The loss of moisture from swaths drying in the field has been investigated using bulk and multi-layer micrometeorological models of an idealized swath. The models produced almost identical results for the variations with time of the swaths' mean moisture contents but the multi-layer version showed in addition the results to be expected from tedding, and the effects of transpiring stubble and evaporation from an underlying moist soil surface on swath drying. The models reproduced in broad detail changes of swath moisture, including rain and dew intercepted by the swath, which had been observed in experiments on grass wilting. However, there appeared to be under-estimation of the rate at which the swath tissue absorbed moisture when the swath contained surface water. The bulk model reduces to a very simple formula when used with typical swath resistances, revealing the importance of both sunshine and vapour pressure deficit in promoting drying, and demonstrating the adverse effect of wind; the model lends itself to the routine classification from daily climatological data of days suitable for hay drying.

A long-term rotation experiment testing the effects of applying K fertilizer in combination with N fertilizer and cropping treatments, and two experiments comparing the effects of residual and freshly-applied K together with N treatments over 3 years, all on boulder-clay soils, together with two detailed studies of the effect of K on the growth of wheat on a chalk soil very deficient in K, are described and the results discussed.

Restricting the K supply had little effect on the growth of wheat until stem elongation began, but from then the growth of almost all organs was affected. It is concluded that there is no one mechanism by which lack of K in the soil restricts yield. It can decrease the area of the upper leaves, the dry matter produced in the upper internodes and ears, reduce the number of grains per unit area and the size of grain, but which of these is most important in a particular crop will depend on other cultural and environmental conditions.

It is argued that boulder-clay soils should not be considered as a single class when giving advice on K manuring; more experiments are required to make practical recommendations more precise.

Milk yield of 270 Rahmani, Ossimi and Barki subtropical Egyptian ewes rearing single lambs during three successive lambings in 2 years was estimated over 12 weeks of the lactation using a lamb-suckling technique. The ewes received either normal or high level of feeding during late pregnancy and lactation.

Ossimi and Rahmani ewes showed significantly (P < 0·01) higher total milk production than the Barki. Milk yield declined sharply for the Barki ewes after the 6th week of lactation. Breed variation failed to attain statistical significance in the first 4 weeks of lactation. The highly fed ewes produced significantly (P < 0·01) more milk at different stages of lactation than the normally fed ones. High level of feeding, however, is not recommended for subtropical non-dairy ewes as it is not economic. Spring-lambing ewes produced significantly more milk during the first 8 weeks of lactation, while the summer-lambing ewes were more persistent in their milk yield in the last 4 weeks of lactation.

Neither age of ewe nor body weight significantly affected milk yield. Correlation coefficients between milk yield and body weight at lambing are small and range from 0·00 to 0·24.

Milk yield of 240 single-suckled ewes from Rahmani, Ossimi and Barki subtropical non-dairy Egyptian sheep, in addition to 64 twin-suckled Rahmani ewes, was estimated over two lambing seasons using three methods of measuring, i.e. lamb-suckling (plus residual milk), oxytocin technique and hand milking.

For single-suckled ewes, the oxytocin technique resulted in higher (P < 0·05) estimates of milk yield during the first 4 weeks of lactation than lamb-suckling. However, over 12 weeks of lactation the two methods showed closely similar estimates. Hand milking produced 31·6% less milk than the other two methods.

For twin-suckled ewes, the lamb-suckling method produced significantly (P < 0·05) higher estimates than the oxytocin technique. Estimates obtained by hand milking were 65·2 and 50·8% less than that of the other two methods, respectively.

In a previous study (Bromfield, Debenham & Hancock, 1980) sulphur deposited in rainwater was measured in central Kenya some 450 km from the Indian Ocean. The study reported here was complementary and measured sulphur deposited in 1979 at the Kenya coast, adjacent to the Indian Ocean, in a small but important agricultural area. Sodium was also measured since it is an element of marine origin, present in air in particulate form, and can be compared with sulphur which is largely present in the air in gaseous form.

The influence of various factors like breed, season, level of nutrition, age and body weight was studied in indigenous (Marwari and Magra) and exotic (Corriedale) rams in respect of semen quality and sexual behaviour under the arid conditions of Jodhpur in the Indian desert. None of these factors except breed and level of nutrition affected semen quality. The breeds differed significantly only in respect of percentage abnormal sperms. The values for all the physical characteristics except sperm concentrations wore slightly lower in the Corriedale. Supplementary concentrate feeding resulted in significantly higher concentrations only of fructose and citric acid in the semen. The physical characteristics of the semen were only slightly superior in the feed-supplemented group of animals. The breeds differed significantly in respect of libido characteristics, with the Corriedale exhibiting the longest reaction time and the lowest number of matings in 30 min. These characteristics were, however, not affected by the other factors mentioned above.

Soils of various agronomic histories were fumigated with chloroform, and the resultant increased production of CO2 and mineral-N measured and expressed as biomass C and the flush of mineral-N production (FN), respectively. Biomass C and FN contents of grassland soils were greater than those of arable soils, and significant correlations with macro organic-matter content were found. Biomass C contents varied from 7 to mg C/100 g soil in arable soil and from 31 to 222 mg C/100 g soil in grassland or woodland. The proportion of soil organic C that was contained within the biomass ranged from 0·3 to 4·0%, whilst FN comprised from 1·0 to 11·7% of total soil N. FNcontents ranged from 1·1 to 13·2mg N/1OOg soil for arable soils, and from 2·5 to 31·7 mg N/100 g soil for grassland and woodland. Application of organic manures increased biomass C and FN contents in grassland soil.

The growth in body weight of 91 stags from weaning to 15 months of age and of a smaller number from 15 months to maturity was examined using observations from a farmed stock kept on hill land. Growth rate in winter from 3 months to 10 months of age was proportional to feed allowed and was 35 % greater than for hind calveskept under similar conditions. Growth rate in the subsequent summer was greater for stags than for hinds in sixout of seven instances. After 15 months of age, stags continued to increase in body weight and their weight thus continued to diverge from that of hinds such that at 87 months the average weight of the surviving nine stags was 132 kg and that of the surviving 47 hinds, 78 kg. It is estimated that the equilibrium weight of stags was 154kg.

Growth and yield components of a semi-dwarf spring wheat (Triticum aestivum L., cv. GWO 1809) were determined under three different atmospheric CO2a concentrations (350, 675 and 1000 μ1/1) in controlled environment chambers of the Duke University Phytotron. CO2 enrichment enhanced tiller and head emergence and increased the number of head-producing tillers and the total dry weight of the plants. Total leaf area, stem height and root/shoot ratio of the plants were greater at high CO2 concentrations than at low. Net assimilation rate (NAR) increased with increasing CO2 concentration and decreased with plant size. There was little effect of CO2 enrichment on leaf weight ratio (LWR) and leaf area ratio (LAR) and no significant effect on specific leaf area (SLA). The weight and number of seeds were significantly higher with increasing CO2 concentration. The results of this study provide evidence that important changes in plant growth and development may occur during the next century if global CO2 enrichment continues. Some of these changes would have important ecological impact in natural and managed ecosystems in the future.

The Guadalcanal Plains encompass approximately 460 km2 with both forest and grassland phases. Mean annual rainfall is 2160 mm, with a drier season from June to October, but soil moisture deficits seldom occur. Soils are freely to imperfectly drained brown loam to clays (Ustropepts). Soil analyses show available P concentrations of 15–17 μg/g, adequate K, Cu, Zn and Mn, and high Ca and Mg, but sulphate sulphur is low. A nutrient omission trial gave significant negative responses to the omission of P, K, S and Mo. However, responses to P applications were not obtained in the field with Centrosema pubescens, but significant responses to K and S were found under a cut and remove system. Yield response in the grasses Brachiaria decumbens and B. mutica to applied N was markedly limited in the absence of applied S, even though B. mutica was able to maintain S concentrations in herbage at 2–3 times those of B. decumbens. Without applied S, S contents and N:S ratios in B. decumbens were inadequate for beef cattle, but adequate in B. mutica except at high N inputs (300 kg/ha/year). Application of 40 kg S/ha to the legume C. pubescens increased yields by approximately 50%, reduced incidence of Cercospera leaf spot, and gave increased N concentrations. For establishment of sown mixed pastures on the Guadalcanal Plains we recommend the basal application of 20 kg P/ha, 50 kg K/ha, 30 kg S/ha and 0·15 kg Mo/ha, with 30 kg S/ha applied every 2 years.

Animal production was compared on three pastures, Brachiaria mutica (para), B. decumbens (signal) and Panicum maximum cv. Hamil (hamil) each sown with a common legume mixture of Centrosemapubescens (centro), Macroptilium atropurpureum cv. Siratro, and Stylosanthes guianensis cv. Endeavour (stylo), at four stocking rates, 1·8, 21·87, 31·86, and 41·85 animals/ha, over 4 years on the GuadalcanalPlains, Solomon Islands.

Mean live-weight gain per head over the four stocking rates and 4 years on para pastures was 01·847, on signal pastures 01·838, and on hamil pastures 01·828 kg/head/day. Mean production per hectare at the optimum stocking rates were: para at 3.6 animals/ha, 607 kg; signal at 31·86 animals/ha, 442 kg; hamil at 21·87 animals/ha, 362 kg/ha/year.

The high stocking rates of 31·86 and 41·85 animals/ha caused the hamil pastures to decline to the stage where they were destocked in the 4th year of grazing.

Superior production on para pastures was not simply related to green dry matter (GDM) on offer. In the 1st year of grazing, GDM was highest in hamil pastures, but in the 2nd year highest in para, and in the 3rd year mean yields were similar in all pastures, but were very low at the 31·86 and 41·85 animals/ha stocking rate in the hamil pastures.

Para pastures maintained highest legume contents. The quadratic relationship between live-weight gain/head and legume content was significant over all pastures and stocking rates. Live-weight gain (LWG) per head increased up to 15% legume content, after which there was little change. Yield of green leaf, percentage green leaf, and sward bulk density did not appear to be related to LWG/head. Para pastures had lower values for all these components than the other pastures.

Chemical factors contributed to the higher animal production from para pastures. Para leaf maintained consistently higher in vitro dry-matter digestibility values. Na content of para averaged 01·812%, whereas other species were 01·801 to 01·802%, and below the critical level (01·805%) for animal intake. N and S in leaf material, and Cu in total tops were also consistently higher in para grass.

Results of this grazing trial suggest that selection of grass species on the basis of quality including dry-matter digestibility and mineral content, on ability to persist with increasing stocking rate, on compatibility with legumes, and on growth habit are more important than selection for dry-matter yield.

Two similar experiments were conducted in consecutive years using a total of 26 pregnant beef cows. The two groups of 13 cows were given 2 kg molassed sugar-beet pulp (SBP)/day for the last 16 weeks of pregnancy and 3 kg SBP/day for the first 6 weeks of lactation with oat straw ad libitum. One group was given 250 g of a fully soluble liquid supplement (LS) containing urea, phosphoric acid, calcium and sodium chloride, trace elements and vitamins poured on to the SBP. The other group received no supplementary phosphorus but was given the same amounts of supplementary nitrogen (as crystalline urea) and calcium (as calcium carbonate) together with the same amounts of sodium chloride, trace elements and vitamins as were present in the LS. The LS provided 3.7 g P/day. The overall mean phosphorus intakes of the two groups were about 5.5 g (unsupplemented) and 10.5 g P (LS)/day.

During pregnancy, reduced phosphorus intakes did not affect either the voluntary intake or digestibility of the straw. There was, however, a reduction in the blood phosphorus concentration for the cows which did not receive LS.

After calving, the voluntary straw intake, digestibility of straw organic matter, metabolizablo energy intakes and blood phosphorus concentrations of the cows which received no phosphorus supplement were severely reduced. Using the present data and that from an earlier, similar experiment, a highly significant relationship was established between blood phosphorus concentration and voluntary straw intake during the period 5.6 weeks after calving for those cows with a blood phosphorus concentration below 1.0 mmol P/l. This relationship was voluntary straw intake (kg D.M./day) = 1.55 + 5.01 × blood phosphorus concentration (mmol/1).

These results, obtained with individually fed, housed cattle, tend to suggest that a total phosphorus intake of only about 10.12 g P/day (of which 3.7 g was in the form of phosphoric acid) was adequate to maintain normal blood phosphorus concentration and voluntary straw intake and digestibility by these beef cows over the last 16 weeks of pregnancy and the first 6 weeks of lactation. This should be contrasted with the results of a similar experiment conducted earlier which clearly indicated that a daily intake of about 12 g P/day derived solely from sugar-beet pulp and oat straw was markedly inadequate.

A field and a glasshouse experiment were carried out to assess in winter wheat genotypes the interrelationships between stem and ear development, and to relate these to number of grains and yield. Capelle-Desprez (gai/rht2) and Hobbit ‘s’ (Gai/Rht2) were used together with four F4 lines from the cross between them. Two of the lines were homozygous for gai/rht2 and two lines homozygous for Gai/Rht2. Within each pair of homozygous lines there was a contrast between a tall and a short genotype.

There were no consistent differences in shoot apex morphogenesis between the genotypes, and, in general, similar numbers of spikelets and floret primordia were initiated in all genotypes. This contrasts with the hypothesis that genotypes based on Norin 10 (Gai/Rht2) have a fundamentally different pattern of ear morphogenesis. The main differences between genotypes were in dry-matter partitioning to stem and ear prior to anthesis and these were associated more consistently with the dwarfing gene than with height per se. Gai/Rht2 genotypes partitioned more dry matter to the ear during its development and less to the stem and this was reflected in greater ear weight at anthesis, more fertile florets and grains per spikelet, a higher harvest index and higher grain yield than the gai/rht2 genotypes. Although similar numbers of floret primordia were initiated in all genotypes, assimilate partitioning during development determined the proportion which developed into fertile florets at anthesis.

The leaching behaviour of a highly saline-sodic, moderately permeable, sandy-loam soil was evaluated under continuous and intermittent submergence conditions in a longterm field study in the presence of rice and subsequent wheat and sesbania crops. Leaching curves with respect to both desalinization and desodification showed that leaching efficiency was considerably higher with intermittent than with continuous submergence. The curves were useful in determining the amount of leaching water needed for a given mode of water application to reduce harmful levels of salinity and sodicity to acceptable ones. Empirical equations were determined to fit the experimental data. Their comparison with another empirical equation from published bare-field data of this site showed that leaching efficiency under crops was higher than under fallow. From the desodification leaching curve, it is concluded that in reclamation of these soils there is no need of the application of any amendment like gypsum. The soil salinity and sodicity data recorded at different growth stages and crop yields showed that leaching during the rice growing season, under intermittent submergence without previous leaching, decreased salinity and sodicity throughout the top 100 cm of the soil to levels safe for the successful cultivation of rice and subsequently the relatively deep-rooted crops of wheat and sesbania.

Crops of potatoes grown on 0·2–0·3 ha in each of the years 1971–8 at Stockbridge House Experimental Horticulture Station achieved total tuber yields of 70–94 t/ha. Yield was determined by the period and rate of tuber growth. The observed period of growth varied from 96 to 132 days and the rate from 0·55 to 0·90 t/ha/day. Rate of growth had the greater influence on variability of yield between the years. The number of tubers produced per unit area had little influence on their total weight, but had marked effect on their size. Adequate water supply was essential for very high yields. Experiments indicated that current recommendations for potash fertilizer can be adequate but that nitrogen and phosphate fertilizer use may need to be enhanced for very high yields. For high yields, the number of seeds planted per hectare may need to be higher than normally recommended in order to avoid the production of large tubers unsuitable for the ware market.

A series of glasshouse and growth-cabinet experiments were carried out to investigate aspects of flower and pod production in Phaseolus vulgaris L. (French bean). Abscission of flowers and immature pods varied between 45 and 80% in the seven cultivars tested, with flowers which opened first being most likely to produce mature pods. Seed yield was only slightly reduced and sometimes increased by the removal of opened flowers for periods of up to 15 days from the start of anthesis depending on the conditions under which plants are grown. It was demonstrated that plants compensated for flower removal by setting pods from flowers which opened later. Similarly, when opened flowers were removed from alternate nodes plants compensated by setting pods from flowers which opened on nodes not being deflowered.

The physiological basis for premature abscission of reproductive structures in grain legumes is discussed.

The true and apparent metabolizable energy (TME and AME) of a range of indigenous feedingstuffs and finished feeds were determined by rooster bioassay techniques adapted to suit a small nutrition laboratory.

The AME and TME of some common feedingstuffs were similar to the values published elsewhere. The AME of two finished feeds were similar to their zero-N corrected metabolizable energy values determined by the conventional total collection method. The mean ±S.E. endogenous and metabolic excreta energy per bird for 24 h was 70·4 ± 2·94 kJ.

The winter-heading cauliflower varieties St Thomas, St Gwithian, St Agnes, Janavon, St Hilary, St Buryan, BB74605, St David and St Keverne were grown at Trefloyne, Tenby for 3 years from 1977 to 1980. Plants of all varieties were sampled periodically to determine the rate of curd expansion, the final number of leaves, the time of curd initiation, and the distribution of dry matter within the plant.

The patterns of development of leaf area were similar in all varieties. Dry-matter distribution was similar for all varieties except for root growth; later-maturing varieties had a greater dry weight of root and a higher proportion of the total dry matter as root, than early varieties. Early rates of curd growth declined with later-maturing varieties and it is suggested that there may be a relationship between the time of curd initiation, root growth and the rate of curd growth.

The mean total number of leaves formed before curd initiation varied from 49 to 102 depending on the variety and year. The earliest varieties St Thomas and St Gwithian took co. 120 days to reach 50% curd initiation and matured in 6–7 months from sowing while the late variety St Keverne took over 200 days to reach 50% initiation and more than 11 months to mature. The time interval between 50% initiation and 50% maturity increased with later-maturing varieties but on the basis of accumulated day degrees > 6 °C it declined with later varieties. The latter also matured more uniformly than earlier varieties when using an accumulated day-degree scale > 6 °C as a time scale.

The results suggest that the low temperature threshold below which curd induction occurs may vary with variety. There was also evidence that the base temperature for curd growth is lower with later-maturing varieties.

In four experiments in different years, plants of four winter-heading cauliflower varieties with mean numbers of leaves and leaf initials varying from 9·5 to 16·5 were stored for periods of 14–24 days at different temperatures from 0 to 5 °C. Cold treatment tended to delay the time from sowing to 50% maturity but did not reduce the spread in the time of maturity of individual plants within a population. The reasons for this are discussed.

Lures containing the synthetic pheromone components (E)- and (Z)-citrals, geraniol and nerolic and geranic acids made new hives, not previously occupied by honeybee colonies, more attractive to caged honeybee swarms than unbaited hives (20 out of 20 tests). The lure also made old hives, previously occupied by colonies, more attractive to caged swarms (19 out of 20 tests) and to swarms in natural conditions (12 occupied compared with none without the lure). Adding (E)-9-oxo-2-decenoic acid (part of the queen's mandibular gland pheromone) to the lure increased its attractiveness to caged swarms (20 out of 20 tests). Practical implications in beekeeping are discussed.