The course of free proline accumulation in leaves, stems, roots and ears was examined during the development of the wheat cultivars Yecora and Generoso grown in the field with or without irrigation. More negative values of leaf water potential were associated with higher amounts of free proline in the various organs. In most cases, proline accumulated more readily with increasing water stress before heading than after ear emergence in the leaves, stems and roots of both varieties. Differences between the two cultivars concerning the sensitivity of the mechanisms inducing proline accumulation to water stress existed mainly in the reproductive phase: Generoso accumulated proline more readily than Yecora. There is evidence that the increased amounts of free proline in Generoso can be associated with more effective dehydration and drought avoidance mechanisms.

Changes in Cu concentration in the livers of adult Scottish Blackface (B), Welsh Mountain (W) and B × W ewes fed diets containing 4, 9, 17 and 29 mg Cu/kg D.M. were measured over a 28-week period. Measurement continued during two further periods of 18 weeks when first all sheep were fed the diet containing 4 mg Cu/kg D.M. and finally, when 4 mg Mo/kg D.M. was added to this diet.

During the first period the increase on all diets was least in B ewes and, apart from the 4 mg Cu/kg D.M. diet, greatest in W ewes; this difference increased as the Cu in the diet increased. The rate of increase for all ewes diminished towards the end of the period. All breed types retained proportionately less Cu in their livers as the Cu in the diet increased; at one extreme B ewes fed 17 or 29 mg Cu/kg D.M. retained equal amounts.

When during the second period all sheep were fed the 4 mg Cu/kg D.M. diet the Cu concentration in their livers decreased, the rate of decrease being greatest for ewes whose mean concentration in the liver was highest, but at similar concentrations the decrease was greater in B than W ewes. During the final period the decrease was faster and was again associated with the mean Cu concentration, but the decrease was not significantly affected by breed.

Throughout the trial, W ewes had the highest concentration of Cu in their plasma, whilst B ewes and ewes fed the 4 mg Cu/kg D.M. diet throughout had the lowest concentrations both in plasma and in their kidneys at slaughter.

The results show that breeds differ in their ability to retain Cu from the diet in their livers. The magnitude of these differences depends on the intake of Cu and Mo from the diet and is affected by the concentration of Cu in the liver. Breed differences in the absorption and endogenous loss of Cu are suggested.

The effects of treading and the return of excreta on a Lolium perenne-Trifolium repens sward defoliated by sheep set-stccked at high and low stocking rates were examined. Sward performance was measured inside ‘graze-through’ cages which allowed defoliation without treading and excreta return, and outside where sheep grazed either fitted with harness to prevent the return of excreta or unharnessed to allow the normal return of excreta. Live-weight gain was measured from excreta return and non-return swards. The treatments imposed had large effects on herbage growth and botanical composition.

At a stocking rate of 25 yearling wethers/ha, sheep excreted about 1·1 kg N/ha/day, which increased soil N and led to an increase in herbage growth of about 26 %. The return of excreta increased ryegrass tiller density and this was partly responsible for a 26% reduction in the proportion of clover in the sward; the weight of clover was 13% loss where excreta were returned, and on this treatment stolon length at the end of the experiment was similar to that at the beginning. Doubling the stocking rate increased the N returned via excreta to about 1·3 kg N/ha/day, and this increased herbage growth by 53% but suppressed the proportion of clover by 21%, though not the weight of clover. Clover stolon length decreased during the experiment at this stocking rate, both with and without the return of excreta. Sheep live-weight change benefited from the stimulus to herbage growth where excreta were returned at the high stocking rate, but not at the low stocking rate.

Treading by 25 sheep/ha increased soil compaction but had no significant (P > 0·05) overall effect on herbage growth and botanical composition. However, treading by double the number of grazing animals significantly reduced herbage growth by 10%, plant root weight by 47% and the proportion of clover in the sward by 11%.

Differences in sward performance between stocking rates were due more to the difference in defoliation intensity between these stocking rates than to either treading or the return of excreta.

Labelled fertilizer N (15N depleted ammonium sulphate) was used to investigate both soil and fertilizer N use by winter wheat established in contrasting seed beds, these being soil cultivated to 20 cm depth or left undisturbed. The crop's response to, and recovery of, a range of N levels from 0 to 280 kg/ha given as a divided application in spring, were measured over two seasons. It was found that during the first season the direct-drilled wheat took up, on average, more fertilizer N but less soil N than wheat in cultivated soil, probably through differences in organic-matter mineralization. The different cultivation systems produced similar grain yields at all rates of applied N; however, when no fertilizer N was given, dry-matter production and soil-N uptake by the crop in the undisturbed soil were substantially less than by the crop in the cultivated soil. Crop recovery of the fertilizer N at harvest was between 29 and 40% of that given. After harvest, an average of one third of the applied fertilizer N was found in the top 60 cm of the soil profile. In the following season on the same plots a second winter wheat crop, receiving no fertilizer N, was drilled. At harvest there was shown to be an increase in grain yield and soil- and fertilizer-N uptake at the higher srates of N given in the previous season. In spite of this the recovery of the labelled residues was small, no more than 6% of the original application, or 15% of the residues remaining in the soil, irrespective of cultivation system.

A branching peduncle individual was observed in a population of cow pea Vigna unguiculata (L.) Walp. cv. Ife Brown. Normal plants have unbranched peduncles with flowers arranged in alternate pairs at distal ends of the peduncles. However, the mutant plant has branched peduncles with flowers arranged in pairs alternately along the branches as well as at the ends of the branches. The branches arise in the axils of stipulate trifoliate leaves which develop on the peduncles. The normal plant has between one and four pods per peduncle, whereas the mutant is capable of carrying between two and ten pods per peduncle. The branching trait is under genetic control, involving a single gene with the normal peduncle completely dominant over the mutant. Evidence for the genetic control and its possible usage is discussed. Data on some agronomic properties of the mutant are also presented.

Hydrolysis and sorption reaction of pyrophosphate (PP) in soils and uptake of PP by maize were studied using some acid soils from southern Nigeria. Rate of hydrolysis varied with the soil type, and half-lives of hydrolysis ranged from 10 to over 40 days in unsterilized soils and more than 40 days in all cases when the soils were sterilized. An appreciable fraction (over 40%) of the added PP resisted hydrolysis, the effect being more pronounced in the sterilized soils.

Sorption of both PP and orthophosphate (OP) by soils followed the Langmuir isotherm. The adsorption capacity and bonding energy index for all soils were greater for PP than for OP.

A short-term glasshouse experiment showed that PP was as good as OP as a source of P to maize. When the soils were limed to pH 6, PP appeared to be superior to OP.

In two field experiments, ground limestone (2·5–20 t/ha), dolomite (4·25 t/ha) and gypsum (3·75 t/ha) were applied to acid krasnozems (Forthside, pH 5·6 and Elliott, pH 5·1), and poppy capsule and morphine yields, leaf nutrient contents and soil chemical properties were measured.

Capsule and morphine yield increased more than two-fold at Forthside as the pH in the surface soil (0–150 mm) increased from 5·6 to 6·1, and by 30-fold at Elliott where the pH increased from 5·1 to 6·0. Capsule morphine concentration was depressed by high rates of ground limestone at both sites but maximum morphine yields of 15·7 kg/ha at Forthside and 11·3 kg/ha at Elliott occurred at the highest rate of ground limestone. Gypsum did not increase yield at Elliott, but at Forthside the gypsum and ground limestone treatment of equivalent calcium content increased yields to the same extent.

The lowest yields at each site were associated with calcium concentration in the leaves at flowering of less than 1% and marginal or high amounts of extractable soil Al at Forthside and Elliott respectively. Concentrations of Ca, P and Mo in leaves were increased by lime applications but leaf concentrations of N, P, Mn, B and Mo on low yielding plots were considered to be in the normal range.

Poppy yield responses to liming were attributed primarily to alleviation of aluminium toxicity but the effects on yield of reductions in soluble Al and increases in available Ca were confounded by application of ground limestone.

Field studies were carried out to determine the sources of photosynthate for developing pods and to assess the effect of defoliation and flower removal at different stages on the performance of lentil. The leaves of flowering nodes were the primary source of assimilate to pods. Removal of 25–75% of leaves reduced seed yield by varying degrees depending on crop growth stage. The plants compensated for the loss of foliage to some extent, possibly through increased efficiency of the remaining leaves. One complete or 50% defoliation reduced seed yield to different extents at the vegetative, flowering, early pod formation and late pod formation stages, the greatest effect being seen at flowering and early pod formation. Plants compensated considerably by production of new leaves when defoliated at the vegetative phase. Increased moisture supply greatly enhanced the compensation ability of the lentil plants.

Removal of all flowers up to 1–2 weeks after an thesis under unirrigated conditions and up to 3 weeks after anthesis in irrigated conditions did not adversely affect the seed yield. Flower removal beyond this period resulted in a significant reduction in seed yield. Little seed yield was obtained when flower removal was continued for either 6 or 8 weeks under unirrigated conditions. The plants compensated for the loss of earlier-formed flowers by setting pods from later-formed flowers. Compensation was greatly enhanced when the crop was irrigated during the reproductive phase. There was relatively little or no effect of the deflowering treatments on the number of seeds per pod or weight per seed. The flowering period of the deflowered plants was extended and their senescence was delayed. When 25% of the flowers were removed at different intervals during the reproductive phase, seed yield was not adversely affected. An increased intensity of flower removal decreased yield but the decrease was not proportional to the degree of flower removal. The plants apparently compensated by setting new pods.

Little reliable information is available on the range and variability of the copper content of the wool of sheep (Underwood, 1977), although the effect of Cu deficiency on keratinization and pigmentation of wool is well known (Ryder & Stephenson, 1968) and the Cu content of hair has been suggested as a possible aid in diagnosis of hypocuprosis. Results from Kellaway, Sitorus & Leibholz (1978) showed that, in cattle, Cu in hair and plasma decreased in animals when the concentration of Cu in the liver fell below 20 mg/kg D.M. An experiment carried out jointly by the Animal Breeding Research Organisation and the Animal Diseases Research Association to investigate breed differences in the long-term accumulation of Cu in sheep gave an opportunity to investigate both the range of Cu concentrations in wool and the relationship between the Cu content of the liver and wool Cu.

Pyrethrum is a small bushy perennial crop cultivated for its flowers which have insecticidal properties. Pyrethrins, the active principles in the flowers, are contact insecticides causing nervous breakdown leading to paralysis and death of insects. Kroll (1963) and Parlevliet, Muturi & Brewer (1968) have shown that the flower yields of pyrethrum could be improved by applying P fertilizer whereas N and K fertilizers did not increase the yields. On the other hand, Mwakha (1979a, b) showed that pyrethrum responds to N fertilizer on soils deficient in N. The present investigation was carried out to study the response of pyrethrum to various rates of application of N, P and K and sources of phosphorus.