The activity ratios of potassium in dynamic equilibrium with a submerged soil planted with rice were determined fortnightly for 10 weeks. The simple activity ratio, aK(aCa + aMg)-1, and the modified activity ratio to include the activity functions of Fe2+ and Mn2+ as aK/(aCa+ aMg)½ + B(aFe)½ + C(aMn)½, gave linear relationships when plotted against the change in exchangeable K content of the soil. The modified activity ratio of potassium correlated better with potassium concentration (r = 0·91) in and potassium uptake (r = 0·84) by rice than the simple activity ratio (r = 0·86 and 0·81 respectively).

Submergence for 6 weeks almost doubled the potential buffering capacity of potassium, PBCK, showing that the submerged soil sustained a low level of potassium in the soil solution for a long time.

A negative intercept of the plot of equilibrium labile K, Kel, on the ‘quantity’ axis, against the modified activity ratio showed that there is some non-labile K which equilibrates with the soil solution during growth. The value of this intercept (3·40 mequiv/kg soil) is a measure of non-labile K.

Three pastures, pangola–clover, setaria, and tropical grass–legume, were grazed for a 9-month period by 12 steers of initial live weight of 199 kg on each. For the first 5 months live-weight gains were, respectively, 1·2, 0·76 and 0·43 kg per day, mostly higher than could be expected for estimated dietary energy concentrations of 10·1, 8·9 and 8·7 MJ of metabolizable energy (ME) per kg of dry matter. The high live-weight gains were not explained satisfactorily by dry-matter intakes as measured from faeces voided and dietary digestible dry matter, but were possible if published values for the requirements of ME for growth and fattening were too high. Cell wall, in vitro digested cell wall and nitrogen in separated leaf and stem fractions were useful indices for evaluating pasture for grazing cattle, but they did not predict live-weight gain.

In this paper, the first of a series of three in which fat deposition is examined in 42 castrate male Hereford and Friesian cattle, details are given on the experimental material and procedures used in all papers. Whole body composition (anatomical and chemical) and the partitioning of fat within the body are also reported in this paper.

Four, two and 15 animals were slaughtered at 6, 13 and 20 months of age, respectively, after ad libitum feeding of a complete pelleted diet.

The Friesians were heavier than the Herefords, having 10%, 20% and 14% heavier empty bodies at 6, 13 and 20 months, respectively.

At the same age, the Friesians had a greater percentage of empty-body weight as carcass muscle, carcass bone, total body water and total body ash than the Herefords but a lower percentage as dissectible fat and total body lipid. An analysis of linear body measurements showed no difference between breeds in the stage of development of external body dimensions at 20 months of age, and it was concluded that at the same age and stage of development of live weight or size, the Friesians were leaner than the Herefords.

Relative growth coefficients of the fat depots showed late developmental growth in some intra-abdominal depots (omental and perirenal–retroperitoneal) but not in another (mesenteric). Relative growth coefficients of the omental, mesenterie and intermuscular depots were different between breeds. The Herefords deposited more dissectible fat subcutaneously than the Friesians whereas the Friesians deposited more in the intraabdominal depots. A multivariate index of fat partitioning, which was not influenced by age or stage of development of the fat depots, was not significantly correlated with fatness, suggesting no direct link between the pattern of fat partitioning and body-fat content.

Breed differences in the distribution of fat within the subcutaneous and intermuscular depots were minor compared with the large difference in the partitioning of fat between depots. It was thus concluded that the factors controlling fat partitioning do not influence the distribution of fat within depots.

The number of pepper seedlings (Capsicum annuum L.) surviving transplanting in a glasshouse decreased from 100% in the control to 84 ± 6,55 ± 8, and 18 ± 6% in field soil containing 1, 5 and 25 propagules of Phytophthora capsici Leonian per gram soil, respectively. When detached leaves were inoculated with a sporangial suspension at 15 and 31 °C, an incubation period of 24 h was required before an infection level of 50% was reached. Incubation at 27 °C for 4 h resulted in 60% of the leaves infected. Neither sporangia nor mycelia survived a week in leaf tissue if the relative humidity was 47% or less or if the temperature was -12 or 40 °C. Recovery of sporangia from inoculated stem pieces (2 cm long) stored for 1 week at 25 °C was reduced from 1455 to 30 sporangia per stem piece when the relative humidity was reduced from 100 to 87%. P. capsici could not be isolated from inoculated leaf tissue 2 days after being placed on the soil surface in a field, but was easily isolated after 14 days if buried. The distribution of disease within a test field followed the field's drainage pattern. Splashing rain and run-off water appear to be the main means of spread. Combined rainfall for days 3, 4, 5 and 6 prior to symptom development correlated with disease incidence (r = 0·53, P < 0·01).

The size and number of recognizable fat cells (diameters greater than 5 μm) were examined at several sites in 42 Hereford and Friesian steers. Four, two and 15 animals from each breed were slaughtered at 6, 13 and 20 months of age, respectively, after ad libitum feeding.

For the 15 animals of each breed slaughtered at 20 months, biopsy samples of adipose tissue were removed at 10, 13 and 17 months from the 12th rib, midloin, rump and perirenal sites. Samples from these sites and from the brisket (subcutaneous), prescapular (intermuscular) and omental sites were also removed from the carcasses of slaughtered animals. Fat cell diameter (microscopic technique) and dry matter (from which lipid content was predicted) were measured on all samples. Measurement of fat depth (ultrasound) and surface area at the subcutaneous sites allowed changes in relative number of cells to be estimated during growth.

From biopsied samples it was apparent that the perirenal depot grew almost exclusively through cell enlargement in both breeds. In contrast, the subcutaneous depot grew principally through cell enlargement to about 13 months of age and thereafter through both increase in number of cells and cell enlargement. The trigger for this increase in number of cells was possibly a critical average cell size, although this clearly did not operate in perirenal fat.

Slaughter samples showed that cellularity changes with growth were similar in the perirenal and omental depots (intra-abdominal) whereas changes in the prescapular (intermuscular) site tended to parallel those in the subcutaneous depot.

In relation to fat-free body weight (and therefore taking body size into account) both breeds had similar numbers of intra-abdominal and prescapular fat cells, but the Herefords had approximately double the number of subcutaneous fat cells compared with the Friesians.

Botrytis allii, grey mould, is the major cause of bulb and seed yield losses of growing onion seeds in Israel. Nursery treatments with iprodione or vinclozolin significantly decreased the number of diseased onion bulbs which were supplied to the farmers from 24% in the control to 8% in the treated plots and resulted in higher yield of seed with increases of 45% in seed weight per plant. Onion bulbs under non-irrigated conditions in the mountains were found to be more susceptible to the disease, as well as to secondary infection, than irrigated onions that were grown in the plains. Chemical treatment of the bulbs before planting significantly reduced the rate of secondary infection in the field and decreased seed losses. The survival of B. allii propagules and their importance as a primary source of inoculum in growing onions for seed were studied in the central mountainous region of Israel. From 197 to 1532 B. allii propagules per g soil were found in the field plots, this as the result of only one season growing onion seed. Ninety-one per cent of the total planted healthy bulbs were infected in the highly contaminated plots after 150 growing days. The surviving B. allii propagules reduced the seed yield, from 14·4 in the less contaminated plots to 10·4 g/plant in the highly contaminated.

The results of 62 comparative digestibility and nitrogen balance trials of Asiatic water buffalo and Zebu cattle fed the same roughage or mixed diet were analysed to test for species differences in various nitrogen input-output relationships. The influence of dietary metabolizable energy content on the utilization of dietary or apparently digested nitrogen (ADN) was also investigated.

There was no difference between buffaloes and Zebus in their ability to digest dietary nitrogen. The true nitrogen digestibility was calculated to be 81% and the metabolic faecal nitrogen excretion to be 0·36 g N/lOOg dry-matter intake. The buffaloes had lower rates of excretion of urinary nitrogen per unit increase in ADN, and at the same intake of ADN (143 mg/kg live weight/day), they had the higher nitrogen balance: 58 v. 48 mg/kg live weight/day. Dietary metabolizable energy content did not affect the utilization of digested nitrogen.

Estimates of metabolic faecal nitrogen and endogenous urinary nitrogen excretions and of maintenance requirements for digested nitrogen were similar to those of tropical large ruminants reported by other workers. On low-quality (0·8% N) or medium-quality (1·6% N) diets, it was calculated that buffaloes would have nitrogen balances.

Food utilization in relation to growth of body components, and fat mobilization and its hormonal control in vivo, were examined in 15 Hereford and 15 Friesian steers which were slaughtered at 20 months of age. Changes in body composition between 6 and 20 months were calculated from the body composition of these animals and from an additional four and two steers from each breed slaughtered at 6 and 13 months of age, respectively.

The Friesians consumed more food overall (14%) and grew more rapidly (14%), but their intake in relation to metabolic body weight was not different from that of the Herefords. Although the Friesians deposited more protein in relation to lipid there was no breed difference in food conversion ratio, and maintenance requirement relative to empty-body weight0·75 was estimated to be 7% greater in the Friesians than the Herefords. Friesians therefore had a lower efficiency of conversion of food energy to body energy. It is speculated that the higher maintenance requirement of the Friesians was due to a faster rate of protein deposition and a higher proportion of visceral organs with an associated higher rate of protein turnover.

Changes in plasma concentrations of free fatty acids (FFA), insulin, growth hormone (GH), adrenaline and noradrenaline were examined in response to fasting at 12 and 20 months of age. Inaddition plasma concentrations of glucose, thyroxine (T4) and triiodothyronine (T3) were measured at 20 months of age.

At both ages, FFA concentration increased almost linearly with duration of fasting and was not different between breeds. It was therefore unrelated to fat partitioning and a poor index of breed differences in metabolic and body type. Within breeds, the rate at which FFA concentration increased during fasting was correlated with estimated maintenance requirement (r = 0·53). This suggests a different relationship between FFA utilization and maintenance requirement in the two breeds.

During fasting at 12 months of age, Friesians had higher concentrations of plasma GH and noradrenaline. At 20 months of age they had higher concentiations of glucose, insulin and catecholamines. There was no obvious hormonal explanation for the observed differences in body composition or growth efficiency. Correlations between indices of fat partitioning and maintenance requirement were low, suggesting no direct link between the two traits.

Three adjustment methods using control plots to adjust for soil variation in a modified augmented design (Lin & Poushinsky, 1983) were studied by simulation. The results show that adjustment by design structure (row and column correction factors) is best when soil variation is relatively uniform in one or two directions, while adjustment by regression analysis is best when the variation is multi-directional. Adjustment using the control plot as a fertility index is least satisfactory. A modified augmented design in a replicated experiment is generally inferior to a balanced lattice square design but is competitive when the percentage of environmental variation attributable to soil factors is less than 70% of the total variation.

Yield variability of spring barley and winter wheat varieties is investigated in National Institute of Agricultural Botany trials sown to assess the influence on varieties of fungicide treatment. The extent of the variation in relative variety performance due to years and centres is estimated for untreated and treated yields and for yield response to fungicide. The consequences for the design of future trials systems are considered.

Fertilization of four field bean cultivars was examined in irrigated and non-irrigated plots. The overall fertilization of the ovules examined was 33%; in irrigated plots it was 25% and in non-irrigated plots, 41%. Only 48% of fully formed flowers had at least one fertilized ovule. Fertilized ovules occurred most frequently at the first ovule position in the ovary (nearest the stigma), and this frequency declined at successive ovule positions. There was in general a higher fertilization percentage at the upper flowering nodes while fertilization percentage dropped from the first flower position in a raceme to the last. At all the flowering nodes and raceme-flower positions, the cultivars Erfordia and Outlook generally had a higher fertilization frequency than Maris Bead or TI. The significance of these results is discussed.

The size of the sink on two indeterminate (cv. Hampton and cv. TGM 119) and two determinate (cv. Bossier and cv. TGM 294) cultivars of soya beans were reduced by continuously limiting the number of pods developing at each fruiting node to either one or two, starting from 2 weeks after anthesis, in three field experiments (early 1980, late 1980 and early 1981). Thiswas in order to evaluate the effects of sink size on the development of pod and seed characteristics as well as to quantify the inter-relationships between these characters under humid tropical conditions.

Persistently reducing the number of pods developing at each fruiting node consistently significantly reduced the number of pods per plant, the pod and seed dry weights per plant, the total number of seeds per plant and the harvest index (seed weight as a proportion of total dry weight) in all cultivars when compared with the control. On the other hand, the treated plants of all cultivars generally had longer pods, heavier individual pods and seeds, more seeds per podand greater leaf area and leaf dry weight as well as greater specific leaf weight than the control plants. Compensation indices (percentage increases in size over control) were 25–30% for weight per pod and seed weight per pod; 11–16% for weight per seed and number of seeds per pod and 2–5% for pod length in the treated plants.

Most of the characters measured (except individual weight of pods and seeds, seed weight per pod and number of seeds per pod) had significant interaction effects of sink size, cultivar and season; season had the highest correlation ratio, followed by cultivar, and sink size had the least. Also, nearly all components of seed yield were positively highly significantly correlated with one another; the number of seeds per pod and the number of pods per plant accounted for 76% of the variation in seed dry weight per plant.

It would seem therefore that under the prevailing humid tropical conditions, the most important component of seed yield in soya bean is the number of seeds per pod, as affected by the sink size.

A correlation coefficient of r = 0·985 (P < 0·01) between the number of fertilized ovules at each cultivar-ovule position (Rowland, Bond & Parker, 1983) and the number of mature seeds for each cultivar-ovule position indicated an extremely close relationship between fertilized ovules and seed set in four field bean cultivars. This suggests that unreliability in seed yield in field beans could be due to variability in frequency of fertilization as well as in frequency of abortion of seeds and of whole pods.

Frequency of ovule abortion occurred differentially among cultivars and this abortion rate varied according to the flowering node and flower position within a raceme. Under stress conditions single-seeded pods were preferentially aborted. The data suggest that a way to increase the average number of seeds per pod is through increased frequency of ovule fertilization.

The incidence of lamb mortality from birth to 8 months of age has been studied over a 6-year period in an upland, grassland flock of sheep comprising the Scottish Blackface, Cheviot and Welsh Mountain breeds and the crosses among these breeds. Each breed and cross-bred type was maintained at varying levels of inbreeding. Approximately half the lambs which died were stillborn or dead on the day of birth, nearly 40% died thereafter but before weaning and about 10% after weaning.

Post-mortem examinations on 586 of the 632 lambs which died from among the 2453 born attributed death on average to two causes per lamb. Approximately 11% of the causes were stillbirths or delayed births; 11% were cases of dystokia; congenital defects of various types accounted for about 10% of the causes; 25% made reference to weakly lamb, exposure or starvation; 14% to infectious diseases and 16% to noninfectious diseases. The extent to which causes of death occur together is examined.

Breeds differed in mortality rate with the Welsh the lowest and Cheviot the highest. Cross-breds were better than the average of the pure breeds but this advantage emerged only in the period between 3 days and. 6 weeks of age. Inbreeding, both of dam and of lamb, increased mortality. Lambs from dams which were crosses of inbred lines had the best survival. Litter size, type of rearing, parity of dam, sex of lamb and birth weight also had significant effects on mortality rate.

The modelling of the redistribution of soluble salts in soils, in which it is assumed that the amount of water transferred from layer to layer is related to the excess over field capacity of the water content of a layer, is critically examined.

The equation obtained from the dispersion equation by neglecting the diffusive term is solved for the leaching of surface-applied nitrates. It is shown that, by comparing the finite-difference form of this equation to the algebraic formulation of Burns' (1975) model, the two approaches are essentially the same, but that Burns makes approximations that are too inaccurate. In particular, it is incorrect to relate the transfer of water to the excess over the field capacity of the water content of the layer. Burns' model, when applied correctly, requiresmany calculations to be performed, which is costly of computer time. However, it is unnecessary in this problem as the analytic solution is simple and quick to apply.

The incidence of a number of causes of death of lambs around the time of birth was examined in relation to breed, inbreeding, birth weight, birth type, sex of lamb, week of birth and parity. Data were from a grazing flock on an upland farm over a 6-year period. The breeds were the Scottish Blackface, Cheviot, and Welsh Mountain and the crosses among them. Each breed and cross was maintained at five levels of inbreeding ranging from zero to 59% inbreeding coefficient.

The incidence of delayed birth varied significantly among the breeds and crosses with the Welsh having the lowest incidence. Compared with the pure breeds the crosses showed a lower incidence of both delayed birth and preparturient deaths, but significantly only for the latter.

Dystokia was classified according to whether it arose from the relative dimensions of lamb and dam or from malpresentation. For both types the heaviest lambs had the highest incidence but the association with birth weight was much stronger for dystokia involving dimensions. Breed variation was not significant, but cross-breds had the highest frequency for the dimensions category and the lowest for malpresentation. Singles were at greater risk than twins as were lambs born to a first parity.

Congenital defects as a cause of death were divided into six categories. Only skeletal defects varied significantly among breeds and the incidence increased with inbreeding, but crosses of inbred lines did not have the lowest frequency. For congenital defects overall and for hydrocephalus and hydronephrosis in particular, line crosses (noninbred) had the lowest incidence and 25% inbred lambs the highest, the frequency declining with further inbreeding. None of the other factors considered affected variation in the incidence of any of these defects to a significant extent.

Liver rupture and brain haemorrhage were most frequent in heavy lambs, singles and lambs born to a first parity dam.

The incidence of Sclerotinia sclerotiorum (Lib.) de Bary infection in poppies (Papaver somniferum L.) was assessed 9 days before dry maturity in a field experiment which incorporated the effect of nitrogen and phosphorus fertilizer and fungicidal sprays. Infection occurred mainly on the lower stem in the leaf axils.

Nitrogen fertilizer (100 kg N/ha) had no effect on the incidence of Sclerotinia infection but phosphorus fertilizer (100 kg P/ha) increased the incidence from 19% of plants infected to 39%. Fungicides (2 kg benomyl, 50% a.i., plus 2 kg mancozeb, 80% a.i./ha) applied at 10-day intervals from flowering till harvest reduced the incidence of Sclerotinia infection to one third that of non-sprayed treatments.

Sclerotinia infection occurred late in the crop and had little effect on the dry-matter yields of terminal main-stem capsules, lateral branch capsules or stem and leaves but it did influence the distribution of morphine within the plant. The morphine concentration of terminal capsules was lowered by 13% but the concentration of lateral capsules increased by a similar amount giving a total capsule morphine concentration and yield which was similar in both infected and non-infected plants.

The morphine concentration of the stem and leaves of infected plants was 75% greater than that of uninfected plants but the overall morphine concentration of total plant was similar in both infected and non-infected plants. This distribution pattern was interpreted as a result of the restrictive influence of Sclerotinia infection on the vascular system which disrupted the normal translocation of morphine.

The digestibility, the voluntary intake and the nitrogen balance of 108 diets corresponding to 94 silages prepared from 20 fresh crops were measured in growing sheep. Series of silages were made from the same fresh forage. Each series included two controls: a direct-cut silage without additive and a direct-cut silage with formic acid, with a variable number of experimental silages with different additives.

Rumen ammonia concentration, measured on rumen-fistulated sheep, decreased when an additive was used. It increased with nitrogen intake and was inversely related to the organic-matter digestibility and the crude-fibre digestibility. It varied with the silage composition.

The crude-protein digestibility of direct-cut silages without additives was similar to or slightly higher than the crude-protein digestibility of the fresh crops. The addition of formic acid depressed the digestibility, but the addition of formaldehyde decreased it even more. The urinary nitrogen loss was higher for silages without additive than for the fresh crops and was decreased by the addition of formic acid. The addition of formaldehyde to formic acid had an additive effect.

Retained nitrogen was lower in silages without additives (12% of nitrogen intake) than in parent crops (15·7%). It increased when formic acid (15·8%) was added. The addition of formaldehyde at a low rate (1·5 l/t green fodder) to the formic acid did not increase the nitrogen retention whether expressed in g/day or as percentage of nitrogen intake, but the addition of formaldehyde at a high rate (3·5 l/t green fodder) to formic acid decreased nitrogen retention. The other additives based on cereals or whey did not improve the nitrogen balance compared with formic acid. Nitrogen retention differed according to plant species.

Retained nitrogen increased with digestible organic-matter intake and nitrogen intake. It increased with the silage water-soluble carbohydrate content. The higher the silage fermentation product content (ammonia, lactic acid, propionic acid), the lower the retained nitrogen. It appears that the nitrogen value of silages can be high provided that the silages are well preserved and that excessive protein breakdown is avoided.

Three silages were prepared from a second cut of perennial ryegrass, using additives of 2 l formic acid/t fresh crop together with formaldehyde at either 0, 47 or 100 g/kg crude protein (CP) in the crop. The silages were offered to appetite either alone, or with supplements of maize starch or maize starch + urea, to 18 British Friesian steer calves, half of which were rumen-cannulated. The maize starch and urea supplements were provided at 184·4 and 18·9 g/kg total dietary dry matter (D.M.) respectively.

The low contents of volatile fatty acids and ammonia N in each silage indicated that they were well preserved. Formaldehyde treatment reduced protein degradation in the silages and reduced total acid content. There was a small increase in butyric acid content at the low application of formaldehyde, and the content of 2,3·butanediol increased with formaldehyde application.

Formaldehyde treatment depressed intake, although the decline at the high level of application was less when calves were given the starch + urea supplement. Supplementation with starch reduced silage D.M. intake, although total D.M. intake was unaffected, and increased digestible organic matter (OM) intake. The addition of urea to the supplement further increased total D.M., digestible OM and digestible energy intakes. The apparent digestibilities of D.M., OM, N, cellulose and energy were depressed by formaldehyde treatment. Starch supplementation increased the apparent digestibility of D.M. and OM but depressed that of N and cellulose. The deleterious effect on cellulose digestibility was most evident at the high application of formaldehyde. Starch + urea supplementation further increased the digestibility of D.M. and OM, and increased N digestibility. Both supplements increased energy digestibility.

N retention was improved by formaldehyde treatment, particularly when the starchfurea supplement was provided. Supplementation with starch did not improve the utilization of dietary N, but reduced N retention on the formaldehyde-treated silages.

Within the rumen, ammonia-N concentration declined with increasing application of formaldehyde, and was increased by starch + urea supplementation. There was a tendency for the molar proportion of acetate to increase, and that of propionate and butyrate to decrease with increasing application of formaldehyde. Starch supplementation resulted in a small increase in the molar proportion of butyrate.

The apparent rate of digestion of silage in nylon bags in the rumen was reduced by the high application of formaldehyde. On this silage diet, rate of digestion was further depressed by supplementation with starch, but improved by supplementation with starch + urea. The apparent rate of digestion was also depressed when a reference silage (the control) was incubated in the rumens of calves on the high formaldehyde silage, indicating that the adverse effect of formaldehyde was partly due to an effect on the rumen environment. However, it is also possible that formaldehyde reacted with cell wall components, inhibiting fibre digestion.

It was concluded that formaldehyde treatment, but not starch supplementation.

The incidence of lamb mortality from weakness at birth, underdevelopment, exposure and starvation was examined over 6 years in an upland flock and analysed in relation to breed, breeding system and other factors. These causes accounted for more than a quarter of the deaths and contributed to many more.

The frequency of death due to these causes was greater in lambs light at birth. The incidence of these causes of death differed significantly between the breeds, Scottish Blackface, Cheviot and Welsh Mountain and their crosses, but for the separate categories breed variation was significant only for the incidence of death by starvation, which was also less frequent in cross-breds than purebreds. Mortality from several of these causes was increased by inbreeding (25–59%), but decreased by crossing inbred lines. Lambs born to line-cross or other non-inbred dams had a relatively low incidence of these various causes of death. For underdeveloped lambs variation due to maternal inbreeding was significant. When classes were adjusted for difference in birth weight, breed variation in mortality was greatly enhanced but variation due to inbreeding much reduced.

Slightly more twins than single-born lambs died from these causes and triplets fared worst, but such variation was significant only for death from exposure. Mortality from these causes varied significantly with parity of dam, being highest in the first, and mortality in males was slightly but not significantly higher than in females.