature increased the proliferation rate of the pathogen in fish. In the salinity experiment, the incubation salinity of E. tarda was at 0, 10, 20 and 30 g L−1, respectively, and the fish with mean weight of 50 g were cultured in natural seawater of 30 g L−1. The results of one-way anova in 4-day LD50 test showed that incubation salinity significantly affected virulence. Virulence was lower when the salinity of the incubation medium was at 0 and 30 g L−1, higher at 10 and 20 g L−1. The results of isolation test were in accordance with those of LD50. At 20 g L−1E. tarda had a faster proliferation rate than that at 10 g L−1.

Notes: This study evaluated the apparent digestibility coefficients (ADCs) of dry matter, protein, lipid, energy, calcium, phosphorus, and essential and non-essential amino acid availability of animal and plant protein sources in practical diets for the carnivorous fish, largemouth bass Micropterus salmoides (8.0±0.5 g; 10.0±0.3 cm). Fish were conditioned to accept artificial feed and those stocked in plastic cages were fed pelleted test diets. Diets contained 30% of the ingredient tested mixed with 70% of a reference ration (RD) containing 40 g 100 g−1 of crude protein, 19.85 kJ g−1 crude energy, and 0.5% of chromic oxide. Cages were then transferred to cylindrical, conical-bottomed aquaria (200 L) where the faeces were collected by sedimentation in a refrigerated container. All the tested ingredients had high ADCs for protein and lipid; ADCs of amino acids of varying protein sources showed significant differences (P〈0.01). Plant protein sources did not significantly influence the ADCs of diets. The results allow the inference that the availability of amino acids in plant and animal protein sources varies considerably.

Notes: The present study was conducted to study probiotics treatment in the post-larval diet of Macrobrachium rosenbergii. Three hundred postlarvae (average weight, 114–118 mg±0.11) were divided in five experimental groups each with four replicates. The experiment was conducted for 60 days. Experimental diets were identical in all the aspects except for variation in the probiotics strain. T1 and T2 groups were fed Lactobacillus acidophilus (140×1011 CFU 100 g−1) and L. sporogenes (24×107 CFU 100 g−1) respectively. The T3 group was fed L. sporogenes bioencapsulated in Artemia nauplii. T4 was the control group (without probiotic) whereas T5 was fed Artemia along with control diet. The bacteriological study indicated that the gut microflora of postlarvae are devoid of lactic acid bacteria. The probiotic strains were found to have inhibitory effects against the gram-negative bacterial flora present in the gut. Growth of the probiotic fed groups was significantly higher (P〈0.05) than the control group. Significantly higher growth (P〈0.05), per cent weight gain (132.5%), specific growth rate (1.41%), feed efficiency ratio (FER) (0.45), protein efficiency ratio (1.29) and protein gain (161.6%) were recorded in T3 group fed Artemia bioencapsulated L. sporogenes over the control group (P〈0.05). Although insignificant (P〉0.05), growth-promoting effects of L. sporogenes were found to be higher than L. acidophillus. Survival of the postlarvae was not affected by probiotics in the diet.

Notes: The contribution of epiphytes associated with physical substrates to the nutritional requirements of post-larval shrimp, Penaeus esculentus Haswell, was determined in high-density rearing systems (3000, 6000 and 11 000 m−3). Stable isotope signatures of epiphytes on polyethylene mesh substrate, AquaMats™ and tank walls were compared with shrimp signatures. Two methods were used: the determination of carbon and nitrogen natural abundance ratios; and 15N-nitrogen enrichment ratios after the addition of 15N-ammonium to tanks. Using the natural abundance technique and a simple mixing model, epiphytes were found to contribute substantially to the carbon requirements of post-larval shrimp (39–53%). This was despite the addition of formulated feed at satiation levels. There was no indication of a reduced contribution of carbon from epiphytes to shrimp nutrition at higher shrimp densities. The lack of a difference in the 15N/14N ratios of the two food sources meant that mixing models could not be used to calculate the contribution of nitrogen from epiphytes vs. artificial feed to shrimp nutrition. Using the 15N-nitrogenenrichment method, the amount of nitrogen contributed by epiphytes to shrimp nutrition over 24 h could be determined. This method showed that nitrogen from epiphytes was assimilated by shrimp. 15N-enrichment methods provided a more accurate alternative to natural abundance techniques, particularly when the stable isotope signals ofthe food sources are similar. This experiment hasshown the benefits in providing substrates for P.esculentus in high-density rearing systems to provide an additional food source for shrimp.

Notes: Mass selection in Oreochromis niloticus, Stirling strain, was used to obtain a red colour homozygous dominant population from a base population containing wild type and red fish with black blotches. Each selection generation included 28–80 breeders in a 1:1 male:female ratio and a density of 1 pair m−2.First selection for red colour was done when fry reached 3 g, discarding those exhibiting wild type colouring or with a high black blotch incidence. Second selection was done before fish began the reproduction stage. To determine if red-coloured fish were homozygous, a progeny test was done with the fifth selection generation using eight individual crosses of red males with wild type females and wild type males with red females. Red colour proportion increased from 5.6% in the first generation to 100% in the fifth generation. All fry in the progeny test were red colour, inferring that the population was homozygous dominant (RR). Accumulated inbreeding rate in the fifth selection generation was 1.79%. The selection process did not affect fecundity as fry production in red colour females was similar to that in wild type females. Mass selection to obtain a red homozygous population in O. niloticus, Stirling strain, was appropriate and was also effective in reducing black blotch incidence in the same species.

Notes: In the freshwater area of Vietnam's Mekong Delta, Barbodes gonionotus (Bleeker), Cyprinus carpio L. and Oreochromis niloticus (L.) are often reared together in rice fields. The survival rate and specific growth rate (SGR) of C. carpio showed a large variance. To understand the underlying reasons for this variation, we used multiple regressions for the variables SGR and survival rate, using the results of eight experiments in such polycultures at the Co Do rice–fish experimental station. The SGR of C. carpio declined with increasing rice density. Interspecific competition with O. niloticus also had a negative effect on C. carpio SGR. When fertilizer or manure is added to the trench of the rice–fish field or when extra food can be given to the fish, O. niloticus seems more appropriate than C. carpio. The survival rate of C. carpio depended on season, C. carpio stocking weight and density and the biomass of wild fish species. To obtain higher survival rates, one should stock fewer fish but of a larger size, after thorough eradication of wild fish species.