No description available.

The principal aims of this work were to investigate dispersal activity of spiders commonly found in agricultural crops, and to study the influence of both crop type and farm operations on spider assemblages and populations. Work was also conducted to develop and test an improved trapping method for samplmg aerially dispersing (ballooning) spiders. Objectives were to determine whether common farmland species exhibited species-specific differences in dispersal activity. Behavioural data from wind chamber studies were also related to field data to establish i f seasonality in dispersal was related to seasonal changes in dispersal motivation or variation in ground population densities. Ground population data were used to determine if field-scale differences in spider assemblage were related to crop type, and if crop-specific management was associated with variable impacts on spider populations. The improved trapping method ('stick and bottle' trap) was observed to increase catch sizes significantly (F(i,i8) = 30.11, P < .0001) compared to climbing-sticks with trapping adhesive. Total catch size over an eleven day period was 564 spiders. The use of an 'interception net' increased catch sizes threefold. Average loss of spiders from the traps was 9.1% ± 7.7% for daylight hours between 09:00 and 17:00. 5 The common Imyphiid spiders Engom atra, Oedothorax fuscus and Tenuiphantes tenuis were observed to display different patterns of dispersal over time. Patterns were similar for closely related species. Under wind chamber conditions, ballooning related activity in E atra comprised almost one third of total activity time yet was vitually absent in O. fuscus. Erigone atra was observed to balloon more frequently than O. fuscus m the field - it is suggested that factors influencing the tendency to balloon are different for these species. Ground populations related positively to balloonmg activity for Oedothorax spp. females and dentipalpis males. For other species the high efficiency of the trapping method may have reduced applicability to local ground populations Seasonal differences in ballooning motivation observed in E atra females in the wind chamber were likely related to differences in seasonal temperature affecting activity and not ballooning motivation Variation in spider assemblage composition was observed for fields under different management and crop production. Correspondence analysis suggested vegetation structure may mfluence the abundance of some species Set-aside was observed to have a higher proportion of non-lmyphiid species than other fields Oedothorax fuscus was dominant in almost all crops which could relate to its affinity for grass leys which predommate m the landscape. Harvesting m cereals and grass were seen to negatively impact spider populations with declmes of 96% and 83% observed respectively withm nme days of harvestmg Post harvest emigration was thought to contribute to these reductions Harvesting in maize however had a neglible impact on spider populations with relative high densities of adults overwmtering in maize stubble

Triazole fungicides, such as tebuconazole, have been pivotal in the control of both foliar and seed/soil-borne diseases of many crops, including cereals, since their introduction in the 1970s. Although routinely applied as a foliar spray, tebuconazole is also used as a seed treatment. The systemic nature of the fungicide may confer protection of plants from disease during the early stages of development. However, application rates are limited to between 1 and 7 g active ingredient (AI) per 100 kg of seed due to seed application causing reduced germination and stunting during early plant development. A novel technique whereby fungicides, including tebuconazole, are encapsulated using yeast cells as pre-formed microcapsules may provide a solution to the problem of phytotoxicity and allow seed treatments to be applied at higher rates, resulting in a reduction in total fungicide application required during the growing season. Several batches of microencapsulated tebuconazole were produced using yeast from different sources. These where tested for their potential for uptake, retention and subsequent delivery of the fungicide. The release of tebuconazole from the different yeast batches into water was assessed over a time course using liquid-liquid extraction (LLE) and GCMS. Results showed no differences in the release characteristics of tebuconazole observed between batches. Further to this the age of the batches tested was found to have no effect on release of tebuconazole into water, suggesting shelf-life would not be a problem with this technology. Repeated washing of a sample of microencapsulated tebuconazole with water suggested that the novel formulation could provide the gradual delivery of tebuconazole. An investigation of the phytotoxic effect of tebuconazole, applied as seed treatments at higher than recommended rates (40 g AI per 100 kg seed), showed the microencapsulated formulation had a significantly reduced impact on germination and early plant development, when compared to two commercial formulations of the fungicide, Mystique and Raxil. Further analysis, of the amount of tebuconazole accumulated by plants grown from treated seed, using solid phase extraction (SPE and GC-MS), showed there to be initially less fungicide in plants treated with the microencapsulated formulation. As plant development continued, the amount of tebuconazole recovered from plants treated with both the microencapsulated and conventional formulations became similar. Variation in the results, between replicate samples and also between growth stages led to a series of experiments investigating the possible effect of the growth environment and seed sowing density on tebuconazole uptake. However, no significant effects of these factors were observed. A comparison of the uptake of seed-applied microencapsulated and conventional formulations of tebuconazole between 2 and 19 weeks after sowing, showed there to be no significant differences between formulations used in the concentration of the fungicide accumulated in plants. However, a pronounced increase in plant accumulation of the fungicide was consistently observed between 17 and 19 weeks. It was suggested that this might be associated with roots becoming densely packed within the compost, encouraging fungicide uptake from the compost in the localised dressing zone around the seed. It was shown that tebuconazole became readily bound to the loam-based compost used during the research. Experiments conducted in 1m columns, containing tebuconazole applied to specific compost layers within the columns, confirmed the ability of wheat roots to recover the fungicide from the compost when they made contact with the specific layers.

For this study, the energy crops Miscanthus x giganteus, Arundo donax and Phalaris arundinacea were planted at sites across Wales. Non-destructive methods of estimating crop yields were developed the most significant relationship for Miscanthus was between mean shoot height and mean shoot dry weight, whereas for Arundo it was between mean shoot volume and mean shoot dry weight although these estimates were over-estimates of actual crop yield when scaled up to field size. Yield estimates were obtained from destructive sampling for Phalaris and these were shown to be under estimates of whole crop yield. Crop growth data were compared in relation to soil type, soil chemistry and climatic conditions. Soil clay content and soil preparation were identified as of utmost importance to Miscanthus and Arundo success, but had no effect on Phalaris crops. Both Arundo and Miscanthus showed sensitivity to air temperatures during the growing season. Delaying harvest of both crops produced material with decreased moisture and mineral content, although results were not significant in all cases. The nitrogen, phosphorus and potassium content of leaves were higher than that in the cane, and harvest following leaf abscission was recommended. Arundo did not senesce completely during the winter period, and produced harvested material with higher mineral content than Miscanthus. Both crops required further drying to meet moisture content requirements for combustion crops. Phalaris was the only crop to meet moisture content and mineral content threshold levels, although the results were not consistent across sites. Leaf chlorophyll content was significantly correlated to above ground plant mineral content. Organic and inorganic fertilisers were applied to the three crops, and produced no response in Phalaris. Both Miscanthus and Arundo increased growth in response to high phosphorus levels, and generally in response to high fertiliser applications. At recommended application rates cattle manure showed most effect.

Using barley (Hordeum vulgare L.) as a phytometer, comparisons were made of the three systems of farm management (Organic, Mixed and Stockless), maintained as a long-term experiment by the Soil Research Association (Pye Research Centre) at Haughley in Suffolk. Special attention being paid to the geochemicals of the crops/soil system. Significant differences were indicated between both 'total' and 'available' geochemicals of the three soil systems. The differences of available geochemicals are undoubtedly related to the differing long-term management, especially the continuous and predominant use of organic manures and mulches on both the Organic and Mixed systems. The unexpected differences in total geochemicals (significantly more Ca, Mg and K in the Organic soils) is tentatively explained on the basis of deterioration of soil structural characteristics in the Stockless system, leading to interruption of the supply of geochemicals by capillary water. The data collected allowed crude geochemical budgets for the farm systems to be attempted and the work was, therefore, supplemented by the lysimeter studies. The indications for this work are that the geochemicals in the Organic soil are more readily 'available' to leaching than those of the Stockless soil. Phytometry, using both the old "Rika' barley variety used in the long-term experiment, and the new varieties 'Julia' and 'Sultan', did not, in the main, back up the above findings. This was especially true of the field experiments when environmental factors other than geochemical supply, probably govern the performance of the barley. However, in the majority of cases where significant differences were shown, the Organic system always shows better performance of the plant or greater flux of geochemicals into the plants than the Stockless system. No indication of a developed dependence of the barley on the three farm systems was obtained. Nitrogen fixation by soil microorganisms appear to be unimportant on the Haughley systems.

Miscanthus spp. are woody, perennial and rhizomatous grasses which have potential for high growth rates. The rapid growth and high biomass yield of Miscanthus spp. with low fertilizer inputs make it a genus of interest for the production of biofuel. It is already used for heat and electricity production. Four developmental stages were detected in Miscanthus giganteus stems over the growing season in field collected material using light microscopy and data obtained from the measurement of stem heights, length of internodes and biomass yields. M. giganteus tissues attained 'maturity‘ by October-November after which, no further cell wall development was observed. These growth stages were used as a basis to study development of lignification in M. giganteus at different harvesting times. Early-harvested material of M. giganteus was observed to be immature having very low lignin content with subsequent development and increase in lignification in different cell types. At the time of maturity (October-November), the crop acquired its maximum degree of lignification. Development of tissues and lignification also differed conspicuously at different heights in the stem. Upper internodes of the stem appeared immature with lower lignin content whilst basal internodes were more mature and highly lignified. Development of tissues and lignification within the stem of M. giganteus proceeded acropetally. Saccharification yield analysed using NREL protocols fluctuated with growth stage and degree of lignification throughout the season. Saccharification yield was highest at the beginning of cell wall expansion stage (July), lower during August-September, higher at cell wall thickening stage (October) and then was lowest during maturation and senescence (November to January). The bottom internodes with thick cell walls showed higher glucose yield after saccharification than the upper internodes in which cells were still elongating and expanding. Saccharification levels and patterns in M. giganteus did not vary substantially at different geographic locations and observation from the flowering species Miscanthus sacchariflorus and Miscanthus sinensis (as well as on the main material of the study M. giganteus which is non-flowering) also showed that the seasonal saccharification yield, particularly the characteristic reduction in saccharification yield, was not due to a pseudo flowering in M. giganteus. Taken together, the results of saccharification at different harvesting time and at different heights in the stem over one growing season suggest October to be the ideal month to harvest the crop for enzymatic glucose release. Enzymatic degradation by the action of cellulase enzymes on different tissues and cell types in 27 μm transverse sections of M. giganteus stem was also studied under light microscopy from early-, mid- and late-harvested materials. Early-harvested material in July (immature and less lignified) showed the highest rates of cell wall decay, whereas late-harvested material in November and January (mature and with high degree of lignification) showed a low degree of cell wall degradation. The most readily degradable tissues were the phloem, followed by parenchyma and fibre cells. The cortex and epidermis were found to be recalcitrant to the enzymes. However, thin cross section (2 μm) of embedded material showed some evidence at high resolution of degradation of sclerenchyma, fibre cells and some cortex cells under the epidermis. Starch levels determined at different times over one growing season and at different heights in the stem showed significant influences of stem age and geographic location. Different locations influenced the concentration of starch. The starch concentration was not uniformly distributed throughout the plant and was higher in mature (bottom) internodes than younger (upper) internodes.

The use of arsenic contaminated groundwater for crop irrigation has resulted in elevated arsenic concentrations in the agricultural soils of Bangladesh. Rice is the main crop and a vast quantity of ground water is needed for its cultivation, especially in the dry season. The presence of high concentrations of arsenic in the soil and continuing use of arsenic contaminated irrigation water may affect the rice germination, early seedling growth, uptake and accumulation of arsenic in rice plant parts. A germination study with eight Bangladeshi rice varieties showed that Purbachi was the only variety which showed tolerance up to 4 mg As L-1 for arsenite and up to 8 mg As L-1 arsenate. In a seedling toxicity experiment, no varietal resistance was observed for either arsenite or arsenate. Arsenic toxicity to rice seedling resulted in inhibition of root growth and reduced shoot height. High affinity uptake (0 to 0.0532 mM) kinetics for arsenite and arsenate with 8 rice varieties, covering two growing seasons, Boro (dry season) and Aman (wet season), showed that uptake of both arsenite and arsenate by Boro varieties was less than that of Aman varieties. Arsenite uptake was carrier-mediated, and was taken up at approximately the same rate as arsenate at lower substrate concentrations (high affinity range), while at higher substrate concentrations (low affinity uptake range) uptake of arsenite was much higher than arsenate. Suppression of arsenate uptake was observed with increasing phosphate concentration, while the uptake of arsenite was independent of phosphate concentration indicating that arsenite was not taken up into root by phosphate transporter. Uptake of organic arsenic species was much lower than that of organic species. In long-term growth experiments, rice growth and yield were affected significantly by arsenate containing irrigation water. Arsenic concentrations in rice root, straw, husk and grain increased significantly with increasing arsenate concentration in irrigation water.

The performance of cereal mixtures and of genotypes within mixtures was examined in experiments carried out near Aberdeen from 1969 to 1971. Three field trials tested mixtures of barley cultivars having differences in maturity, plant height and leaf habit. In one trial different mixing ratios and nitrogen levels were used. In three other trials mixtures of barley and oats were grown, and the effects of different cultivars, densities, and sowing arrangements investigated. Two pot experiments, examined the effect of twelve fertility treatments on thirty-five combinations of four, barley cultivars in 1969, and two barley, one oats and one wheat cultivar in 1970. In the field trials the grain yields of barley cultivar mixtures were similar to the means of the components grown in pure stand. In the pot experiment with barley cultivars mixture means consistently exceeded pure stand means at each fertility level, although the overall increase was only 3%. Differences from mid-component yields did not appear to be related to ratio of mixing, but a slight increase in yield occurred as the number of components in the mixture increased. In experiments with mixtures of barley and oats, a combination of Midas barley and Karin oats gave consistently higher yields than the mean of the components and slightly higher yields than the better component. The performance of this mixture was maintained over different sowing patterns and seed rates, but where sowing was arranged to give an advantage to one component of the mixture at the expense of the other, mixture yields were less than where both components; were closely mixed. The increased yield of the Midas-Karin mixture was attributed to the greater tillering of Midas in mixture than in pure stand, brought about by less competition before heading, and to a higher weight per grain of Karin in mixture than in pure stand - a result of its greater height after heading and the favourable disposition of its panicles- and upper leaves in the canopy. Total light interception was measured in mixtures of cultivars and species. Though there were instances where mixtures intercepted more light during the growing season than pure stands, it was difficult to relate these to increased grain yields. Light interception measured in the Midas-Karin mixture from before ear-emergence showed that only one mixture in six consistently intercepted more light than the mean of the components. The interaction of mixtures with replicates or fertility treatments was used as an estimate of stability in all experiments. Where two trials with barley mixtures formed part of a larger series, stability was also estimated from the regression of mixture yield on location mean yield. In no case was the stability of yield greater for mixtures than for pure stand, though in the pot experiments there was some indication that four-component mixtures were the most stable. In general, mixtures reflected the pure stand stabilities of their components. Competitive ability was measured using the method of Williams (1962) in some experiments, and the method of de Wit in all experiments. Where the two methods were used together, they showed good agreement. Competitive ability among barley cultivars appeared to be most closely associated with plant height, tall cultivars yielding more in mixtures; than in pure stands and short cultivars less. Competitive ability was most often shown in an increased number of fertile tillers. Barley was a better competitor than oats in the 1970 pot experiment and in one of the field trials. Levels of foliar disease were generally low, though there was some evidence of a buffering effect in mixtures of genotypes differing in susceptibility to pathogens, and disease levels were, if anything, slightly lower in mixtures than pure stands. Lodging occurred in few trials and it appeared that some support was; given to weaker-strawed genotypes in mixtures by stronger-strawed ones. In one trial, where a barley cultivar susceptible to head loss was included, losses, were comparatively less in mixtures than in pure stands.

No description available.

In field trials on soils of known copper status, plots of oats and "barley were given foliar and seedbed copper treatments, and in factorial pot experiments, oats under various conditions of water supply and illumination were also grown on deficient and treated soil. The following conclusions were made from the results of observations and experiments. In fields on a few farms in South East Scotland, copper deficiency is lowering cereal yields and sometimes causing withertip. The soils in these fields are in the Eckford or Hobkirk Series, and have an E.D.T.A. extractable copper level of about 0.5 p.p.m. Withertip is seen most frequently when the preceding winter is dry, but there appears to be no correlation between its occurrence and weather conditions during the growing season. Oat plants, nevertheless, generally absorb less copper from sandy soil at about 80% water capacity than from soil at 40%, and the uptake in young plants may be decreased when illumination is reduced. On deficient soils, similar increases in grain yield appear to be caused by foliar treatments of 5 and 10 lb. per acre copper oxychloride, although even 0.8 lb. is sufficient to cure withertip. Field seedbed oopper dressings are less effective at raising grain production than foliar treatments, and cause no response in straw yield. Under greenhouse conditions, on the other hand, copper treatment of deficient soil may increase both grain and straw yields, no evidence was found of copper toxicity in the field, but a temporary reduction in the yield of young plants in pots occurred when sandy soil contained about 8 p.p.ra. applied copper. The concentration of copper in barley plants is generally higher than that in oats, although there are varietal differences in oats, "barley and wheat. The concentration is also higher in young plants than in those at maturity, and is influenced by moisture and light conditions. In the field, foliar treatments and moderate applications of copper to the seedbed have little effect on the copper level in mature plants, hut a heavy soil dressing in pots may raise the concentration in the "rain. Copper deficient oat plants contain a larger concentration of moisture than copper treated plants. Iron absorption may be reduced in young oat plants containing a high level of copper, and small copper dressings on a deficient soil may cause an increase in uptake of manganese. E.B.T.A. extraction of field soils gives a guide to the availability of copper near deficiency levels, and generally recovers 20 to 30% of foliar applications and about 50% of soil dressings for up to two years. The applied copper remains readily available to plants. The sampling date, however, influences the result of an E.D.T.A. extraction of a soil, particularly after copper treatment. The comparatively high concentration of copper in urban rain water makes copper deficiency unlikely in or near built up areas.