Changes in dry weight and 14C contents of categories of shoots that did and did not survive to produce ears were examined in winter wheat grown in micro-plots in 1982–4. The weight of a group of tillers when dead was similar to their maximum dry weight when living. By anthesis dead shoots exceeded living ones in number but contributed less than 10% of total shoot dry weight.

14CO2 was supplied, near the time that number of shoots was maximal, to tillers in axils of first (T1) and third (T3) main stem leaves; T1 usually survived and T3 usually died. The percentage of 14C in the plant retained in T1 was 78–94%. That retained in T3 ranged from 9 to 81%. Little 14C moved from dying shoots into the rest of the plant in two experiments. In another, perhaps 70% of the 14C in living tillers was transferred as they died but this represented only a small proportion of total plant weight. 14C not retained in tillers to which it had been given was found in all parts of the plant, including about 7% in grain.

Previous research has shown that sewage sludge can act as a source of nitrogen and phosphate fertilizer. Fen peat soils are organic soils derived from plant material and are known to differ from mineral soils in their plant-nutrient availability. The work reported in this paper compares the effects of liquid digested, liquid raw and dewatered digested sludge with inorganic nitrogen and phosphate fertilizers on a typical fenland rotation of winter wheat, sugar beet and potatoes.

It is concluded that sludge can replace inorganic nitrogen and phosphate fertilizer on fen soil, and it appears that applications of sludge containing large amounts of fresh organic matter can act as a soil conditioner and produce higher yields than can be obtained from the use of fertilizer alone.

A field experiment is described in which three rates of pig and cow slurry were applied to a ryegrass sward over a period of 16 years. The experiment included control plots and plots receiving fertilizer supplying 200 kg N, 32 kg P and 160 kg K/ha per year.

The slurry nutrient concentrations were similar to published values. Pig slurry was more variable than cow slurry and both varied significantly from year to year. Slurry was applied at 50, 100 or 200 m3/ha per year, with each rate divided into three equal applications.

Even the highest slurry application rate did not depress herbage yield, which showed a typical response curve to the amount of soluble nitrogen applied. The ammoniumnitrogen content of slurry (61% on average) gave an adequate measure of its effect on herbage yield when it was applied three times per year in spring and summer.

Recovery of phosphorus in the herbage averaged 30% from pig slurry, 40% from cow slurry and 66% from-fertilizer. Pig slurry supplied more phosphorus than did cow slurry, and herbage phosphorus content was significantly correlated with the amount applied. Much of the slurry phosphorus may have been organically bound and not available to plants in the short term.

Recovery of potassium from pig slurry and fertilizer was nearly 90% and from cow slurry about 70%. Cow slurry supplied potassium in excess of crop requirements so that it accumulated in the soil under the largest dressing. Soil phosphorus reserves declined under the smallest dressing of cow slurry but were maintained at higher application rates. The pig slurry produced a marked accumulation of phosphorus under the largest dressing. The substantial accumulations of phosphorus and potassium from pig and cow slurry respectively gave marked penetration of the soil below 10 cm depth only at the highest application rate. The data suggest that at rates typical of farm practice significant losses of phosphorus and potassium from the rooting zone would be unlikely to occur.

The main invading plant species were Agrostis stolonifera L. and Poa spp. Small slurry dressings produced a similar botanical composition to that of plots given fertilizer. Increasing slurry application rates decreased the proportion of L. perenne and increased that of A. stolonifera but only under the largest dressing did L. perenne fall to a small proportion of the sward and A. stolonifera become very dominant. L. perenne made maximum contribution to herbage dry-matter yield early in the season while the proportion of A. stolonifera increased as the season progressed.

Under these conditions even extremely large slurry dressings did not depress herbage yield and may not necessarily have reduced herbage quality despite marked changes in sward botanical composition.

F2, monosomic analysis involving crosses between the monosomic series of a resistant wheat variety, Chinese Spring, and a susceptible variety, Sicco, has located a major gene locus, designated Dfql, on chromosome 2B of wheat which determines the differential response of these varieties to treatment with the wild oat herbicide, difenzoquat. The allele from Chinese Spring conferring resistance is dominant and studies of the responses of Chinese Spring single chromosome substitution lines and nullisomic–tetrasomic lines for chromosome 2B indicate that this allele actively promotes resistance to the herbicide. It is suggested that this gene may prevent inhibition of DNA synthesis in the apical meristem, which is the site of action of the herbicide (Pallett & Caseley, 1980).

Other chromosomes were also implicated as carrying ‘modifier genes’ which affect the ratio of resistant: susceptible plants in F2 monosomic families, namely 1D, 2D, 3A, 3B, 5B and 5D. These chromosomes may affect the retention and translocation of the herbicide to the target site and hence the threshold of response.

The simple inheritance of difenzoquat resistance indicates that it should be easy by conventional breeding techniques to transfer the resistance into susceptible varieties.

During 5 h of acute heat exposure (41 °C), there were increases in the heart rate from 43±2 (S.E.) to 51 ± 1 beats/min, respiratory rate from 26±4 to 86± 16 breaths/min and rectal temperature from 38·5 ± 0·1 °C to 39·7 ± 0·2 °C. The flow rate of liquid from the rumen and body water turnover significantly increased while biological half life of chromium-51 ethylenediaminetetra-acetate in the rumen and tritiated water decreased from 12·9 ± 2·5 and 87·7 ± 6·8 h to 9·3 ± 2·0 and 49·2 ± 5·7 h respectively. An increase in blood volume during acute heat stress occurred with an increase of both plasma and cell volume. An elevation of plasma water coincided with an increase in plasma protein and glucose. There is evidence that the increase in plasma water during heat exposure came from extravascular tissue space and/or from the digestive tract.

The reliability of the soil series as a basis for crop yield prediction was examined by comparing the influence of soil and management (inter-farmer differences) on the variance of barley grain yield. Yields of barley were measured from farmers' fields for 2 years and in undisturbed soil cores for 5 years. Fields on different soil series within farms and on the same soil series across farms were used. Linear stepwise regressions of yield on a number of soil properties were also examined to assess the relative influence of soil and management on the properties that were significant to yield.

The results show that generally, soil classification has a strong influence on yield variance, but there is clear evidence that the influence of management, specifically the cumulative effect of P and K fertilizer applications, is considerable. Thus in an undisturbed core, for the first 3 years when N, P, K and Mg were applied, the influence of soil was stronger than that of management, but this was reversed in the 4th year when P and K were not applied. Similarly in the field, the influence of soil was stronger in the 1st year, but this was reversed in the 2nd year, although on different field-farm combinations. In all cases, the influence of neither soil nor management was significantly stronger than the other.

The results of the regression studies also confirmed those of yield variance in that in general, neither soil nor management has exclusive control of the yield variance. The soil was significantly stronger than management in the control of only coarse sand content at 0–15 cm out of the four soil properties (including Mg and pH (0–15 cm) and K (15–30 cm)) which were significant to yield in the cores. On the other hand, management was significantly stronger than soil in the control of only available P at O–15 cm out of the three soil properties (including Cu and Mg both at 0–15 cm) that were significant to field yield.

It is concluded that for soil classification to be a reliable basis for yield prediction and/or agrotechnology transfer, the effect of management must be emphasized.

Field experiments conducted during the winter seasons of 1982–3 and 1983–4 in semi-arid rainfed conditions of north-west India indicated that sowing of Brassica species at the right time can considerably increase productivity. Sowing in the middle of October with daily mean temperatures around 26 °C produced 1·5 t/ha against 0·9 t/ha obtained from the crops sown 1 month later with daily mean temperatures around 20 °C. Under such conditions Brassica juncea cv. Pusa Bold (medium in stature and duration and bold seeded) gave the highest (1·66 t/ha) yield. Eruca sativa could withstand sowing at still lower temperature (19 °C). Increasing temperatures in the second fortnight of February adversely affected the productivity of a late-sown crop by reducing the reproductive phase.

Field experiments made in 1984 and 1985 compared the effects of ammonium chloride with those of other nitrogen fertilizers applied to winter wheat in spring. The dressing was divided, 40 kg N/ha in March and 160 kg N/ha in April. In both years take-all in July was at levels which usually decrease yield, and take-all ratings were greatest in plots treated with ‘Nitro-Chalk’ (calcium ammonium nitrate) and least in plots treated with ammonium sulphate, but the differences were not statistically significant. Ammonium chloride and the other treatments, urea and ‘Nitro-Chalk’ with potassium chloride, had intermediate effects and the ranking of treatments according to disease was consistent in both years. In 1984 the mean yield was 8·27 t/ha, range 7·92 t/ha (with ammonium chloride) to 859 t/ha (with ‘Nitro-Chalk’) and in 1985, 821 t/ha, range 7·;42 t/ha (with ‘Nitro-Chalk’) to 8·55 t/ha (with ammonium sulphate). In both years treatments had no significant effects on yields and the relationship between yield and disease was obscured in 1985 because of highly correlated disease and block effects.

Whereas applying spring nitrogen all in the ammonium form seemed to decrease take-all slightly, the effects on yields of winter wheat were inconsistent. There is no evidence of extra benefit to be gained from applying the ammonium as ammonium chloride to crops at risk from take-all in this country, but there may be some benefit in applying KCl with ‘Nitro-Chalk’ top-dressings in the spring.

In rainfed lowland rice areas of intermediate deepwater (15–50 cm), transplanting in greater depths of water (50–60 cm) with clonal tillers (double transplanting) from 20 or 40- to 50-day-old-transplanted crops of similar environment increased grain yield significantly compared with seedlings of the same age (60 or 80- to 90-day-old) from a nursery. The grain yield did not decrease significantly when the clonal tillers were removed at 20 or 40 days after transplanting compared with that of the undisturbed crop. The practice of double transplanting (clonal propagation) increased tiller production and the number of panicles, and the crop could tolerate better the greater depths of water and thereby give greater grain yield.

The phenology of the emergence of brassica pod midge from overwintering sites and its subsequent infestation of winter oil-seed rape crops on a farm in southern England was studied over 3 years. Two generations occurred each year. The first generation of adults emerged from mid-May or early June until early July from overwintering cocoons in soil at sites where oil-seed rape had been grown in the previous year or years. Many females and a few males migrated to flowering winter rape crops where eggs were laid in the pods. Mature larvae dropped daily from the pods from early or mid-June until late July or early August, and formed cocoons in the soil. The second generation of adults emerged from late June until mid-July or early August to lay further eggs in the crop. Larvae from these eggs dropped to the soil to diapause within cocoons for up to 3 years.

The importance of molybdenum, sulphur, iron, zinc and cadmium dietary antagonists to ruminant copper metabolism was investigated at the farm level in an attempt to explain the widespread occurrence of bovine hypocupraemia in recent years.

From 22 of the most severely hypocupraemic regions of England, six areas with as wide a range of geological, pedological and topological situations as possible were selected for detailed field work. This involved the collection of topsoil and herbage samples from approximately 15 farms per area with hypocupraemic stock. Possible causal factors of bovine hypocupraemia were then considered on the basis of three criteria: critical concentrations of copper, molybdenum, sulphur, iron, zinc and cadmium in pasture herbage; Cu:Mo ratios in herbage; and copper availability predictions for ruminants.

Absolute copper deficiency and molybdenum-induced bovine hypocupraemia were clearly demonstrated at the farm level. The results also confirmed that dietary sulphur, in particular, plays a significant yet previously unrecognized role in the widespread incidence of bovine hypocupraemia in industrialized Britain. Antagonism due to iron orginating from soil-contaminated herbage was evident, but not common. No evidence was found to support the occurrence of zinc- or cadmium-induced hypocupraemia in the areas examined.

Data from several trials with large numbers of barley and durum wheat varieties conducted mainly under dryland conditions in a Mediterranean climate were used to study the effects of heading date and its stability on consistency of performance.

Heading date was expressed in relation to one or more control varieties, because of the significant genotype × environment interactions. Data from trials during 1969–85 were used to determine optimum heading date in order to aid selection for consistently high-yielding varieties. For rainfed barley in Cyprus this optimum range was between 2 days after and 5–8 days before heading of Kantara barley and for rainfed wheat 1 day after to 4 days before heading of Karpasia durum wheat. It is suggested that by selecting at one environment single plants from segregating populations or lines from nurseries and yield trials, having heading date within the optimum range, the chances of selecting consistently high-yielding lines are increased.

The genotype and environment significantly affected heading date. Stability of heading date was genetically controlled. Early varieties tended to be more variable than late varieties of both barley and durum wheat. Lines with the lowest values for variance of heading date gave low yields under variable conditions because they were very late. The consistently high-yielding lines of barley and durum wheat had variance of log transformed heading (s2log2) 0·025–0·050.

In durum wheat, lines with the lowest variance were later in heading date than the optimum for Cyprus environments. The absolute values of variance of heading date of varieties varied with year, but significant positive correlations were obtained between years (r = 0·84 for durum wheat and r = 0·55 for barley, P < 0·01).

Barley, which is considered a safer crop for the driest parts of the Mediterranean countries, heads a few days earlier than durum wheat but its better performance may be attributed also to its ability to grow faster than wheat in the winter months.

Using data from rotation studies in which barley or woollypod vetch were included, both cut for hay and preceding barley for grain, it is shown that forage barley gave higher dry-matter yield than woollypod vetch (3·74 v. 2·92 t/ha per year). However, the latter gave feedingstuff of higher nitrogen concentration and yield (86 kg N/ha per year for vetch v. 55 kg N/ha per year for barley). Rainfall was an important factor in controlling the yield of the two forages and the comparison between them in different years and sites. Barley following woollypod vetch gave higher grain yield than when following forage barley (2·36 v. 1·91 t/ha). Rotation sequences which included woollypod vetch had higher output of nitrogen (N) than input of fertilizer N with a positive value of 44–60 kg N/ha per year. In rotations where forage barley was followed by barley for grain the N balance between output and input was 5–6 kg N/ha. Total soil N was similar in the different rotations at the end of a 7-year period.

Oestrous and ovarian activity were studied throughout the year in 29 subtropical Rahmani ewes using both vasectomized rams and intravaginal electrical resistance measurements. Percentages of ewes in oestrus and of ewes ovulating were consistently high throughout the year with a detectable drop in spring months. The drop was more pronounced and lasted longer in oestrous activity than in ovarian activity. About 33% of the ewes showed continuous ovarian activity throughout the year while almost all ewes had periods of behavioural anoestrus.

Effects of artificial light regimen on oestrous and ovarian activity were investigated in 21 Rahmani ewes over a 6-month period from January to June. Oestrous and ovarian activity were slightly lower in the light-treated (L) group than the control (C) group during the period of abrupt increase in daylength. With gradual decrease in daylength, the percentage of ewes showing oestrus was markedly higher in the L than in the C group (84·6 v.37·5% during May).

It was concluded that daylength change, although limited in this region, is a main factor controlling the seasonal changes in oestrous and ovarian activity in subtropical Rahmani sheep.

Two separate short-term rotation experiments were conducted during 1982–5 in order to study the production and effect on subsequent barley of legumes grown in Cyprus. The treatment crops, seven legumes and three cereals, were grown in 1982–3 and in 1983–4 growing seasons and barley was grown in the subsequent growing seasons (1983–4 and 1984–5).

Among the treatment crops, cereals gave equal or higher dry-matter yields, but equal or lower nitrogen yields compared with legumes. Barley, the test crop, which followed the treatment crops, gave lower grain and nitrogen yields when following cereals than after legumes. There were differences among legumes in their residual effect on the subsequent crop.

In two separate field experiments with green gram (Vigna radiata L. Wilczek) and black gram (Vigna mungo L. Wilczek), the effect of seed treatment of molybdenum at 4, 8 and 12 g of sodium molybdate/kg seeds as well as foliar nutrition of sodium molybdate at 0·4, 0·8 and 1·2 kg/ha was evaluated on the nodulation characteristics and leghaemoglobin content of nodules and growth and yield of crops. Both seed treatment and foliar application of sodium molybdate were found to be superior to controls in respect of the number of nodules per plant and dry weight of nodules. The leghaemoglobin content of nodules in both crops was maximal in the treatments with the highest dose of seed treatment followed by the highest dose of molybdenum for foliar sprays. Molybdenum favourably influenced the growth of green gram and black gram by increasing the number of branches and leaves and by nearly doubling the leaf area index. This resulted in increased D.M. and yield of pods.

The effect of three herbicides and an insecticide combination on nitrogen fixation in three paddy soils was investigated in a laboratory incubation study. The influence of pesticide combination on N2 fixation was evaluated in the presence and absence of rice straw under flooded and non-flooded conditions. In a non-flooded alluvial soil single or combined application of butachlor and carbofuran significantly stimulated N2 fixation. There was no effect on N2 fixation when thiobencarb was applied alone; but with thiobencarb in combination with carbofuran higher N2 fixation occurred. Both oxadiazone and thiobencarb had no effect on N2 fixation under flooded conditions, but in combination with carbofuran the N2 fixation was high. In acid sulphate saline Pokkali soil, rice straw application stimulated N2 fixation; the stimulatory effect of carbofuran either alone or in combination became more pronounced under flooded conditions. N2 fixation was low in a laterite Sukinda soil and the effect of pesticides was not changed by rice straw amendment. A uniform stimulation of N2 fixation occurred in soils when carbofuran was applied either singly or in combination with other herbicides tested. Results indicate that the effect of pesticides on N2 fixation varied with the rice straw application and water regime.

Eighteen bulls were used to investigate the influence of feeding frequency on feed consumption, nutrient utilization and nitrogen metabolism in growing zebu cattle.

Results indicated higher feed intake, nutrient utilization and average daily live-weight gains for animals fed two or three times daily compared with those fed once daily. Feed efficiency and feed cost per kg gain as well as nitrogen metabolism also increased as the frequency of feeding increased from once to three times daily.

More frequent feeding could evidently be of practical advantage in intensive beef cattle production where zebu cattle are raised on tropical hay diets.

A 2-year field study to investigate the potassium nutrition of groundnut in the lowland tropics showed that a low rate of K is beneficial to the crop. Applied K significantly increased leaf N, seed S, seed P, seed Fe, seed oil and protein content of groundnut. Leaf Ca significantly decreased with increased K application but K treatments significantly increased the seed and shell Ca. Potassium and Ca concentrations were highest in the leaf and lowest in the shell and seed respectively. The significant increases in shell P, shell Ca and shell Fe with increased K application would greatly improve the groundnut shell quality as an animal feed component. The relationship between seed oil and protein content was positive and significant.

Linkage was detected between brown planthopper resistance and anthocyanin or nonanthocyanin pigmentation in rice cultivars. The crossover values were: 21·9–37% for leaf sheath, 31% for junctura, 41% for auricle, 12·5–40% for ligule, 14·32–1% for leaf tip and margin, 19·7–37% for stigma, 19·7–36% for apiculus and 46·7% for pericarp colour. Genes governing resistance and black hull colour or glabrousness of leaf blade assorted independently. The genes identified and designated for brown planthopper resistance and pigmentation have been tentatively proposed to linkage groups II, IV and V.