Since 1997, the EuroSOMNET project, funded by the EU-ENRICH programme, has assembled a metadatabase, and separate experimental databases, of European long-term experiments that investigate changes in soil organic matter. In this paper, we describe the WWW-based metadatabase, which is a product of this project. The database holds detailed records of 110 long-term soil organic matter experiments, giving a wide geographical coverage of Europe, and includes experiments from the European part of the former Soviet Union, many of which have not been available previously. For speed of access, records are stored as hyper-text mark-up language (HTML) files. In this paper, we describe the metadatabase, the experiments for which records are held, the information stored about each experiment, and summarize the main characteristics of these experiments. Details from the metadatabase have already been used to examine regional trends in soil organic matter in Germany and eastern Europe, to construct and calibrate a regional statistical model of humus balance in Russia, to examine the effects of climatic conditions on soil organic matter dynamics, to estimate the potential for carbon sequestration in agricultural soils in Europe, and to test and improve soil organic matter models. The EuroSOMNET metadatabase provides information applicable to a wide range of agricultural and environmental questions and can be accessed freely via the EuroSOMNET home page at URL: http://www.iacr.bbsrc.ac.uk/aen/eusomnet/index.htm.

The neutron probe (NP) is used widely to measure changes in soil water storage in research and more recently to aid irrigation scheduling. Its accuracy is rarely questioned and most of the relationships between soil water changes and productivity are based on its use. A field experiment was conducted at Cambridge University Farm in 1999 to address whether the NP could accurately measure changes in soil water content (SWC) under irrigation or substantial rain (>10 mm). The experiment was a replicated split-plot design with four irrigation treatments allocated to the main plots, and surface profile (ridge, flat) and crop (potato cv. Saturna, bare soil) treatments allocated to the subplots. The mean results from four NP access tubes per plot installed to measure soil moisture deficit (SMD) across the row-width were analysed. The NP was inconsistent in measuring known irrigation or rainfall input. In relatively dry soil (SMD>40 mm), the NP generally measured 93 to 110% of 18 mm of irrigation within 4 h of irrigation. The NP recorded much less water applied as irrigation in wetter soil, and often only 40 to 70% of the applied irrigation (18 or 36 mm) was measured. There were occasions when the NP did not measure all the water input even when the SMDs before irrigation were greater than the water subsequently applied. Some of the ‘missing’ water might be attributed to drainage, however, results from an additional experiment using an open-topped tank of soil showed that the NP was unable to detect all the water added to the soil, particularly where the water was largely confined close to the soil surface. Replicated measurements of the change in SMD in the field experiment were precise for a given event and treatment (mean S.E. = 1·3 mm) but were not accurate when compared against the input measured in rain gauges. It was concluded, that the NP could not be used reliably to measure changes in soil water storage after irrigation or substantial rain. For periods when there were minimal inputs of water, there was a closer correlation between changes in SMD measured by the NP and those predicted by a modified Penman–Monteith equation than after substantial inputs of water. However, for predicted changes in SMD of c. 20 mm, there was a range of c. ±5 mm in the changes in SMD measured by the neutron probe.

The value of the NP for monitoring SMDs where there is irrigation, or substantial rain, must be seriously doubted. Consequently, its limitations for scheduling irrigation, testing models or quantifying the effects of treatments on crop water use in potatoes must be appreciated, especially where the areal sampling limitations of single access tubes positioned only in the ridge centre have not been addressed.

Experiments in three dry years, 1993/94, 1994/95 and 1995/96, on a medium sand at ADAS Gleadthorpe, England, tested responses of six winter wheat cultivars to irrigation of dry-matter growth, partitioning of dry matter to leaf, stem and ear throughout the season, and to grain at final harvest. Cultivars (Haven, Maris Huntsman, Mercia, Rialto, Riband and Soissons) were selected for contrasts in flowering date and stem soluble carbohydrate. Maximum soil moisture deficit (SMD) exceeded 140 mm in all years, with large deficits (>75 mm) from early June in 1994 and from May in 1995 and 1996. The main effects of drought on partitioning of biomass were for a decrease in the proportion of the crop as lamina in the pre-flowering period, and then earlier retranslocation of stem reserves to grains during the first half of grain filling. Restricted water availability decreased grain yield by 1·83 t/ha in 1994 (P<0·05), and with more prolonged droughts, by 3·06 t/ha in 1995 (P<0·001) and by 4·55 t/ha in 1996 (P<0·001). Averaged over the three years, grain yield responses of the six cultivars differed significantly (P<0·05). Rialto and Mercia lost only 2·8 t/ha compared with Riband and Haven which lost 3·5 t/ha. Losses for Soissons and Maris Huntsman were intermediate. In the two years with prolonged drought, the biomass depression was on average greater for Haven (6·0 t/ha) than for Maris Huntsman (4·2 t/ha) (P<0·05). Thus, the grain yield sensitivity of Haven to drought derived, in part, from a sensitivity of biomass growth to drought. Harvest index (HI; ratio of grain to above-ground dry matter at harvest) responses of the six cultivars to irrigation also differed (P<0·05) and contributed to the yield responses. The smallest decrease in HI of the six cultivars with restricted water availability was shown by Rialto (−0·033); this partially explained the drought resistance for this cultivar. The largest decrease was for Maris Huntsman (−0·072). The cultivars differed in flowering dates by up to 9 days but these were poorly correlated with grain yield responses to irrigation. Stem soluble carbohydrate at flowering varied amongst cultivars from 220 to 300 g/m2 in the unirrigated crop; greater accumulation appeared to be associated with better maintenance of HI under drought. It is concluded that high stem-soluble carbohydrate reserves could be used to improve drought resistance in the UK's temperate climate, but that early flowering seems less likely to be useful.

A range of three generations from each of three populations of Cambridge Composite Cross Five of barley spanning a period of 18 years of cultivation in Cambridge was evaluated for grain yield over 2 years in the field in 1991 and 1992. The design of the experiment was a randomized complete block with two replications. In 1991, the yield of the best composite cross generation was 78% that of Atem, a commercial variety bred for N.W. European conditions. In the drought-affected year, 1992, three of the composite cross generations performed better than Atem. It is suggested that composite cross populations may be useful in deriving lines for low-input agriculture.

A 2-year split-plot field experiment investigated the influence of selected sulfonylurea herbicides including chlorsulfuron mixtures and presowing seed treatment using triadimenol/imazalil/fuberidazole (Baytan Universal 19·5 WP) on the incidence of naturally occurring net blotch (Drechslera teres (Sacc.)) Shoem of barley. All the herbicides examined provided effective and season-long weed control at a similar level that no significant differences in weed density and weed dry weight were found amongst herbicide treatments. Significant (P<0·05) increases in disease prevalence over the weedy check were recorded in herbicide treated plots throughout the evaluation period, but disease severity remained unaffected. Presowing seed treatment with Baytan Universal provided significant control of net blotch of barley compared with the control throughout the evaluation period. No phytotoxicity was observed in any of the treatments.

Ease of removal of the husk of oats from its enclosed kernel, hullability, affects the efficiency with which oats are milled. Hullability of a range of oat varieties was examined using a mechanical dehuller from autumn-sown trials in Northern Ireland, 1996–98, and in the Republic of Ireland, 1997–98. Varieties differed greatly in hullability, the spring variety, Barra, having good hullability while the winter variety, Gerald, had poor hullability. Differences between the varieties were largely consistent from site to site and from year to year despite large differences in the amounts of grain remaining unhulled from trial to trial. Although secondary grains were easier to dehull than primary grains, differences in the structure of the grain populations did not explain variation in hullability of the varieties. This study highlights the need for an investigation of the effects of agronomic factors on hullability.

A diagnostic survey carried out in 1997 to obtain baseline information on the farming situation in Transkei area of South Africa, showed that agriculture in this area was characterized by low technological inputs which invariably led to low agricultural outputs. The main farming system of the majority of the farmers (98%) was based on intercropping involving maize, beans and pumpkin combined in an haphazard fashion.

Based on the above findings, two field experiments were set up in 1998 designed to bring out the best planting combinations for maize/beans and maize/pumpkin intercrops which could be introduced to the farmers. Effect of weeding on the intercrops was also investigated.

In both intercrops, intercropping adversely affected the plant heights and circumferences of the component crops. Also, the yield of the individual crop in each intercrop was depressed by intercropping compared with its sole yield. In maize/beans intercrop, the yield of maize was depressed by 15% and that of beans by 13%. However in both intercrops, productivity as measured by Land Equivalent Ratio (LER) was the highest with maize at 10000 plants/ha combined with beans at 150000 plants/ha (2·60) with weeding while the combination with the best LER (1·50) in maize/pumpkin intercrop was at 30000 plants/ha of maize combined with pumpkin at 2500 plants/ha, with weeding. However, before any final recommendation is made, the profitability of each combination has to be considered.

Weeding was found to enhance intercrop yields in maize/bean combination by 35% and by 30% in maize/pumpkin combination.

Twenty-one elite sorghum lines were assessed for resistance to foliar, peduncle, rachis, grain and overall panicle anthracnose under natural infection at Samaru and Bagauda in 1996 and 1997. Three genotypes (R 6078, IS 14384 and CCGM 1/19-1-1) were completely resistant to all forms of the disease while Nagawhite was completely resistant to foliar, peduncle and rachis but moderately resistant to panicle anthracnose. The data indicate vertical disease progression from leaves onto peduncle and the rachis. More genotypes were susceptible to grain than rachis anthracnose thus indicating that grain infection could be direct or through vertical progression and direct pathways.

The proanthocyanidin (PA) status of 116 accessions from the Leucaena genus representing 21 species, 6 subspecies, 3 varieties and 4 interspecific hybrids was evaluated under uniform environmental and experimental conditions at Redland Bay, Queensland, Australia in October 1997. The PA content of lyophilized youngest fully expanded leaves was measured spectrophotometrically by the butanol/HCl assay referenced to L. leucocephala ssp. glabrata standard PA and expressed as L. leucocephala ssp. glabrata PA equivalents (LLPAE). Considerable interspecific variation in PA concentration existed within the genus, ranging from 0–339 g LLPAE/kg dry matter (DM). Taxa including L. confertiflora, L. cuspidata, L. esculenta and L. greggii contained very high (>180 g LLPAE/kg DM) PA concentrations. Similarly, many agronomically superior accessions from L. diversifolia, L. pallida and L. trichandra contained extremely high (up to 250 g LLPAE/kg DM) PA concentrations, although these taxa exhibited wide intraspecific variation in PA content offering the potential to select accessions with lower (120–160 g LLPAE/kg DM) PA content. Commercial cultivars of L. leucocephala ssp. glabrata, known to produce forage of superior quality, contained low amounts of PA (33–39 g LLPAE/kg DM). Artificial interspecific hybrids had PA contents intermediate to those of both parents. Lesser-known taxa, including L. collinsii, L. lanceolata, L. lempirana, L. macrophylla, L. magnifica, L. multicapitula, L. salvadorensis and L. trichodes, contained undetectable to low (0–36 g LLPAE/kg DM) quantities of PA and have potential as parents to breed interspecific hybrids of low PA status and superior forage quality. Extractable PA was the dominant PA component, accounting for 91% of total PA within the genus. Regression analysis of accession ranks from different experiments compared to these results indicated that genetic regulation of Leucaena spp. PA content was consistent (P<0·01) under different edapho-climatic environments. The distribution of PA within the Leucaena genus did not concur with the predictions of various evolutionary and phylogenetic plant defence theories.

Body mass was measured and body composition and energy requirements were estimated in sheep at four air temperatures (0 °C to 30 °C) and at four levels of energy offered (4715 to 11785 kJ/day) at a time when the sheep reached a constant body mass. Final body mass was affected mainly by metabolizable energy intake and, to a lesser extent, by air temperature, whereas maintenance requirements were affected mainly by air temperature. Mean energy requirements were similar and lowest at 20 °C and 30 °C (407·5 and 410·5 kJ/kg0·75, respectively) and increased with a decrease in air temperature (528·8 kJ/kg0·75 at 10 °C and 713·3 kJ/kg0·75 at 0 °C). Absolute total body water volume was related positively to metabolizable energy intake and to air temperature. Absolute fat, protein and ash contents were all affected positively by metabolizable energy intake and tended to be related positively to air temperature. In proportion to body mass, total body water volume decreased with an increase in metabolizable energy intake and with an increase in air temperature. Proportionate fat content increased with an increase in metabolizable energy intake and tended to increase with an increase in air temperature. In contrast, proportionate protein content decreased with an increase in metabolizable energy intake and tended to decrease with an increase in air temperature. In all cases, the multiple linear regression using both air temperature and metabolizable energy intake improved the fit over the simple linear regressions of either air temperature or metabolizable energy intake and lowered the standard error of the estimate. The fit was further improved and the standard error of the estimate was further lowered using a polynomial model with both independent variables to fit the data, since there was little change in the measurements between 20 °C and 30 °C, as both air temperatures were most likely within the thermal neutral zone of the sheep. It was concluded that total body energy content, total body water volume, fat and protein content of sheep of the same body mass differed or tended to differ when kept at different air temperatures.

Hydrogen sulphide (H2S) is a common toxic air pollutant and is emitted from decomposing manure at animal facilities. However, there have been only a few studies of H2S emissions from animal buildings, especially those involving long-term, high-frequency measurements. In the current study, H2S emissions from two, 1000-head pig-finishing buildings in Illinois, USA, were monitored with a high-frequency measurement system for 6 months in 1997 during two, partial, pig-growth cycles. Air sample streams were continuously taken from the pit headspace, and the pit and wall fan exhaust air. Hydrogen sulphide concentration was measured at each location with H2S converters and sulphur dioxide (SO2) analysers during 16 or 24 sampling cycles per day, resulting in 4544 sampling cycles and 219 days of reliable data. Building ventilation rate was the summation of pit fan and wall fan airflow rates. Airflow rates of the underfloor manure pit fans were measured directly with full-size impeller anemometers or calculated from airflow/voltage relationships of the fans. Airflow rates of the wall fans were calculated from fan operation and differential static pressure data and fan performance curves. Mean H2S emission was 0·59 kg/day per building, 0·74 g/day per m2 of pit surface area, or 6·3 g/day per animal unit (AU = 500 kg animal weight). The determination of H2S emission per AU was restricted to 193 days when building occupancy was at least 700 pigs per building. Higher temperatures and building ventilation rates resulted in significantly higher H2S emissions per AU.