Grain yield of barley (Hordeum vulgare L.) in northern Syria is limited by water stress and extremes of temperature. The present study compared the grain yield of two barley cultivars, Harmal (spring type, cold-sensitive, early heading) and Arabi Aswad (winter type, cold-tolerant, medium early heading), under varying rainfall and temperature. Grain yield was obtained from three sites in northern Syria for seven seasons (1984/85 to 1990/91), resulting in 18 site × season combinations, here called environments. Multiple regression models, containing one rainfall and one temperature variable, were used to quantify yield responses to environmental fluctuations.

Total seasonal rainfall was the variable most strongly correlated with the grain yield of Harmal, accounting for 62·8% of the variance. For Arabi Aswad, rainfall from November to January gave the best fit, accounting for 61·8% of the variance. December and January rainfall had the highest contribution to the yield of both cultivars; the contribution of March rainfall tended to be negative. The overall yield response to seasonal rainfall was 11·89 kg/ha/mm for Harmal and 8·57 kg/ha/mm for Arabi Aswad; the expected grain yield at the driest site was c. 1270 kg/ha for both cultivars. The addition of a temperature variable gave a better fit, accounting for c. 80% of the variance in grain yield for both cultivars if winter rainfall was combined with number of night frosts in spring. It reduced the expected yields at the driest site to c. 986 kg/ha. Arabi Aswad had a lesser response to both rainfall and frost than Harmal.

In environments where low yields are due to both water and temperature stress, farmers are advised to grow Arabi Aswad because its lesser sensitivity to environmental fluctuations will ensure a better yield stability.

White clover (Trifolium repens L.) is well adapted to the cool moist climate of Atlantic Canada, where it improves digestibility and protein content in pastures, but little is known about its role in pasture stockpiled for autumn grazing in this region. The objectives of this study were to determine the effect of autumn harvest dates on dry matter yield and clover content in herbage mixtures. Two experiments conducted in Nova Scotia between 1985 and 1991 on two different soil types showed that the effects of autumn harvest dates were inconsistent from year to year. Herbage growth rates ranged from 11 to 41 kg/ha per day between early September and mid-October. Clover content was generally lower in August–early September than in November harvests and declined in subsequent years irrespective of harvest date or forage species. Kersey White and Sonja white clovers were the highest yielding cultivars. Crude protein declined in late autumn harvests whereas acid detergent fibre tended to increase, and there were differences between years. Forage quality was significantly better in tall fescue (Festuca arundinacea Schreb.) than orchardgrass (Dactylis glomerata L.)/white clover mixtures.

Fungal spoilage of animal feed silage occurs frequently. In spoiled silage of sugarbeet press pulp sampled in The Netherlands during the period 1986–90, 40% of the samples were infested by Penicillium roquefortii. Other fungi of health significance included Aspergillus fumigatus (8% of all samples) and Byssochlamys spp. (4 % of all samples). P. roquefortii is also the dominant spoilage mould in maize silage. However, no PR-toxin could be detected in 25 lumps of P. roquefortii-intested maize silage, although one lump contained a fluorescent substance, with an Rff-value close to that of PR-toxin. This silage sample was not mutagenic, but had a cytotoxic effect towards Salmonella typhimurium in the Ames test. All P. roquefortii-infested lumps contained fluorescent fungal metabolites which were absent in samples taken at 5 cm distance from the corresponding lumps in the silage heaps. It is recommended that lumps of fungal-infested silage are removed before feeding the silage to cattle.

A half-diallel design, with parents, involving a random sample of nine partially inbred (S1) lines was used to examine the genetic control of bolting in a broad-based North-West European sugarbeet breeding population. The diallel was analysed using the Hayman (1954a) and Jinks & Hayman (1953) analyses. Additive genetic effects were shown to be highly important and significant dominance effects were found. A general trend for bolting resistance to be dominant was detected but there was also evidence that the control was ambidirectional. Furthermore, the dominance effects seemed only partially effective. Some indication of epistatic effects was found, although the possibility that this was spurious, caused by failures in the genetic assumptions required by the analyses, is discussed. The genetic control of bolting in the breeding population appeared complex.

An advancing and devernalizing treatment for sugarbeet seed has been developed which, in England, allows sowing to be brought forward safely by c. 10 days to around 10 March. Experiments done each year from 1988 to 1991 were used to assess the value of this change. They showed that sugar yield increased by 0·048 t/ha/day because seed advancement resulted in more rapid emergence, and by 0·042 t/ha/day as a result of earlier sowing. As an average of all appropriate data from experiments in England since the 1950s, the advantage of sowing in March is 0·035 t/ha/day. However, the actual change in sowing date which the farmer might achieve will depend on soil type and rainfall. Daily rainfall and evaporation data for eastern England in March and April were used to predict the number and distribution of available machinery work days. On this basis, the average sowing date was predicted to advance by 9 days. Thus the sugar yield improvement which could be produced by advancing and devernalizing beet seed is equivalent to 9 days at 0·035 t/ha/day, plus 0·19 t/ha, or c. 0·5 t/ha. In practice, this should translate into an increase of 0·35 t/ha, or c. 5% of the average yield.

The response of groundnut to different amounts of irrigation water and the effect of irrigation on the occurrence of chlorosis during the establishment period of the crop were studied in south-west Cyprus in 1984–88. The irrigation requirement of groundnut for the entire growing season was found to be 480 mm. Under-irrigation resulted in a soil water deficit and reduced production. Application of water in excess of requirement also reduced yield. Daily evapotranspiration under optimum soil moisture conditions increased from 1·5–2·0 mm at the beginning of the growing season to 7·0–7·5 mm at full crop development; it then decreased to 2·0–3·0 mm by the end of the season. In soils of low CaCO3 content, neither frequent water application nor over-irrigation during the crop establishment period caused any chlorotic symptoms or affected yield.

Lentil (Lens culinaris Medikus) is a rain-fed crop in North Africa and West Asia whose yields are limited by the amount and distribution of rainfall and winter cold. This study aimed to quantify the effects of climatic variables on lentil seed yields through the fitting of simple empirical models to trial data of two cultivars sown at six sites, 1983–89, representing 31 environments in Syria. The ranges over environments were 152–527 mm for total season rainfall and 1–52 for the number of frost nights. Overall, the total seasonal rainfall accounted for 40·8% of the variance in mean seed yield (1·27 t//ha, S.D. 0·82) with a response of 5·68 kg/ha/mm. A multiple regression model with monthly rainfall from November to May explained 67·6;0% of the variance in mean seed yield. From November to February the response of seed yield to rain was < 10 kg/ha/mm; rain in March, the period of late vegetative growth, made the most important contribution to seed yield. The response to April rain was negative. At Tel Hadya (the most frequently used site), the total seasonal rainfall accounted for 79·8% of the variance in mean seed yield, and the addition of the number of frost nights to the model improved the fit to 92·7%. Winter cold had a smaller effect on yield than rainfall, with no consistent overall effect, but differences over regions. The cultivars contrasted in their responses to drought (78S26002 was superior to ILL4400 at seasonal rainfall levels down to 134 mm) and the number of frost nights at Breda and Tel Hadya (78S26002 was more susceptible to cold than ILL4400). Thus, despite the predominant influence of rainfall on yield, the genetic variability in response to moisture and cold shows the scope for selection under rainfed Mediterranean environments.

Three field experiments in Eastern England, in which 15N-labelled fertilizer had been applied to winter wheat, were used to measure the persistence of the labelled N remaining in soil and stubble at harvest and the availability of this N to up to four subsequent wheat crops. A portion of the labelled fertilizer N quickly became stabilized in the soil, with only small and ever-decreasing amounts recovered by subsequent crops. Combining all sites, all years and all applications of fertilizer, 6·6±1·92 (S.D.) % of the labelled fertilizer remaining in soil (0–70 cm) plus stubble in the year of application was taken up by the next wheat crop, i.e. by the first ‘residual year’ crop. A further 3·5±0·39% was taken up in the second residual year, 2·2±0·43% in the third and 2·2% in the fourth. Loss of residual labelled N was more rapid from a sandy soil than from two heavier-textured soils, particularly in the first residual year. After four residual crops on one of the heavier soils (at Rothamsted), 16% of the labelled N remaining in soil (0–70 cm) and stubble in the year of application had been taken up by the crops, c. 29% had been lost from the soil/crop system and 55% remained in the soil.

A computer model is presented that describes the flow of nitrogen between crop and soil on the field scale. The model has a compartmental structure and runs on a weekly time-step. Nitrogen enters via atmospheric deposition and by application of fertilizer or organic manures, and is lost through denitrification, leaching, volatilization and removal in the crop at harvest. Organic nitrogen is contained within three of the model compartments – crop residues (including plant material dying off through the growing season), soil microbial biomass and humus. Inorganic nitrogen is held in two pools as NH4+ or NO3-. Nitrogen flows in and out of these inorganic pools as a result of mineralization, immobilization, nitrification, leaching, denitrification and plant uptake. The model requires a description of the soil and the meteorological records for the site – mean weekly air temperature, weekly rainfall and weekly evapotranspiration. The model is designed to be used in a ‘carry forward’ mode – one year's run providing the input for the next, and so on. The model also allows the addition of 15N as labelled fertilizer, and follows its progress through crop and soil. Data from a Rothamsted field experiment in which the fate of a single pulse of labelled N was followed over several years were used to set the model parameters. The model, thus tuned, was then tested against other data from this and two contrasting sites in south-east England. Over a period of 4 years, the root mean square (R.M.S.) difference between modelled and measured quantities of labelled N remaining in the soil of all three sites was c. 7·5 kg N/ha, on average. The root mean square error in the measurements was c. 2·5 kg/ha. Similarly, the R.M.S. difference between modelled and measured recovery of labelled N by the crop was 0·6, compared with 0·3 kg/ha in the measurements themselves.

Red deer stags in New Zealand were given a series of immunizations against GnRH at 9–12 months of age (spring/early summer) in 1989 and 1990 and the effects upon plasma concentrations of luteinizing hormone (LH) and testosterone during the rut (15–17 months; autumn) and upon body growth to slaughter at 22 months (spring) were studied in two experiments. Control animals showed a sharp peak in plasma LH and testosterone concentration during late summer/early autumn, just preceding the rut, with scrotal circumference increasing to a maximum during the rut; body growth stopped during the rut in Expt 1 but not in Expt 2. Immunization caused the development of significant antibodies against GnRH during late spring and summer, and reduced but did not eliminate the increase in plasma LH and testosterone and scrotal enlargement leading up to the rut. Immunization did not affect body growth or voluntary feed intake during the rut in either experiment, but in Expt 1 early immunization significantly increased growth during both the pre-rut and post-rut periods. Immunization did not effect dressing out percentage, slightly increased carcass fatness in Expt 1 but not Expt 2, and reduced velvet antler growth by 12 months of age.

The effects of plane of nutrition on blood flow in the portal vein (PBF) and on the rate of clearance of progesterone from the circulation (MCR) were measured for 14 or 24 h in six ovariectomized gilts given 1 or 3 kg of food per day. On a body weight basis, PBF was significantly increased by the increase in food intake from a mean for all gilts of 14·9 ml/kg.min (1·34 litres/min) on 1 kg to 21·6 ml·kg. min (1·96 litres/min) on 3 kg, a mean increase of 45 %. Metabolic clearance of progesterone was increased by a similar percentage, 47·1%, from 41·0 ml/kg.min (3·70 litres/min) to 60·3 ml/kg.min (5·67 litres/min) by the increase in food intake. Both MCR and PBF were lowest between 04.00 and 06.00 h, increasing after each feed except that when 3 kg/day was fed the MCR remained high throughout the period between meals. In two gilts, blood flow in both the portal vein and hepatic artery (HAF) was measured. The mean PBF and HAF for each pig were 40·6 and 5·8, and 32·4 and 35 ml/kg, min respectively. HAF was 11·2% of total hepatic blood flow.

Ten young crossbred Finnish Landrace sheep and eleven young crossbred Damascus goats with liveweights ranging from 14 to 50 kg and of different ages and body condition, were used to develop equations to predict the body composition (chemical) in the intact body and dressed carcass of young sheep and goats. After injection with tritiated water, the animals were slaughtered and their carcasses partitioned into anatomical body components which were each analysed for chemical composition (water, fat, protein, ash) and energy content. From these components, the energy content and chemical composition of the intact bodies were calculated by summation. Apart from organ and gut fat, the two species had a similar body component composition. Goat intact bodies were more hydrated and had less fat, but were similar to sheep in protein and ash content. The energy concentration in their body components was also similar, but goats had a lower energy concentration in their intact bodies. Total body water, energy content and dressed carcass were predicted accurately by the derived equations, but fat, protein and ash were predicted with less precision.

The effects of dietary deficiencies of phosphorus (P) and nitrogen (N) were studied in 28 lambs allotted to seven treatments for 18 weeks. The lambs in four treatments were offered roughage-based diets ad libitum containing high (H) or low (L) levels of P (4·13 or 0·98 g/kg dry matter (DM)) and N (108 or 68 g crude protein/kg DM). The lambs in the remaining three treatments were fed the same quantities of DM of the HNHP diet as the lambs receiving the three deficient diets (HNLP, LNHP and LNLP). A dietary deficiency of P caused a reduced DM intake and liveweight gain, lower yields of N and DM in carcass muscle and reduced DM, N and P contents of bone. A dietary deficiency of N resulted in reductions in DM intake, liveweight gain, DM digestibility, N balance, and in carcass muscle and bone DM and N. The deficiencies of N and P were not additive in lowering food intake but were additive in reducing the mineralization of the bones. The DM intake of the lambs offered their diets ad libitum was closely correlated to the log of the plasma inorganic P and urea N concentrations (R =0·72). Feeding lambs with restricted quantities of diet HNHP resulted in higher liveweight gains and DM and N digestibilities than when any of the deficient diets were offered. Measurement of the N content of the lambs by a neutron capture gamma ray analysis technique showed that the changes were occurring progressively over the experimental period. The P content of the metatarsal bone, measured by a neutron activation technique, showed progressive changes. Although the faecal endogenous losses of P were related to P intake, high urinary losses were observed in those lambs which had their food intake limited by low dietary N alone, or had their food intakes restricted. The total endogenous P losses of the lambs were most closely dependent upon the DM intake and plasma inorganic P together. The efficiency of P absorption was high (> 0·75) in all lambs except for those given the HNHP diet ad libitum. The glucose entry rate was reduced in the lambs offered diets deficient in either N or P. Mechanisms by which the N and P deficiencies reduce DM intake are discussed.

Broiler chicks reared under three environmental temperatures (7·2, 23·9 and 35 °C) in the Southeastern United States of America in 1988/89 were precision-fed to levels which were c. 70, 90, 110 and 130% of the consumption observed in ad libitum-fed controls at 23·9°C, in order to examine the limitations imposed by feed intake upon growth rate, feed efficiency and survival. Ad libitum-fed birds that were housed at 7·2, 23·9 and 35 °C consumed feed at 12·1, 9·4 and 8·5% of body weight, respectively. Liveweight gain of birds consuming feed ad libitum was depressed by 26 and 46% in the 7·2 and 35 °C environments respectively. Increasing feed intake by precision feeding exceeded ad libitum consumption in the 23·9 and 35 °C environments, but not at 7·2 °C. Consumption of feed above thermoneutral ad libitum levels failed to increase (p <0·l) liveweight of carcass gain. Ration digestibility and dressing out percentage declined (P < 0·05) at the higher feed intake levels in the 7·2 °C environment.

The hulls (seed coat) of tannin-free, white-flowered and tannin-containing, coloured-flowered faba beans (Viciafaba L.) were used in three experiments (1989–90) to investigate the effect of tannins on the apparent metabolizable energy corrected to zero nitrogen retention (AMEN) and apparent metabolizable nitrogen (AMN) of broiler chick diets.

In Experiment 1, the effects of four rates of hull inclusion from one white- and one colouredflowered cultivar (0, 28, 56 and 84 g/kg) on dietary AMEN and AMN were studied. There was a significant response of AMEN to hull inclusion rate (P <0·001) but no inclusion rate × cultivar interaction. For dietary AMN there was a significant effect of hull inclusion rate (P <0· 001) but no inclusion rate x cultivar interaction.

Experiment 2 consisted of two parts. In both, the total concentration of hulls was 227 g/kg but the ratio of white- to coloured-flowered hulls was varied in five increments; initially over the range 0·42–16·58 g/kg dry matter (DM) and subsequently, with another cultivar, 0·44–7·85 g/kg DM. Synthetic lysine and methionine were added to ensure that the basal diet was not limiting in these amino acids. A significant effect of tannin intake on dietary AMEN and AMN was detected across the greater range of tannin concentrations (P <0·001) but not across the smaller one.

Experiment 3 evaluated three pairs of near-isogenic faba bean lines differing only in the gene governing tannin content and flower colour. Diets were formulated using three bean inclusion rates; 200, 400 and 600 g/kg. At each rate the white- and coloured-flowered lines were mixed in the ratios 100:0, 75:25, 50:50, 25:75 and 0:100. The response in carcass nitrogen retention (CNR) to tannin intake was assessed at each bean inclusion rate and for each pair of lines.

There was a significant effect of tannin intake on CNR in only one of the nine comparisons and in that case CNR increased as dietary content increased.

It was concluded that faba bean tannins can have a negative effect on the dietary AMEN and AMN for chicks when present at a sufficiently high dietary concentration. However, the highest dietary concentration of faba bean tannins in Expt 3 was 10·52 g/kg DM, giving a maximum daily intake of 1·03 g tannins for the two-bird experimental unit. At concentrations and intakes up to this there was no evidence to suggest that faba bean tannins had a significant adverse effect.