The deposition of dust and the sulphur it contained were measured at 10 sites for three dry seasons in northern Nigeria. Amounts of dust deposited varied between seasons and sites depending on the concentration of dust in the air and the duration of dust storms. Deposits ranged from 226 to 52 kg/ha (mean value 146) measured in a south-westerly direction across the area studied; the S deposition ranged from 0·099 to 0·429 kg/ha (mean value 0·226). The most south-westerly sites received plant ash from clearing fires which increased the S deposited, but not the net gain of S to the whole area. The agricultural significance of the results is briefly discussed and other sources of atmospheric-S are considered.

In 92 field experiments in Tanzania's major cotton-growing area south and east of Lake Victoria mean yield without fertilizer was nearly 900 kg/ha of seed cotton. The mean direct effect of 224 kg/ha of single superphosphate with 202 kg/ha of ammonium sulphate was 380 kg/ha of seed cotton; with twice as much fertilizer the increment was 525 kg. First and second residual responses made important contributions to the total effect of superphosphate. In most zones the response to each fertilizer was large but in Nassa response to superphosphate was small; in Nzega yields were small and there was no response to ammonium sulphate, perhaps because Calidea dregei caused abscission of bolls; on the acid soils of Ukerewe Island yields and responses to superphosphate were small.

Data are given to show the average amounts of plant nutrients in the soils most used for cotton. Correlations of yields with soil chemical data suggest that some soils lack enough calcium for large yields. A long-term experiment at the Ukiriguru research farm (Le Mare, 1972) showed that productivity of impoverished soil growing cotton every year was recovered and improved by lime with phosphorus and nitrogen fertilizers: the experiments throughout the cotton area indicated that those results were widely relevant.

The results of 216 field experiments with sugar beet (1957–69), testing K and Na fertilizers, were re-examined. There were only small increases in yield with K or Na on peat or peaty mineral soils but on mineral soils, 100 kg K/ha without Na increased sugar yield by about 0·4 t/ha and 100 kg Na/ha without K increased yield by 0·6 t/ha. Although the average response per kg of nutrient was approximately in inverse proportion to their atomic weights, K and Na were only partially interchangeable; their relative effects differed from field to field and year to year.

K seemed most effective in years with more than 80 mm rainfall in March–April but responses were halved when rainfall was 50 mm or less. Sowing date and the interval between giving fertilizer and sowing also influenced response to K; with late-sown crops, K fertilizer given within two weeks of sowing was usually ineffective. Response to Na differed much less with season so Na was on average more effective than K, especially in dry springs. It seems, therefore, that instances of near-perfect substitution between K and Na fertilizers result from chance combinations of weather and crop husbandry.

Since in some experiments yields from a combined dressing exceeded those from either nutrient alone, and as the weather is largely unpredictable, both K and Na fertilizers should be given on all mineral soils, except those very rich in K, to be certain of avoiding yield loss. Texture and exchangeable soil K and Na also affected both the amount and rate of response, but did not much influence optimal fertilizer dressings and so are not very useful for making differential fertilizer recommendations.

The major nitrogenous components of gastric juice were determined in sheep with innervated pouches in the fundic and pyloric regions of the abomasum.

Fundic secretions contained mean levels of 36–55 mg total-N/100 ml in the fluid fraction, and pyloric secretions contained 38–70 mg/100 ml. Of this, 65–76% and 75–91% could be attributed to protein, in the fundic and pyloric secretions respectively. Tungstic acid was found to be the most suitable precipitant of proteins in the gastric juice.

Dissolved mucin accounted for 2–16% of the total-N in the fluid fraction of the fundic secretions, and for 6–14% in the pyloric secretions. Urea + ammonia contributed 2·8–13·4% of the total-N.

The daily output of nitrogen by the fundic region of the abomasum, including that contributed by the cellular debris and visible mucus, was calculated at 0·46–2·4 g. The comparable values for the pyloric region varied between 0·05 and 0·37 g N/day.

The electrophoretic patterns of the abomasal secretions were similar to those reported for human gastric juice.

Comparisons of the effects of harvesting sugar-beet seed by the traditional method of tripodding with barn drying, swathing followed by threshing with a pick-up combine or desiccation with diquat followed by direct combine harvesting showed that there were no consistent or large effects on seed yield, germination, monogermity or size distribution. Thus the best method will be the one which is easiest and/or cheapest, which at present is swathing followed by pick-up combine threshing.

Sprays of NAA or 2,4,5-T at 10 or 100 mg a.i./l water before or after flowering had no effect on seed yield or germination and efforts to restrict the loss by shedding of large viable seed failed. Neither chemical decreased germination percentage by setting parthenocarpic seed. Attempts were made to dwarf the 2 m high seed crop to make it suitable for direct combine harvesting. Daminozide sprayed at 1000, 5000 or 10000 mg a.i./l water before or after the winter did not affect plant height, seed yield, germination, monogermity or size distribution. Chlormequat chloride applied similarly dwarfed plants by up to 18% but this was not enough to give a crop less than 1 m high suitable for direct combine harvesting. It did not affect seed yield, germination, monogermity or size distribution. Ethephon sprayed at 10, 100 or 1000 mg a.i./l water when plants were bolting had no detected effects. Chlorflurecolmethyl was sprayed at 10 or 100 before bolting or 1, 10 or 100 mg a.i./l water afterwards. Plants sprayed with the 100 mg/1 solution were dwarfed to less than 1 m high but the treatment was unsuccessful because it greatly reduced seed yield and germination; monogermity was not affected but a much greater proportion of seed fell into the small size grades.

The common use of range by different types of animals may be more efficient than separate grazing by each type in that they may be complementary in their utilization of forage. Also, under certain pasture and range conditions the danger of permanent damage by over-grazing can be critical. This paper presents a method of assessing the optimum carrying capacity of range under single or common use subject to constraints on the level of utilization of forage plants. The joint optimum carrying capacity for the animal types may vary as the management objective varies between maximum profit, maximum animal gain or maximum utilization of forage, all subject to the same protection against over-grazing.

A model is presented which considers the effects of competition between pairs of individuals in binary mixtures. Competitive effects are defined in terms of two parameters; a monoculture effect (Mo) which measures competition between like individuals and a mixture effect (Mi) which relates to competition between unlike individuals. If the data from a particular density replacement series conform to the proposed model the ratio of Mi to Mo can be used to determine whether it would be more advantageous to grow a mixture of the two components concerned or a pure stand of the better component. Where appropriate the optimal composition of the mixture may also be estimated. Theoretical considerations suggest that a 50:50 ratio only represents the optimal composition of a mixture when the two components possess a similar expression for the character concerned.

The model has been applied to dry weight data collected over two growing seasons from a glasshouse experiment which contained 5 genotypes of Lolium perenne grown as monocultures and in all 10 binary combinations. Each combination was represented by three mixture proportions. For the majority of these density replacement series the model was satisfactory, with mixture effects tending to be of greater significance during the first of the two growing seasons. Failure of the model was in general due either to a specific form of competition, which maintained the performance of the mixtures at the level of the better monoculture, or to the presence of more complex forms of competition.

The implications of this model for the development of productive herbage mixtures are briefly discussed, whilst the possible effects of invasion by unsown grass species upon the productivity of a pure sward are also outlined.

In simulated swards of perennial ryegrass the production of aerial tillers, in which the growing point has been raised some distance above ground level by internode extension, depended upon the genotype and management. In both genotypes studied decreasing the height of defoliation from 10 to 2·5 cm nearly halved the incidence of aerial tillering, while the presence of a mulch of chopped straw at the base of the sward more than doubled the occurrence of these tillers. The effects of management are also discussed in relation to herbage production. The differences between the genotypes in the degree of aerial tillering suggests that selection for reduced aerial tillering may be of benefit.

One side of the carcasses from 145 beef animals was weighed, measured and quartered. Measurements were made in the exposed eye muscle region which was then photographed. Measurements were made from the photographs and the quarters were jointed. Each joint was separated into lean, bone, intermuscular fat, subcutaneous fat and ‘other tissues’. The material is described in terms of breed, sex and side weight. Details of the measurements made are given and the methods of jointing and tissue separation are described. The latter was different in three groups of 30, 72 and 43 animals. The overall carcass composition in terms of lean, bone, intermuscular fat plus ‘other tissues’, and subcutaneous fat for the three groups is summarized and the reasons for including ‘other tissues’ with intermuscular fat are given.

Wool samples from 49 ewes representing four breeds of sheep, Ossimi, Rahmani, Barki and Merino were used to study the seasonal variation in wool growth. The first three breeds are of the local carpet-wool types of Egypt.

Consistent differences were found between breeds in diameter and length of fibres (i.e. genetic effects). These effects were not modified by the environment (i.e. time of year) although the latter had different effects on diameter than on length. Medullation, however, was not consistent from breed to breed in all seasons (i.e. there was genotype x environment interaction). It is concluded that seasonality in wool growth exists under the semi-arid conditions of Egypt in local breeds but to a lesser extent in imported Merino sheep.

The data described in Part I of this series (Pomeroy et al. 1974) were analysed by regression methods, to see how, and how well, estimation of total carcass composition (simplified to bone, lean and fat) can be achieved in situations where the beef side cannot be fully dissected, but can be measured as an intact side, quartered and the cut surface photographed, or where sample joints can be dissected. Equations are given, based on the largest group (Group II, 72 animals) of the three previously described, and the advantages to be gained from quartering the carcass, photographing the cut surface, and dissecting a sample joint are quantified. These equations have been tested by applying them to the other two groups, I and III of 30 and 43 animals.

The frequency of natural crossing in 1972 was estimated, in two subsets of a composite cross grown in F6 in Nairn and in Fife, as 2·61±0·25% and 4·59±0·35% respectively. The estimated inbreeding coefficients of the parental generations were less than would be expected if all types of pollination were equally fertile and gave equally fertile offspring.

Six spring varieties of oats were sown in a glasshouse in winter and in spring. The grain was analysed for oil, protein and kernel content and 1000-grain weight, and the maturation period was measured.

Oil content varied from 2·4 to 7·9% and protein content from 7·9 to 16·3%. Varietal differences in oil content between varieties were recognized and these were maintained at both sowing dates.

Winter sowing, in comparison with spring sowing, resulted in an increase in oil and kernel content and 1000-grain weight, and a decrease in protein content. The increased oil content was partly due to increased kernel content, while the decrease in protein content was partly due to changes in 1000-grain weight.

The maturation period was not affected by sowing date, but was positively correlated with oil content. Oil and protein content were not negatively correlated, and there were indications that it may be possible to select varieties which will produce grain high in both oil and protein.

A technique is described in which cereal seedlings after germination and hardening under controlled conditions in a growth chamber were subjected to freezing in tubes immersed in a solution of ethylene glycol. Susceptibility to freezing was estimated by measuring electrical conductance on the linear 0–100 scale of a standard ‘Avometer’ using platinum probes inserted near the base of the lamina of the first leaf. The use of the technique is illustrated by two experiments with winter barley cultivars chosento represent a wide range of winter hardiness. Although significant cultivar differences in mean conductance existed prior to freezing, adequate differentiation was obtained by measurements after freezing only. The differentiation of these cultivars on mean conductance values after freezing was well correlated with their established winter hardiness.

It is concluded that the technique is sufficiently sensitive for the preliminary screening of early generation material but that, because of significant cultivar × hardening-duration interactions, advanced breeding lines should be tested over a range of hardening and freezing regimes.

In two experiments frozen heather (Calluna vulgaris, L. Hull), which contained 85–90% of the current season's shoots, was offered ad libitum to castrated male sheep. In one experiment, heather harvested in July, September, November and March was offered to six sheep per harvest, D.M. digestibility fell from 55.9% in July to 41.9% in March, with the greatest decline occurring after flower development in August. There were no significant changes with season in voluntary intakes, which were low, ranging from 29 to 39 g D.M./kg W0.75/day. Apart from the July harvest, intakes of digestible D.M. were insufficient to maintain the sheep. The apparent digestibility of N(14·3–42·2%) and plasma urea N values (5–6 mg/100 ml) were low and undigested N of dietary origin in the faeces was high (25–45%). Sheep offered the September, November and March harvests were in considerable negative apparent balances of N and it was calculated that the sheep were in a negative balance of truly digested N. In a second ex-periment, heather harvested in August from pioneer, building and mature stands was offered to six sheep per harvest. There were no significant differences between stands in voluntary intake and digestibility.

Ammonium nitrate was applied to a kikuyu (Pennisetum clandestinum) dominant pasture at annual rates of 0, 134, 336 and 672 kg N/ha. Each nitrogen (N) rate treatment was continuously grazed at three stocking rates (SR) designed to apply similar grazing pressures at each N level and covering a range from 2·2 to 16·6 Angus weaner cattle/ha.

The N status of these pastures was periodically assessed 8–10 weeks after seasonal N applications by temporarily excluding stock and measuring D.M. and N response to additional ammonium nitrate application. Pasture growth response to additional N was constant and independent of SR and of annual N rate over the range 0 to 336 kg N/ha, despite wide variation in pasture availability. N concentration of plant shoots was increased by high SR and rate of N uptake was not significantly affected by SR. Pasture growth rate was positively related to annual N rate.

Herbage yield of kikuyu leaf, stem and litter on offer, was negatively related to SR but weight of underground organs was unaffected. Increasing SR increased the proportion of leaf and the rate of tillering. Pasture availability was positively and linearly related to N rate from 0 to 336 kg N/ha and maximal at 336 kg N/ha; the size of the litter fractions and underground organs was generally independent of N rate. N% in leaf and stem was reduced at low SR; N% of leaf, stem, litter, rhizome and root was positively related to N rate which was more influential than SR. The effect of SR on the size and relative distribution of the N in plant tops and litter fraction is discussed.

Kikuyu dominance was positively related to N rate and independent of SR. White clover invaded at No and N131 levels especially at a high SR.

Four young females of four ruminant species, namely cow, buffalo, sheep and goat were used to study the utilization of sun-cured berseem hay (20·6% CP) fed in long form during a 28-day experimental period. Voluntary intake of hay was estimated during the last 10 days and digestibility of feed nutrients and nitrogen balance during the last 6 days.

The digestibility coefficients of dry matter (D.M.), organic matter (OM), crude protein (CP), crude fibre (CF), ether extract (EE) and nitrogen-free extract were higher for sheep and goat than for cow and buffalo but such differences were significant for D.M., OM and CP only. The daily D.M. intake was 3·56, 3·17, 0·92 and 0·63 kg/animal and 82·5, 81·2, 70·4 and 65·1 g/kg W0.75 in buffalo, cow, sheep and goat, respectively, but intake of total digestible nutrients (TDN) relative to metabolic body size was similar for all species.

Buffalo was superior to the other three species and cow to sheep and goat in ability to retain nitrogen. Berseem hay fed ad libitum supported a daily gain of 742, 500, 71 and 31 g in young female buffaloes, cows, sheep and goats, respectively. Digestible CP values of 13·33, 13·47, 15·38 and 15·01% and TDN values of 59·8, 57·6, 70·4 and 77·6% were obtained for cow, buffalo, sheep and goat, respectively.

Two groups of five and six ewes were studied through two separate winters by monthly wool and skin samples in an attempt to follow the changes leading up to fleece casting, which occurred extensively in only two animals.

Although no fleece break was observed, the animals that cast most showed the biggest decrease in fibre diameter. They also had a decrease in staple length where the wool was not cast.

Follicle inactivity increased during the observations reaching a peak at the end of the winter, and the animals that cast most had most follicle inactivity. It is concluded that casting was associated not with fleece break but with increased follicle inactivity coupled with premature release of the fibres from the follicles.

Individual live-weight gain (LWG) of Angus weaner cattle continuously grazing (Pennisetum clandestinum) pasture was negatively and linearly related to stocking rate (SR) and independent of ammonium nitrate (N) application rate at similar grazing pressures.

Live-weight gain varied from 380 to 1056 kg/ha according to N rate in 1970–1 and from 637 to 1477 kg/ha in 1971–2. Calculated SR giving maximum LWG/ha was 3·4, 4·7, 7·6 and 9·8 animals/ha for the 0, 134, 336 and 672kg N/ha treatments respectively in 1970–1 and 6·1, 5·7, 9·1 and 10·6 animals/ha for the same treatments in 1971–2. Highest response to applied N (1·9 and 3·4 kg LWG/kg additional N in successive years) occurred between N131 and N336; response was greater at low and intermediate SR than at high SR. Carcass weight, quality score, depth of subcutaneous fat and area of eye muscle were negatively related to SR; SR's giving maximum output per unit area caused a reduction of ca.25% in production per head and adversely affected carcass quality at 18 months of age.

LWG/head was independent of feed availability in spring and summer and was positively related to availability of green kikuyu up to 600 kg D.M./head in the autumn/winter period.

Three field experiments are described in which the effect of plant density and date of stopping (removal of the apical bud) on the development of yield in several Brussels sprout cultivars was studied. In a fourth experiment, the effect of a leaf removal treatment was designed to assess the possible remobilization of dry matter to the buds from senescing leaves.

A total plant dry weight of 1·2 kg/m2 was achieved with a hybrid cultivar at commercial densities. Although the crop growth rate was low in midsummer, growth continued until mid-October. Bud dry weight yield was curvilinearly related to plant density with 2 plants/m2 giving the highest yields of 0·35 kg/m2 in stopped crops in November. Rapid bud growth did not begin until September but the increase in bud dry weight continued into December and January. Early stopping increased bud dry weight yield and the ratio of bud weight to total shoot weight. In November, bud dry weight accounted for 25–40% of the total shoot dry weight for most treatments.

In the leaf removal experiment, estimated net photosynthetic rate of the crop was greater than the bud growth rate up to the end of the experiment and there was no significant effect of removing leaves just prior to natural senescence on bud dry weight.

The production and partition of dry matter is discussed in comparison with other vegetative crops. It is found that the proportion of total dry weight partitioned to the useful parts in Brussels sprouts is comparatively low. Factors controlling the date at which rapid bud growth begins are discussed. It is concluded that the dry matter in the axillary buds is derived from photosynthesis occurring at the time of bud growth and that the remobilization of dry matter from other plant parts is not of great importance.