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.

Forty-eight sows were partially hysterectomized on day 10 (day 0 = 1st day of oestrus) of the oestrous cycle such that the isolated-contralateral ovary received either an ovarian or an ovarian and uterine blood supply. These two treatments were examined for their ability to affect corpora lutea (CL) function when 10, 20, 40 and 80 cm (12 sows/group) of the ipsilateral uterine horn remained intact. Sows with only 10 cm of uterine tissue failed to return to oestrus when observed until day 40. When 80 cm of uterine tissue remained, all the sows recycled between days 20 and 24. As the length of uterine horn increased from 10 to 80 cm the contralateral ovary became susceptible to luteolysis. At these lengths (20–40 cm), increased blood supply to the contralateral ovary afforded the luteal cells resistance to luteolysis (uterine length × blood supply interaction, P < 0·05). An additional four sows received 125I-labelled microspheres for purposes of determining CL blood flow following these alterations of blood supply to the isolated ovary. Blood flow to the CL was increased in three of the four sows when the isolated ovary received an additional uterine blood supply. Results from these experiments support the concept of an involvement of blood flow in the regulation of CL function.

In Expt 1, 34 individually-penned Finn Dorset ewes of mean live weight 68 kg were synchronized in oestrus and mated to Suffolk rams. From mating until day 28 of pregnancy each received daily 15 MJ of metabolizable energy (ME) and 225 g crude protein (CP). From day 28 to slaughter on days 34, 41, 48 or 55 half of the ewes continued on this feeding regime and half had their daily intake reduced abruptly to 7·5 MJ of ME and 112 g CP. The mean number of ovulations per ewe was 4·03 (range 2–8) and the mean number of viable foetuses at time of slaughter 3·35 (range 2–6). The combined loss of ova (fertilization failure and early embryonic death) was 14·6% and detectable foetal deaths 2·2%. Level of feeding had no significant effect on these measures or on foetal growth. Foetal growth from 34 to 55 days was described by the equation

In w = 0·962–18·613 e-0·0272t–0·00091t(f–3),

where w = foetal weight (kg), t = age (days) and f = litter size. Within-litter variability measured as the S.D. of In w (kg) was 0–081 for twins, 0·108 for triplets and 0·106 for quadruplets and higher multiples.

In a second experiment Suffolk × Finn Dorset embryos were transplanted at the rate of two per uterine horn into 15 recipient Finn Dorset ewes. Embryo survival was 72% and foetal weights at 60 days varied from 67 to 146% of the mean value of 66 g. Withinlitter variation in foetal size was only about 70% of that expected for foetuses developing from the variable distribution in their initial positioning that occurs naturally. The correlation between foetal weight and placental weight at day 60 was 0·72 (P < 0001) indicating that the association between foetal weight and placental weight in prolific ewes is not confined to late pregnancy.

The results of both experiments are consistent with the hypothesis that the greater within-litter variability in birth weight in large litters is controlled by events in early pregnancy.

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.

The proportions of cross-bred and selfed seed were estimated in up to four consecutive generations of Throws MS winter beans on three farms where farm-saved seed was regularly used.

Within one stock the percentage of cross-breds rose a significant amount from 31 to 46, whilst in another stock no change was detected over four consecutive generations. On the third farm a change of stock mid-way through the period of the survey was associated with a highly significant increase in proportion of cross-breds.

In general a rise in outcrossing was not followed by a significant fall as would be expected if cross-breds have a greater tendency than inbreds to self pollinate, but the possible role of a regulatory mechanism is discussed as are implications of the range in outcrossing within stocks for variety trials and commercial production of winter beans.

Estimates of outcrossing frequency made in two crops in 1983 were slightly lower than some obtained in 1974–6 but no lower than those reported in 1951 thus providing no evidence of any long-term change in levels of natural cross-breeding in field beans in England.

Six field experiments, three each during 1982–3 and 1983–4, were conducted on a sandy loam soil to study the effect of varying levels of nitrogen, phosphorus and potassium, in the absence and presence of farmyard manure (FYM) (30 t/ha), on the number of tubers and yield of potato in three grades. Increase in nitrogen, phosphorus and potassium application, in the absence or presence of FYM, did not significantly affect the total number of tubers/m2 but did affect the number of tubers in different grades. An increase in nitrogen and potassium significantly decreased the number of tubers/m2 in small (< 25 g) and increased in medium (25–75 g) and large (> 75 g) grades at 45, 60, 75 and 90 days after planting. Increase in the application of phosphorus increased the number of tubers/m2 in the small grade and decreased it in the large grade but did not affect the number in the medium grade. Increase in nitrogen and potassium application decreased the tuber yield in the small grade and increased it in the medium and large grades. Applied phosphorus increased the yield in the small and medium grades and decreased it in the large grade. The increase in the yield of tubers with increase in nitrogen and potassium application was found to be caused by an increase in the number of tubers in the medium and large grades at the expense of the small grade; however, with applied phosphorus the increase in yield was due to increase in the weight of individual tubers within the small and medium grades. FYM application decreased the number of tubers in the small grade and increased it in the medium and large grades. The response of potato to nitrogen increased and to phosphorus and potassium decreased with the application of FYM.

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.

Testicular and epididymal sperm reserves were determined in six sexually mature Mujjafaranagri rams. The testes and epididymides weight were 151·4±5·49 and 20·7±0·164 g respectively. The total spermatids/g were 78±21·8×106, while daily sperm production per ram was estimated to be 4·46×109 when corrected for tunica albuginea weight. The number of spermatozoa in the caput, corpus and cauda epididymides were 3·18, 2·56 and 16·29×lO9 respectively and they represented 14·4, 11·6 and 73·9% respectively of the sperm reserves on that side. The total epididymal sperm reserve per male ram was about 44·06×109 spermatozoa.

In 1984 and 1985 a field experiment on a grass ley on a light sandy soil at Woburn Experimental Farm, Bedfordshire, tested injected aqueous urea and broadcast prilled urea, applied alone or with a nitrification or urease inhibitor. Aqueous urea, prilled urea and ‘Nitro-Chalk’ were applied as a single 375 kg N/ha dressing, and prilled urea and ‘Nitro-Chalk’ also as three 125 kg N/ha dressings. The nitrification inhibitor nitrapyrin or a mixture of sodium trithiocarbonate (STC) plus potassium ethyl xanthate (KEtX) was injected with aqueous urea. The nitrification inhibitor dicyandiamide (DCD) or the urease inhibitor phenyl-phosphorodiamidate (PPDA) was broadcast with prilled urea.

The nitrification inhibitors significantly retarded nitrification of both aqueous and prilled urea. PPDA reduced ammonia volatilization from 375 kg N/ha broadcast as urea, and hence losses to the atmosphere, which otherwise ranged from 13 to 33 kg N/ha.

Nitrapyrin or STC and KEtX increased yield and nitrogen uptake in both years when urea was injected in January. Nitrapyrin also increased yield and nitrogen uptake in 1985, but not in 1984, when urea was injected in March, whereas the STC and KEtX mixture was then either detrimental or ineffective. DCD increased yield and nitrogen uptake from a single dressing of broadoast urea only in 1985. PPDA increased yield and nitrogen uptake from a single broadcast dressing of urea in both years, but had little effect when applied with divided dressings.

In 1984 a divided broadcast dressing of ‘Nitro-Chalk’ gave the largest yield and nitrogen uptake, but in 1985 aqueous urea injected with nitrapyrin in January or without or with a nitrification inhibitor in Maroh and prilled urea broadcast as a divided dressing all gave a larger yield. Similarly, a single application was generally more effective as ‘Nitro-Chalk’ in 1984, but as urea in 1985.

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.

A 28-month trial was carried out under extensive grazing conditions to examine the effects of giving water to Boran cattle once daily, once every 2 days, and once every 3 days, with cattle having ad libitum access to water serving as the control. In the dry season, the weight and condition of lactating cows given water every 3 days declined more rapidly than that of cows given water daily. Calving rates and birth weights were unaffected by treatments although when compared with cows given water ad libitum, birth weights were depressed by 2·5 kg in all treatments. Thirty steers showed no treatment differences in 28-month weights despite a depression in dry-matter intake in the dry season by animals given water every 3rd day. In contrast, 210-day weaning weights were significantly depressed by 9 kg when cattle drank water every 2 days and 14 kg when they drank every 3 days compared with calves given water daily. Total water consumed was depressed in all classes of stock by 5–10% under the 2-day regime and by 25–34% under the 3-day regime when compared with cattle given water daily. The results show that giving water every 3 days can be carried out indefinitely with all classes of stock with only minor effects on cattle productivity under the climatic conditions in which the trial was held. The management implications of giving water every 2 or 3 days to cattle under extensive, pastoralist and ranching conditions are discussed.

The growth and grain yield of winter wheat were measured in plots which had been direct drilled, mouldboard ploughed or shallow-tine cultivated for 10 consecutive years. The experiment was carried out on a non-calcareous clay soil prone to winter waterlogging. In 1985 the crop grew well on all cultivations and grain yield, average 7–2 t/ha, was similar in all treatments and no adverse effects on wheat growth or on grain and straw yield were observed.

Sodium chlorite increased the degradability of fibre from a range of mature grass forages inoluding barley straw by 40–50 digestibility units when comparisons were made using ground (1 mm sieve) material incubated either in vitro with cellulase or in nylon bags in the rumen. However, when fed to sheep, chlorite-treated barley straw was digested to a similar degree to untreated straw (49 and 57% respectively), but intake was significantly reduced (385 and 790 g/day respectively). The poor in vivo utilization of chlorite-treated straw coincided with high proportions of propionic to acetic acid in the rumen (0·85, cf. 0·28 with untreated feed) and absence of rumen fungi. Rumen pH and ammonia concentrations were not significantly different between diets. When incubated in nylon bags in the rumen of animals fed the corresponding diet, both untreated and treated straw (< 1 mm) were well colonized with micro-organisms, as measured by cystine accumulation which showed peaks on the fibres after 24 and 72 h. While large numbers of fungal sporangia were observed after 24 h incubation on digesta from untreated forage, no fungi could be detected on the chlorite-treated material. Cystine accumulation on the untreated straw after 72 h was not associated with a secondary growth of fungi.

Although barley straw chaff, ground (< 1 mm) after treatment with chlorite, was highly degraded in nylon bags in the rumen and with cellulase in vitro, larger particles (1 cm) suspended in nylon bags in an animal fed chlorite-treated straw actually gained weight, probably due in part to the degree of microbial colonization.

It was demonstrated that abiotic chemical precipitation could account for a major proportion of iron hydroxide deposition in drainage water. In filter-sterilized (0·22 μm) drainage water samples from ochreous sites 84% of the total iron in solution was precipitated within 48 h. It was also shown that ferric hydroxide precipitates could catalyse the precipitation of ferric hydroxides in drainage water exposed to the atmosphere.

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.

Fourteen cow peas were tested for susceptibility to infestation and damage by Callosobruchus maculatus (F.) in the laboratory. IT81D-897 and Popse showed the lowest damage over a 3-month test period. 100-seed weight was not significantly correlated with seed damage.

The developmental period of G. maculatus was significantly longer in IT81D-897 and Popse than in other cow peas tested. Percentage adult emergence and fecundity of females were also lowest in these two cow peas.

Sheathed filamentous bacteria, Leptothrix spp. and Gallionella spp., were observed in ochre samples from sites in England and Wales. Thiobacillus ferrooxidans was found in acidic samples (pH < 4·0) and in ochre from drainage water of near neutral pH suggesting that it can contribute to ochre formation over a wide range of drainage water pH, Heterotrophic bacteria capable of growing in artificial media of low pH and complexdegrading heterotrophic bacteria were also isolated. Some ochre deposits could be described as either pyritic or filamentous but the majority of samples fell between these extremes and had various combinations of T. ferrooxidans, sheathed filamentous bacteria and other heterotrophic bacteria.

The characteristics of three fractions obtained by physical separation from each of 19 cattle slurries are reported, with the aim of investigating their behaviour in the soil. The fraction retained on a 1 mm sieve (F1) was the poorest in nutrient content. The fraction passing through a 1 mm sieve but retained in Richard's apparatus on a cellulose membrane of 2·4 nm pore radius (F2) contains most of the slurry's organic N and Pand most divalent cations (Ca2+ and Mg2+). F3, which passes through the cellulose membrane, contains most of the slurry's inorganic N and most monovalent cations.

The individual fractions are both chemically and physically much more homogeneous than the slurry as a whole, and their relative proportions are well correlated with the slurry's density and dry-matter content (P < 0·001), so that this kind of fractionation may confidently be expected to provide an analytical scheme facilitating research on the behaviour of slurry after its application to soil.