The joint action of two pyrethroid insecticides with several foliar fertilizers against the fourth-instar larvae of Spodoptera littoralis was determined. The rate of development of tolerance throughout three successive generations to insecticides alone and their combinations with fertilizers was also assessed. The results indicate that the toxicity of the insecticides tested was greatly enhanced by using fertilizers in admixture with each of them. Moreover, the inclusion of such fertilizers in spray emulsions slows down the development of tolerance to both insecticides. The synergistic action of fertilizers and the decrease in the induction of tolerance to insecticides can be attributed to the presence of inorganic ions and to decreasing the pH of both acidic experimental insecticides resulting in increasing the penetration rate of the internal membranes of the cotton leafworm.

In a 2-year field study conducted at Lucknow (26·5° N, 80·5° E and 120 m altitude), plant height, leaf area index, dry-matter accumulation and N uptake of opium poppy (Papaver somniferum L.) followed a sigmoid path. After attaining a peak of accumulation at 120 days, dry matter declined in plots given N fertilizer but remained static in the control. N application (50, 100, 150 and 200 kg/ha) increased the opium, seed and morphine yields compared with the control. Morphine concentration (%) in the opium, however, increased up to 100 kg N/ha and decreased when N doses exceeded that level. Divided application of N, i.e. half at sowing and remainder at the stem elongation stage, proved beneficial for opium, seed and morphine yields.

The selenium concentration of cereal grain and herbage from 131 farms in England and Wales was, in general, low: the proportions of samples with values below 0·03 mg/kg D.M. were 60% for grain (primarily barley, from 96 farms) and 39% for conserved herbage (primarily hay, from 131 farms). Values for fresh herbage from 12 farms were similar to those for conserved herbage. There were no significant differences in selenium concentration among herbage species. For all samples, those from the Cambridge area contained more selenium than those from other parts of England and Wales.

Evaluation of some insecticides against nine strains of S. littoralis, selected with decamethrin and foliar fertilizers separately and their combinations for three successive generations, was conducted to elucidate the effects of fertilizers on the tolerance pattern. The results indicate that the selection with fertilizers induced a low level of tolerance to both cyolane and profenofos. The LC50 of chlorpyrifos for all fertilizers' strains was lower than that of the susceptible strain. The efficiency of cyolane and fenvalerate on strains developed by the selection with decamethrin-fertilizer combinations was remarkably increased. Since the selection with fertilizers has induced a tolerance to some insecticides such as cyolane and profenofos and as the efficiency of these insecticides was enhanced on strains developed by the pressure of decamethrinfertilizer combinations, it is preferable to use decamethrin simultaneously in admixture with foliar fertilizers for pest control.

Seven out of ten chemical extractants were found to be promising for the evaluation of critical limit and response of wheat grown in pots to Cu application in Sub-Himalayan hill and forest soils of recent alluvium origin. The critical limit of available Cu using DTPA-CaCl2(pH 7·3), DTPA-NH4HCO3 (pH 7·6), EDTA-(NH4)2CO3 of pH 8·6, EDTANH4OAc (pH 7·0), n-NH4OAC (pH 7·0), n-NH4OAC (pH 4·8) and n-Mg(NO3)2 of pH 5·9, was 0·66, 1·73, 1·95, 1·38, 0·13, 0·20 and 0·47 mg Cu/kg, respectively. The amount of Cu extracted by these extractants was positively and significantly correlated with ‘Bray's percent yield’. Apart from ‘Bray's per cent yield’, the Cu extracted by most of these extractants was positively and significantly correlated with Cu concentration in the third leaf of wheat, Cu uptake by wheat shoots and organic carbon content of the soils, and negatively correlated with soil pH but the value of this relationship did not approach the 5% level of significance. n-Mg(NO3)2 of pH6·7, N-NH4NO3 and 0·1 n-HCl were found to be ineffective extractants. Among chelating agents, DTPA-CaCl2 was found to be most and EDTA-NH4OAc least promising extractant. N-NH4OAC (pH 4·8) proved to be better than N-NH4OAC (pH 7·0). The critical Cu concentration in the third leaf of wheat was 8·8 mg Cu/kg, below which responses in dry weight to Cu application may be expected.

Computer programs have been developed to evaluate sequential variety selection systems using Monte Carlo and numerical integration methods.

These methods are described in the paper and applied to official U.K. cereal variety testing. The consequences of alternative selection systems are examined.

Changes in distribution of amino acid nitrogen of chopped wheat plants ensiled at shooting and flowering when wilted, and at the milk and dough stages as fresh material, were determined as affected by addition of 0·8% propionic acid (PrA) or 2·2% urea phosphate-calcium propionate (UP-CaPr). Analyses were carried out after an ensiling period of 90 days and after a further aerobic exposure period (AE) of 7 days.

Total amino acid (TAA) contents in the dry matter (D.M.) during the fermentation period and in the AE were stable in untreated material (UM) and treated material. Concentration of essential amino acids decreased during fermentation, this decrease being higher in the UM. The free amino acids were low in the fresh material (18·6% of TAA) but increased in the ensiled material to ca. 71 % of the TAA in the silage. In the AE this level was 63% in UM and 69% in treated material. The ammonia-N contents increased during fermentation in UM and especially in the UP-CaPr treatments, while the opposite occurred in the PrA treatments.

The concentrations of and changes in 21 amino acids (AAs) are given. The highest AA concentrations recorded in the fresh material were those of arginine, lysine, glutamic acid, alanine, leucine, proline and glycine. The most marked increments in AAs as a result of fermentation were those of ornithine, γ-amino butyric acid, threonine and methionine. Marked decreases were observed in glutamine, arginine and glutamic acid. PrA increased mainly arginine, asparagine and glutamine, whereas γ-amino butyric acid decreased; UP-CaPr increased arginine, asparagine, lysine and glutamic acid (in silage only) and reduced γ-amino butyric acid and glutamine (in AE only).

A whole crop computer simulation model of winter wheat has been written in FORTRAN and used to simulate the growth of September- and October-sown crops of Hustler wheat at Rothamsted for the years 1978–9, 1979–80 and 1980–1. Results of the simulations, which are for crops with adequate water and nutrients, are compared with observations from experiments at Rothamsted. The model uses daily maximum and minimum temperatures and daylength to calculate the dates of emergence, double ridge, anthesis and maturity of the crops and the growth and senescence of tillers and leaves. In the simulations, the canopy intercepts daily radiation and produces dry matter that is partitioned between roots, shoots, leaves, ears and grain. Partial simulations, using observed LAI values, produced dry matter in close agreement with observations of late-sown crops, but consistently overestimated the total dry-matter production of the early-sown crops. Full simulation described satisfactorily the average difference in dry-matter production to be expected with changes in time of sowing, but did not give as close correspondence for individual crops. A grain growth submodel, that linked maximum grain weight to average temperatures during the grain growth period, correctly simulated the observed growth of individual grains in the 1981 crop. The benefits to be obtained by combining whole crop modelling with detailed crop observations are discussed.

An experiment was made on a clay loam soil to compare direct drilling, shallow cultivation and ploughing for spring barley over a period of 3 years (1975–7). At a uniform rate of fertilizer application (75 kg N, 40 kg P2O6, 40 K2O/ha) combined drilled with the seed, the mean grain yields over 3 years were 5·89, 6·07 and 6·13 t/ha, respectively, direct drilling producing significantly less grain than shallow cultivation or ploughing in 1975 only.

For 1975 and 1976 the mean uptake of nitrogen by shoots of barley at anthesis was 25 kg N/ha less after direct drilling than after ploughing but in 1977 there was no difference. The smaller uptake of nitrogen by direct-drilled barley in 1976 was more likely caused by less available nitrogen in the soil than by smaller root systems. Soil strength (cone resistance) and soil bulk density of the direct-drilled treatments were greater than those of the ploughed and shallow cultivated. Although concentration gradients of extractable phosphorus and potassium formed in direct-drilled and shallow-cultivated soils, the quantities of these nutrients in the top soil differed little between the treatments. After 3 years there were more deep burrowing earthworms (particularly Lumbricus terrestris) in tilled than in untilled soil.

A computer simulation model of canopy development in a crop of winter wheat is described. The principal features of the model are the simulation of the emergence, growth and senescence of individual leaves and the production of tiller groups (cohorts) during a defined phenological period, with their survival depending on cohort age and shoot population density.

Comparison is made between the model output and early- and late-sown crops from three seasons. The behaviour of the model in response to changes in leaf senescence and tiller production is discussed for crops sown in 1978.

Three experiments were carried out in which nitrogen was applied to spring barley (cv. Midas) either all in the seed bed or as a divided dressing with 10 or 25 kg/ha in the seed bed and 50 or 60 kg applied at emergence or 10, 20, 30, 40, 50, 60 or 70 days after emergence. Applying part of the nitrogen as a top dressing up to 30 days after emergence and 50 days after emergence had no significant effects on the grain and straw yields respectively, compared with applying all the nitrogen in the seed bed. Grain yields were progressively reduced with top dressings from 40 days after emergence (first node stage) onwards. Applications at 60 or 70 days did not give more grain yield than the no-nitrogen control, but gave straw yields which were intermediate between the no-nitrogen and seed-bed nitrogen treatments. Top dressing at 40 days after emergence stimulated tiller survival but did not improve grain yield because there were fewer grains per ear. Thousand-grain weights were lowest with top dressings at 50 days after emergence and grain nitrogen increased progressively with delay in top dressings from 30 days after emergence onwards.

The effect on phosphorus and calcium metabolism of a high rate of Ca infused directly into the blood of 10-month-old sheep, already receiving an adequate Ca and P intake, has been studied by a combination of balance and radioisotope techniques. Ca retention was significantly increased during the infusion and most of the extra Ca was retained in bone. Urinary Ca excretion also showed a small but significant increase and the efficiency of Ca absorption a small but significant decrease. Because of the close association of Ca and P in bone, the increased skeletal retention of Ca resulted in an increased skeletal P retention and hence an increased demand for P. This increased P demand was met partly by a decrease in the rate of endogenous faecal loss of P and partly by an increase in the rate and efficiency of P absorption. Because the increase in P demand was relatively small, it was not possible to decide whether the endogenous faecal loss of P can be reduced in response to increased demands to the level found at zero P intake as suggested by the Agricultural Research Council (1980) or whether higher losses at normal P intakes are inevitable.

Downward movement of potassium (K) was studied in the soil profiles of a longterm fertilizer experiment. The distribution of different forms of K and the percentage K saturation of the CEC of soil, at various depths of the differentially treated plots, indicated that applied K moved down to 75 cm depth in the high-K plots after nine cycles of a maize-wheat-cow peas crop rotation. However, movement of K was not noticed in plots not given K fertilizers. Plant uptake of K far exceeded the amounts of applied K. Application of K fertilizer reduced the release of K from the non-exchangeable reserves. Forms of K and the percentage K saturation of the CEC of soils were significantly correlated.

Experiments using intact seedlings and detached leaves failed to confirm previous reports that ammonia gas is evolved from barley leaves during the establishment of infection by the powdery mildew fungus Erysiphe graminis f.sp. hordei.

In the experiments using intact seedlings infection did, however, lead to greater concentrations of ammonium nitrogen in the senescing leaves and, in one experiment, the subsequent evolution of ammonia gas from these seedlings. Losses of nitrogen as ammonia gas from crops are probably small, but it is possible that under some circumstances they may represent a significant proportion of the otherwise unexplained nitrogen losses and hence be important in experiments which aim to study the nitrogen balance of crop-soil systems.

One fast-growing acid-producing Rhizobium strain 995 of Vigna radiata was screened for growth behaviour in acid, saline and alkaline media. It grew well in yeast-extract mannitol broth of wide pH range as well as varying concentrations of NaCl, Na2SO4 and MnCl2. Variation in nodulation and N2-fixation efficiency occurred on different varieties of green gram, while strain characteristics were not affected by soil stress.

If atmospheric carbon dioxide concentration continues to increase, plant growth and crop yield could be affected. New Yorker and Better Boy cultivars of tomato (Lycopersicon esculentum) were used to investigate possible intraspecific variation in the response of crop species to increased CO2. Because precipitation and temperature are predicted to change with the increasing atmospheric CO2 concentration, the response of the two cultivars to the interaction between CO2 and water stress was also examined. Seeds of the two cultivars were germinated and grown under controlled environmental conditions, in either 350 or 675 μ1 CO2/1.

The plant water status of the two cultivars was inherently different but was little affected by the CO2 concentration when the plants were well watered. When water was withheld for 5 days the total leaf water potential and osmotic potential decreased in both CO2 treatments but less rapidly in high CO2 than in low. Under low CO2 total leaf water potential decreased to a lower value than osmotic potential. The differences were due, at least in part, to the reduced stomatal conductance and transpiration rate under high CO2.

Increased CO2 ameliorated the detrimental effects of drought stress on plant growth. The results indicate that increased CO2 could differentially affect the relative drought resistance of species cultivars.

The effects of coat colours on thermal balance, behaviour and weight gain were studied. Measurements of thermal balance were made over 36 days in strong sunshine on highly contrasting coat colours of three white and three dark steers in each of two breeds, Brahman (B) and Shorthorn (S), and three light- and three medium-red steers in Brahman Hereford-Shorthorn cross breed (BX) where there was less contrast in coat colour. Each steer was measured for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. For B, the difference between colours in mean rate of environmental heat gain at the skin was 64 ± 22·5 W/m2 and for S, 44 ± 20·5 W/m2, while the difference in mean rate of evaporative heat loss, between colours for B and S respectively was 44 ± 15·1 and 42 ± 14·3 W/m2. However, only within S was rectal temperature significantly higher in steers which were dark red and the reasons for this are discussed. Within BX the range of colour shades diminished during the experiment so thermal effects of colour were small. Colour had significant effects on growth; these effects were greatest in S where white steers gained 0·13 kg more per day than dark red ones. There were also differential effects within colour groups on activities at pasture; light steers spent more time in the sun and grazing than dark ones. In addition to colour, deep or woolly type coats negatively affected growth (P < 0·05), time spent in the sun (P < 0·05), and grazing time (P < 0·05); however, between animals within breeds the magnitude of the adverse effect of coat type on growth and behaviour was greater in dark- than light-coloured steers. These results provide evidence that coat colour is a trait which, interacting with coat type, exerts an influence on performance of cattle under heat stress.

Vigorous cauliflower plants sometimes bear abnormally small curds, yet this common problem has received little recognition or attention from research workers. Curd size is often reduced towards the end of the harvesting period of a crop, and this is more marked if environmental conditions reduce mean curd size and lengthen the time to maturity. Small late curds may be a consequence of their slow growth rather than their late initiation. Cultivars differ in their tendency to produce plants with late maturity and small curds. This may not be due to genetic differences within cultivars. Moreover, breeding to eliminate or reduce this condition may not be possible without affecting overall maturity time and curd size.

Grass silage was incubated in polyester bags in the rumens of Jersey heifers for 2, 12, 24 and 48 h. The total (D + L) and D-amino acid contents of the silage and of the silage residues remaining after rumen incubation were determined. In addition, the contamination of the silage residues by rumen bacterial protein was measured by using 35S as a marker of rumen bacterial protein. The amino acid profile of the residual silage dry matter differed markedly after 2 h of rumen incubation from that of the original silage; thereafter progressive changes in the amino acid composition of the residual silage dry matter occurred between 2 and 48 h of rumen incubation. The D-alanine content of the original silage was higher than that of D-glutamic acid. Both these D-amino acids disappeared almost completely from the silage after 2 h rumen incubation; between 2 and 48 h rumen incubation the quantities of D-alanine and D-glutamic acid in the residual silage dry matter increased. The residual silage dry matter contained more D-glutamic acid than D-alanine and these acids were in a similar proportion to that found in rumen bacteria; thus it was concluded that D-amino acids in the residual silage dry matter resulted from contamination of the residues by rumen bacteria. Contamination of residual silage protein by rumen bacterial protein increased with length of rumen incubation; the extent of contamination was similar for each incubation time whether assessed using 35S or D-amino acids as markers of rumen bacterial protein. However, this contamination by rumen bacterial protein did not markedly alter the degradability of silage protein calculated from the disappearance of silage N incubated in sacco.

Three groups of red deer hinds of 9–10 years of age were grazed upon an indigenous hill pasture (A), an improved species grass sward (predominantly perennial ryegrass) maintained at < 1500 kg D.M./ha (B), and one maintained at 2000 kg D.M./ha (C) from immediately after calving on 29 May until weaning on 22 September. Numbers of hinds in each treatment were 8, 6 and 9 respectively. Milk yields of hinds were estimated on swards A and C by the calf-suckling technique and hind and calf live-weight changes and hind grazing behaviour were recorded on all three swards during lactation.

Hinds on award C yielded on average 60% more milk over the lactation period than hinds on sward A, day 40 yields being 2·2 and 1·5 kg/day respectively. Calf growth rates (treatment A, 257 ± 9·5, B, 324 ± 12·1 and C, 369 ± 14·5 g/day) were higher on the improved species sward than on the hill sward and higher on the improved sward with the greater herbage mass. On treatments A and C calf growth rates were significantly (P < 0·05, r = 0·69) correlated with milk yield throughout lactation. At weaning, calves on sward C were 7·5 and 4·5 kg heavier than those on swards A and B respectively. Biting rates were lower (33 v. 56 bites/min) and grazing times higher (11.7 v. 6.0 h) on sward A than swards B and C. The poorer performance of hinds and their calves on sward A was considered to be due to a lower quality of diet ingested, and to behavioural limitations on intake occurring when hinds graze indigenous swards of relatively high species diversity. These results are discussed in relation to the grazing behaviour of cattle and sheep on similar swards.

The significance of the results to red deer farming in the U.K. is briefly discussed.