The deposition of S in rainwater was measured at ten locations in central Kenya, monthly for 1 year (1977–8). Amounts deposited ranged from 1·58 to 3·81 (mean 2·47) kg S/ha. Concentrations ranged from 0·10 to 0·17 (mean 0·12) mg S/l rainwater. The washout factor (w) was 200 and the vertical deposition velocity (Vg) for dry deposition was 0·31 cm/sec. Two locations were affected by local anthropogenic emissions. The agricultural significance of these results is briefly discussed.

The N, P and K contents of leaves, straw and grain of the durum wheat Kyperounda, the aestivum wheat Pitic 62 and Athenais barley under semi-arid conditions (150–400 mm) as influenced by N and P fertilizers are reported (N rates: 0–105 kg/ha; P rates: 0–26 kg/ha).

Fertilizer N increased linearly the N content of the leaves, straw and grain as well as the K content of leaves and straw, but slightly reduced P content of the grain. Straw K content was increased relatively more in Athenais barley. Such increases of N and K content occurred beyond the N rates giving maximum grain and sheaf yields. Increased K content of the straw resulting from fertilizer N is wasteful where the straw is removed, and accelerates depletion of soil K. Durum wheat grain containing more than 2–8% N showed less than 6% yellow berry (mealy grains) but at lower N contents yellow berry could be high or low depending on location.

Fertilizer P did not significantly influence the P content of any of the components analysed even though it increased grain and straw yields, particularly in the drier years.

Blood samples were taken at 9, 10 and 11 weeks of age from 230 male Hereford × Friesian calves, the progeny of 12 Hereford bulls. Concentrations of blood glucose, serum albumin, inorganic phosphate and sodium were measured and correlated with body weights and growth rates until slaughter at 19½ months of age.

Correlations between growth rates and glucose concentrations (0·44) and between growth rates and albumin concentrations (0·38) were observed until 4 months of age. Similar correlations between body weights and blood glucose or albumin concentrations persisted until 6 months of age. By 10 months, however, the correlations had begun to decline, and by slaughter they had become insignificant.

Correlations between growth rates and inorganic phosphate or sodium concentrations were smaller, and also decreased with age.

The effect of hypoglycaemia on growth rate was compared with the effect of enzootic pneumonia. Although the 10% of calves with the lowest glucose concentrations were growing 24% more slowly than the other calves at the time of sampling, this growth depression was not related to pneumonia, and they subsequently made up for most of the early loss of growth.

Three blood samples were also taken from 22 Hereford bulls. No significant correlations were observed between the blood composition of the bulls and the body weights or weight gains of their progeny.

Lesion development and growth of Xanthomonas malvacearum (E. F. Smith) Dowson were followed in seedlings of different cultivars of cotton (Gossypium hirsutum L.) after inoculation of hypocotyls. There was a close relationship between numbers of the parasite and length of hypocotyl lesion. Disease development could be accurately determined by measurement of lesion length from 2 to 3 days after inoculation until growth of the parasite ceased. Growth patterns of the parasite in vivo took the form of a distinct period of exponential (phase 1) growth followed by relatively little, if any, further increase in numbers (phase 2 growth). The duration of phase 1 growth was related to host resistance and environmental factors.

Body-weight gain, protein efficiency ratio (PER), standardized protein efficiency ratio (Std PER) and gross protein value (GPV, GPV1 and GPV2) bioassays were compared with nitrogen incorporation efficiency (NTE) for their accuracy and precision to determine protein quality of fish meal (FM), groundnut cake (GN), mustard cake (MS) and cottonseed cake (CS) for poultry. Results showed that all the bioassays were significantly (P < 0·05) correlated with NIE and were equally effective in ranking the samples of FM, GN, MS and CS according to their protein quality although body-weight gain procedure was less sensitive.

The adsorption of oxamyl under various conditions of time, pH, temperature, organic matter and exchangeable cations on illites and kaolinites was examined. The first order reaction indicated diffusion-controlled adsorption, maximum adsorption occurring at pH 6–5 which is near the pK value of oxamyl. Exchangeable cation in the order Na > H > Ca, organic matterand increasing temperature decreased adsorption. Adsorption isotherms and the molecular structure of oxamyl point to a reaction mechanism for oxamyl association with acid- and base-saturatedclays which involve either protonation or co-ordination of exchangeable clay cations to the carbonyl of the amide structure.

Two methods for calculating the flow of digesta and its constituents from the concentrations of two markers, 51Cr-labelled chromium EDTA (51Cr-EDTA) and 103Ru-labelled ruthenium phenanthroline (103Ru-P), and digesta composition were compared in fistulated sheep fed once daily and in other fistulated sheep fed continuously. One method uses the marker concentrations to calculate the flow of whole digesta directly (double-marker) whereas the other uses the markers to calculate separately the flow of fluid and non-filtrable particles, the sum of which is digesta flow (two-marker).

When feed was given continuously, flow values calculated using the double-marker method and the two-marker method, which requires a correction to be made for nonideal behaviour of 51Cr-EDTA, did not differ. When feed was given once daily, the double-marker method consistently overestimated flow relative to the corrected twomarker method but the differences were extremely small (less than 0-8% for digesta flow and 0-5% for nitrogen flow). 51Cr-EDTA as a single marker slightly overestimated digesta flow (up to 2·3%) but grossly overestimated nitrogen flow (up to 22·5%); 103Ru-P as a single marker grossly underestimated both digesta flow (up to 30·5 %) and nitrogen flow (up to 23·1%).

It was concluded that the double-marker method is to be preferred when the diet is given continuously or frequently at fixed intervals. When the diet is given once daily, the two- and double-marker methods can be expected to give similar values. Single markers should not be used for estimating the flow of digesta and its constituents when samples are taken from a simple cannula.

The present study was made to evaluate the protein quality of 11 samples of fish meal (FM) covering a wide range of nutrient content to find a suitable laboratory method for predicting nutritive quality. The nutrient content of the samples ranged from 34 to 62% in crude protein, 28 to 48% in true protein and 0·99 to 2·87% in available lysine. The true protein content of FM was further partitioned into myogen, myosin and stroma proteins. The stroma protein accounted for 61% of total crude protein suggesting that a large portion of FM comprised scales, viscera, cartilage, bones and other inedible parts of fish (head, tail, etc.). Neither true protein nor its different fractions was found suitable to detect differences in protein quality of FM although there was an inverse relationship between stroma protein and nitrogen solubility.

Available lysine content and relative nutritive value (RNV) were found accurate and reliable laboratory tests for assessing the protein quality of FM. The linear equations to predict gross protein value (GPV) from available lysine content and RNV are

GPV = 11·2×% available lysine+34·5;

GPV = 0·55×RNV+51.

The correlation coefficients between biologically assayed and predicted GPV from available lysine and RNV were 0·71 and 0·62, respectively. The findings suggest that the screening of FM samples for their nutrient content is essential before compounding diets for different categories of chickens.

After a preliminary period in which they were all fed maize straw plus a proteinmineral supplement, 18 Merino wethers were divided into six groups and fed straw, proteins and minerals as before, plug pellets containing maize grain so that these constituted 0, 78, 156, 235, 313 and 393 g/kg of the total daily intake.

The diets provided sufficient protein so that NH3 and branched-chain volatile fatty acids were not limiting for growth of the fibre-digesting bacteria in the rumen.

The intake of straw, the digestibility of cellulose and hemicellulose, and the mass of cellulose and hemicellulose digested per day declined linearly as the proportion of pellets in the diet increased above 78 g/kg. This decline was not related to the pH of the ruminal contents which was unaffected by the feeding of up to and including 235g pellets/kg diet, and which, with one exception, was only 2–6 pH-hours below pH 6 when more grain was fed.

As the proportion of pellets in the diet increased the number of cellulolytic bacteria in the rumen declined to an extent which correlated well with the decrease in mass of cellulose digested per day. There was no change in the relative proportions of the predominant genera.

There was no decrease in the number of xylanolytic bacteria in the rumen as more pellets were fed, but there was an indication of a change in the predominant genera producing diffusible xylanases.

It is concluded that some factor, in addition to nutrient limitation and pH, may play a role in the decrease in intake and digestion of roughage when starch is fed. It is suggested that starch or sugars derived from it may per se inhibit the synthesis and/or activity of the rumen cellulases and hemicellulases.

Seven high-oil sunflower eultivars were grown in 1976 and 1977 at selected locations in Ghana, to evaluate the potential of sunflowers as an oil-seed crop for the lowland tropics. All eultivars flowered and matured earlier than observed under temperate conditions. Yields were between 75 and 1600 kg/ha at 9% moisture content. Oil contents ranged from 41 to 47% with a higher proportion of oleic acid (about 54%) than linoleic (about 38%). It is concluded that sunflower production is feasible and could become as important as that of existing annual oil seeds.

Progressive colonization of adventitious, seminal and lateral roots of wheat by Gaeumannomyces graminis var. triticiwas monitored for 18 days after direct inoculation of roots. Adventitious roots supported greater colonization by superficial runner hyphae above and below inoculation sites than did seminal roots due to more rapid establishment of colonization. Subsequent rates of superficial runner hyphal growth along the two types of root were not significantly different. In contrast with seminal and lateral roots, adventitious roots did not show any dark stelar discoloration during the period of observation. Both the rate of growth of superficial runner hyphae and of advance of dark stelar discoloration were substantially slower on lateral roots than on seminal roots. After an initial period of equal growth above and below inoculation sites, superficial runner hyphae grew more slowly below than above these sites on all three types of root.

In a field study, the effect of N, P, K and their combinations on the growth, yield and nutrient uptake pattern by mesta (Hibiscus cannabinus L.) was studied. No effect of N, P, K on growth characteristics like plant height and base diameter occurred up to 60 days. Effect of fertilizer treatments on plant growth was observed only after 90 days. The effect of N was more pronounced than P and K. Initially, growth of leaves was higher than both the bark and the wood. Nutrient concentration was at a maximum in the early stages of growth but declined with age and became steady at about 60 days. The quality of fibre obtained after 120 days of growth was assessed and the effect of nutrients on quality is discussed.

A study was made to evaluate the protein quality of groundnut cake (GN), mustard cake (MS) and cottonseed cake (CS) and to find a suitable laboratory test for predicting the protein quality of these cakes for chicks. Different oilseed cakes varied considerably in their crude protein, true protein and crude fibre content. The nitrogen solubility was higher in GN (87·7%) followed by MS (78·7%) and CS (60·9%). A similar trend was evident with regard to in vitro protein digestibility. The GN protein was, however, lower in available lysine (2·54%) than MS (3·97%) or CS (3·19%). The albumin, globulin, prolamin and glutelin fractions accounted for 74·1, 57·0 and 48·0% in GN, MS and CS, respectively. The nitrogen solubility, globulin content and modified relative nutritive value (RNV) correlated (P < 0·05) with gross protein value (GPV). The accuracy and precision of various regression equations for predicting the quality of protein in GN, MS and CS are discussed.

Linear relationships between both total and tuber dry-matter yields and the amount of radiation intercepted by potato crops are demonstrated. Their existence suggests that, in the absenceof disease and drought, the essential objective in the production of this crop is to maximize radiation interception. This paper critically assesses the influence of factors which the grower can control on light interception and estimates potential yields for specific environments. The implications of this analysis for growers, breeders, research and the whole industry are discussed.

The length and weight per unit length of individual internodes of mature reproductive tillers of S. 24 and S. 23 perennial ryegrass and S. 345 and S. 143 cocksfoot were examined under three manurial treatments. At the lower level of nitrogen application successive internodes generally increased in length from the base upward. With additional nitrogen there was an increased proportion of tillers in which internodes near the base of the stem were longer than those immediately above them; lateheading tillers were most affected.

Nitrogen increased the weight per unit length of upper internodes of all four varieties; the effect was most marked in S. 23 ryegrass. In the two ryegrasses, nitrogen reduced the weight per unit length of the basal internode.

At maturity the upper internodes had lower dry-matter digestibility values than the lower. Nitrogen reduced the dry-matter digestibility of upper and lower internodes.

The results are discussed in relation to selection criteria in variety synthesis.

Estimates of the energy contents of the foetuses, placentae, foetal fluids, empty uteri and maternal empty bodies at 88 and at 144 days of pregnancy were obtained from a comparative slaughter experiment on Finnish Landrace × Dorset Horn ewes. Over this period the mean daily intakes of metabolizable energy (ME) for ewes with twin, triplet or quadruplet foetuses were 11·2, 12·0 and 12·2 MJ respectively (low plane of feeding) or 14·4, 15·2 and 15·3 MJ (high plane of feeding), total numbers of ewes being 15, 23 and 7 respectively. The diet contained 8·2 MJ of ME and 153 g crude protein per kg dry matter. All six categories of ewe lost energy from maternal empty-body tissues between 88 and 144 days at mean daily rates of 2·7, 4·1 and 4·9 MJ (low plane) and 1·4, 2·7 and 3·6 MJ (high plane), according to litter size. Rates of energy deposition in the gravid uterus were 0·72, 0·93 and 1·07 MJ/day respectively, and were not affected by plane of nutrition. Estimates of heat production from these balance data were confirmed by direct measurements made on about half of the ewes.

Estimates of the gross efficiency of utilization for foetal growth of the combined energy from maternal tissue and from ME intake, after allowing for maternal main–tenance, were similar for each litter size but were 0·14 and 0·11 on the low and high planes of feeding respectively. Consideration of these together with other published observations suggested that efficiency of utilization of ME in pregnancy increases linearly with the ME concentration of the diet and at concentrations below 10 MJ/kg dry matter is less than the efficiency of utilization of energy derived from maternal tissue loss.

Cowpea is an important food legume crop of arid and semi-arid regions of the tropics. In such climates whether a determinate or indeterminate type of growth habit would be more useful is not clear. In the present study a determinate and indeterminate cultivar of cowpea were grown at two population densities under rainfed conditions for 2 years. Grain yield was higher in the indeterminate variety for both years. At higher density more dry matter was produced but it had no effect on grain yield. Nitrogen analysis showed that it moved from leaves to developing pods. However, a large amount of nitrogen was still left in vegetative parts in contrast to cereals. Pod development was completed in 19 days and the rate of dry-matter accumulation during the peak period of growth was as high as 120 mg/day per fruit. It was difficult for the plant to cope with this high demand for photosynthates. It is suggested that more pods can develop on a plant provided the growth rate of individual pods is slower and extended to a longer period.

The average of 160 intercalving periods of 47 imported and 33 home–reared purebred Holsteins in western Nigeria during 1967–75 was 628( ± 45) days. The probable effects of seven variables including origin of cow, sex of calf, season of calving, age of cow at calving, parity, year of calving and calf birth weight were investigated through an intra-class linear regression model in which the first three factors were treated as qualitative and the last four as quantitative factors. Origin of cow, sex of calf and season of calving did not significantly affect calving interval. Effects of age at calving, parity, year of calving and calf birth weight were highly significant (P < 0·01) but individual effects adjusted for others were not quite significant. These four quantitative factors were, however, highly interrelated; simple correlations which varied between 0·33 and 0·86 were highly significant. Interactions between the two sets of factors were negligible.

The present study was carried out on 39 local Awassi ewes. After parturition, lambs were left to suckle their dams for the first month of age, after which they were separated into two suckling regimes, restricted and continuous.

The average milk yield of ewes in the continuous system was 155·7 kg during the lactation period of 167±6·1 days whereas that of the restricted system was 139·8 kg during a lactation period of 183 ± 5·7 days. However, differences were not significant. Significant differences (P < 0·01), in favour of the continuous system, occurred in the amount of milk suckled by lambs in the different suckling systems from the 8th week onwards till weaning. Measured hand milk showed no significant differences between the two regimes.

Averages of butter fat percentages were 5·63 and 6·69 in the continuous and restricted systems respectively. The total percentage suckled milk, regardless of suckling regime, was 36·7 ± 1·99; averages were 41·6 ± 0·89 and 31·7 ± 3·52 in the continuous and restricted systems respectively.

The averages of commercial milk production from the 9th week after lambing until the end of lactation were 45·9 and 61·7 kg in the continuous and restricted systems respectively (P < 0·01). Averages of butter fat quantities in the commercial milk yield were 3·25 and 5·03 kg in the continuous and restricted systems respectively (P < 0·01).

The weights of lambs in the two suckling regimes started to differ significantly from the 14th to the 46th week of age; lambs reared under the continuous system were 4 kg heavier at the yearling age than those of the restricted system.

It might be worth considering weaning and selling extra lambs at 3 months of age to make full use of the high growth rate encountered in this period. The breeder could also obtain 11·4 kg more milk from ewes from 9 to 17 weeks after lambing in the restricted system than those in the continuous one. It might be advisable to use the restricted system and wean the lambs at 12 weeks of age; the excess milk obtained will outweigh the extra gain in body weight of 1·52 kg encountered in the continuous system.

Maize and cowpea were grown at various replacement ratios (100/0, 67/33, 50/50, 33/67 and 0/100) in field experiments. The experiments were carried out during the early growing seasons of 1977 and 1978 at Ibadan in the rainforest zone of Nigeria. A maize cultivar (FARZ 17) and three cowpea cultivars (Ife brown, New Era and TVu 4557) were used.

Maize sown alone gave a greater yield than all mixtures. The yield of New Era cowpea was no less when grown in mixture with maize than when grown alone; indeed when grown in a 50/50 mixture it was significantly greater.