The effects of ploughing or no-tillage of long-term grass and grass-clover swards on changes in organic C and N pools and on CO2 and denitrified gas emissions were investigated in a 3-year field experiment in 1996–99 near Penicuik, Scotland. The decrease in soil C content between 1996 and 1999 was 15·3 t/ha (95% confidence limits were 1·7–28·9 t/ha). Field estimates of CO2 losses from deep-ploughed, normal-ploughed and no-tillage plots were 3·1, 4·5 and 4·6 t/ha over the sampling periods (a total of 257 days) in 1996–98. The highest N2O fluxes were from the fertilized spring barley under no-tillage. Thus no-tillage did not reduce C emissions, caused higher N2O emissions, and required larger inputs of N fertilizer than ploughing. By contrast, deep ploughing led to smaller C and N2O emissions but had no effect on yields, suggesting that deep ploughing might be an appropriate means of conserving C and N when leys are ploughed in. Subsoil denitrification losses were estimated to be 10–16 kg N/ha per year by measurement of 15N emissions from incubated intact cores. A balance sheet of N inputs and outputs showed that net N mineralization over 3 years was lower from plots receiving N fertilizer than from plots receiving no fertilizer.

A 3-year field experiment was conducted in 1996–98 near Penicuik, Scotland, to investigate the fate of N released after cultivation of previously long-term grass and grass-clover swards. The effects of timing of cultivations (autumn and spring), tillage methods (no tillage, ploughing to 200 mm and ploughing to 300 mm) and fertilizer N for spring (0, 40, 80 and 120 kg N/ha) and winter barley (0, 60, 120, 180 kg N/ha) on yield, N uptake and nitrate leaching were measured.

In 1996, after spring cultivation, on plots previously in grass, spring barley grain yield and N uptake did not respond to N fertilizer, but on plots previously in grass-clover there was a nearly linear response to N. In 1997, the spring barley responded to N fertilizer at all levels. Yields of 1997 winter barley after grass did not show a response above 60 kg N/ha, but increased with fertilizer N up to at least 120 kg N/ha after grass-clover. In 1998, there were strong effects of N fertilizer and cultivation method on grain yield and N uptake of both spring barley and winter barley. Winter barley grain yield was significantly higher in plots previously in grass than in plots previously in grass-clover in 1998, though not in 1997. Winter barley yields were higher than spring barley at the same fertilizer N level.

Throughout the 3 years, the no-tillage plots had consistently lower yields than the ploughed plots, but there was no consistent difference between the ploughed and deep ploughed treatments. There were strong interactive effects between tillage and previous sward in 1997. No-tillage under spring barley generally yielded lower than ploughing due to difficulties in weed control and the frequent anaerobic conditions in the soil.

Annual leaching losses were relatively small (6·4–19·6 kg N/ha). In 1996–97, more N was leached from the plots left in stubble following spring barley than from those planted with winter barley after either spring barley or grass in 1996, but in 1997–98 more N was leached from plots in winter barley than from those in over-winter stubble. Nitrate leaching was least under no-tillage, though the effect was not significant.

Twelve perennial ryegrass (Lolium perenne L.) varieties of different ploidy and maturity classifications were compared under a frequent cutting management in their second harvest year, equivalent to the simulated rotational grazing system employed in UK testing protocols. Varietal differences in canopy structure (proportion of lamina, green leaf mass, sward surface height, extended tiller height, bulk density) and in herbage nutritive value factors (water-soluble carbohydrate content and proportion of linoleic and α-linolenic fatty acids) were assessed and their importance evaluated with reference to total herbage production. Significant variety variation (P<0·001) was recorded in the annual means of all the canopy structure characteristics. Significant differences associated with ploidy were also recorded, with tetraploid varieties having significantly higher values than diploids in most plant characters, indicating better intake characteristics for these grasses. Temporal patterns of variation associated with maturity were also observed in several characters, thus making it impossible to designate a single assessment that would be representative of the annual ranking of varieties. Water-soluble carbohydrate concentration differed significantly (P<0·001) between varieties and although the tetraploids tended to have high contents, the highest value of all was recorded in a diploid variety, which had been selectively bred for this trait. The varieties did not differ in total lipid content but there were significant differences in the proportion of linoleic acid between varieties (P<0·001) while the proportion of α-linolenic acid differed between varieties (P<0·001), ploidy (P<0·001) and maturity (P<0·05) classes.

Overall evaluation of the extensive variety variation highlighted the need for better quantification of animal responses to differences of these magnitudes, before the high workload of including them in routine variety testing protocols could be justified. Potential for breeding improvement in these factors was also indicated and the future prospects for their use in farmer decision support systems was considered.

A greenhouse experiment was carried out from January–May 2001, to evaluate the effects of elemental sulphur inoculated with Thiobacillus, compared with gypsum, in the amendment of two saline sodic soils (Neosol Fluvic Salic sodic) from the Brazilian semi-arid region, and on growth of the tropical legumes cowpea and yam bean, inoculated with specific rhizobia strains. The treatments consisted of sulphur rates (0·6, 1·2 and 1·8 t/ha) and gypsum (1·8 and 3·6 t/ha), and irrigation water containing the salts NaHCO3, MgCl2, CaCl2, NaCl and KCl, with electrical conductivity 0·2 dS/m at 25 °C. There was a treatment with no sulphur or gypsum applied. The correctives increased Na+ and electrical conductivity on leached solution, and decreased soil pH and exchangeable cations, especially Na+. Sulphur inoculated with Thiobacillus was more efficient than gypsum, reducing soil-exchangeable sodium. Sulphur with Thiobacillus in Soil 1 reduced pH (8·2 to 4·7) and electrical conductivity of the soil saturation extract (15·3 to 1·7 mS/cm) to values below those used for classification as saline and sodic soil. The growth of the tropical legumes cowpea and yam bean was increased by rhizobia inoculation when soil ameliorants were used, especially sulphur in combination with Thiobacillus.

Trifolium species are native to the Mediterranean Basin where they are an important component of permanent pastures. A number of species have become naturalized in Australia and are agriculturally important in annual pastures. To understand the importance of genetic and ecotypic variation in the adaptation of Trifolium species to a new environment, seeds of three predominantly inbreeding and two predominantly outcrossing species of Trifolium were collected from 12 sites in Sardinia in 1998. Detailed ecogeographic information was collected at each site. The progeny were grown at the University of Western Australia Field Station at Shenton Park, Western Australia in 1999, and were scored for 10 morphological characters. Spatial analysis was applied to the data to improve the estimation of accession means, and to investigate the relationship with environmental variables that characterized the sites of collection. The spatially adjusted means were used as the basis for a principal components analysis. Ecogeographical factors at the sites of collection, particularly soil pH, are suggested to be more important than breeding system in determining the extent of genetic variation within the species. The species that showed the greatest genetic variation between accessions were the predominantly inbreeding species T. glomeratum and T. subterraneum, and the predominantly outcrossing species T. nigrescens. It is suggested that the wide genetic variation of these three species is largely due to their being in an ecogeographic environment close to their optimum, and to the possession of a mating system that is neither completely outcrossing nor completely self-fertilizing. The remaining two species, T. tomentosum and T. resupinatum, both occur more frequently on alkaline soils, and it is suggested that for the collected accessions of these two species the acid soils of Sardinia are a stressful environment that does not promote high levels of genetic variation.

Results from field experiments with mobile pests and air-borne pathogens are subject to bias as a result of inter-plot interference. Serially balanced designs (SBDs) allow interference to be estimated but other designs may be better for decreasing such effects. To investigate this, systematic replicated designs, comparing sprays applied at different times to control powdery mildew of spring barley, were sited in 2 years alongside SBDs testing similar treatments. Yields of grain and assessments of mildew on the leaves were analysed. Results from the balanced designs provided strong evidence of interference in both years but not in a third (when the systematic design was omitted). Estimates of treatment effects from the systematic designs were often, but not consistently, greater than corresponding estimates from the SBDs. A method of analysis from Draper & Guttman (1980) was adapted to produce estimates of the differences between treatments as if applied to all plots of an experiment; this showed larger differences between treatments than the conventional analysis in 1975 and 1976 (when there was appreciable interference), but failed in 1977 when interference was slight. This method fails when applied to the systematic designs; SBDs (which are a subset of all designs in randomized blocks) are probably optimal for this type of analysis. The difficulties of analysing data in the form of percentages or proportions (with consequent non-orthogonality) are discussed.

By providing both spatial and temporal information remote sensing may function as an important source of data for site-specific crop management. This technology has been used for nitrogen application strategies to obtain optimum yield and grain quality. Here, the objective was to use early repeated remotely sensed multi-spectral data to predict grain yield and quality for winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.). The crops were sown with two different seeding rates and a wide range of nitrogen strategies were applied. Multi-way partial least squares regression (N-PLS) was used to predict grain yield and protein content. The results were compared with unfold-PLS1 and PLS1 using reflectance data from the last measurement day. Both single reflectance wavelengths and selected vegetation indices were used simultaneously. The results reveal that all models can make a good prediction of yield in both crops with unfold-PLS1 and N-PLS as the best. However, estimation of grain protein content at harvest was very poorly determined in barley, as no relation between the reflectance measurements and barley protein content was obtained. The relation between reflectance measurements and protein content was slightly better in wheat, where especially N-PLS improved the prediction of grain protein content. The overall conclusion of the present experiments is that data from repeated measurements of reflectance used in multi-way partial least squares regression before heading improved the prediction of grain yield and protein content in wheat and barley.

Experiments were designed to examine differences in some morpho-physiological characters among wheat genotypes in response to drought stress at anthesis and maturity and to determine the relationships between these characters. In three sets of experiments, one set was evaluated under well-irrigated conditions and two sets under drought stress conditions by developing terminal drought stress at anthesis in one set and at maturity in the other, for 2 years. Genotypes differed in their response at both stages of plant growth for grain yield, days to heading, excised-leaf water loss, leaf membrane stability and relative water content under drought stress. Under irrigated conditions differences in the genotypes for water retention traits were not clear. There were significant genotype×environment interactions. Terminal drought stress resulted in reduced mean values and variability for all characters. The varieties WH 147 and WH 147(U) showed a combination of drought resistance, water retention and high grain yield, whereas C 306, Kharchia 65 and Hindi 62 showed a lower percentage injury in plasma membrane and better water retention in the leaves. Drought resistance index was associated with other characters.

Sodic soils are widespread, especially in the Indo–Gangetic plain. Amelioration with gypsum is effective, especially when combined with growing a crop of rice. However, it has proved difficult to generate new varieties of sodic-tolerant rice, because of the difficulties of screening – other than in the field, where spatial variation of sodicity is notoriously high. Growing plants at high pH in solution culture in a controlled environment is problematic, because of the effects of pH on nutrient availability. This study evaluated a system of growing rice in a nutrient solution with added Tris but without minor nutrients, which were supplied in a foliar spray. Performance was evaluated from the change in weight and in appearance and correlated with performance in soil. Growing rice in the presence of Tris (4 mM, pH 8·6) provides a means of evaluating genotypic differences in response to sodicity.

The mechanisms and host plant responses that are indicative of tolerance to the African rice gall midge, Orseolia oryzivora Harris & Gagne were investigated in four promising donor rice cultivars, Cisadane, Bw 348-1, Tox 4093-17-1 and ITA 306 (local check), in a screen house at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Results indicated that Cisadane was tolerant to infestations on the basis of higher (P<0.05) percentage seedling survival, production of significantly higher number of fertile tillers, productive panicles and significantly higher grain yield per infested plant than the control. Both single infestation at one larva per plant and adult infestation once at 14 days after seeding were positively correlated to higher fertile tiller production per infested plant (at 80 days after transplanting) and higher grain yield per infested plant at maturity. The grain yield per infested plant was significantly higher (P<0.05) in the tolerant variety (Cisadane) than in the control.

The contents of phenolic compounds, protein precipitation capacity (PPC) and in vitro gas production of tropical browse species were evaluated. The stoichiometric relationship between in vitro gas measured on incubation of tannin-containing browses in buffered rumen fluid and calculated from short chain fatty acid (SCFA) production was investigated. Crude protein (CP) contents in the browses ranged from 54 to 300 g/kg dry matter (DM). Total phenol (TP), tannins (T) and condensed tannins (TP and T as tannic acid equivalent; CT, as leucocyanidin equivalent) ranged from 17–250, 7–214, and 0–260 g/kg DM respectively, and PPC from 0 to 1066 μg BSA precipitated/g DM. CP content of browses was negatively correlated with TP, T, CT and PPC. A significant correlation was observed between per cent change in gas production on addition of polyethylene glycol (PEG) and the contents of phenolics (r = 0.76 for both TP and T). Addition of PEG to tannin-containing browses increased in vitro gas production. PPC was significantly correlated with TP (r = 0.87; P<0.001), T (r = 0.83; P<0.001), and CT (r = 0.41; P<0.05). A good relationship (R2 = 0.94; P<0.001) was observed between measured in vitro gas production and that calculated from SCFA. The molar proportions of SCFA were not affected by the inclusion of PEG (P>0.05). The relationship between in vitro gas measured on incubation of browse leaves and that calculated from SCFA allows prediction of SCFA from gas production.

Large areas of the Central Asian Republic of Kazakhstan are classified as desert and semi-desert rangelands and are subjected to severe climatic extremes. The sparse vegetation of these rangelands supports mainly grazing sheep, which are raised for wool and meat production. These two products are important to the national economy and the livelihood of the rural population. The extremes of climate cause periodic shortages of fodder availability that, together with the lack of drinking water and adequate animal shelters, can cause severe animal loss, particularly during the winter but also in other seasons. Desert rangeland improvements have been instigated by the introduction and planting out of palatable drought-resistant fodder shrubs to augment the natural species, many of which appear to have survived only because they are unpalatable and/or inedible. To determine the edibility of 15 natural species, Karakul sheep were observed grazing and/or browsing them and identified those species that were edible. It was predicted that the sheep would selectively browse from shrubs with low phenolic concentration, high estimated metabolizable energy content, high crude protein content and low fibre content. To test this prediction, the shrub foliage was analysed and edibility by sheep was related to chemical composition and estimated metabolizable energy content. Six of the 15 plant species were edible. The only significant factor in determining whether plants were eaten was total phenolic content – plants eaten had a content of 17·7±6·3 g/kg DM whereas plants not eaten had a content of 66·4±129·6 g/kg DM. Metabolizable energy, protein and fibre contents did not affect edibility of the plants.