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 mug 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(.)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.
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/m(2) 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.
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 investigating effects of foliar disease control on wheat grain protein concentration (GPC) are reviewed. Fungicidal control of rusts (Puccinia spp.) and powdery mildew (Erysiphe graminis) increased or had no significant effect on GPC in almost all cases, whilst control of the Septoria spp. often resulted in reduced GPC, but with exceptions. Reasons for these differences are discussed with reference to host pathogen interactions. Irrespective of infection strategy (biotrophic or necrotrophic), controlling severe infection increased nitrogen yield and the proportion of above-ground crop nitrogen that was partitioned to the grain. Similar effects are recorded for above-ground biomass and dry matter harvest index. The relationships between fungicide effects on green flag leaf area duration (GFLAD) and GPC were examined and shown to be unaffected by mode of action of the fungicide. Interactions between fungicide use and cultivar, nitrogen and growing season are related to the amount and type of pathogen present, and environment. An economic analysis demonstrated that fungicide effects on GPC should not affect the choice of fungicide or application programme, but that applications of foliar urea at the start of grain filling can deliver a cost-effective method of eliminating GPC reductions that may occasionally result from fungicide use.
Three field experiments were conducted on sandy-loam soils comparing the effects of triazole, strobilurin and oxazolidinedione fungicides applied at flag leaf emergence and again at ear emergence to wheat between 1998 and 2000. Cultivars Hereward and Consort were included in all 3 years, Cockpit in 1999 and 2000 and Charger in 1999. Foliar disease, green area of the flag leaf, grain weight and moisture content were assessed weekly during grain filling and senescence. Grain yield, 1000 grain weight (TGW) and specific weights were measured at harvest maturity. Septoria tritici was the dominant disease in all cultivars except Cockpit, where Puccinia striiformis caused most damage. Consort was more affected than Hereward by S. tritici in all years. Effects of fungicides on disease control were usually reflected in green flag leaf area duration (GFLAD), with large gains in Consort and Cockpit. In 2000, however, fungicides increased GFLAD of Hereward and Consort by similar amounts. Apical grains had smaller water content than medially placed grains. Maximum water content was positively influenced by fungicides where significant disease was controlled before maximum grain weight had been attained. Grain weight in Hereward was less affected than other cultivars by fungicides in both positions. Grain filling rates varied between cultivar and ear position by inconsistent and small amounts, but large and significant gains from fungicide treatment were made in grain filling periods. These varied from 0.16 days per day GFLAD in Hereward to 0.69 days per day GFLAD in Consort in apical grains in 2000. Gains in GFLAD were associated with increased yield, TGW and specific weight, but these relationships varied with cultivar. Increases in GFLAD by fungicide in Hereward in 2000 occurred much later relative to grain filling and thus after the time of maximum grain water content, resulting in smaller gains in filling duration, yield, TGW and specific weight than that seen in Consort. There was no evidence of differing relationships between GFLAD and yield for the different fungicide groups used in these experiments.
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 a-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 a-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.
Tocopherols are the most important compounds having antioxidant activity in Sunflower seeds. The objective of the present research was to study the genetic and environmental variation for tocopherol content and composition in sunflower. Thirty-six sunflower hybrids were grown at 13 locations across all major areas of sunflower cultivation in southern Spain. Seed yield, 100 seed weight, oil content and tocopherol content and composition were determined. Tocopherol content ranged from 314.5 to 1024.5 mg/kg seed and from 562.8 to 1872.8 mg/kg oil. The tocopherol fraction was largely composed of alpha-tocopherol, which accounted for 88.4% to 96.3%, of the total tocopherols. Both genotypic and environmental effects were significant for tocopherol content and composition. For alpha-, beta- and total tocopherol content, the effect of the genotype was larger than that of the environment, whereas the latter had a greater effect on gamma-tocopherol content. Genotype x location interaction was significant for alpha-, gamma- and total tocopherol content. Tocopherol content was not correlated with seed oil or seed yield, indicating the possibility of selecting for this trait without affecting the performance of the genotypes.
Four field experiments were conducted to investigate the effects of seed rate on yield and quality of wheat. Despite some small and inconsistent effects of seed rate on radiation-use efficiency and harvest index, the responses of PAR interception, above-ground biomass and grain yield generally followed similar asymptotic increases as seed rate increased. In one experiment, when nitrogen fertilizer was withheld, biomass and grain yields did not respond to increases in seed rate despite increases in PAR interception. In one experiment, grain yield followed a parabolic response to seed rate with apparent reductions in yield at very high seed rates. Plants compensated for low population densities by increased production and survival of tillers and, to a lesser extent, increased grain numbers per ear. Net tiller production continued until the main stems flowered or later. Effects of seed rate on grain specific weight and thousand grain weight were small and inconsistent. Hagberg falling number increased linearly with seed rate in three experiments, associated with quicker maturation of the crop. Grain protein concentration declined with increase in sowing rate according to linear divided by linear or linear plus exponential models depending on whether the grain yield response was asymptotic or parabolic. Discolouration of the grain with blackpoint increased with seed rate in the most susceptible cultivar, namely Hereward. The economic consequences of these effects on yield and quality are discussed.
The effects of straw incorporation (early and late cultivation) and straw burning were contrasted in a split-plot study examining the impact of long-term straw residue management, and six fertilizer nitrogen (N) rates on soil mineral nitrogen, crop fertilizer N requirements and nitrate leaching losses. The experiments ran from 1984 to 1997 on light-textured soils at ADAS Gleadthorpe (Nottinghamshire, UK) and Morley Research Centre (Norfolk, UK). Soil incorporation of the straw residues returned an estimated 633 kg N/ha at Gleadthorpe and 429 kg N/ha at Morley on the treatment receiving 150 kg/ha per year fertilizer N since 1984. Straw disposal method had no consistent effect on grain and straw yields, crop N uptake, or optimal fertilizer N rates. In every year there was a positive response (Pearly incorporate >late plough. The incorporation of straw residues induced temporary N immobilization compared with the treatment where straw was burnt, while the earlier timing of tillage on the incorporate treatment resulted in slightly more mineral N compared with the later ploughed treatment. Fertilizer N rate increased (P<0(.)001) soil mineral nitrogen at both sites. At Morley, there was more organic carbon in the plough layer where straw had been incorporated (mean 1(.)09 g/100 g) rather than burnt (mean 0(.)89 g/100 g), and a strong positive relationship between organic carbon and fertilizer N rate (r(2)=93(.)2 %, P<0.01). There was a detectable effect of fertilizer N on readily mineralizable N in the plough layer at both Gleadthorpe (P<0(.)001) and Morley (P<0(.)05). At Morley, there was a consistent trend (P=0(.)06) for readily mineralizable N to be higher where straw had been incorporated rather than burnt, indicating that ploughing-in residues may contribute to soil nitrogen supply over the longer term.
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 deepploughed, 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 N-15 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.
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 x 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.
This work evaluated the effect of seed size and morphology on the development and biomass of durum wheat seedlings. Three different seed-grading sizes selected by sieving were used in glasshouse experiments, and a set of three developmental and 23 biomass-related indices were measured on eight genotypes, at two moisture levels. The influence of seed size on seedling development was studied at high and low temperatures (22/12 degreesC, and 15/5 degreesC day/night temperatures, respectively), in growth chambers. The area of the seed and the area of the embryo were the seed morphological traits most affected by seed size. Seed size was strongly associated with seedling development and seedling biomass until the complete extension of the first two leaves, at the fourth leaf stage. The rate of first-leaf growth and the area of the first leaf were the developmental and biomass traits, respectively, most sensitive to seed-grading size.
Nutrient intake, digestibility and live-weight changes were compared for groups of grazing cattle on two Swiss Alpine pastures in different regions (R1 and R2; both > 1500 in above sea level) during 2 years (1997 and 1998). The R1 site was an improved pasture, while R2 was an unimproved pasture of poor nutritional quality. Replicated over 2 years, R1 groups comprised four Scottish Highland suckler cows together with their calves and four Brown Swiss dairy cows (17.8 kg/day milk) kept at high stocking rates (approx. 7 cows/ha) in short rotations (intensive management system). R2 groups comprised four Highland cows with calves managed at low density (approx. 0.4 cows/ha) and set-stocked (extensive management system). Grazing seasons lasted 77 days at R1 and 127 days at R2. Intake, digestibility and faecal excretion were estimated by the slow-release alkane indicator method. Average dry matter intakes in kg/day and g/kg W-0.75/day (in parentheses) were 17.4 (151) for dairy cows at R1 and, significantly lower, 12.7 (133) and 11.1 (111) for beef cows at R1 and R2, respectively. Herbage dry-matter intake of calves was 1.2 kg/day at both locations. Calf weight gains measured over 77 days (0.69 kg/day) were similar at the two sites and thereafter declined only slightly at R2. The N content of the herbage selected was similar in the two regions, but in other respects the herbage at R2 was of significantly poorer nutritive quality as indicated by the lower digestibility of organic matter and neutral detergent fibre at R2 compared with R1. Through feed selection, nutrient intake by beef cows was sufficient to gain weight. In contrast, dairy cows at R1 lost on average more than 50 kg of weight. Calculations were made and discussed regarding N utilization and urinary N loss,and measured faecal N and mineral excretion to allow a quantitative assessment of nutrient returns to the sward. We conclude that Highland beef cattle make poorer use of improved Alpine pasture than dairy cows though they utilize pastures of poor nutritive quality under extensive management without loss of productivity.
A model is presented which will predict mean age at first egg (AFE) for pullets of laying strains reared under non-limiting environmental conditions but exposed to a single change in photoperiod during the rearing stage. An initial analysis of 12 previously reported trials involving a wide range of genotypes showed that the response to an increase in photoperiod is not simply the inverse of the response to an equal decrease in photoperiod applied at the same age. Maximum sensitivity to a reduction in photoperiod was found shortly before onset of lay, whereas maximum sensitivity to an increment in photoperiod was observed at around 10 weeks of age. Two experiments were conducted to provide further data. The first compared the effect of 3-h increases in photoperiod from 8 h to 11 h or from 11 h to 14 h with the double increment from 8 h to 14 h and also tested a reduction from 11 h to 8 h, all imposed at 17 weeks of age. AFE was advanced to a similar extent by the changes from 8 to 11 h and from 11 to 14 h (9.8 and 10.9 days respectively). Response to the double increment was not additive: AFE on this treatment was 13.3 days earlier than for constant 8 It controls. Reduction in photoperiod from 11 to 8 h at 17 weeks delayed AFE by 18.7 days compared with constant 11-h controls. In the second experiment, pullets of two strains were transferred from 8 to 16-h photoperiods and from 16 to 8 h at 5, 7, 9, 15, 17 and 19 weeks of age. Controls were kept on constant 8 and constant 16-h days. Transfer from 8 to 16-h photoperiods at 5 weeks of age had no effect on AFE. At 7 weeks there was a bimodal response with some pullets subsequently showing advanced maturity and others not. Maximum stimulation of early maturity (31 days on average for the two genotypes) was obtained at 9 weeks of age and response to stimulation declined linearly with age thereafter. The delay in AFE resulting from a reduction in photoperiod (16 to 8 h) increased linearly between 0 and 15 weeks. At 17 and 19 weeks, the response was bimodal, with some pullets maturing at the same age as long-day controls and others showing delayed maturity. Using all this evidence and some other unpublished data, a model is developed to predict AFE as a function of mean photoperiod and change in photoperiod during the rearing phase. Elements are incorporated to allow for the insensitivity of pullets younger than 50 days to an increase in photoperiod and the effect observed late in rearing when a change in photoperiod comes too late to alter AFE for the most precocious individuals in a flock. Two coefficients are required to adjust for genotype. One describes mean AFE for the genotype when reared on constant daylength and the other defines the rate at which age effects the response to a single change in photoperiod.
Mycorrhizal and non-mycorrhizal tomato plants (Lycopersicon esculentum Mill. cv 'Amalia') were subjected to water stress by withholding irrigation water for 72 hours and then reirrigated for 120 hours. Water stress reduced root mycorrhizal colonization, although the presence of the fungus Glomus clarum stimulated tomato plant growth. During the stress period the effect on the growth was more pronounced in aerial biomass than in the root biomass. The decrease in the soil water potential generated a decrease in leaf water potential (Psi(1)) and leaf turgor potential (Psi(t)), particularly in the non-mycorrhizal plants. Although the absence of osmotic adjustment provoked the loss of turgor in stressed plants, both Psi(1) and Psi(t) recovered after a short reirrigation period. Mycorrhizal infection improved photosynthetic activity (P-n) and stomatal conductance (g(s)) in non-stressed and stressed plants. These increases were accompanied by higher root hydraulic conductivity values, indicating enhanced water uptake in drought conditions. Neither P-n nor g(s) fully recovered after rewatering. The beneficial effect of the mycorrhizal symbiosis on the water status of tomato plants stimulated plant growth.
Many authors report on the effect of rice-fish culture on rice yields. Some reports show increased rice yields, others show no effect or even decreased yields. To verify the impact of rice-fish culture, data gathered over eight experiments (1995-1999) at the Co Do experimental rice-fish station, Vietnam, were analysed through multiple regressions with rice yield and different yield components as the dependent variables. We used eight independent variables: season, water depth, rice variety, rice seeding rate, and the effective stocking density (ESD) of silver barb, Nile tilapia, common carp and snakeskin gourami. Season had the biggest impact on nearly all dependent variables. Rice yields in the wet season were on average 2.42 t/ha lower as compared to the dry season. Higher water levels decreased the number of panicles/m(2) and the rice yield. The rice seeding rate affected the yield component variables, but had no impact on the rice yield. Silver barb feeding decreased the number of panicles/m(2) but this was compensated by an increased number of grains/panicle. Snakeskin gourami had a positive effect on panicles/m(2) and, together with common carp, on sink capacity, probably through improved nutrient cycling in presence of fish and improved nutrient uptake by the rice plant. Snakeskin gourami had a negative effect on the ripening ability, whereas Nile tilapia had a positive effect. Fish did not have any impact on the rice yield. Increased water level and reduced rice arable area, the main two requirements for rice-fish culture, result in lower rice yields from rice-fish systems as compared to monoculture systems.
This study compared phosphorus (P) speciation and the relationship between bicarbonate extractable (Olsen) P and 0(.)01 m CaCl2 extractable P (a measure of potentially mobile P) in soils from plots of the Park Grass experiment started in 1856 at IACR-Rothamsted, UK and with and without nitrogen as (NH4)(2)SO4 and with and without calcium carbonate (CaCO3, lime). A point, termed the change point, was noted in Olsen P, above which 0.01 m CaCl2-P increased at a greater rate per unit increase in Olsen P than below this point. Previous findings have shown a change point for soils with a pH > 5.8 at 56 mg Olsen P/kg and at 120 mg Olsen P/kg for soils below this pH. Soils given (NH4)(2)SO4 annually since 1856 and with lime periodically since 1903 mostly had a pH between 3.7 to 5.7, some of these (NH4)(2)SO4 treated soils were limed to pH 6.5 and above from 1965. Irrespective of their pH in 1991/92 all the soils had a similar change point (120 mg Olsen P/kg) to that found for other soils with pH 5.8) where there was less exchangeable Al to be precipitated. This was confirmed with solid-state P-31 nuclear magnetic resonance, which indicated that for soils of similar total P concentration and pH, there was twice as much amorphous Al-P in soils given (NH4)(2)SO4 compared with those without. Changes in pH as a result of applications of (NH4)(2)SO4 or lime can greatly change the concentration of potentially mobile P due to the effects on Al solubility. Although there was less potentially mobile P in soils with pH < 5.8 than in soils above this pH, it is usually advised in temperate regions to maintain soils about pH 6.5 for arable crops.
The possibilities for increasing total grain yield in organic cereal production through manipulation of crop rotation design were investigated in a field experiment oil different soil types in Denmark from 1997 to 2000. Three experimental factors were included in the experiment in a factorial design: (1) proportion of grass-clover and pulses in the rotation, (2) catch crop (with and Without) and (3) manure (with and without). Three four-course rotations were compared. Two of the rotations had 1 year of grass-clover as a green manure crop, either followed by spring wheat or by winter wheat. The grass-clover was replaced by winter cereals in the third rotation. Annual manure was applied as slurry in rates corresponding to 40 % of the nitrogen (N) demand of the cereal crops. Rotational grain yields of the cereal and Pulse Crops Were calculated by summing yields for each plot over the 4 years in the rotation. The rotational yields were affected by all experimental factors (rotation, manure and catch crop). However, the largest effects on both dry matter and N yields were caused by differences between sites caused by differences in soils, climate and cropping history. The rotation without a green manure crop produced the greatest total yield. Dry matter and N yields in this rotation were about 10 % higher than in the rotation with a grass-clover ley in 1 year in 4. Therefore, the yield benefits from the grass-clover ley could not adequately compensate for the yield reduction as a result of leaving 25 % of the rotation Out of production. There were no differences in dry matter and N yields in grains between the rotations, where either spring or winter cereals followed the grass-clover ley. The N use efficiency for ammonium-N in the applied manure corresponded to that obtained from N in commercial fertilizer. There were only very small yield benefits from the use of catch crops. However, this may change over time as fertility builds Lip in the system with catch crops.
Atriplex nummularia L. (atriplex) foliage and urea-treated straw have been used as nitrogen supplements for Barbarine lambs given Opuntia ficus-indica f. inermis (cactus) and their effects on feed intake, diet apparent digestibility, nitrogen balance and daily gain have been evaluated. Twenty-four lambs (mean live weight 19.9 +/- 2.79 kg) were randomly allocated to one of four experimental groups, groups 1-3 received freshly cut pads of cactus ad libitum. Group I was supplemented with 600 g untreated barley straw (C + US), while group 2 received 600 g urea-treated straw (C + UTS). Group 3 received 600 g untreated straw and 400 g atriplex (C + A). The amount of atriplex was calculated so that groups 2 and 3 receive iso-nitrogenous diets (i.e. C + UTS and C + A). Group 4 (US + BW) received a diet commonly offered to sheep by Tunisian smallholders, untreated straw ad libitum and 400 g of ground barley grain and wheat bran mixture (50:50). A growth trial (60 days) followed by a digestibility trial (8 days) were performed in 1999. Irrespective of dietary treatment, cactus intake was high, averaging 500 g dry matter (DM)/day. It was not affected (P > 0.05) with N supplementation, as urea-treated straw or atriplex. Sheep fed cactus-containing diets drank considerably less (P 0.05) on sheep growth (31.4 and 39.7 g/day, respectively). It is concluded that cactus may be considered as an emergency feed and water source for sheep in arid and semi-arid zones. Nitrogen supplementation of cactus-based diets with urea-treated straw or atriplex foliage improved the feeding value of these diets and consequently sheep growth. A cactus-based diet, supplemented with atriplex, promoted similar growth in sheep as the commonly used diet (US + BW).
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.