The influence of three rates of each of N, P and K fertilizers on the availability of native and applied Mn to wheat was studied in a field experiment on an alluvial soil of the Indo-Gangetic plain. Increasing dressings of N as ammonium sulphate resulted in consistently higher yields and Mn uptake by the crop. Concentration of Mn in the grain increased with increasing N dressings when native Mn and Mn fertilizer supplied this nutrient but it was unaffected inplants sprayed with Mn. Adding P as superphosphate tended to lower the concentration of Mn in the grain when relying on native or applied Mn but it significantly enhanced the crop yield and total Mn uptake. Applying K as muriate of potash slightly depressed Mn uptake by plants. Potassium had a more pronounced effect in the absence of P fertilizer. The concentration of Mn in thestraw was not significantly affected by N, P and K fertilization.

A Phalaris tuberosa and Trifolium repens pasture was grazed continuously at stocking rates varying from 2·5 to 37·1 sheep per ha between 1964 and 1969. During this period herbage availability and composition, basal cover, root weight, water infiltration, soil moisture content, bulk density and chemical composition of the soil were measured at intervals.

As stocking rate was increased, herbage availability, root weight, basal cover, soil pore space and the rate of water infiltration declined, and bulk density and the nitrogen and calcium contents of the herbage on offer increased. In periods of below-average rainfall, soil moisture and nitrate levels were greater when herbage was of low availability.

Herbage production was calculated from estimates of herbage consumption and of litter decomposition, and averaged 8·45 t dry matter/ha/year; it was insensitive to changes in stocking rate over the range from 2 to 22 sheep/ha. The ratio, herbage consumption/ pasture production increased by 0'045 per unit increase in stocking rate.

Three different methods have been used to estimate the contribution of bacterial nitrogen to the total nitrogen in rumen digesta from calves receiving ground diets containing different levels of digestible energy and in which part of the nitrogen was supplied as urea. The method based on the ratio of 2, 6-diaminopimelic acid (DAP)-N to total N for rumen contents and rumen bacteria was not successful because the bacterial fraction isolated from pooled rumen contents contained a similar concentration of DAP to whole rumen digesta. The main source of error in the method based on the nucleic acid N/total non-NH3-N ratio for whole rumen contents and bacteria was probably the variability in the ratio for bacteria growing under different conditions. The method utilizing differences in the amino acid composition of the diets, a bacterial fraction and rumen content estimates bacterial protein rather than bacterial nitrogen. The chief limitation is the different rate of degradation of different dietary proteins. Bearing in mind these limitations calculations by the nucleic acid method gave mean values of 61–94 % bacterial nitrogen in the total nitrogen of rumen contents 3 h after feeding four different diets. Values recorded by the amino acid composition method varied between 66 % and 82 % bacterial protein N in the total protein N of rumen contents. The proportional contribution of bacteria increased as the digestible energy content of the diet was decreased in both cases. However, since the ruminal total protein N concentration fell as the digestible energy content of the diet was reduced, the actual concentration of bacterial protein N decreased with decrease in dietary digestible energy.

Estimates were made at monthly intervals between January and December 1965 of the intake and nutritive value of the diet of unmated Merino ewes grazed continuously at stocking rates ranging from 2·5 to 37·1 sheep/ha. Oesophageally fistulated sheep were used to estimate intake and nutritive value.

Drought conditions existed during the experiment. Digestibility declined linearly with increasing stocking rate. The intercepts of the relationship between digestibility and stocking rate differed between months, being at a maximum in spring. Nitrogen content was also greatest in spring but did not change consistently with increasing stocking rate. Organic-matter intake declined linearly with stocking rate and increased asymptotically with total herbage available, the asymptotic relationship being the more precise. Neither relationship differed significantly between months. Organicmatter intake/ha increased continuously with increasing stocking rate and the maximum intake was predicted to occur at a stocking rate greater than that at which the sheep survived.

The progression of sprouting was observed in water-yam (Dioscorea alata) and whiteyam (D. rotundata) tuber pieces planted in moist sawdust. Soon after planting, white callus-like protuberances (sprouting loci) were seen on the tuber surface, followed by the appearance of one or more differentiated shoot buds on the sprouting locus. Sprouting loci appeared more readily on the upper and lower parts of each tuber piece than on the sides. Large tuber pieces sprouted more rapidly, had larger and more numerous sprouting loci, and gave rise to more shoot buds than small tuber pieces.

Anatomical examination showed that the shoot bud resulted from the activity of a layer of meristematic cells lying close to the tuber surface. Extensive cell divisions commenced in this layer after planting, and some of the resulting cells soon differentiated into the shoot bud.

Sectional and intrasectional variations in muscle fibre diameter over a restricted axial range were examined in seven bovine muscles from foetuses, calves and steers. Significant sectional variations were found in four muscles, while two muscles showed significant intrasectional variations. The results indicate that sampling sites require accurate definition in comparative studies of muscle fibre diameter.

Two extensor muscles of the foreleg, m. extensor carpi radialis and m. extensor digitorum communis showed neither sectional nor intrasectional variation in muscle fibre diameter and appear to be more satisfactory muscles for use in muscle fibre growth studies than m. longissimus thoracis et lumborum.

A comparison of mean muscle fibre diameter in 60 pairs of contralateral muscles showed that there were no significant differences in 52 of the muscle pairs.

From 1969 to 1971, 743 animals (indigenous Zebu and European dairy cattle, lactating or dry cows and heifers) received oestrous cycle synchronization treatments at government-owned and private ranches and farms in the Tanzanian highlands (West Kilimanjaro); 445 matching animals served as controls. Treatment schedules consisted of chlormadinone acetate (CAP) given daily for 14 days (10 mg/day) orally; or a single CAP injection (50 mg) followed by 4 or 5 days of oral treatment (10 mg/day) 9–12 or 11–15 days later. In addition, some groups received either estradiol valerate (5 mg) together with the CAP injection, or 10 mg/day mestranol from day 11 to 15, together with CAP; one treatment group received 1000 i.u. of HCG after the last CAP medication and were inseminated 12 and 24 h thereafter. Animals were either inseminated or bred naturally. With all treatment schedules, good synchronization, unimpaired fertility and consistently a significant reduction of anoestrus was achieved. Oestrogen treatments had no effects; treatment with 1000 i.u. of HCG was unsuccessful. Management factors, food supply and phase of reproductive life had significant impacts on treatment success and fertility. Synchronization can be used successfully under a wide range of management conditions to unfold existing potentials of artificial insemination in Bos indicus and Bos taurus in the tropics.

The effect of variety and spacing on growth, development and yield of cassava and the relationship between growth, development and yield in three cassava varieties were investigated during the 1971 and 1972 growing seasons. Msitu Zanzibar outyielded Aipin Valenca and these two varieties in turn outyielded Amani 4026/16. The varietial effect was associated with differences in the rate of bulking. Increase in plant density led to an increase in the yield of tubers per hectare, the mean increase with increasing plant density being greater in Aipin Valenca than in either Amani 4026/16 or Msitu Zanzibar. Increase in plant density from 12000 to 18000 plants/ha led to a decrease in root tuber yield in Amani 4026/16. The calculated optimum density for maximum yield was 6·7, 6·4 and 5·6 plants/m2 respectively for Msitu Zanzibar, Aipin Valenca and Amani 4026/16. The spacing effect on tuber yield was associated with differences in the rate of bulking. Aipin Valenca was usually taller than the other varieties and, in general, increase in plant density increased the height of the plants.

Final total dry matter/m2 was greater in Aipin Valenca and Msitu Zanzibar than in Amani 4026/16 and, with the exception of the last variety, total dry matter/m2 increased with increasing plant density. Total dry matter produced per plant was greater in Msitu Zanzibar than in Aipin Valenca and these two varieties had greater dry weight per plant than Amani 4026/16. In the three cassava varieties, the dry weight per plant increased with decreasing plant density.

A greater proportion of the total dry matter was diverted into the root tubers of Aipin Valenca and Msitu Zanzibar than in Amani 4026/16. Generally, increase in plant density decreased the proportion of total dry matter diverted into the root tubers. Mean crop growth rate increased with increasing plant density while mean net assimilation rate and relative growth rate decreased with increasing plant density. Amani 4026/16 and Aipin Valenca had a greater mean crop growth rate and a greater net assimilation rate than Msitu Zanzibar. Mean relative growth rate was greater in the latter than in the former two varieties.

Leaf area index and leaf area duration were greater in Msitu Zanzibar than in the other two varieties and these tended to increase with increasing plant density.

There was a close and positive relationship between rate of bulking and root tuber yield and the lack of a positive relationship between leaf area duration and tuber yield is discussed.

Wool production and wool characteristics are reported for a 5-year period in which sheep grazed Phalaris tuberosa–Trifolium repens pastures at stocking rates ranging from 2·5 to 37·1 sheep/ha. The utilization of nutrients for maintenance and wool production were calculated over shorter periods.

Maximum wool production/ha was always recorded at the highest stocking rate attained. The highest annual maximum was 111 kg clean wool/ha in 1963–4. The decline in wool production/sheep/unit increase in stocking rate was greatest during winter and the amplitude of the seasonal rhythm in wool production increased with stocking rate.

At high stocking rates wool count increased, staple length and character declined, colour and handle improved, soundness tended to decline and fibre entanglement (cotting) to increase particularly during drought. Live-weight gain/sheep also declined with stocking rate, the rate of decline being greatest during drought. Maximum live-weight change/ha was attained at a lower stocking rate than maximum wool production/ha.

The maintenance requirement of grazing sheep was estimated to be 58·3 kcal metabolizable energy/day/kg live weight and did not vary consistently with stocking rate. The value was 79% greater than the requirements for penned sheep estimated from fasting heat production.

Efficiency of wool production was defined as wool grown/100 g digestible organic matter intake (ED) and as wool grown/100 g nitrogen intake (EN). EN declined linearly with increasing stocking rate but the intercepts differed between months, and were least in late winter and early spring. En declined with stocking rate in winter and increased during summer. At low stocking rates, ED showed some variation throughout the year but this was much greater at high stocking rates.

Paspalum plicatulum was grown at Brisbane in boxes of sand receiving basal nutrients and frequent irrigation; weekly levels of ammonium nitrate application were varied according to growth and development stage.

The rate of tiller appearance increased to a maximum 40–50 days after sowing and almost ceased thereafter. Tiller leaf number, survival, fertility, inflorescence branching, seeds per raceme and seed size were positively related to tiller age. Young tillers were more sensitive to variations in nitrogen supply than old tillers.

Adequate nitrogen nutrition during the vegetative phase from sowing to floral initiation (93 days) increased tiller and hence inflorescence density; increased inflorescence branching was compensated by fewer seeds per raceme. Good nitrogen nutrition during the phase from floral initiation to inflorescence exsertion (142 days) increased survival of late-formed tillers and hence inflorescence density; inflorescence branching, seeds per raceme and seed size were also increased. Nitrogen stress during the final maturation phase did not affect seed yield.

Immunoglobulin concentrations were compared in Finnish Landrace and other lambs, born to ewes of their own and of different breeds, to determine if the superiority of the Finnish lambs in obtaining maternal immunoglobulin from colostrum, shown in previous experiments, is due to special qualities of the ewes or of the lambs. The groups compared were, respectively, Finnish lambs born to Finnish, Welsh Mountain or Border Leicester ewes; Finnish, Oxford Down and Soay lambs born to Finnish ewes; Finnish and Merino lambs born to Border Leicester ewes; and Finnish and Southdown lambs born to Welsh Mountain ewes. The immunoglobulin concentrations in the Finnish lambs were in every comparison significantly higher than in the other breeds, and were not related to the breeds of the dams.

Wether sheep were fed on six forage diets, namely, (1) barn-dried low-N hay, (2) barndried low-N hay plus urea infused intraruminally at 12·6 g/24 h, (3) dried sainfoin, (4) dried lucerne, (5) fresh red clover and (6) dried and pelleted red clover. The proportions of amino acids in the diet and in samples of digesta from the duodenum and ileum were determined.

The relative proportions of individual amino acids in the duodenal digesta showed little variation despite the differences in intake and the variation in the proportions of amino acids in the feeds. Only the proportions of methionine, lysine, 2:6 diaminopimelic acid (DAPA) and aminoisobutyric acid (AIB) showed significant (P < 0·01) variation with respect to diet. In the ileal digesta the proportions of methionine, leucine, tyrosine, phenylalanine, glutamic acid, proline, glycine, alanine, AIB and DAPA showed significant variation by diet.

With all diets except lucerne the quantity (g/day) of total amino acids presented at the duodenum was higher than the quantity ingested. There was no correlation between the quantity of total amino acids presented at the duodenum and the quantity disappearing within the small intestine.

The duodenal digesta contained a significantly higher (P < 0·001) proportion of essential amino acids than did the ileal digesta. This difference was most marked with the diets which supplied a low amino acid intake.

With all diets there was little apparent absorption of DAPA in the small intestine.

Welsh mountain sheep were subjected to a number of stressful treatments including minor surgical interference, restrictive handling and adrenaline administration. A decline in plasma calcium concentration was consistently observed following treatment, and this was accompanied by the elevation of plasma NEFA levels. There was a highly significant negative correlation between these changes.

Subcutaneous adipose tissue taken by biopsy from adrenaline-treated sheep showed an increase in calcium concentration which was significantly correlated with the depression of plasma calcium concentration.

In vitro incubation of omental fat with adrenaline showed there was an uptake of calcium by adipose tissue from the medium, which was dependent on time and log dose of adrenaline.

The results are discussed in the light of the possible effect of calcium transport into adipose tissue on calcium homeostasis during periods of severe calcium loss.

Lower concentrations of the herbicide M15 stimulated the in vitro cellulose digestion and V.F.A. production by rumen micro-organisms. The herbicide Cotoran enhanced cellulose digestion but had no effect on V.F.A. production. The herbicide Dalapon decreased cellulose digestion and had little effect on V.F.A. concentrations. The herbicide 2,4·D had little or no effect on the in vitro cellulose digestion and V.F.A. production. The in vitro microbial activity was inhibited by the pesticide DDT. The effects of M15 2,4·D and DDT on V.F.A. production decreased with time. When the rumen fluid was fractionated, the V.F.A. production by the bacterial fraction was not significantly altered by the addition of 2,4·D and M15, whereas the activity of protozoal fraction was greatly enhanced. The response of V.F.A. production by washed suspensions of rumen ciliate protozoa to the addition of pesticides and herbicides was remarkably similar to that of rumen contents. Feeding M15 (60 ppm) increased the ruminal V.F.A. over those in the control sheep whereas 2,4·D had no or little effect.

Consideration is given to the prospects of producing F1 hybrid varieties of perennial ryegrass, Lolium perenne, and other herbage grass species for commercial use. In the light of the results of interpopulational hydridization in this and other crop species and of the technical and economic disadvantages inherent in other methods of F1 hybrid seed production, it is concluded that the development of interpopulational F1 hybrid varieties, by the field interpollination of parent populations, is a desirable and worthwhile breeding objective.

Six successive trials with three adult rams (Sudan desert sheep) were conducted with the main object of finding a suitable index for the prediction of the nutritive value of protein in non-legumes for ruminants.

The mean change in the concentration of ruminal ammonia, blood urea and ruminal V. F. A. 3 h after feeding legumes was considerably greater than after feeding the nonleguminous hays. Among the legumes berseem hay gave the least change in the concentration of ruminal ammonia, blood urea and V. E. A. The leguminous hays produced more gas under in vitro conditions than the non-legumes. Berseem hay produced the greatest volume of gas. Butterfly pea hay and lubia hay gave more or less similar results. Among the non-legumes the desert grasses gave the lowest values.

Of all the feeds studied maize hay gave the highest nitrogen retention, followed by berseem hay. Despite this superiority of maize hay, the overall mean nitrogen retention of legumes was much greater than that of the non-legumes. Among the non-legumes dry desert grasses displayed a negative nitrogen balance.

Regression equations based on the present data indicated that nitrogen retention only of leguminous hays could be always predicted from changes in blood urea concentrations. The present results also showed that the nitrogen retention of non-legumes and to a lesser extent that of all feeds taken together (i. e. legumes and non-legumes) can be assessed by using volume of gas produced in vitro (i. e. rate of in vitro fermentation).

Sixteen factorial experiments made from 1969 to 1971 on Northern Ireland pastures measured effects on yield of 0, 180 or 360 kg of N, 0, 30 or 60 kg of P and 0, 150 or 300 kg of K/ha/year both with and without 138,000 1 of slurry/ha.

Without slurry, pasture yield was almost always substantially increased by nitrogen, slightly by potassium and hardly at all by phosphorus. There was a slight positive interaction between nitrogen and potassium, but no other interactions. Response to nitrogen was not linear and therefore was lower than has been obtained in many British trials.

Slurry sharply reduced response to nitrogen and virtually eliminated response to phosphorus and potassium. The NH4-nitrogen content of slurry gave an adequate measure of its effect on pasture yield. The nitrogen, phosphorus and potassium contents of the most concentrated slurries were 15, 29 and 36 times respectively those of the most dilute batches. Hence considerable imprecision is brought into a fertilizer programme when slurry is applied.

As manuring on individual fields can never be precise, the fertilizer phosphorus and potassium needed for grassland is best assessed by considering the farm as a whole. A nutrient balance can show if the farming system is gaining or losing phosphorus and potassium. The amounts of fertilizer phosphorus and potassium needed are those which cover any deficits on the farm as a whole.

Rates of added P required for maximum yields of ryegrass grown in pots and of field tobacco and maize were related to functions of P intensity (I) and capacity (AQ/AI, or C) in soils. It was found that log I alone was negatively correlated with optimum fertilizer for ryegrass and tobacco, but not for maize. Capacity alone had little relationship with P requirements of tobacco but was significantly correlated, although having opposite effects, with those of ryegrass (positive) and maize (negative). Optimum fertilizer rates for all crops were best accounted for by multiple regressions including intensity and a capacity term together, using log C when P requirements were increased (ryegrass in pots, R2 = 0.94) or √C when they were decreased by increasing capacity (field tobacco, R2= 0.96; and maize, R2 = 0.98). Inclusion of both capacity terms with log I in regression was of no advantage with ryegrass and tobacco, but with maize all three terms contributed significantly to the correlation, log C tending to increase and √C to decrease fertilizer needs.

Herbage samples from 16 trials testing the effects of N, P and K fertilizers and slurry on grassland were analysed for % N, P, K, Ca, Mg and Na. The data were examined to see if a fertilizer policy designed for optimum yield should be modified after taking pasture mineral content into account.

The correct fertilizer nitrogen policy appears to be to apply nitrogen for the desired yield and to disregard any effects on mineral content. The correct fertilizer policy for phosphorus and potassium is to steer a middle course between depleting soil reserves and accumulating undesirable excesses. The quantities of phosphorus and potassium which should be applied to cut grass to maintain the status quo in the soils are discussed. The amount of phosphorus and potassium added in slurry must be allowed for in this calculation. As the amount of slurry available depends upon the farming system, an effective fertilizer policy for phosphorus and potassium can only be devised by studying the farm as a whole.

At the first cut, the slurries provided on average 115 kg NH4-N/ha, 114 kg K/ha and 86 kg P/ha. Slurry potassium was somewhat less than half as effective as fertilizer potassium in increasing % K in the herbage at the first cut. Furthermore, the herbage recovered only 0·8 kg of the 86 kg of slurry phosphorus. In the short term, slurry was only just over 10% as effective as fertilizer phosphorus, presumably because much phosphorus in it is organically bound.

Fourteen trials on spring barley and eleven on winter wheat, grown in the east of Scotland, compared the effects on yield of liquified anhydrous ammonia and solid ammonium nitrate at various levels of application.

For grain yield, the optimum N level in these trials was about 100–113 kg N/ha. The object of including in the trials N input levels higher than optimum was attained. Yield response to the two forms of N was similar for both wheat and barley at the different N input levels.

Winter injection of anhydrous ammonia was less efficient than spring application. Injection of anhydrous ammonia into young wheat resulted in frequent reduction of plant population and, on occasion, loss of yield.

At equivalent rates, anhydrous ammonia caused less lodging than ammonium nitrate; it also appeared to be less readily leached from the soil. Ammonium nitrate gave more rapid early growth and this led to a greater proneness to leaf disease.

Considering the complexity of storage and injection equipment required to handle anhydrous ammonia, it is questionable if these agronomic advantages justify its use on cereals where rates of use do not also confer the benefits of cheaper unit cost of nitrogen.