A total of 187 animals (mainly Friesian dairy heifers) on nine farms in Wharfedale, Nidderdale, Calderdale and the Vale of York were weighed, condition scored and blood sampled on three occasions during the grazing season 1977. On each site, half of the animals each received two injections of a Cu preparation (200 mg Cu total), one in May and one in July. Herbage samples were taken in May, July and September.

Despite the fact that many animals started the experiment with low blood total Cu concentrations, growth rates during the experimental period were all satisfactory (lowest mean value 0·70 kg/day) with a significant increase due to treatment being observed on only one site. The Cu treatment, however, had a significant effect on blood and plasma total Cu values with the treatment either increasing the level to normal in animals which had started with low values, or maintaining the value in animals starting with near normal concentrations. On certain sites, animals in the untreated group ended the experiment with very low blood and plasma total Cu values (0·02–0·03 mg/100 ml). To prevent the possibility of a Co deficiency on some sites interfering with the experiment, all animals received a Co bullet initially. Despite these, concentrations of vitamin B12 in serum samples taken during and at the end of the experiment were low by present interpretation. This suggests either that Co bullets were an ineffective treatment or that the present interpretation of serum vitamin B12 concentration in bovines is incorrect.

The calculated concentrations of available Cu estimated from herbage analysis indicated that on most sites the value was below the optimum for the growing cattle under study. The results of the experiment suggest that even when blood Cu values and herbage available Cu values are low a growth response to Cu injections may not occur over the course of a grazing season.

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.

Six silages were prepared from a primary growth of red clover using additives of 21 formic acid/t fresh crop together with formaldehyde at 0, 16, 34, 52, 77 or 117 g/kg crude protein (CP) in the crop. These silages were offered to appetite, either alone or with a urea supplement at 19·4 g/kg total dietary dry matter (D.M.), to 60 British Friesian steer calves with an initial mean live weight of 106 kg.

Formaldehyde treatment restricted silage fermentation, the effect increasing with level of application. However, butyric acid and 2, 3-butanediol content increased at intermediate levels of application. Protein degradation in the silages was reduced by formaldehyde treatment, as evidenced by a decline in ammonia-N and an increase in insoluble-N content with increasing level of formaldehyde application. The recovery of applied formaldehyde in the silages was low (less than 13%) but increased with level of application.

Intake, live-weight gain and feed conversion ratio followed quadratic trends, with formaldehyde having a deleterious effect at high levels of application. The decline in these production measurements was associated with declines in the apparent digestibility of D.M., organic matter (OM), N and energy with increasing level of formaldehyde application, although there was no effect of formaldehyde on cellulose digestibility. Urea supplementation tended to increase intake and live-weight gain at formaldehyde levels greater than 34 g/kg CP, and apart from the expected increase in N digestibility, did not affect the digestibility of other dietary components. As urea supplementation did not overcome the adverse effects of high levels of formaldehyde application on intake, live-weight gain and digestibility, it appears that the supply of rumen-degradable N was not the major limiting factor on these diets.

N retention followed a quadratic trend with level of formaldehyde application, increasing at intermediate levels (30–50 g/kg CP) and then declining markedly at the highest level of application. A similar trend was evident when N retention was expressed as a proportion of live-weight gain, suggesting possible formaldehyde effects on carcass composition. However, carcass composition data did not confirm any formaldehyde effect. Urea supplementation did not affect N retention, and N balance data indicated poor utilization of the supplementary urea N.

When considering the use of formaldehyde, relative to a formic acid control, in additives applied to red olover at ensiling, these data demonstrate little advantage in favour of formaldehyde and serious disadvantages when large quantities of formaldehyde are applied.

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.

Nitrogen (0, 150 kg N/ha), sulphur (0, 50, 150 kg S/ha) and molybdenum (0, 400 g sodium molybdate/ha) fertilizers were applied to kale sown in spring on soils either low (4 mg/kg, site L) or high (22 mg/kg, site H) in sulphate (SO4-S). The plots were harvested after growing periods of 100, 160 and 220 days. Dry-matter (D.M.) yields were determined on each occasion and comprehensive plant analyses carried out on material harvested at 160 days.

Nitrogen application increased both the D.M. yield and nitrate content of kale grown at both sites, and increased S-methyl cysteine sulphoxide (SMCO) content in kale grown at site H and in the plots receiving S fertilizer at site L. Glucosinolate content was unaffected by N application in kale grown at site H, but was higher in the absence than in the presence of N in kale grown at site L. Molybdenum fertilizer had no effect upon D.M. yield or upon any aspect of plant composition.

At site H, S fertilizer application produced a range of soil SO4-S values from 10 to 23 mg/kg on day 160 and had no effect upon either kale D.M. yield or composition. At site L, corresponding soil SO4-S values ranged from 4 to 9 mg/kg; as soil SO4-S was reduced, concentrations of plant sulphate declined first, followed by SMCO and then protein-S (% D.M.), with the reductions in SMCO and sulphate being more pronounced in the presence of N application. Glucosinolate and nitrate contents, and the yields of D.M. and protein N, were unaffected by restricting fertilizer S supply.

It was concluded that SMCO synthesis in kale is stimulated by the application of N when soil SO4-S values are high, but is progressively reduced as soil SO4-S declines below 9–10 mg/kg, particularly if N is applied at the same time to stimulate synthesis of plant protein and hence the incorporation of S into protein. Use of this technique to produce kales of low SMCO content for animal feeding is discussed, utilizing tests to define soils initially low in SO4-S. It was further concluded that sulphate and SMCO function as storage of S that is taken up in excess of requirements for plant protein synthesis, thus explaining their ease of manipulation by soil fertility practices.

Horses fed various species of tropical grass hays containing more than 0·5% total oxalate were in negative calcium balance of up to 41 mg/kg live weight/day in mineral balance experiments. In most cases, a concurrent negative phosphorus balance of up to 22 mg/kg live weight/day was measured. These results were in contrast to those obtained when grass hays low in oxalate were fed. Magnesium balance was little affected by oxalate. The degree of negative calcium balance could not be reconciled with total calcium and total oxalate concentrations, but could be explained if a major fraction of calcium in the grasses was in the form of calcium oxalate crystals and if calcium in this form was unavailable for absorption. It is suggested that soluble oxalates exert a variable but smaller effect on absorption of the remaining calcium fraction of the grasses. In general, nutritional secondary hyperparathyroidism may occur in horses grazed solely on pastures in which calcium to oxalate ratios are less than 0·5, such ratios usually being found in grasses containing more than 0·5% total oxalate.

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.

Body composition of 324 steers from Angus dams by ten different sire breeds was compared at constant age. Progeny of the large European breeds and the Friesian attained heavier fasted live weights and carcass weights than the local Angus and Hereford breeds. Friesian cross-breds had the lowest dressing percentage. The Blonde d'Aquitaine and Limousin crosses had the lightest bone weights and this was reflected in high meat yields. The European breeds had the leanest carcasses, the traditional beef breeds the heaviest subcutaneous fat weights and the dairy breeds the heaviest internal fat weights. The results are discussed in relation to overseas findings.

First (I1), second (I2) and third-generation (I3) inbreds were compared with openpollinated spring-sown onion populations in field trials at five sites over 2 years. The open-pollinated populations were earlier maturing and gave higher yields and a lower proportion of bullnecked plants than the inbreds but the latter had a lower proportion of unmarketable double bulbs. The mean level of expression of each character differed considerably between individual trials. The effect on sprouting within each year resulted from factors operating prior to storage; bulbs from all sites were stored at Wellesbourne in a common environment yet large differences in the proportion of sprouted bulbs from different sites occurred by the following spring.

Interactions were found between the type of population (inbred and open-pollinated) and the macro-environment. Inbred populations showed a greater linear response to environment for yield, skin colour and proportion of bullnecked plants, but were less responsive for percentage of double bulbs.

The results are discussed in relation to the evaluation procedures for inbreds.

Selections for high (H) and low (L) number of ears were made from crosses between three pairs of winter wheat varieties. By the F5 generation there were consistent, heritable differences between H and L selections in each cross. In an irrigated trial the H lines outyielded the L lines even in one experiment where compensatory increases occurred in the weight of grain per ear of the L lines. Drought for the 5 weeks before an thesis reduced the final number of ears of the H lines by 14% but did not affect the final number of ears of the L lines. This reduction in the final number of ears of H lines resulted in them being outyielded by L lines by 8%. Drought from anthesis to maturity did not significantly reduce grain yields of either H or L lines below their values under full irrigation.

When fully irrigated, the evapotranspiration of H and L lines from 1 April until maturity was approximately 360 mm. The drought before anthesis reduced water use to about 320 mm, there being no difference between selections in total water use by the crops during this period. However, the L lines extracted significantly more water from the soil below a depth of 0.9 m during this drought than the H lines, and this appeared to make the L lines less susceptible to drought at this stage. Water use by the crop during the late drought could not be reliably estimated because by this time water was being extracted from below the level of the neutron probe access tubes.

It is concluded that in an environment where a pre-anthesis drought is unlikely to occur, varieties with high ear-bearing capacity may give the best yields. Selection for types showing a limited tillering capacity may prove to be an effective compromise in regions with erratic rainfall where pre-anthesis droughts can occur.

Three experiments were conducted to assess the effects of several methods of dietary presentation of 250 g/day of a fully soluble liquid supplement (LS) on the voluntary intake of oat straw by non-productive cows fitted with a rumen fistula (Expt 1), pregnant beef cows (Expt 2) and lactating beef cows (Expt 3). In each case the cows received fixed daily amounts of barley (2 kg for Expts 1 and 2; 3 kg for Expt 3). LS contained (g/kg) about 1100 crude protein (as urea), 30 calcium, 15 phosphorus and 50 salt plus trace elements and vitamins. In Expt 1, provision of LS in either the drinking water, or via the rumen fistula or sprayed on to the straw increased voluntary straw intake by about 12%. In Expt 2, provision of LS, whether by spraying on the straw or in a molasses lick, increased straw consumption, but giving LS in the drinking water did not. In both Expts 1 and 2 the digestibility of the oat straw was not significantly affected by the dietary supplement, any increases in metabolizable energy intake being reflexions of increased intakes. In Expt 3 there was no difference in the voluntary intake of oat straw by group-fed lactating beef cows offered LS in either the drinking water or as a molasses lick.

Giving LS sprayed on the straw, or incorporating it into a molasses lick to housed animals, are convenient and practical methods of supplementing ruminant diets to increase their voluntary straw consumption. Inclusion of LS in drinking water gave inconsistent results, but the method warrants further investigation.

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.

A sheep-feeding experiment was carried out to assess the nutritional value of algae meal as a protein supplement in ruminant diets. The algae, mainly Chlorella, were grown in sewage ponds, harvested by flocculation with alumina (Al2(SO4)3.18H2O), and then drum-dried. Eight young rams, divided into two equal groups, were offered a basal concentrated diet, to which algae meal or soya-bean meal (SBM) was added to contribute 50% of the dietary nitrogen (N).

The digestibility values of dry matter (D.M.) were 69·3 and 79·3%, and those of organic matter (OM) were 75·3 and 82·2% for the algae diet and the SBM diet, respectively.

Nitrogen digestibility of the algae diet was 16% lower than that of the SBM diet and the calculated value of N digestibility in algae meal was 61·7%. However, there was no difference between treatments in the daily amount of retained-N or in the proportion of digested N which was retained in the body.

The algae meal contained 5·7% aluminium. This was probably the reason for the much lower P absorption in the algae diet (6·67%) as compared with the SBM diet (29·5%).

Ammonia-N concentration was lower and total volatile fatty acids (VFA) concentration was higher in the rumen of the algae diet-fed sheep. However, the VFA profile was similar for both diets.

Sewage-grown algae could perhaps be used as a protein supplement for ruminants, provided that the harvesting technology is directed to produce a low-mineral, low-aluminium, young biomass, which would be highly digestible and would not interfere with P absorption.

Conformation of carcasses from 98 steers from ten different sire breeds was classified according to two visual systems and two objective measurements, which were related to both commercial and dissected carcass composition of their hindquarters. The visual carcass conformation systems, unlike the objective systems, accounted for only a small percentage of the variation in some carcass traits after adjusting for the weights of the right hindquarter and of dissected fat from that hindquarter. Of the carcass conformation systems tested, the objective measurement of area appears to be the best predictor of carcass traits, with the variation in the weight of meat being reduced by 13·4% (P < 0·001) by the inclusion of area measurements. It is suggested that an objective assessment of carcass conformation might be of use in a national carcass classification or grading system.

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.

An experiment was carried out over a 3-year period at two locations in the central rainlands of Sudan under rainfed conditions at one site and under supplementary irrigation at the other to study the effects of cultivars and cultural practices on growth and grain yield of sunflower. Four cultivars, namely, Manohurian, Peredovik, Hungarian-A and Hungarian-B and four intra-row spacings of 15, 30, 45 and 60 cm (in rows 60 cm apart) were tested with three sowing dates starting on 15 July and following at 15-day intervals. Manchurian outyielded the other three varieties under supplementary irrigation whereas under rainfed conditions the reverse was true. This was attributed to the relative earliness in flowering of the varieties and their moisture requirements. Manchurian was the tallest with the thickest stem and a larger head at both locations compared with the other three varieties. Under rainfed conditions, the early sowing date of 15 July gave a significantly higher grain yield than the other two sowing dates, with the last sowing date of 15 August giving significantly least. This is attributed to decreasing moisture availability with delayed sowings. But under supplementary irrigation the effect of sowing date was less marked. Contrasting effects of sowing dates on plant height and stem circumference were obtained under the two systems of production. Under rainfed conditions there was a decrease in plant height and stem circumference with delayed sowing, whereas under supplementary irrigation the reverse was true. A contrasting response of plant height to spacing was also obtained; wider intra-row spacing was associated with taller plants under rainfed conditions and shorter plants under supplementary irrigation. Wider spacing was associated with thicker stems and larger heads at both locations. On the evidence obtained, 45 cm intra-row spacing is recommended for rainfed planting and 30 cm intra-row spacing for irrigated production of sunflower.

The CO2 exchange of leaves, pods and peduncles was measured in cowpea crops grown at Ibadan, Nigeria, using a portable infra-red gas analysis system. Most leaves had maximum rates of photosynthesis (Pm) of about 1·4 mg CO2/m2/sec and maintained this value for 20 days from full expansion. Early leaves had slightly slower rates. Pm decreased when leaf temperature exceeded 35 °C. The maximum efficiency of photosynthesis, ɛm, was about 2 g CO2/E (0·045 mol CO2/E). ɛmdecreased with temperature for leaves, but increased for pods. The latter response probably results from the effect of the high CO2 concentrations within the pod on the ribulose disphosphate carboxylation reaction. Water shortage reduced Pm but not ɛm. Pods and peduncles had a slightly negative CO2 exchange rate at light saturation but this was considerably less than the rate of CO2 evolution in the dark.

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.

A study was made of the relationship between yields in particular size grades of carrots and onions and the number of plants per unit area with a view to providing adjustments to yields for differences in plant densities. It is concluded that the relationship for individual small grades cannot be fitted consistently by a single mathematical equation but that estimates of yields in small grades are best obtained by fitting a common equation to the accumulated yield at the limits of the grade and obtaining the yield by difference. Eleven previously published equations which have been shown to fit the relationship between total yield and plant density for a number of crops are compared with one newly developed for graded produce. It was found that the latter,

where y = yield/ha, ρ = number of plants/m2 and A, B and C are constants, generally leads to the best fits when a large range of densities is present, but it is argued that, for adjustment of yields for small differences in densities such as are obtained in variety trials, a simpler equation such as a second degree polynomial is equally effective.