A field study in India in 1987 evaluated the effects of flooding at either tillering (25 days after sowing) or flowering (50 days after sowing) or at both on growth, yield and mineral composition of Pennisetum americanum L. Leeke in a moderately sodic soil (pH 8·5, exchangeable Na 18%).

Flooding for 1, 2, 4 or 6 days at tillering or flowering significantly reduced tillering, plant height, dry matter content, ear length and 1000-grain weight and resulted in a 6·3, 150, 21·6 or 26·6% reduction in grain yield, respectively. Flooding decreased oxygen diffusion rate, restricted root growth and decreased ion uptake, especially of N, P, K and Zn, and led to higher absorption of Na, Fe and Mn. The detrimental effects were greater when the crop was flooded at both stages.

Silastic implants of different lengths (0·5–4 cm) containing oestradiol were implanted in wether or ewe lambs, which were slaughtered at 14 or 23 weeks of age. Live weight gain and carcass weight of lambs was increased marginally by oestradiol treatment. Oestradiol decreased the percentage of fat in the carcass, while increasing the percentage of carcass water. Older lambs had a greater response to oestradiol treatment for the weights of the carcass protein and ash. The female reproductive system was affected by oestradiol with the ovarian weights being depressed and the uterine weights increasing. The uterus was especially sensitive to oestradiol at 14 weeks of age. Oestradiol increased the weight of protein in lamb carcasses, especially in the older lambs of this study.

A total of 51 grass swaths was dried in a wind tunnel under controlled conditions of temperature and humidity. The swath treatments covered a range of conditioning treatments, crop types, maturities and porosities. Drying rates of the swaths were related to crop and swath properties to establish which variables were important in influencing the overall drying rates of the swaths. Multiple regression analysis was used to assess the statistical dependence of drying rate on variables reflecting crop and swath properties: the dependence on swath structure was approximately four times greater than the dependence on crop conditioning. Improved swath drying rates could be achieved by lesssophisticated machinery than the current mower conditioners.

Responses of cultivars of Lolium perenne with contrasting winter hardiness to hardening and dehardening at different temperatures were studied in controlled-environment experiments in 1984/85. After hardening at 2 °C, the hardy cultivars Premo and S23 had faster initial rates of change of LT50 (lethal temperature at which 50% of plants were killed), measured on seedlings in an artificial freezing test, and achieved a greater degree of cold tolerance than the susceptible cultivar Grasslands Ruanui. When acclimated at higher temperatures (4–10 °C), the hardier cultivars were better able to develop increased cold tolerance than Grasslands Ruanui. Plants of Premo and S23, previously hardened at 2 °C, maintained their cold tolerance when transferred to warmer temperatures (4–12 °C) better than Grasslands Ruanui, which dehardened even at 4 °C.

The responses of the cultivars to hardening and dehardening temperatures under controlled-environment conditions were reflected in seasonal changes in hardiness, measured as cold tolerance of tillers sampled during fluctuating temperatures of a typical maritime winter (1977/78) at Aberystwyth, UK.

In a field which had been grazed by dairy cows for 26 years, the bulk density of both total soil and fine earth increased rapidly with depth down to 10–12 cm, but decreased below this depth. The bulk density was approximately twice as great in the 10–12 cm as in the 2–4 cm layer. Total porosity in the 10–12 cm layer was only 22%.

Slitting the soil to penetrate the compacted layer approximately doubled net herbage accumulation and the net uptake of N, P and K, raising herbage production and uptake of nutrients from a low level to an acceptable one. Slitting tended to increase the concentrations of nitrate-N and K in herbage, but had little effect on the concentration of total N. Slitting increased the weight of ash-free root in the 10–20 cm depth range.

Various measures of skeletal size were made on five or six occasions on 30 Dorset Horn and 30 Corriedale sheep (10 entire males, 10 females and 10 castrated males) commencing at 1 month of age (live weight 10 kg) and then at increments of 10 kg until 55 kg. After weaning at 6–7 weeks, they were fed ad libitumon a high-quality diet. The data sets for each sheep were analysed separately and, where appropriate, pooled equations for sex and breed were generated. Within both breeds, males had the widest shoulders at any given age and, within the Corriedales, males had the deepest chests. Dorset Horns grew faster than Corriedales and, except for leg length, were larger and heavier at corresponding ages.

At any given live weight, there was no difference between sexes within breeds and the breeds had similar chest depths. The Corriedales had longer legs and smaller shoulders than the Dorset Horns at all weights and, when heavier than 30 kg, were also larger in other body dimensions.

The lentil (Lens culinaris Medik.) cultivars Titore and Olympic were sown at Canterbury, New Zealand, on eight dates, from April to November in 1984 and in May and August in 1985. Of the four important physiological growth stages (sowing to emergence (S–E), emergence to flowering (E–F), flowering to physiological maturity (F–Pm) and physiological maturity to harvest (Pm–H)), the duration of all except E–F depended upon accumulated thermal time above 2 °C. The mean accumulated thermal times for E–F, F–Pm, Pm–H were 116, 565 and 293 °C days, respectively. Stage E–F required from 1165 °C days for an April sowing to 509 °C days for a November sowing. There was a highly significant positive relationship (r2 = 0·99) between the rate of development during E–F and mean temperature. Photoperiod also affected development rate.

Neither of the two cultivars studied had a vernalization requirement for the induction of flowering. In both years, the development rate during E–F was highly dependent upon photoperiod-corrected temperature. The relationships presented show that development of lentil crops in Canterbury can be accurately predicted using accumulated temperature and photoperiod-corrected temperature.

The C3 and C4 plant components in extrusa samples from oesophageally fistulated cattle can be estimated by δ13Canalysis. However, contamination with saliva containing bicarbonates could cause bias in the estimation of the C3 or C4 components. Saliva from animals fed C4 and C3 diets had δ13C values of – 4.37/103 and –15.97/103, respectively. Both values showed a large positive shift of c. 10 units relative to the diets, but the difference between feeds was maintained in the saliva. On theoretical grounds, contamination of the ingested feed with saliva should have caused a small (1·3–3·4% legume) negative bias when estimating legume percentage in the diet. This did not occur when saliva of known (PC was added to mixtures of C3 and C4 forages which were dried, ground and analysed for δ13C. It is postulated that CO2 was lost from bicarbonate when saliva was dried in contact with fresh plant material, and so no significant bias was detected. It would appear that the δ13C technique can be used to estimate the proportion of C3 and C4 components in oesophageal extrusa samples without significant bias from salivary contamination.

In field studies of two varieties in Cambridge, UK, in 1985 and 1986, the percentage of total incident radiation intercepted by potato canopies with complete ground cover was as low as 80% for some plots but approached 100% in dense canopies. Although percentage ground cover is useful for assessing canopy growth, it is not wholly suitable for estimating light interception and may lead to serious errors in calculation of efficiency of conversion into dry matter.

The functional relationships between loge diameter and loge weight, and between length and diameter of the storage roots in carrot and red beet were described by two linear equations. These equations were fitted to data from three red beet and two carrot experiments. The agreement between the fitted and observed data was close. With increasing plant population density of red beet, the slope of the relationship between length and diameter decreased and the intercept increased. Although these changes in slope and intercept were statistically significant (P < 0·05), their magnitude was of negligible practical importance. The relationship between loge diameter and loge weight was little affected by length; the relationship between length and diameter was little affected by loge weight.

Using these equations in independent experiments, the diameters of roots of both species were predicted from measured root weights. The roots were then assigned to various commercial diameter grades on the basis of either the measured or the predicted diameter. Except for a few roots of red beet greater than 85 mm in diameter, there was close agreement between the observed and predicted number of roots in each grade.

Any model which predicts root weight might be extended to predict yield of marketable size grades, using these equations as a calibration between weight, diameter and length.

A two-year field experiment on a mollisol at Pantnagar showed that organic sources of N gave generally higher rice yields than the equivalent split dressing of prilled urea (PU). In 1985/86, Sesbania green manuring (40 kg N/ha) and PU (40 kg N/ha) and, in 1986/87, Sesbania (40 kg N/ha) + Azolla (40 kg N/ha) gave significantly higher yields than a split application of 80 kg N/ha as PU. Yield increases were attributed to significant variations in panicles/m2, filled spikelets/panicle and nitrogen uptake by the crop. These components, and grain yield, were significantly correlated with wet soil NH+4-N, which was increased by organic manuring. Wheat grown after each rice crop showed significant residual effects of the different sources of N applied to rice.

Densities of physiologically independent plants of white clover were studied in New Zealand in pastures stocked at 22·5 ewes plus lambs/ha by set stocking, rotational grazing or a combination of both systems. Plants were sampled once a month for 1 year (1984/85) by taking turves and washing out the plants. Numbers of growing points and stolon dry weight per plant were obtained. At each sampling fifty, 50 mm diameter pasture plugs were taken from each sward and growing point density and stolon mass/m2 of white clover were measured. The density of white clover plants in the swards was estimated on the basis of both stolon dry weight and number of growing points.

The two estimates gave similar results. There was a trend of lowest densities in set-stocked pastures (334/m2), intermediate densities in combination management pastures (431/m2) and highest densities in the rotationally grazed pastures (553/m2). The overall mean density of white clover plants was 439/m2 and the range was 193–811/m2.

The structure of swards under the three systems of grazing differed and this was considered to contribute towards the variation in density of white clover plants in the various swards.

Effect of timing of pregnant mares's serum gonadotrophin (PMSG) injection combined with a progestagen-impregnated vaginal sponge on fixed-time artificial insemination with fresh, undiluted semen during the nonbreeding season was investigated. PMSG injection 2 days before sponge removal (group A) caused significantly earlier oestrus than injection at the time of sponge removal (group B). Lambing percentages in a total of 320 ewes after fixed-time insemination at 36 h (64·1%) and 48 h (47·2%) in group A, and 48 h (59·5%) and 60 h (39·5%) in group B were not significantly different from those resulting from ‘at oestrus’ insemination (500% and 511% in groups A and B, respectively). The present results indicate that the optimum time for fixed insemination may depend upon the time of PMSG injection associated with progestagen treatment.

The voluntary feed and water intakes of five llama × guanaco crossbreds (New World camelids) and five sheep, and their abilities to digest various feed components and to utilize nitrogen, were compared using a diet of threshed ryegrass straw in New Zealand in 1987.

The camelids ate more than the sheep, but intakes were similar relative to metabolic live weight (mean 37·6 g dry matter/kg W0·75 per day). They drank 0·62 times as much water as sheep per kg W0·75, and 0·57 times as much per g DM intake (P < 0·05). Mean apparent digestibilities of dry matter (47.7%), energy (41·6%) and cell-wall fractions (48·4%) were similar in both species, in spite of the sheep selecting a higher-N component of the diet. Variation in digestibility (e.g. organic matter digestibility) among individual sheep was inversely associated with the percentage of cell-wall constituents consumed. The faeces of camelids contained a significantly higher proportion of particles longer than 0·5mm than those of the sheep (17 v. 11% total DM), indicating a slightly larger threshold to passage from the forestomachs in the camelids.

All animals were in negative N balance during the trial, but net loss of N was less in the camelids than in the sheep (27·6 and 49·5 g N/100 g N intake, respectively; P < 0·05), because of lower urinary N excretion (36·5 and 60·3 g N/100 g N intake, respectively; P < 0·05) of the camelids. The results suggest that camelids may be better suited than ruminants for production from poor-quality feeds, especially if water supply is limited.

The growth and yield of maize grown on an unploughed newly opened secondary forest in Nigeria in 1985–87 was studied. In each year, trash was either removed or burnt in situ and each of these treatments was given N fertilizer or none. In the first year, only N fertilizer increased yields. In the second and third years, yields were increased by N fertilizer and by trash burning. Trash burning consistently increased the amount of P in the soil.

Experiments in 1986–88 compared the spring field bean cultivars Alfred, Minden, Ticol and Troy, grown on clay-with-flints soil at Rothamsted, at row spacings of 12 and 48 cm, and compared two pest and pathogen control programmes based on (i) ‘standard’ control of Ascochyta fabae, Ditylenchus dipsaci and seed-borne viruses and (ii) ‘enhanced’ control of Sitona lineatus, bean leaf roll virus via the vector Acyrthosiphon pisum, Botrytis fabae and Uromyces viciae-fabae in addition to the pests and pathogens in the ‘standard’ control.

With standard control, Minden had the largest mean seed yield of 4·6 t/ha; with enhanced control, Alfred was best with 6·1 t/ha.

The yield benefits of enhanced control ranged from 0·2 t/ha on Ticol in 1986 to 2·4 t/ha on Alfred in 1988. They were related to the control of weevils (S. lineatus), chocolate spot (B. fabae) and rust (U. viciae-fabae). At 1989 prices, the cost of materials used for enhanced control would be repaid by a yield increase of 0·3 t/ha.

The closer row spacing increased yields by 0·15 t/ha on average but effects differed greatly between years. Benefits were largest in 1986 when plants were shortest and in that year were largest for the shorter cultivars.

It is suggested that trials of field bean cultivars should always include a test of pest and pathogen control.

Tannin content of the testa was estimated in crosses among six Vicia faba lines of diverse origin using the vanillin-HCl method. Additive genetic variance was predominant in the inheritance of tannin content. Two white-flowered parents possessed different genetic information for tannin content when the pleiotropic effect of genes for white flowers was eliminated. The genes controlling red testa (r), spotted flower (Sdp) and yellow pigment on the flower (yf) negatively influenced tannin content in the testa. Breeding for low tannin content in Vicia faba is feasible and selection can be based on plants with yellow-spotted flowers and red testas.

Signal grass (Brachiaria decumbens Stapf.) given 100, 200, 300 and 400 kg N/ha and protected from defoliation by growing in cages was evaluated for tiller height, tiller density and dry matter (DM) yield in 1979 and 1980.

Nitrogen rate had highly significant linear effects on tiller height and density and DM yield of the grass at each age of pasture regrowth and at all the ages of pasture regrowth combined in 1979 and 1980. The quadratic effect of N rate was not significant in either year.

The positive linear responses shown by the growth of tillers and the overall yield of the grass at N rates up to 400 kg/ha suggest that further work, using N rates above 400 kg/ha, is needed to ascertain the optimum N requirement of this grass.

Four adult (4·5–7 years old) swamp buffaloes (Bubalus bubalis)and four adult (4–5 years old) Ayrshire cattle (Bos taurus) were housed in climate chambers maintained at 20° or 33 °C and given ad libitum access to a medium-quality, complete pelleted diet (AA6) or a lower-quality pelleted diet of alkali-treated barley straw supplemented with urea, sulphur, minerals and vitamins (ATS). Using a balanced double cross-over design, each animal was studied at each temperature and whilst consuming each of the two diets in experimental periods lasting 20 days. On day 13 of each period, animals were given single doses of two nonabsorbable markers, and food intake and complete collections of faeces were measured for the remainder of the period. Blood samples were taken at the end of each period.

Voluntary food intakes on a per kg body weight (W) or per kg W0·75 basis were significantly higher for the cattle than for the buffaloes, although this difference was reduced with the lower-quality diet and at the higher temperature. Cattle appeared to be more heat stressed at 33 °C than the buffaloes, but species had little effect on digestion or gastro-intestinal mean retention time. Calculations suggested that a greater proportion of digestion of ATS than of AA6 occurred postruminally.

A 4 x 4 Latin square design experiment was performed at the Ruminant Research Centre, Cockle Park Farm, University of Newcastle upon Tyne, in 1986 to determine the effect of grinding molassed sugarbeet pulp (MSBP) to varying degrees of fineness on overall apparent digestibility in wether sheep when the product constituted 90% of dry matter intake. A product (designated S) consisting of the pelleted screenings of unground MSBP was significantly less digestible than the other three products. No significant difference in overall apparent digestibility was observed between unground, coarsely ground and finely ground MSBP prepared from the same batch.

In a 4 x 6 randomized block design experiment, mature wethers equipped with rumen, duodenal and ileal cannulae were fed, in two meals, 1000 g concentrates and 100 g chopped hay per day. The concentrates consisted of 820 g mixture of barley and MSBP, 167·5 g soyabean meal, 10 g vitamins and minerals and 2·5 g chromic oxide per kg (fresh weight). The ratio of MSBP: barley was 1:3, 1:1 or 3:1 and the MSBP was either unground or finely ground. The aim was to determine the effect of replacing MSBP with barley on the nature of the rumen fermentation, overall apparent digestibility of the diet and the efficiency of rumen microbial protein synthesis (using 35S as a microbial marker).

There were no significant differences between the six diets in overall apparent digestibility of dry matter and organic matter, but N digestibility increased significantly (P > 0·05) as barley replaced MSBP in the diet. As before, the particle size of MSBP had no effect on overall apparent digestibility of the diet. The quantity of microbial N was reduced (nonsignificantly) and the efficiency of rumen microbial protein synthesis decreased (P > 0·05) compared with the other treatments when sheep were fed diets in which the ratio of MSBP: barley was 1:1. The particle size of MSBP had no effect on these factors.

As barley replaced MSBP in the diet, the mean pH of rumen fluid, calculated over 24 h, tended to decrease and there was a significant increase (P > 0·05) in the length of time that the rumen fluid was below pH 6. There were no significant differences between treatments in the concentration of ammonia-N in the rumen fluid. The dilution rate of rumen fluid (measured using 14C-Cr EDTA and Co EDTA as markers) decreased (P > 0·05) when MSBP replaced barley in the diet, and ground MSBP gave rise to lower (P > 0·05) dilution rates than unground MSBP. There were no significant differences between treatments in the ruminal concentration of total volatile fatty acids (VFAs) or the proportions of individual VFAs.