Volatilization of ammonia (NH3) from slurry applied in the field is considered a risk to the environment and reduces the fertilizer value of the slurry. To reduce volatilization a better understanding of the slurry–soil interaction is needed. Therefore, the present study focuses on measuring NH3 volatilization as affected by differences in infiltration. Livestock slurries with different dry matter (DM) composition and viscosity were included in the experiments by using untreated cattle and pig slurry, pig slurry anaerobically digested in a biogas plant and pig slurry anaerobically digested and physically separated. NH3 volatilization was measured using dynamic chambers and related to infiltration of the livestock slurries in the soil by measuring chloride (Cl−) and Total Ammoniacal Nitrogen (TAN=ammonium (NH4+)+NH3) concentrations in soil at different depths from 0·5 to 6·0 cm from the soil surface. The slurries were applied to sandy and sandy-loam soils packed in boxes within the chambers. There were no significant differences in relative volatilization of NH3 from untreated cattle and pig slurries, but anaerobic digestion of pig slurry increased volatilization due to increases in pH. However, physical separation of the digested slurry reduced the volatilization compared with untreated slurry, due to increased infiltration. In general, the volatilization decreased significantly with increased infiltration. The present study shows that NH3 volatilization from applied slurry can be related to infiltration and that infiltration is related to slurry composition (i.e. DM content and particle size distribution) and soil water content. The infiltration of liquid (measured by Cl− infiltration) was affected by soil water potential, therefore, Cl− infiltrated deeper into the sandy loam soil than the sandy soil at similar gravimetric soil water values. Dry matter (DM) and large particles (>1 mm) of the slurry reduced infiltration of liquid. A high proportion of small particles (<0·025 mm) facilitated infiltration of TAN.

Information on the variation in susceptibility to lodging between barley varieties under different environments can be used for local prediction. It can also be used to identify varieties that are robust to environmental variation. Efficient methods to obtain analogous information on the local yielding capacity of crop varieties have recently been established. The present paper extends the use of these methods for the analysis of dichotomously measured performance characteristics, the susceptibility to lodging, in particular. The procedures examined were based on generalized linear models in which the expected conditional mean of the susceptibility to lodging was used as an explanatory variable to express the environmental effects of a given environment. Through the use of logistic transformation the approach extends previous methods developed for continuous response variables to binary response variables. Models were subsequently used to obtain measures of susceptibility to lodging of each barley variety in terms of environmental variation. While the emphasis is restricted to lodging, similar methods can also be applied to other performance characteristics.

Motes are cotton (Gossypium spp.) ovules that fail to ripen into mature seeds. These aborted ovules represent a loss in yield and can cause imperfections in yarn and cloth quality. The present study was conducted to determine whether 10 widely grown cotton cultivars differ in some boll characters that are undesirable for the textile industry. The bolls at the first positions of fruiting branches formed at 1st (bottom), 6th (middle) and 11th (top) nodes of the main stem were compared in 10 varieties in 2 years for the number of motes and their weights, mote production frequency, and long fibre mote frequency within a boll.

Mote frequencies and mote weights were affected by varieties and years. Moreover, mote frequencies were higher at the bottom and middle plant positions compared with the top position.

Fibre length for long fibre motes ranged from 18 to 21 mm. In both years, cultivars Deltaopal, Sayar 314 and Suregrow 125 had consistently lower mote and long fibre mote frequencies. Thus, these cultivars could be useful in breeding programmes to improve seed-set. Cotton breeders also need to consider long fibre motes in plant improvement studies.

A simulation study using the Seasonal Analysis program of the Decision Support Systems for Agrotechnology Transfer (DSSAT 3.5) suite of models was conducted from 2001 to 2003 under a subhumid subtropical climate. The models CERES-Rice and CERES-Wheat in DSSAT 3.5 were calibrated and validated for transplanted rice, direct seeded rice and wheat crops using the soil and weather parameters of Kharagpur, West Bengal, India. The weather generator program, SIMMETEO, was used to generate future weather scenarios based on weather data from 9 consecutive years. These weather scenarios were used in the seasonal analysis program to run each treatment combination with 20 replications. The results of both biophysical and economic analyses of the Seasonal Analysis program predicted an application of 120 kg N/ha along with both rice and wheat crop residues at 4 t/ha for rice, whereas the economical analysis, specifically the Mean-Gini analysis, showed that application of 80 kg N/ha along with both rice and wheat crop residue incorporation at 4 t/ha as the most dominant management options for wheat. The present study revealed that the generated future weather data were reliable and DSSAT could successfully use it to predict the future crop yields under different management practices and select the best one for sustainable production of rice and wheat crops by DSSAT.

Climatic and soil conditions in Uruguay are marginal for white clover (Trifolium repens L.). Plants were collected from four sites, in different parts of the country, multiplied vegetatively, and the populations planted into each of the four sites. Plant survival and internode length (indicating growth potential) were recorded at intervals during the 55-week period after planting. On the site with the highest annual rainfall and lowest summer water deficit, one fifth of the plants survived at least 55 weeks, whereas on the site with the highest annual evaporation almost all the plants had died within 20 weeks. There was some evidence of adaptation to a ‘home’ site in both plant survival and growth potential. Thus, on three of the four sites, populations from the ‘home’ site survived better than the average of the non-‘home’ populations. Also, internode length was greatest (9·5 mm on average, compared with a mean of 5·6 mm for the experiment as a whole) in a population from a site with soil relatively high in available P, when planted into its ‘home’ site. Plant breeders could consider producing different white clover cultivars to suit different conditions of moisture supply and available P.

Outcomes of developmental yield formation processes in oats, namely number of panicles/m2, number of grains/panicle, mean grain weight and incidences of aborted and tertiary grains, were measured in a series of experiments in Northern Ireland and the Republic of Ireland in 1997/98 and 1998/99. Seed rate (200 and 300 seeds/m2), nitrogen (0–200 kg/ha) and plant growth regulator (chlormequat chloride) treatments were applied to the spring oat varieties Aberglen and Barra in one spring- and two autumn-sown experiments, and to the winter varieties Gerald and Image in one autumn-sown experiment. Large variation in number of panicles/m2 and grains/panicle was observed between the experiments and varieties and in response to seed rate, with number of grains/panicle generally being inversely related to number of panicles/m2. At the higher rates of nitrogen rate both number of panicles/m2 and grains per panicle increased. Mean grain weights were relatively constant and were largely determined by variety. Chlormequat chloride had relatively little effect on the yield components, the most consistent being small reductions in mean grain weight.

Tertiary grains occurred rarely in the varieties and agronomic treatments used in the programme but were more frequent at higher rates of nitrogen in most of the experiments. Numbers of aborted grains were usually higher where grain numbers were higher although the effects of variety, seed rate and nitrogen on aborted grains were not consistent. Structure of the grain population, i.e. the relative proportions of primary and secondary grain, was stable despite the large differences in number of panicles/m2, spikelet numbers and mean grain weight.

The greater yield and growth enhancing effects of nitrogen compared with seed rate and plant growth regulator were apparent in responses by developmental processes active later in the life cycle, namely production of tertiary grains and grain filling.

Wide variation in number of panicles/m2 (c. 200–450) and number of grains/panicle (c. 55–145) produced in the crops grown under a very full expression of agro-ecological conditions in this programme was accompanied by small variation in mean grain weight (c. 38–47 mg/primary grain and c. 22–29 mg/secondary grain) and in numbers of tertiary (<2/panicle) and aborted grains (<10/panicle). Plasticity of development throughout the life cycle, manifested both as the established yield components and in numbers of tertiary and aborted grains, was largely effective in ensuring stability of mean grain weight and quality in oats.

Trials at Tulloch, Aberdeen (sandy loam soil, 820 mm rainfall) and Woodside, Elgin (light sandy loam, 730 mm) compared organically managed crop rotations containing different proportions of spring oats, swedes, potatoes and grass/clover leys (0·50 and 0·67 of the rotation at Tulloch; 0·38 and 0·50 at Woodside). The trials simulated farm conditions through the use of grazing animals and the recycling of farmyard manure. The rotations at each site gave similar financial outputs. Yields of oats were higher where these were grown after the main ley phase of the rotation than where they were grown later in the rotation (more ears/m2 and grains/ear), but were not significantly higher after a 4-year ley than after a 3-year ley at Tulloch. It was concluded that all of the rotations were agronomically and financially sustainable. Cereal yields showed large year-to-year variations but little indication of a progressive decline. There were only small changes in soil organic matter, soil P and soil K. Increased early summer weed cover in the arable crops was not matched by increases in weed invasion in the grass/clover leys and did not appear to be affecting yields.

Cratylia argentea (Desv.) O. Kuntze is a drought-tolerant tropical shrub legume that can help to ensure continuity of forage supply in smallholder systems either through direct grazing or as a cut-and-carry plant for fresh foliage or silage. A collection of 38 accessions was characterized agronomically and nutritionally. High diversity was detected between accessions. Time to flowering ranged from 217–329 days after transplanting seedlings to the field and from 129–202 days after cutting. Flowering is probably induced by reduction of day length. Seed production was high but variable. Dry matter production ranged from 190–382 g/plant in the rainy and from 124–262 g/plant in the dry season, content of in vitro digestible dry matter from 589–690 g/kg, crude protein content from 184–237 g/kg and fibre content from 403–528 g/kg (neutral detergent fibre, NDF), 240–335 g/kg (acid detergent fibre, ADF), and 9–13 g/kg (acid detergent fibre-bound nitrogen, N-ADF). Accessions CIAT 18674 and CIAT 22406 were identified as promising for further study. They were superior to the commercial cultivar in terms of dry matter (DM) production, particularly in the dry season. Further research is required to determine the prevailing reproduction strategy of C. argentea and to quantify outcrossing-rates. Multilocational trials with a selected set of accessions should be conducted under different environmental conditions.

Australian lupin and cotton yield monitor data were analysed using spatial models from the Matérn class of spatial covariance functions. Despite difficulties with the spatial disposition of the data, the analysis supports the statistical model in which the variation is a linear combination of white noise and the de Wijs process. The de Wijs process, also called the logarithmic covariance function, is a generalized covariance function that is conformally invariant and suggests that there is variation at all spatial scales. The present work also indicates that anisotropy and convolution are properties of yield monitor data and that it is hard to distinguish the two. The degree and causes of anisotropy require further investigation. Fitting this model is relatively easy for small, precision-agriculture datasets and open source software is available to this end. Comparing the de Wijs model with more general models in the Matérn class is computationally intensive for precision-agriculture datasets.

The alkane patterns of the dominant forage species of the typical steppe grassland in Inner Mongolia were clarified, and the effects of species, sampling time and site on the concentrations of alkanes were evaluated. The results showed that alkanes with odd-numbered carbon chains in the range C25 (n-pentacosane)–C35 (n-pentatriacontane) were predominant in cuticular wax in five dominant grasses of the typical steppe. The C31 (n-hentriacontane) alkanes were always present in the highest concentration in the grass species, especially in the Stipa daicalensis and Stipa grandis. Samples of Artemisia frigida contained not only high concentrations of odd-chain alkanes, but also the even-chain ones compared with other species. The effects of species and sampling time on alkane concentrations were significant, accounting for 0·912 and 0·067 of the total variance, respectively. The site effects on odd-chain alkanes were less than on even-chain. The results of principal component analysis indicated that the patterns of alkane concentrations in the five dominant species could be clearly distinguished during the whole growing season. Therefore, it should be possible to achieve accurate and precise estimations of intake and diet composition of grazing animals of the typical steppe grassland in Inner Mongolia using the alkane technique.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirty-eighth meeting of the group, chaired by Professor A. Kassam of the University of Reading, was held in the Kohn Centre at the Royal Society, 6 Carlton House Terrace, London on Friday, 31 March 2006 when the following papers were read.

Soil organic carbon storage encompasses both soil productivity and environmental capabilities. The influence of fertilizer (nitrogen and phosphorus) levels (0 NP, 0·5 NP, 1·0 NP (recommended standard) or 1·5 NP) on total system productivity, sustainable yield index and soil organic carbon storage in Vertisols (Typic Haplustert) under groundnut and fallow-based cropping systems were examined in a field experiment over 6 years. The aim was to identify a system that provided an acceptable balance between total system productivity and soil organic carbon restoration. The experiment comprised two rainy season crops (groundnut or fallow) and five post-rainy season crops (wheat, mustard, chickpea, sunflower or summer groundnut), each post-rainy season crop with four levels of NP fertilizer. The total system productivity was 130% higher in the groundnut-based than in the fallow-based system and was in the order: groundnut–groundnut>groundnut–chickpea>groundnut–wheat>groundnut–mustard>groundnut–sunflower. The sustainable yield index was highest in the groundnut–groundnut system. The gross C input was relatively higher in the groundnut-based system but the C loss rate was greater. The amount of residue needed per ha per year to compensate for loss of soil organic carbon was estimated to be 4·3 t in the fallow-based and 7·6 t in the groundnut–based cropping system. Though the total system productivity was greater in groundnut–groundnut and groundnut–chickpea systems, soil organic carbon declined. The groundnut–wheat system contributed more C, particularly root biomass C, than other systems, improved the restoration of soil organic carbon and maintained total system productivity. It was concluded that current fertilizer recommendations are adequate for maintaining yields in groundnut-based systems but the addition of crop residues at regular intervals along with fertilizer is necessary to maintain restoration of soil organic carbon.

Alternate 2·4 m wide strips of a mixture of birdsfoot trefoil (Lotus corniculatus L.) with white clover (Trifolium repens L.) (BW), and of red clover (Trifolium pratense L.) (RC) were offered in the proportions (by area) of 0·80[ratio ]0·20, 0·67[ratio ]0·33, 0·33[ratio ]0·67 and 0·20[ratio ]0·80 to yearling heifers in groups of three for periods of 3 days over four replicates in time, balanced for effects of previous treatments. Observations on the distribution of grazing activity and biting rate were made over 3 h periods each evening, and on the morning of Day 2. Biting rates were consistently higher on BW than RC (52·3 v. 46·3±0·59 bites/min, P<0·001). Initially the animals showed a strong tendency to concentrate grazing on the sward of smaller proportional area, but the selection coefficient (log θ) changed from positive to negative with time as herbage on minority strips was depleted. These results are discussed in the context of concepts of partial grazing preference.

Glutathione S-transferases (EC 2.5.1.18, GSTs) are a family of multifunctional enzymes that play important roles in oxidative stress resistance. In the present study, it was investigated whether expressing Suaeda salsa GST in transgenic rice (Oryza sativa L. cv Zhonghua No.11) could confer resistance to abiotic stress. Several types of stress, including salt, paraquat and chilling were applied. It was shown that following paraquat applications, the activity of GST, catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) increased significantly in the GST transgenic plants compared with non-transgenics. Following NaCl and chilling stresses, only SOD and CAT activities increased markedly in the transgenics and there were no significant differences in GST expression between transgenics and non-transgenics. Moreover, in stressed plants, the generation of H2O2 and Malon dialdehyde decreased more in the transgenics than in non-transgenics. These results imply that expression of the Suaeda salsa GST in transgenic rice could enhance abiotic stress tolerance and the antioxidant enzymes of the active oxygen-scavenging system might play integral roles in the protection of plants from oxidative stress.

One hundred and twenty Spanish landraces of peas (Pisum sativum L.) collected in different micro-climatic areas, together with three commercial varieties and one breeding line, were subjected to molecular characterization using Inter Simple Sequence Repeat (ISSR) amplification. Landraces originated from 7 to 1427 m asl. Most accessions were collected in temperate areas with dry Mediterranean humidity regimes. ISSR markers detected high levels of variability between accessions and were useful for identification of individuals and clarification of genetic relationships between them. The 18 groups obtained with molecular data were not significantly related to 21 agro/climatic regions. Clustering based on climatic and ISSR characters differed because the data types present different aspects of genetic diversity. These results will be applied to establish a pea core collection at the Plant Genetic Resources Centre of the Spanish National Institute of Agriculture and Food Research and Technology (CRF-INIA).

The Erosion and Productivity Impact Calculator (EPIC) has been used to determine the effect of different cropping systems and management practices on soil productivity in the Loess Plateau of China. However, its crop growth and soil water balance submodels have not been verified in this region. The objective of the present study was to evaluate the ability of EPIC to estimate soil water content (θ in m3/m3), seasonal evapotranspiration (ET in mm/season) and crop yield (Y in t/ha) for winter wheat and maize. A 20-year field experiment was conducted at the Changwu Agro-ecological Experimental Station of the Loess Plateau, and divided into a calibration period and a validation period. Data from calibration (1984–94) were used to optimize the four most sensitive parameters of the EPIC crop yield submodel, whereas data from 1994 to 2004 were used for validation. For both crops, there were no significant differences between measured and estimated long-term means of the three variables (P=0·05) for either the calibration or validation periods. EPIC estimated all three variables with a small relative root mean square error (RRMSE), i.e. the ratio of root mean square error to the mean value. For wheat and maize, the calibration period resulted in respective RRMSE values of 0·112 and 0·100 for θ, 0·121 and 0·116 for ET, and 0·135 and 0·147 for Y. During the validation period, the RRMSE values obtained were 0·090 and 0·085 for θ, 0·129 and 0·135 for ET, and 0·169 and 0·149 for Y, for wheat and maize, respectively. The performance of EPIC in estimating annual values of θ, ET and Y was variable. For validation, EPIC explained 65, 79 and 64% of the measured variations of θ, ET and Y, respectively, for wheat, and 60, 70 and 67% for maize. The EPIC-estimated long-term average values of the three variables were not significantly different from measured values for winter wheat and maize during the calibration and validation periods. It can therefore be used in the gully region of the Loess Plateau to define alternative cropping systems and management practices.

The European Union has limited the maximum nitrate (NO3−) content allowed for industrial processed spinach (Spinacia oleracea L.) to 2000 mg/kg fresh weight in order to avoid human pathologies associated with uptake of high amounts of nitrate. Nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD) allow changing of the molecular form (NH4+ or NO3−) in which soil mineral N is available for plants. Enhancing ammonium nutrition has successfully reduced the amount of nitrate accumulated in plants in hydroponic culture. Therefore, fertilizers containing NIs have been proposed to reduce nitrate accumulated by vegetables grown in field conditions. Basammon Stabil® (BS) and Entec 26®-(E26) are commercial fertilizers containing DCD and DMPP respectively. In the present paper, the effect of applying ammonium sulphate nitrate (ASN), BS and E26 at three rates (0, 150 and 250 kg N/ha) to spinach crops cultivated under Mediterranean growing conditions for industrial processing is analysed. During 1998 and 1999, eight field split-plot trials with four replicates were carried out in the Ebro Valley, northern Spain, during different seasons and with various soil types. The fertilizer effects were influenced by the season and the type of soil. In spring, fertilizers containing NIs increased the mineral N (Nmin) in the soil and greatly reduced nitrate accumulation in the crop. In autumn, with less solar radiation, the nitrate accumulation was more than 2000 mg/kg fresh weight on many occasions and the effect of NIs was smaller. The present paper concluded that, under Mediterranean growing conditions, DCD can reduce nitrate accumulation in spinach between 18 and 61% and DMPP between 33 and 84%, without reducing yield or changing other quality characteristics. NIs are especially useful in the spring, when soil temperature is low and solar radiation interception by the crop is high.

This working group, which is concerned with operational research methods and applications to agricultural science in its broad meaning (i.e. including Forest Management and Fisheries), was formed in 2003 within the European Association of Operational Research Societies (EURO). The first meeting of the group was held at the former Silsoe Research Institute two years ago. The next meeting will be held in 2007 within the XXII EURO Conference in Prague. The group intends to start regular meetings at approximately yearly intervals in association with the EURO Conferences. The second meeting of the working group, chaired by Dr. L. M. Plà of the University of Lleida and organized as a stream within the XXI EURO Conference, was held at the University of Iceland in Reykjavík from 3rd–5th July 2006 where the following papers were read.

The effects of manipulation of sward maturity on ingestive behaviour and diet selection of grazing cattle were tested in two experiments using legumes which are equally preferred by cattle. Yearling heifers, in groups of three, grazed plots formed by alternate 2·4 m wide strips of a mixture of birdsfoot trefoil (Lotus corniculatus L.) and white clover (Trifolium repens L.) (BW) and strips of red clover (Trifolium pratense L.) (RC). The treatments comprised four combinations of each of the two swards at two contrasting levels of maturity/height replicated over four successive 3-day periods, in an order which balanced the effect of previous treatments. Observations of the distribution of grazing activity and biting rate were made over 3-hour periods each evening and in the morning of Day 2.

Rate of biting was generally greater on immature than mature swards, and on BW than on RC, with little evidence of interactions between these effects. The animals demonstrated partial preference throughout the two studies, the proportion of grazing time devoted to BW being 0·40±0·010 in Expt 1 and 0·47±0·017 in Expt 2. The distribution of grazing time between sward type and maturity combinations was influenced progressively by herbage mass and height contrasts as strips were grazed down. An overall analysis using the results from these studies and a companion experiment indicated differences between studies in partial preference for BW and RC which appeared to be related to variations in sward morphology.

Seventeen supersweet Shrunken-2 (sh-2) maize lines and progenies of their crosses to two sh-2 hybrid testers were investigated for factors responsible for differences in field emergence in Korea in studies carried out in the field, greenhouse and laboratory. The lines and their testcrosses showed significant genetic variation for emergence. Two lines showed significant positive general combining ability (GCA) for emergence while two other lines had significant negative GCA effects. Because none of the specific combining ability effects was significant, emergence was primarily influenced by additive gene action, and could, therefore, be improved by recurrent selection. Seed weight was significantly (P<0·05) correlated with emergence for inbreds (r=0·63) and testcross progeny involving the tester with the lower mean seed weight (r=0·54). Two lines also showed significant positive GCA effects for seed weight. The lines with positive GCA effects for emergence were different from those with positive GCA for seed weight, indicating that factors other than seed weight influence field emergence. The severity of Fusarium infection of seeds of the lines was significantly correlated to germination (r=−0·61, P<0·05) and emergence (r=−0·67, P<0·01), suggesting that practices that prevent pathogenic field infection, such as timely harvest and treatment with fungicides, are crucial for high seed quality. The field emergence of sh-2 inbred parents did not give an indication of emergence in hybrid combinations.