The yields of four tropical grass/legume pasture mixtures were studied over a 4-year period. These mixtures had the following composition: H, Cynodon nlemfuensis var. robustus, together with the legumes Centrosema pubescens (Benth.), and Stylosanthes gracilis (H.B.K.); J, Pennisetum purpureum (Schum.) plus the two legumes in H; K, treatment J mixture plus Panicum maximum (Jacq.); and L, a mixture of treatments H, J and K. Each treatment paddock was grazed in rotation between 19 April 1966 and 21 November 1969.

The mean annual dry-matter yields over the 4 years of grazing were approximately 37 ± 5·7, 41 ± 2·6, 44 ± 10·2 and 47 ± 8·7 t/ha for treatments H, J, K and L respectively. The overall mean for the four treatments was 42 ± 5·1 t/ha/annum.

It was observed that the dry-matter yield of the three mixtures in J, K and L, containing the tall grass species, was significantly superior to that of treatment H; however, they were not statistically different among themselves.

After the second year of grazing Stylosanthes gracilis diminished gradually and it was almost absent from the swards by the final year of grazing, while Centrosema pubescens maintained its stand throughout the experimental period.

With the exception of phosphorus and sodium, levels of mineral elements in the pastures were above the recommended allowances for various classes of livestock.

The average level of zinc was only slightly below the recommended value.

Forty-eight cross-bred wether lambs were used to measure the effects of severe feed restriction and realimentation on the body and carcass composition of immature sheep. Ten of the total number of sheep were used as an initial slaughter group, 12 were continuously fed (six at the ad libitum level of intake and six at 70% ad libitum), 26 were progressively underfed and 18 of them were realimented after a mean loss of about 25% empty body weight (EBW).

Shrunk body weight (SBW = weight after an 18-h fast with access to water) was a good predictor of empty body weight (EBW = SBW minus gastro-intestinal contents) and the EBW of continuously growing sheep was a good predictor of body water, protein, fat, energy and ash, but it was not precise after realimentation, particularly in the early stages of refeeding. Restricted continuous supermaintenance feeding did not alter the body composition of the sheep from that of the sheep on the ad libitum intake at any given EBW except slightly to increase the carcass protein content.

Although underfeeding to produce an EBW loss of 25% generally produced changes in the chemical body components which were similar to a reversal of normal growth, body fat did not decrease during the first half of the submaintenance feeding and did not increase during the first 2 weeks of realimentation. Under all circumstances percentage body fat was very closely related to percentage body water.

Sheep realimented at 26 kg (after losing 25% EBW) contained, at 45 kg EBW, more bodywater and protein and less fat and energy than continuously-fed animals of the same EBW. The treatment effects were greater in the carcass and had little effect on the non-carcass EBW, with th e result that the refed sheep had 1800 g more water × protein in a carcass that weighed 700 g more than one from a normally grown sheep of the same EBW. The regression of calorific value of th e ash-free dry matter on body fat as a percentage of ash-free dry matter gave calorific values of body protein and fat as 5·652 and 9·342 kcal/g of ash-free dry matter, respectively.

An experiment is described in which plots of a silt loam soil were compacted by ploughing and rotary cultivation when the moisture content was high. Kale and barley were grown on these plots in 2 years.

Compaction of the soil was not as great as anticipated, but there were marked reductions due to wet cultivation in the dry-matter yield of kale and the vegetative growth of the young barley. Seed yield of barley was relatively unaffected, although there was a significant reduction due to wet ploughing in one year.

The implication of these results for experimentation on the effects of soil structure on crop yield are discussed.

Four swede varieties and their six F1 hybrids were grown for 2 years in plots varying in pH from 4·2 to 8·4. Yields were highest at intermediate pH's and the average yield of the hybrids was greater than that of the parents. The plants on the low pH plots (4·2, 4·6, 4·7) were less infected with mildew than those at high pH (6·7, 7·7, 8·4). There was no marked resistance to mildew amongst the varieties. The response by the parents and hybrids was assessed by regression analysis and showed that the variety Reform was most reactive and Harvester most stable. Stability patterns appeared to be inherited. Inheritance patterns for yield and number of leaves were determined. It was concluded that selection for better swedes should be carried out in environments other than those to which the crop is currently restricted.

Experimental conditions and design were described in part I. Separable lean and fat were highly correlated with the carcass and whole body components of protein and ether extract. The carcasses of refed sheep at 45 kg empty body weight (EBW) had about 1 kg less fat and more lean than carcasses from sheep of similar weight which had been continuously fed. Restricting feed intake to 70% ad libitum gave carcasses that had more protein than those from sheep fed ad libitum both during continuous growth and after realimentation.

Sheep that had lost 25% EBW to 26 kg and then were refed to 31 kg EBW had 34% less separable carcass fat than sheep which had been continuously fed to EBW of 36 kg and then had lost weight from that level to 31 kg EBW, and the separable fat was higher in water content than during normal growth (an effect shown consistently in realimented sheep).

Severe underfeeding rapidly reduced bone water but bone ether extract continued to accumulate. After a period of refeeding, bone fat was rapidly mobilized and bone water quickly returned to normal. During early weight loss following food intake reduction, there was a larger decrease in carcass water than expected, and most of the discrepancy could be accounted for by the disproportionately large loss of water from bone and separable fat.

It is concluded that during early regrowth there is a marked stimulus of lean tissue growth and depressed fat synthesis. After this initial period, growth rate of carcass tissues is not greatly different from that found in continuously growing sheep although there is some evidence of a small positive rate of protein growth effect following through to 45 kg EBW in the refed animals. The ratio of muscle gain to fat gain from 30 to 40 kg EBW was 2·23 in realimented sheep and 1·08 during normal growth.

Dried grass originating from a farm on which herbage had been repeatedly dressed with faecal slurry from pigs given diets containing 250 mg copper/kg had a very variable, but frequently high content of copper. A maximum content of 70 mg Cu/kg dry matter was found. The mean copper content of growing herbage sampled subsequent to this finding was 10·5 mg/kg, while residues of slurry on the soil surface contained 805 mg Cu/kg.

In an experiment involving three groups of eight sheep the utilization and hepatic retention of copper from the solid residues of an aerobic digest of high-copper faecal slurry from pigs was investigated. When these residues constituted 1 or 2% of the dietary dry-matter intake of copper-deficient sheep, rapid increases in plasma copper content, in plasma ferroxidase I activity and in hepatic copper content occurred. Thus copper from this source was readily utilized and retained.

The utilization of copper added to the diet as cupric sulphate was compared with that of copper from dried slurry solids in an experiment with two groups of four sheep. Although the rate of recovery of plasma copper and ferroxidase I activity tended to be slower in sheep given slurry solids this difference was not statistically significant. A significantly slower rate of increase in hepatic copper content resulted from the ingestion of slurry solids.

The significance of these findings is discussed with particular respect to the inadvertent ingestion of residues from the soil surface of pastures dressed with slurry and from the variable inclusion of such residues in herbage uplifted during forage harvesting.

Nine field experiments with sugar beet in 1968–70 tested eight amounts of nitrogen fertilizer (0–290 kg N/ha) on a shallow calcareous loam (Icknield Series), on a deep sandy loam (Newport Series) and on a heavy clay loam (Evesham Series). Top soils and subsoils, sampled during autumn, winter and spring before the experiments, were analysed by several methods for available and potentially-available nitrogen. The largest increases in potentially-available mineral-nitrogen shown by incubation occurred in the calcareous loams every year in both top soil and sub-soil, and the sandy loam, particularly the sub-soil, generally produced least. Attempts to forecast the optimum nitrogen fertilizer dressing from the soil analyses were moderately successful, the best technique being anaerobic incubation of air-dry soil; the date of sampling had little effect. The optimum dressings were always between 0 and 125 kgN/ha, the calcareous loams generally needing least nitrogen fertilizer and the loamy sands most.

Two experiments were made to measure the dry-matter intake of grazing sheep. Three groups of five ewes grazed three plots of young barley. The mean daily drymatter intake per ewe from each group was estimated from the water turnover which was measured by the tritium dilution technique. The mean intake was also estimated by the double sampling technique for measuring standing crops. The mean estimate of one technique was within the standard deviation of the mean estimate of the other. The difference between the mean estimates from each technique did not exceed 18 %. It is concluded that water turnover could be useful for the measurement of the intakes of animals grazing green pastures.

Experimental conditions and design were described in Part I. When compared with continuous growth, there was a 46% increase in rate of gain following refeeding, but no increase in intake per kg0·734 (MBS) per day. Part of the reason for this was the rapid accumulation of body water after realimentation. If the total cost of feed, including that of the weight-loss phase, is used to calculate the feed required per unit of gain, however, the sheep realimented at 26 kg to reach an empty body weight (EBW) of 45 kg had a requirement 27% higher than ad libitum continuously fed sheep taken to the same final EBW.

The only treatment effect on digestibility or metabolizability of the diet that was not accounted for by level of intake was a depression immediately after underfeeding commenced. The metabolizable energy (ME) value later decreased markedly as a result of the relatively high proportion of gross energy lost in the urine (14·4%).

There were no significant differences between normal growth and refeeding in maintenance requirement or efficiency of energy retention above maintenance. The combined figures were 107 ± 14 kcal ME/kg MBS/day and 52 ± 7% respectively.

Growing conditions and testing methods were varied to investigate the use of the Pelshenke test in breeding wheat varieties for good bread-making quality in the United Kingdom. Varieties of winter wheat representing a range of bread-making quality were consistently differentiated. Fresh compressed yeast gave greater varietal differences than did dried yeast but kneading time and grain moisture content were not critical. The values obtained were relatively insensitive to the early stages of germination, to the addition of α-amylase and to variation in grain protein content resulting from N fertilization and irrigation. Thus it appears that the Pelshenke test mainly reflects gluten quality, rather than the whole complex of characters which are integrated by baking tests, and the ranking of the varieties is sufficiently independent of environmental conditions to be of considerable value for selection of early generation breeding material.

Nine field experiments with sugar beet in 1968–70 tested eight amounts of nitrogen fertilizer (0–290 kg N/ha) on a shallow calcareous loam (Icknield Series), on a deep sandy loam (Newport Series) and on a heavy clay loam (Evesham Series). The amount of mineral nitrogen in the top and sub-soils was determined before applying fertilizer and at monthly intervals from May to October in plots given 0, 125 and 250 kg N/ha. The crop on these plots was also sampled at monthly intervals throughout the growing season and the yield and nitrogen uptake determined. The soil analyses indicated that in springs with average rainfall, the leaching losses of nitrogen fertilizer are negligibly small, although there was some evidence that losses may be greatest on sandy loams. In very wet springs such as 1969, with almost double the normal rainfall, losses through leaching are considerable – on average, 40 kg N/ha. Dry-matter yields and response to nitrogen fertilizer differed between the three soils consistently from year to year. On the calcareous loam, neither amount of fertilizer changed the dry-matter yield of roots in any year. The crop on the clay loam needed a small dressing and on the sandy loam a larger dressing of fertilizer for maximum root dry-matter yield. Uptake of nitrogen by the crops usually paralleled the decreases in soil mineral nitrogen although on the clay loam nearly a third of the nitrogen applied could not be accounted for in the soil or plants, suggesting that some denitrification may have taken place. When the amount of nitrogen taken up by unfertilized crops is allowed for, the percentage recovery of applied fertilizer nitrogen at final harvest ranged from 42% on the calcareous loams to 62% on the sandy loams.

An experiment was designed to assess the effect of thermal stress and protein value of the diet on the productivity and some of the blood organic constituents of lactating Holstein cows. Two groups of eight animals each were used in 2 × 2 Latin-square designs with two experimental diets. The percentage of crude protein in the diets was 14.3 and 20.8 %.

Rectal temperature and respiration rate were recorded twice weekly and jugular blood samples were collected at weekly intervals for analysis. Daily feed intake, refusals and milk production per cow were recorded. Representative samples of morning and afternoon milk were taken three times a week for chemical analysis.

Data on respiration rate and rectal temperature suggested that both groups of animals were under thermal stress. However, significantly lower values were found by increasing the protein level of the diet. The higher level of protein significantly increased total milk production, 4 % fat-corrected milk (4 % FCM), total solids, solidsnot-fat, protein percentage and yield, casein and non-protein-nitrogen in milk. The increase in milk production and 4 % FCM was found to be associated with the increase in total feed and total-digestible-nutrients intake but not with crude-protein intake. Protein levels in the diet had no effect on fat percentage and yield nor on whey protein.

The correlation coefficients between respiration rate and rectal temperature with some of the blood organic constituents suggested an inverse relation between thermal stress and the blood organic constituents. The higher level of protein in the diet significantly increased haemoglobin levels but had no effect on oxyhaemoglobin, haemoglobin:oxyhaemoglobin ratio and haematocrit value. Total serum protein was not affected by thermal stress or by the protein value of the diet. Increasing protein levels in the diet increased albumin but decreased the globulin fraction of serum protein. Plasma glucose and non-protein nitrogen were increased by increasing the protein in the diet.

Seeds of okra were sown in moist soil and subjected to heat stress of 45 °C for 10 h on day 0 (day of sowing), day 1 or day 2 after sowing. Stresses on day 0 and, to a lesser extent, on day 1 promoted hypocotyl elongation and accelerated seedling emergence. Stress on day 2 retarded hypocotyl elongation and did not accelerate emergence. The results were similar for seeds sown at depths of 1, 4 or 7·5 cm. For 10-h stresses on day 0, 40 °C was slightly less promotive than 45 °C; but 50 °C or above resulted in no emergence whatsoever. Subjecting dry seeds to 40–60 °C for 24 h before sowing gave no appreciable acceleration of emergence; instead, at 60 °C there was a 24-h delay in the onset of emergence. Seeds were also incubated for 1·5 h in water at temperatures ranging from 40 to 80 °C. Emergence was accelerated at 40 to 65 °C, with the greatest acceleration at 45 °C. It is suggested that incubating the seeds at 45 °C for 1·5 h before sowing could afford a practical means to accelerate field emergence of okra.

Cowpea and hyacinth bean nodulated and grew well at 11–14 h and poorly at 8 h light duration. Nodulation and plant growth increased with increase in light intensity from 1·4 to 17·1 W/m2 but the natural light intensity (228·3 W/m2) inhibited nodulation in July and plant growth in December.

Nodulation and growth of both crops were best at ‘moderate’ temperature and cowpea tolerated ‘warm’ more than ‘cool’ temperatures whereas hyacinth bean showed the reverse situation.

Inoculation improved nodulation of cowpea but not hyacinth bean. Application of nitrogen did not improve the growth of plants affected by light and temperature.

In 18 digestibility experiments with sheep, 9 diets consisting of single-grass hays and 9 diets each consisting of equal quantities of a good and poor quality hay were fed. Correlations between the voluntary intake of organic matter, digested organic matter, total cell wall and digested cell wall in all possible combinations were investigated. There were no significant differences among the simple correlation coefficients for hays fed singly or as mixtures, even though they were eaten in very different amounts. The simple pooled correlationswere significant (P < 0·01) among voluntary intake, digested organic matter and cell wall. The cell wall was significantly correlated with digested cell wall, but there was no simple correlation between voluntary intake and digested cell wall. However, when considered together in a multiple linear model they explained 58% of the variation in voluntary intake compared with 43% explained by the total cell wall alone. The additional variation accounted for by the digested cell wall was significant (P < 0·05).

The relative importance of the total cell wall and digested cell wall is discussed in relation to selection in grass breeding.

A comparison of ammonium sulphate (AS) with and without N-Serve and sulphurcoated urea (SCU) as N sources for sugarcane, studied in a pot experiment, showed that although the tillering, the leaf N concentration and cane yield were increased by adding fertilizer N there were no significant differences between N sources. However, AS and AS + N-Serve depressed the soil pH, especially that of acidic soils, much more than SCU. In a field experiment where AS, urea and SCU were compared on a calcareous soil, it was observed that urea gave significantly lower cane and sucrose yields than AS and SCU when N was applied on the surface, possibly due to greater volatiliization losses from urea. Subsurface application increased the efficiency of urea, although the method of placement had no significant effect on the N efficiency of AS and SCU. AS was as effective as SCU. Thus the coating of urea by sulphur increased its efficiency for sugarcane only when applied on the surface of a calcareous soil.

In order to examine whether high yield of maize could still be maintained at high plant densities by creating an ‘erectophile canopy’ through artificial defoliation of laminae, an experiment at Pantnagar, India, was made on the effect of density, stage and degree of defoliation in two divergent seasons, Kharif (rainy) and spring, of the year 1972. The defoliation treatments were either partial (clipping off the apical half of individual leaves) or complete (full leaf removal) and were imposed at three stages of plant growth, namely when 10 or 16 leaves were fully open or 12 days after silking. These treatments were applied at two plant densities, 60000 and 90000 plants/ha.

Grain yield of maize increased significantly with the increase in population density in the spring season. The trend was diametrically opposite in the Kharif season. Defoliation at the 10th fully open leaf stage produced more grains than defoliating 12 days after silking, which in turn produced more than defoliating at the 16th fully open leaf stage, when plants were in full bloom. Increase in the degree of defoliation at the latter two stages of plant growth reduced grain yield, the effect being more at the 16th leaf stage. However, 50% defoliation at the 10th leaf stage increased grain yield in the Kharif season.

The percentage protein content of grain declined with the increase in population density whereas increase in degree of defoliation increased the grain protein content. Higher protein content of grain was recorded in the spring than in the Kharif season. The leaf protein decreased as the plants neared maturity, especially at the higher degree of defoliation treatments.

Sucrose and reducing sugars declined significantly with the increase in degree of defoliation. The reduction in sucrose was large enough to account for the reduction in total sugar percentage. Similar trends were observed in the sugar-to-protein ratio.

Relationships among quality number, crimp frequency and. fibre diameter of sale lots are reported for a wide range of Australian wools, the quality number appraisals being those of the selling broker and the successful bidder at auction.

Results show that sale lots classified as having the same quality number exhibit a 95% confidence interval of ± 2·5 μm about the mean value. This variation is attributed first to the dependence of quality number on staple crimp frequency and secondly to the strength of the relationship between crimp frequency and fibre diameter.

A comparison of objective and subjective appraisals of the yield of Australian greasy wool sale lots is reported.

Results suggest that although the overall agreement between the two systems of appraisal is good, the subjective estimate of an individual sale lot will only lie within ± 6% of the objective estimate in 95% of cases.

Five groups of four 8-week-old Blackface lambs were used to compare the effects of dietary deficiencies of calcium and/or phosphorus: four were given for 16 weeks a semi-purified diet low in Ca (0·07 %) and P (0·13 %), either unsupplemented (LCaLP) or supplemented with 0·3 % Ca (NCaLP), 0·3 % P (LCaNP) or both (NCaNP), and the remaining group was slaughtered initially.

The only clinical abnormality observed was twisting of the forelegs in group LCaLP. Food intake was depressed by 26 % in LCaNP group, by 41·5 % in NCaLP group but was largely unaffected in group LCaLP. Apparent D.M. digestibility was lower for group NCaLP (57·7 %) than for other groups (61·2 %). Differences in live weight and body fat reflected the differences in food intake between treatments but the weights of fat-free body components were lowest in the groups given low P diets.

The LCaNP diet decreased plasma Ca and increased plasma P but the NCaLP diet had the opposite effects. The LCaLP diet had no effect on plasma Ca and decreased plasma P less than the NCaLP diot.

The three mineral deficient diets caused equally marked decreases in Ca and P retention but did not induce negative balances; they also impaired the quality of bone in the tibia and lumbar vertebra, by reducing both the amount of bone matrix and the degree to which it was mineralized, and produced histological lesions of rickets and osteoporosis. Diets low in P caused a marked fall in Mg content of the skeleton.

Urolithiasis was common in lambs given diets adequate in P.