A total of 25 steer carcasses from a wide range of breeds and carcass weight and fatness were used to examine the relationship between a range of fat thickness measurements and the dissected fat content of beef carcasses. Fat thickness measurements included those on the hot carcass suitable for ‘commercial’ use and others on the cold carcass commonly used in research.

The mean of the measurements of fat thickness from the two sides of the hot carcass between the 12th and 13th ribs (12H) gave the most accurate prediction of carcass fat content (FPCT). The relationship was described by the equation FPCT = 14·61 + 1·85 (12H) (R2 = 0·92; S.E. of prediction of individual FPCT at the mean= ±2·17%).

The mean of four fat thickness measurements made on the quartered surface between the 10th and 11th ribs of the cold carcass was the next most accurate predictor (S.E. = 2·28%) of fat content. Fat thickness measurements made on the hot carcass between the 10th and 11th ribs were the least satisfactory.

Although the hot carcass measurements between the 12th and 13th ribs were made under commercial conditions and included a wide range of types of cattle the prediction of fat content from these measurements had a marginally lower standard error than the prediction based on measurements made under experimental conditions.

Experiments with spring barley in 1975–7 tested fungicides applied to control powdery mildew (tridemorph) or brown rust (benodanil) in factorial combination with six amounts of fertilizer N, applied either to the seed bed soon after sowing, as a later top dressing or half at each time.

Powdery mildew was the principal leaf disease in all three years. It tended to be increased by increments of N and by applying the N late but much less consistently in the first two years, when soils were very dry for much of the growing period, than in 1977 when amounts of rain were much closer to the long-term mean. Tridemorph significantly increased the number of ears in 1975, mean number of grains per ear in 1976 and 1000-grain weight in all three years; it gave net increases in grain yield of 0·55, 0·68 and 0·41 t/ha, respectively, in 1975–7. Yield response to increasing amounts of applied N was greatly increased where mildew had been controlled by the use of tridemorph, and was better where the N had been divided into two dressings than where it had been applied as a single dose. In 1975 and 1977 the biggest responses to tridemorph were obtained with late N but in 1976 yield was increased most by tridemorph where the N had been applied to the seed bed.

Analyses of samples taken in 1977 showed no significant effect of tridemorph sprays on concentrations of either N, P or K in the green crop. By contrast, analyses of grain samples in 1976 and 1977 showed that amounts of N in grain (mg N/grain) were affected by amounts of applied N and by tridemorph, and that there were interactions between these two factors. Concentrations of N in the grain (% D.M.) were also determined by the effects which these factors had on grain size. At small N rates tridemorph mostly increased grain size so that N concentrations were decreased by the fungicide. At large N rates increases in grain size where tridemorph had been applied were accompanied by increases in the N content of the grain (mg N/grain) so that N concentrations were either unaffected (1976) or were increased (1977) by the fungicide. With 90 kg/ha of applied N the fungicide increased the amount of N/ha removed in grain by over 21 % in each year. The apparent recoveries of N in these plots were increased from 66 to 81 % and from 87 to 105%, respectively, in the two years. Tridemorph had no significant effect on concentrations of P or K in the harvested grain but increased average amounts of these nutrients removed in the grain by 17 and 14%, respectively, in 1976 and by 14 and 7% respectively, in 1977.

Examination of black and white, infra-red aerial photographs of the experiments showed that, in each year, the brightness of individual plot images was significantly correlated with grain yield.

Complex designs without division into blocks are especially vulnerable to positional variation. Alternative methods of adjusting for such positional variation were compared in analyses of grain yields. The potential improvements in precision which might be achieved by the appropriate use of such analyses, and the difficulties of ensuring that unacceptable subjectivity and bias are not thereby introduced into the analyses, are discussed.

In a field experiment, the influence of different forms and methods of application of urea nitrogen on the rice rhizosphere soil nitrogenase was evaluated under simulated intermediate deep water situations. Nitrogenase was high when the soil received small amounts of nitrogen and phosphorus with a water level of 20–25 cm. Moreover, during and after the flash floods the nitrogenase activity was considerably increased. There was a significant reduction in the nitrogenase activity when the nitrogen was applied to the shallow water through urea briquettes, but when it was applied either behind the plough or between the rows, the activity was stimulated. Increased water level of about 50 cm for prolonged periods considerably reduced the nitrogenase activity. Results indicate that the method of application of urea nitrogen and the water level influenced the rhizosphere soil nitrogenase activity under intermediate deep water situations.

The C and N in the biomass of soils from eight grassland field experiments where lime had been applied was determined by the chloroform fumigation method. Lime application increased C and N in the biomass by approximately 30% overall, although there was no effect at two sites. In the unlimed plots basal CO2 production, biomass C, and flush of mineral N production (FN) increased with soil pH. Biomass C and FN were correlated with total N content but not with organic C.

Differences in the apparent C/N ratio of the biomass were found in unlimed soils of pH ≤ 4·5 and in those of pH > 4·5, the ratios being 4·2 and 5·8 respectively. For limed soils the ratio was 5·2. It is probable that the chloroform fumigation method is not suited to soils of very low pH, and that the C/N ratio obtained in soils of pH < 4·5 is artificially low.

Number of nodules and leghaemoglobin content of nodules increased with increasing Zn application up to 7·5 μg/g soil. Dry-matter yield and N fixation increased with Zn up to 10 μg/g soil. Both nodulation and N fixation decreased at higher levels. Soil N content showed an initial depletion but increased during the late season. Critical lower and upper levels for maximum N fixation were 1·75–2·5, and 10–14 μg of DTPA extractable Zn/g soil, respectively. In the present studies 5–10 μg Zn/g soil was sufficient for maximum N fixation in chickpea.

The extent and possible mechanism by which spring-sown oil-seed rape plants can compensate for insect or artificial injury to flower buds and pods were investigated by examination of the yield, and its components, of plants collected from commercial fields and those grown in field cages and glasshouses. Plants were able to compensate and in some instances overcompensate for all observed levels of M. aeneus injury or artificial bud removal by the production of more axillary racemes, which may be due to the loss of apical dominance. Artificial injury to the pods or infestation by C. assimilis larvae did not result in a significant reduction in the yield of seed and was compensated for partly by a slight increase in the number of axillary racemes and by slight increases in the number of pods on each axillary raceme and in the 1000-seed weight, and resulted mainly from the diversion of nutrients to other yield-bearing organs. Injury by D. brassicae larvae was partly compensated for in 1975 and at lower injury levels in 1974 and involved a similar mechanism to compensation for C. assimilis injury. These results are discussed in relation to the observed infestation levels in field surveys and current control practices.

A two-pool + time delay model was used to analyse ideal marker concentration patterns generated, using an interactive computer simulation program, from data for the mean retention times of [51Cr]EDTA and [103Ru]phen in the reticulo-rumen, abomasum and caecum-proximal colon and the transit times of these markers through the omasum, small intestine and distal large intestine of sheep. Although providing a reasonably close fit to the generated data, the fitted curves showed small but systematic deviations, indicating that the model does not consistently characterize the kinetics of the markers in the ruminant gastro-intestinal tract.

When the components of the two-pool model were correctly identified, predicted rumen mean retention times (MRT) were within – 1 to + 13% of the observed values. However, identifying the component with the longer MRT as the rumen resulted in up to 2·6-fold overestimation (17·5 v. 6·77 h). The model underestimated the time delay and the overall MRT. It is suggested that the correct identification of the two components can be achieved by the simultaneous use of a solute-and a particulate-phase marker because, in ruminants, they do not behave independently in the caecumproximal colon.

Genetic analysis for eight morphological traits, number of days from sowing to first flower, to complete pod filling, and to first mature pod, height of plant from the ground to the first fruiting node, distance between the first and last fruiting nodes, number of nodes from the ground to the first pod-bearing node, average internode length and number of flowers per axil, was done by following numerical and graphical approaches in a nine parental half diallel. Components as well as the graphical approach showed the importance of non-additive gene effects for height of plant from the ground to the first fruiting node, number of nodes from the ground to the first pod-bearing node and number of days from sowing to first mature pod, while for other traits additive genes were important. The high performance of number of nodes from the ground to the first pod-bearing node and number of flowers per axil was governed by recessive alleles while other traits were governed by dominant alleles. Consequently for developing an efficient plant type hybridization between parents like P23, EC109182, EC109196, LMR200 and LMR8 is advocated. Leafless segregants from the present set of crosses which exhibited potential for high yield in national tests have been isolated.

To determine economic thresholds of pest infestation caged plots of oil-seed rape (Brassica napus L.) were infested with different populations of the seed weevil (Ceutorhynchus assimilis Payk.). Less than one seed weevil per plant resulted in pod infestation levels of seed weevil larvae that by themselves were insufficient to warrant insecticide application, but owing to secondary infestation of pod midge (Dasyneura brassicae Winn.), substantial seed loss occurred. Greater populations of seed weevil adults gave correspondingly larger levels of pod midge and diminishing yields.

In commercial crops individual plants were able to compensate, and even to overcompensate for damage resulting from low levels of pest infestation, but increasing levels of infestation resulted in progressively fewer seeds per plant.

The implications of the results on pest control and further research are discussed.

The effect of ratios of calcium to phosphorus in the diet (varying from 0·6 to 3·6) on the absorption and excretion of P was investigated with four sets of 9-month-old chimaera-derived triplets. A pelleted cereal-based diet supplemented to contain 1·5, 3·1 or 6·2 g P/kg D.M. and 3·4 or 5·4 g Ca/kg D.M. was used in a factorial design.

The additional Ca in the diet reduced the efficiency of absorption of the P supplements in the diet by 0·18 ± 0·04.

The efficiencies of absorption of total P were very similar within but markedly different between (P < 0·001) sets of triplets, the mean values being 0·62, 0·74, 0·82 and 0·84. The fractional absorption of inorganic P alone showed the same ranking and the mean values were 0·47, 0·67, 0·85 and 0·92. These differences between triplets support the view that the individual differences in P metabolism have a genetic basis. The mean absorbability of P in the basic diet (0·77) and in the P supplements (0·73) were similar.

The pattern of excretion of absorbed P between the faecal and urinary route of excretion varied between the sets of triplets; as P intake increased, the additional absorbed P was excreted in faeces by one set, in urine by another and in faeces and urine by two sets. The relative importance of the faecal route was dependent upon the fractional absorption of P secreted into the gut.

Soya-bean meal and rapeseed meal treated with 0, 0·4 or 0·8 g formaldehyde/100 g crude protein (N × 6·25) was incubated in the rumen in nylon bags with 10 and 40 μm aperture.

Disappearance of dry matter and nitrogenous compounds was reduced with increasing formaldehyde treatment.

The proportion of acid-pepsin soluble nitrogen in the undegraded residues of untreated and treated soya-bean meal was similar to the original samples. For rapeseed meal the proportion of acid-pepsin soluble nitrogen in the undegraded residues decreased with increasing rumen incubation time. This reduction decreased with increasing formaldehyde treatment.

Concentration of amino acids in the undegraded residues did not generally deviate from those in the original samples. However, a distinguishable decrease in the methionine concentration was observed in all the rapeseed meal samples and in glutamic acid concentration in rapeseed meal treated with 0 and 0·4 g formaldehyde/100g- crude protein.

Most of the changes due to rumen incubation were smaller using the 10 μm bags than using the 40 μm bags. However, the bag pore size did not play a decisive role in the conclusions of the results given.

Data from nine experiments from 1973 to 1981 which examined the effects of physiological age on sprout and field growth of early potato varieties are reported. Length of longest sprout per tuber and all aspects of field growth were related to number of daydegrees > 4 °C experienced by the seed after onset of sprout growth (measured as the appearance of a 3 mm sprout). It is, therefore, suggested that this scale is an effective measure of physiological age. In Home Guard and Maris Bard, increasing age of seed tubers resulted in earlier emergence and tuber initiation, larger early leaf areas and increased early tuber yields. As growth proceeded young seed produced the largest and most persistent leaf areas and the yields surpassed those of older seed and in some experiments yields decreased with increasing age at the final harvests.

Optimum ages for specific harvesting periods were determined from regressions of tuber yield on age. In both varieties, they decreased with delay in harvesting. However, optimum ages differed in the two varieties and the implications for production and storage of seed and testing of varieties are discussed.

Results of a 2-year study in a rainforest zone of south-western Nigeria to determine the effects of various planting and harvesting times on the yield, HCN, dry-matter accumulation and starch contents of cassava showed that times of planting and harvesting significantly affected all the variables studied. May planting gave highest yield arid starch contents, which suggests that large-scale production of cassava for industrial starch and human consumption should be planted in the month of May.

The harvesting time experiment shows that cassava tuber will continue to increase until the 24th month, although, because of increasing demand for land, it will not be economic to leave cassava on the field for more than 15 months. For optimum starch and dry-matter accumulation, cassava should be harvested between 12 and 15 months.

Several nitrification inhibitors were compared with nitrapyrin, which was taken as the standard, when injected with aqueous urea into ryegrass leys at Rothamsted during 1977–81 and at Liscombe Experimental Husbandry Farm, Dulverton, Somerset, during 1977–9. Injection was done in either autumn or winter or spring.

All the inhibitors slowed down the rate of nitrate formation from the injected urea. Sodium trithioearbonate (STC) was less effective than nitrapyrin and potassium ethyl xanthate (KEtX) less effective than STC. A mixture of nitrapyrin and carbon disulphide was better than nitrapyrin alone, and a mixture of STO and KEtX was better than STC alone.

At Rothamsted, injecting inhibitors in autumn or winter improved yields and N uptakes, probably because they prevented loss of nitrate N by leaching and perhaps by denitrification. STC, STC-KEtX mixture and etridiazole were as good as, and nitrapyrin–CS2 mixture better than, nitrapyrin alone. Injecting inhibitors in spring frequently decreased yields, perhaps because NH4:NO3 ratios were too large, and increased them only when more than 150 mm of rain fell afterwards.

At Liscombe, where rainfall was higher, but soil temperatures were similar to those at Rothamsted, the benefits from using inhibitors in autumn were larger, but there were none from using them in spring.

The production of green beans was studied in sowings made from December to February, September to February, and from October to February in three seasons, and over six oonsecutive seasons for a mid-season sowing.

With September-October sowing the rate of emergence was slow, and establishment sometimes poor. Possible virus disease, and the lack of continuity of setting pods resulting from cool weather, were problems. Good yields were obtained from midseason sowings (31 October-18 December), up to 19·6 t/ha, with good yields for late sowings up to 13·9 t/ha in ^he first three seasons. In another three seasons mid-season sowings (late November-early December) resulted in poor yield due to periods of hot weather (> 35 °C max.) prior to and during flowering.

There was a relationship between quality and yield. The greatest yield and best quality green pods were obtained when conditions favoured rapid growth and rapid setting of pods, and when there was a high rate of pod maturation.

For yield of dry seed the early sowings were best, 3·6 and 2·8 t/ha in two seasons. A total of 460 mm of water was required for the first six sowings, but fell to 360 mm for the mid-February sowing (rainfall plus irrigation).

Although it was possible to grow beans over a 9-month period the January and early February sowings appeared to be the least risk prone with the present cultivars.

Studies were conducted in two consecutive years at Mead, Nebraska, to investigate the relationship between lodging, certain morphological characters and grain yield of sorghum.

Morphological characters correlated with lodging were plant height, length of prepeduncle internode and rind thickness. Lodging was negatively correlated with number of days from sowing to 50% bloom and grain yield but was not correlated with grain weight of the head.

In 68 spring barley crops grown in five experiments at Rothamsted and Woburn between 1980 and 1982, and given adequate K fertilizer, there was a positive correlation (r = 0·76; P < 0·001) between maximum % K in dry matter of young plants and the grain yield at final harvest. In all crops changes in % K in dry matter during the growing season were directly related to changes in fresh weight to dry weight ratio (FW: DW) suggesting that differences in % K in dry matter were the result of differences in tissue hydration. Potassium concentrations expressed on the basis of tissue water were not correlated with grain yield. All crops maintained K concentrations in their tissue water of about 200 mmol/kg tissue water, except at the end of the growing season when water loss during ripening caused a steep rise.

The correlation between % K in dry matter and yield was the result of differences in FW: DW. Within each experiment there was a good correlation between FW: DW and grain yield, but because the relationship was different for each experiment the overall correlation for all crops was poor. The correlation between FW: DW and grain yield within experiments probably arises because crops with a higher FW: DW will have higher specific leaf areas and hence higher relative growth rates and yields.

The influence of various nitrogen and phosphorus sources, applied at the preseeding stage with two placement methods, on maize yield and fertilizer utilization, was studied in two field experiments and a pot experiment with a calcareous, heavy to medium heavy textured recent alluvial soil.

Phosphorus alone had no effect on crop yield. Nitrogen alone or nitrogen (various forms) and phosphorus had a clear positive effect on crop yield. As to the various sources the observed differences in the crop yield of the field experiments were not significant, while in the pot experiment ammonium sulphate gave the highest yields.

The data on the phosphate concentrations in the tops derived from phosphate fertilizer (Pf) indicate that the presence of nitrogen increased the utilization of phosphorus fertilizer. From the tested placement methods the incorporation method appears clearly superior in the pot experiment with a similar trend in the field experiment for all sources except ammonium phosphate-sulphate.

The utilization coefficients of the nitrogen fertilizer sources suggest that ammonium and urea were better utilized than nitrates, that the higher nitrogen utilization reflected higher yields and that phosphorus fertilizer exerted a beneficial effect on nitrogen fertilizer utilization. Finally they suggest that the addition of 120 kg N/ha enhanced the amount of soil nitrogen taken up in the maize grain by 53%.

The canopy of spring wheat grown with an ample supply of nitrogen was generally cooler than the canopy of a nitrogen-deficient crop. The warmer canopy matured 3–5 days earlier. The accumulated temperature difference was sufficient to account for the different times taken to reach maturity.

Six dryland crops (mungbean, cow pea, soya bean, groundnut, maize and sorghum) and two rice cultivars (C·171·136 and IR 36) were grown under rainfed and irrigated conditions on a dryland site with a clay loam soil at the International Rice Research Institute, Philippines. After the first 30 days of growth there was no effective rain, and the rainfed crops encountered different water deficits. Crop productivity, leaf area, plant water status, root distribution, and soil water use were measured.

Neither rice cultivar yielded seed under rainfed conditions, but all other crops did. With mungbean and cow pea there was little difference between the yields under rainfed and irrigated conditions, but groundnut, soya bean, sorghum and maize gave higher yields under irrigation.

The rainfed crops extracted different amounts of stored soil water, ranging from 100 mm for IR 36 to 250 mm for groundnut. The different amounts were associated with different growth durations, rooting depths and rates of soil water depletion from within the root zone. Biological productivity of the six rainfed crops with the C 3 photosynthetic pathway was linearly related to transpiration, which was estimated from soil water extraction and soil evaporation. Biological productivity per unit of transpiration for the two crops with the C 4 pathway was 2·2 times higher than for those with the C 3 pathway. The different seed yields of the rainfed crops were due to differences in harvest index and the chemical composition of seeds, as well as to biological productivity.

The results are discussed in relation to the potential for growing dryland crops after rice in rice-based cropping systems.