Pulverized fuel ash and fiuidized combustor ash were used to modify the availablewater capacity and moisture characteristics of a gravelly sandy loam soil in a study of the effects of fine-particle amendments on crop yield. Intimate incorporation of the ashes into the top-soil at rates of up to 502 t/ha increased the available water retained in the surface 0·3 m of soil by 40–80 %. The increase was mainly water held at potentials of between –0·05 bar and – 1 bar.

Two sugar-beet crops followed by broad beans, salad onions and cabbage were grown in the amended soil. With the highest rate of ash addition yield of the onions was increased by over 30% and of the cabbages by 14%. No improvement in sugar-beet or broad-bean yields resulted from the treatment. Poor growth of the second sugar-beet crop was attributed to a reduced aeration effect but it is suggested that the failure of the increased available water to improve yield consistently in this and a previous experiment was in part caused by rapid evaporative losses from the amended soil.

In five experiments made at Rothamsted from 1966 to 1970 ‘Nitro-Chalk’ (ammonium nitrate–calcium carbonate mixture, 21% N) was broadcast for grass cut for silage, either in a single dose in spring or divided equally for three cuts. The ‘Nitro-Chalk’ was used to evaluate anhydrous ammonia (82% N) in 1966, anhydrous ammonia and aqueous ammonia (approximately 26% N) in 1967, 1968 and 1969, and anhydrous ammonia, aqueous ammonia and aqueous urea (18% N) in 1970. All these fertilizers were applied to give 125, 250, 375 and 500 kg N/ha, except in 1968 when 250, 375, 500 and 625 kg N/ha were given.

Anhydrous ammonia gave smaller yields (of dry matter) than the other N fertilizers except in 1968, a wet year, when it was at least as good as ‘Nitro-Chalk’, but slightly less good than aqueous ammonia. Yields were larger with autumn- than with springinjected aqueous ammonia and larger with either, than with equivalent single doses of ‘Nitro-Chalk’. Yields with aqueous ammonia were also larger than with ‘Nitro-Chalk’ divided equally for three cuts when more than 375 kg N/ha was tested, but smaller with less. Aqueous urea was as good as a single dose of ‘Nitro-Chalk’ but less good than divided ‘Nitro-Chalk’ in 1970, the only year it was tested. ‘Nitro-Chalk’ divided equally for three cuts gave larger yields than when a single dose of up to 375 kg N/ha was given, but with more N than this a single dose was better.

Apparent recovery of N was least from anhydrous ammonia and differed little between autumn and spring injection in 1968, the only year when a valid comparison was possible. Apparent recoveries of N from autumn and from spring-injected aqueous ammonia and from ‘Nitro-Chalk’ broadcast in a single dose differed little, nor did the proportion of the N recovered at each cut. Recovery from ‘Nitro-Chalk’ broadcast in three equal amounts was more uniform, but little larger.

Judged by yield, no more than 375 kg N/ha was justified; grass given this amount of N either as aqueous ammonia or as ‘Nitro-Chalk’ removed approximately 29 kg of N, 3 kg of P (7 kg P2O6), 26 kg of K (31 kg K2O) and 2 kg of Mg (3 kg MgO) per tonne of dry matter produced.

Field experiments were conducted in four provinces of Iran in which sugar-beet yield responses to added nitrogen and phosphorus fertilizers were correlated with soil test values and number of irrigations.

Although significant yield responses to fertilizer application were obtained in all four provinces, extremely few significant relationships were established between soil test values and yield response.

Average crop yield was favourably influenced by the number of irrigations applied in Fare and Khorasan, by organic carbon status in Esfahan and Khorasan and adversely affected by increased soil conductivity in Esfahan and Khorasan. These results were taken to imply an inadequate number of irrigations in Fars and Khorasan. The high calcium carbonate status found in Fars soil adversely affected the level of average yield.

Response to nitrogen fertilizer declined in Fars and Khorasan as the leaf nitrogen exceeded 3·15 and 4·0% respectively. Response to phosphate fertilizer declined in West Azerbaijan and Khorasan when leaf phosphorus exceeded 0·4%.

The effects of fatty acids, at low concentrations (0–005-O5 g/1), on the growth of seven species of rumen bacteria were examined. Anaerovibrio lipolytica(strain 5 S), Peptostreptococcus elsdenii(type 2), Bacteroides ruminicola46/52 and Selenomonas ruminantium(strain 17) were unaffected by addition of oleic acid to the medium. Growth of ButyrivibrioB 835 was stimulated by low concentrations of oleic (< 0–01 g/1), lauric (< 0–1 g/1) or capric (< 0–1 g/1) acids while higher concentrations of these acids were inhibitory. Myristic, palmitic and stearic acids were inhibitory at all concentrations tested. Ruminococcus4263/1 was inhibited at all concentrations of the six acids. Production of methane by pure cultures of Methanobacterium ruminantiumwas also inhibited by the additions of long-chain fatty acids. Oleic acid was the most inhibitory of the series of acids. These results are consistent with the reported effects of lipids on rumen function.

Variation of cotton yields from year to year has been a major problem in the Sudan Gezira for a long time. Previous studies indicated involvement of pest attack, soil nitrogen levels and lengths of growing season in this and suggested that adequate control of these factorswould lead to consistently high yields. Factorial experiments to test this hypothesis, comparing plots sown in early or late August, with or without frequent insecticide spraying and with orwithout nitrogenous fertilizer were therefore carried out at each of five sites in the Sudan Gezira and the first five years’ results are presented.

There were large, positive responses to nitrogen, spraying and early sowing at all sites. Nitrogen and spraying interacted positively, i.e. the response to nitrogen was much greater on sprayed plots and the response to spraying much greater on fertilized plots. Where plots were sprayed, early sowing also increased the response to nitrogen.

Treatment responses varied from year to year in such a way that the optimum combination resulted not only in much higher average yields but also in greatly improved stability of yield from year to year. The average yields, and the response to nitrogen on sprayed plots, were up to the levels which previous regression studies had estimated would be obtained in the absence of serious pest attack and were similar to peak yields in earlier years. During the course of theseexperiments commercial crop practice has changed towards earlier sowing, heavier nitrogen dressing and more frequent spraying, with apparently beneficial effects on yield and consistency of cropping.

The effects of the sowing date of cotton and application of nitrogenous fertilizer to it on the incidence of insect pests were investigated over a 5-year period. Response to frequent insecticide spraying was also determined and the results were related to previously reported interactions between nitrogen, sowing date and insecticide application in their effects on yield and its year-to-year variation. Numbers of jassids (Empoasca lybica de Berg) and whiteflies (Bemisia tabaci Genn) were considerably greater on the fertilized plots. The pattern of pest population change over the season varied with sowing date and also from year to year as did the relative numbers of jassids and whiteflies. Effects of spraying on the yield obtained under different agronomic treatments and in different years were clearly related to effects on numbers of insect pests.

The effect of soil water potential of the root media on the vegetative growth, seed and oil yield of sunflower (var. Record) grown in containers under field conditions was investigated.

The weight of shoots and the total leaf area of plants before flowering significantly decreased with decrease in the water potential of the root media. There was a sharp reduction of shoot weight as the potential decreased from —0–32 to — 1–25 bars and then a further slow decline as soil water potential dropped to — 8'6 bars. There were no significant differences in the 100-seed weights and percentage. of oil among the treatments, but the total number of seeds was significantly different.

The data did not indicate the existence of a threshold water potential above which yield was independent of soil water potential, but rather that yield was a continuously decreasing function of soil water potential.

In this experiment an attempt was made to study the influence of breed and sex on the muscle-weight distribution of cattle. The weights of individual muscles obtained by total dissection from the side of a carcass from each of 63 bulls, 106 steers and 22 heifers representing six, eight and two breed groups respectively were classified into nine anatomical groups using the method of Butterfield (1963). Muscle-weight distribution was then studied by expressing the muscle in each of these groups as percentages of total muscle and also as adjusted mean weight of muscle in each region while statistically adjusting total muscle to a constant level.

Results indicated that breed differences were significant although small for abdominal muscles and muscles of the neck region within bulls and steers, but two breed groups of heifers did not differ. There was no detectable breed influence on the percentage of any other muscle group. Percentages of muscles classified as expensive were found to be remarkably similar among breed groups in all three sexes.

Sex influences on muscle distribution were also appraised. There was a general trend of heifers having a higher percentage in the proximal pelvic limb and abdominal areas than steers, while steers exceeded bulls. This order of sex influence was reversed in the muscles of the neck and thorax region. The influence of sex was conspicuous in areas classified as having expensive muscles, with heifers having a higher percentage of muscles in the high-priced regions than steers and steers being superior to bulls. Sex differences reflect the differential development of bulls compared with the other sexes as they mature. Muscles of the neck and thorax in bulls increase in proportion and other groups (proximal hind and abdominal) decrease. The differentiation of muscles represents a trend toward masculinity from heifer to steer to young bull and finally to old bull proportions.

In a 3-year field experiment, calcined magnesite, Epsom salt, magnesium ammonium phosphate and magnesian limestone gave only small and non-significant increases in yield of a mixed sward but increased the concentration of magnesium in the herbage at all 11 cuts. Magnesianlimestone increased plant magnesium concentrations less than calcined magnesite, magnesium ammonium phosphate or Epsom salt, all of which had a similar effect; each increment of calcined magnesite gave additional increases in magnesium concentration.

Concentration of magnesium in the plant dry matter increased as each season progressed and was linearly related to exchangeable magnesium. At an exchangeable soil magnesium of 1·4 m-equiv./100g soil, Mg concentrations doubled between the first and last cuts. Changes in magnesium concentrations caused by increasing the exchangeable soil magnesium from 0·7 to 1·4 m-equiv./100g soil were less than the seasonal effects.

Pure swards of cocksfoot and perennial ryegrass cut on three occasions and of lucerne cut on two occasions were ensiled in test-tube silos after three treatments: (i) unwilted without additive, (ii) unwilted after the addition of formic acid at 0-23 % of fresh weight, and (iii) wilted to a water content of about 70 %, with no additive. Replicate silos were opened at intervals up to 105 days in order to follow the course of fermentation.

Silages from the final sampling could be divided into two clearly defined groups. Those where the lactic acid content, expressed as a percentage of total fermentation acids (L %T), was over 60 (19 silages) were considered stable while those with a value less than 20 (5 silages) were considered unstable.

The addition of formic acid resulted in a reduction in pH of the ensiled material from 5–86 + 0–12 to 4–60 ±0–11. This value changed little during the first 6 days after ensiling but then fell as lactic and acetic acids were formed. Stable silages made from unwilted crops without additive contained more lactic acid than those made with formic acid, but the converse was true for unstable silages. The ammonia content of silages made from unwilted material was always lower when formic acid had been applied. Wilting before ensiling gave stable silages from all crops.

Procedures for measuring K+ and NO-3 activities in the root zones of field crops, using specific-ion electrodes, were standardized. For K, a 1·0 M-NaCl salt bridge and KC1 standards in water, for NO3, a saturated KC1 salt bridge and KN03 standards in water, and for both electrodes, a 1:0·5, soil: water ratio, and 30 sec equilibration time were found satisfactory.

Recovery of added K in soil pastes by the K electrode and chemical analysis of the soil water extract compared well, but the recovery was about 8% only. The corresponding recovery of added N was about 87 and 95% respectively.

Relative changes in the rates and magnitudes of NO3 and K concentrations were measured with these electrodes, laterally and vertically, in the root zone, during active crop growth, from the N2 ½(PKNaMg), N2 PKNaMg, and N4PKNaMg treatments of the Broadbalk Winter Wheat Experiment.

In all fertilizer treatments, at all times, the nutrient concentrations were most at 45 cm from the crop (in the uncropped area) and least within the cropped area. The differences between these extremes represent nutrient depletion by the crop, the ‘45 cm’ measurementsindicating changes in uncropped, but fertilized, areas.

Soil nitrate depletion by the crop was much more at 12·5 cm and 20 cm depths than at 5 cm. Maximum NO3 depletion was observed during the later stages of crop growth, at ‘pre-panicle emergence’ and at ‘grain filling’. Depletion decreased and the soil NO3 level recovered partially as the crop reached maturity.

Periodic changes in the K concentration at each site and the corresponding K depletions were much less. Periods of IC stress on the soil were few and less clearly demarcated. Soil K concentration started to recover at the ‘grain filling’ stage about a month earlier than with NO3.

Changes in NO3 and K concentrations seem to relate more to the amounts given of each nutrient, than to the N:K ratio in each fertilizer treatment. However, changes in NO3 and K concentrations, and also NO3 and K depletion, occurred consecutively. This indicates an alternating periodicity in the demands of the crop for NO3 and K respectively throughout growth.

Seed of nine F1 hybrid wheat genotypes was produced by wind pollination. In one trial, grown at two seed rates, the extent of heterosis for yield and two yield components was small and was not affected by seed rate. In an adjacent trial the extent of heterosis in three hybrids was found to be affected by seed size.

A study was conducted to determine root development in a stratified and mixed sandy soil in the Sahara sands of Libya. Lucerne (Medicaqo sativa L.), millet (Pennisetum typhoides Burn.)> wheat (Triticum activumL.), grain sorghum (Sorghum bicolor L.), and several other crops were grown on soil that varied in depth to the stratified layers. Root depth and growth were measured by excavating along a representative root at intervals until the crop was mature or until no further root penetration into the subsoil occurred.

Trial plantings showed that none of the root systems of the plants tested could penetrate the stratified layers to any important extent, even with the application of adequate water and fertilizer, although all the layers were sufficiently porous to allow surplus water to drain through them freely. However, a few roots of lucerne, sudangrass, grain sorghum, and millet penetrated 2—3 cm into these layers, and many roots, especially of lucerne, grew into any natural cracks that occurred in these layers. If the compacted layer was loosened by cultivation, all the crops tested rooted normally in the loosened zone.

An experiment at Sutton Bonington in 1971 tested the effects of sowing and harvesting dates on yield of sugar beet. Seed sown on 28 March germinated slowly in the cold soil and crop establishment was poor. From early April until the beginning of May the loss in yield of sugar consequent upon delaying sowing by 1 week was 0·4 t/ha. For later sowings the yield loss was greater. During the harvest period the rate of increase in sugar yield was the same for all sowings. Yields of crops sown and harvested on different dates were closely correlated withthe amount of solar radiation intercepted by the leaf canopy.

Three experiments were made, in which two, four and three sheep were given rations in which increasing amounts of linseed oil fatty acids or Unseed oil were incorporated.

Although the changes in the rumen fermentation patterns were similar in all sheep, in some sheep the lipid metabolism in the rumen appeared abnormal, inasmuch as there was considerable accumulation of palmitic and smaller amounts of myristic acid.

It was concluded that the increases in the concentration of palmitic acid were due to an increased rate of its synthesis in the rumen, and an attempt was made to calculate these rates approximately.

The significance of these results within the context of rumen fermentation, methanogenesis and its inhibition were discussed.

In soya beans (var. 3H55F4/149/1) grown in Tanzania, the total dry matter per plant, pod weight/stem weight, shelling percentage, number of nodes per plant, number of pods per plant, percentage number of nodes with pods, number of filled pods per plant, number of branches per plant, and grain weight from side branches decreased with increase in plant density from 74 to 111, 222, and 444 thousand plants per hectare. Grain yield per hectare decreased by 38, 51, and 72% respectively with the increases in plant population, but yield of total dry matter per hectare showed a significant increase with density. Crop growth rate increased with increasing leaf area, which in turn increased with increasing plant density. Relative growth rate, however, decreased with rising population. Over the range of the densities studied grain yield was positively related to number of side branches but negatively related to dry-matter production, leaf area duration and percentage of light intercepted. The proportion of dry matter accumulated in the pods and side branches decreased with increase in population, whereas the proportion accumulated in the main stem increased. Light seems to be the major factor controlling grain yield in this variety of soya bean, low light intensity under the plant leading to a reduction in the number of side branches, number of pods per plant and number of nodes with pods.

The production rates of bacteria have been measured in the rumen of zebu calves and buffalo calves. The animals were fed green oat continuously at 2 h intervals. [35S]sodium sulphate was fed to the animals for 5 days at 2 h intervals by mixing in the feed. On the sixth day the radioactive feed was stopped and replaced by non-radioactive feed. The decline in the specific radioactivity of bacterial cells in the rumen as a function of time was taken for calculating t/2. Simultaneously rumen volume was determined and pool size of bacterial cells was calculated in the rumen. A mathematical equation was applied to calculate the production rates of bacteria. The production rates of bacteria, on average, were 100·5 and 72·3 mg/min for buffalo calves and zebu calves, respectively.

Growing wether sheep in metabolism cages were fed a low phosphorus diet (0–7 g P/day) and providing 16 g N/day supplemented with either urea phosphate, monoammonium phosphate or dicalcium phosphate and with appropriate additions of urea to give equivalent additional intakes of phosphorus (1–75 g P/day) and nitrogen (4–6 g N/day).

All three sources of phosphorus and nitrogen resulted in similar and significantly improved phosphorus and nitrogen retentions. There were also very similar effects on urine outputs of phosphorus and nitrogen and on the concentrations of phosphorus and urea in the blood of the sheep.

Studies were made of particle size distribution in meals produced from typical ingredients used in pig diets and of dietaries formulated from such ingredients. Each meal was subjected to a sieving procedure through standard sieves and the fractions retained by the sieves were weighed. The modes of expressing the results included moduli of fineness and uniformity and cumulative totals of oversize material, the latter forming the basis of the system preferred. Preliminary investigations into factors of loading weight, time of shaking and reproducibility of results led to the ultimate adoption of a standard technique of mechanical shaking of 100 g loads for 10 min. The technique was used to study particle size distribution in various cereals, cereal by-products, animal and vegetable protein sources and mineral mixtures employed in pig dietary formulations. The studies also included the particle distribution pattern in barley milled at varying grist sizes and in replicated samples of a commercial pig meal.

The suggested technique of characterizing particle size distribution should materially assist investigations into problems of pig health and productivity that appear to be associated with grist size of dietary meals.

In oven-dried whole plants from three regrowths of four varieties of Panicum maximum, leaf and stem of normal and stunted oats at three stages of first growth, leaf and stem of rape and the whole plant of millet, cell wall ranged from 14 to 77% of the organic matter. In vitro digestible cell wall ranged from 13 to 46% of the organic matter and was closely related to the cell wall (residual standard deviation, ± 2·5). In 16 legume hays the average in vitro digestible cell wall was 22·1% of the forage organic matter compared with an average value of 20·5% found previously from in vivo digestibility experiments with legumes. An unsatisfactory feature of the in vitro digestibility determination was that in silages and low quality grass hays, the digestible cell wall was low relative to known in vivo values for these forage types. The separate determinations of cell wall and in vitro digestible cell wall would add to the confidence that can be placed on estimates of in vivo digestibility from laboratory measurements. Often, the determination of cell-wall content is sufficient for this purpose.