A dynamic model is presented in which the problem of predicting P response is broken down into various components, such as:

(a) Weight and P content of emerging seedling.

(b) Normal growth curve of the fully nourished plant.

(c) A ‘deficiency-tolerance’ factor relating depression of relative growth rate to plant P concentration.

(d) An ‘affinity’ term relating sink concentration to P status of plant.

(e) A perirhizal resistance term for diffusive transport to roots.

(f) Capacity and intensity of P supply from the soil. Mass flow supply via the transpiration stream is also included.

By changing parameter values one may attempt to simulate the effect of any of these factors on the shape of the P response curve and any other part of the system throughout crop life. At present the model over-estimates growth at low levels of P supply, but predicted plant P concentrations agree reasonably well with observed data.

Patterns of stem development in late spring/summer regrowths after initial cuts at three growth stages are described. The stages at which the initial cuts were taken were: (a) before stem apices were raised to defoliation level (5 cm), (b) two weeks later when the apices of about 90% of the stem tillers were raised above this height, and (c) four weeks after (a), when the apices of all stem tillers were raised well above cutting height.

Following an initial cut at stage (a) stem development was quickly resumed, the most advanced tillers being devoid of leaf blades. After initial cuts at the later stages there was virtually no stem development until after the fourth week of regrowth.

The greater proportion of stem tillers in the earlier regrowth was not reflected in reduced digestibility during the first six weeks from cutting.

Reproductive (apical) development was generally weak in tillers in which stems developed in midsummer (after cutting at stages b and c); at least two-thirds of these tillers were indeterminate.

The significance of the distinct batch of stem tillers developing in spring is discussed, and the data are also considered in relation to (i) avoiding stemmy regrowths in spring, (ii) stem development and herbage quality, and (iii) summer stem extension and the perennation of the sward.

The distribution of body water in the different body compartments of four highpotassium (HK) and four low-potassium (LK) type sheep of the Marwari breed of the Rajasthan desert was determined after imposing the following watering treatments, viz. watering ad lib., ¼, ½ and ¾ restrictions (each of five days ‘duration with a sevenday normal drinking regime between each treatment) and water deprivation (of three days’ duration). There was no difference in the voluntary water intake of the HK and LK animals. The HK animals normally have a higher blood and plasma volume status than the LK. In both types of animals, the total body water, total blood and plasma volumes and the extracellular, intracellular and interstitial fluid volumes started decreasing as water intake was reduced below 25% of the daily requirement. In both the phonotypes 75% reduction was similar in its effect to complete deprivation. The physiological status of the HK Marwari animals appears to be somewhat superior to that of the LK although both types seem to be equally adapted to the conditions of the habitat.

The growth and yield of four varieties of field beans were studied in field experiments in 1967 and 1968.

Seed yield of the varieties Albyn Tick, Herz Freya, Blue Rock and Maris Bead were similar (averaging 6600 kg/ha) in 1967, but in 1968 Albyn Tick and Herz Freya (averaging 6400 kg/ha) outyielded Maris Bead (5700 kg/ha). Yield in both seasons were substantially more than the national average yields for Britain (about 3000 kg/ha). In 1968, yields were 40% greater at 57 plants/m2 (7100 kg/ha) than at 36 plants/m2 (5100 kg/ha).

Yield was closely correlated with number of pods/plant. The number of pods/node regulated this rather more than the numbers of nodes forming pods. Mean seed weight and seed number/pod varied little between plant densities but variety means were significantly different.

Maximum numbers of immature pods were present in late June. By mid-July 35% of the immature pods had shed, mainly from the middle and top of the range of podbearing nodes.

Three short-term experiments on green-manuring are described. In the first, trefoil (T) and ryegrass given fertilizer N (RN) increased the yield of a following barley crop grown without fertilizer N by 500–900 kg/ha, but did not affect yield of barley given N. In the second, T and RN increased yield by 1400 kg/ha whether or not fertilizer N was given to the barley. Ryegrass without fertilizer N (R) had smaller effects in both experiments. The third experiment (with different treatments) suggested that the effect of trefoil was caused by the greenstuff turned in, not by any physical or microbiological change in the soil.

The effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments.

In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5–25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes.

In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (T1), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6·9, 11·0 and 15·2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9·3, 13·8 and 18·2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change.

A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

Thirteen field experiments were made during 6 years on seed-potato growing farms in south-east Scotland, comparing three rates, 70, 140 and 280 kg K/ha as potassium chloride and four rates of 0–54 kg Mg/ha as kieserite in 3 × 4 factorial experiments.

More than 70 kg/ha of potassium increased total yield only at one site, which had a recent history of low K application and very low available K. Yields were decreased by more than 70 kg/ha of potassium at three sites in a season with abnormally dry conditions just after planting. Applied magnesium had little effect on total yield.

Extra potassium increased ware yield but decreased seed yield, both consistently, probably because the fertilizer damaged some stolons at or before tuber initiation and fewer tubers developed. The ware/seed ratio was generally increased by extra K, but after the dry spring this ratio was unaltered or reduced. Applied magnesium had little effect on the ratio.

Our results suggest that the present rates of K fertilizer, used for commercial seed-potato crops (114–138 kg K/ha) in south-east Scotland are excessive, and a much lower rate of approximately 70 kg K/ha would be adequate except on very low K sites.

Growth rates, chemical composition of the body and wool production were measured with wethers and ewes from two genotypes of sheep grazing at two planes of nutrition. The nutritional treatments were applied after weaning at 12 kg live weight. Animals were slaughtered at 6 kg intervals between 12 and 54 kg live weight.

Dorset Horn × (Border Leicester × Merino) lambs grew 57% faster than South Australian Merino lambs before weaning, produced 22% more wool and contained more fat at weaning.

Post-weaning growth rates on the high and low planes of nutrition were 168 and 78g/day for Merinos and 183 and 116 g/day for Cross-breds. Despite these differences, there was virtually no effect on body composition. Sheep which were starved and re-grown also had a similar body composition to sheep grown continuously.

There was, however, a nutritional effect on wool production. On the high plane of nutrition the rate of wool production was 22% higher than on the low plane of nutrition.

After weaning there were only small differences in the growth rate of the two genotypes but the Merinos grew 30% more wool than Cross-breds on the high plane of nutrition and 39% more wool on the low plane of nutrition. Genotype differences in the fat and protein content of the empty body were small, but Merinos contained more ash, Ca, P and Mg.

After weaning the normal pattern of allometric growth was reversed; at 18 kg live weight the sheep contained a lower proportion of fat and higher proportion of water than at 12 kg live weight. Above 18 kg live weight normal allometric growth was resumed. The fat-free empty body became progressively less hydrated but the ratio of protein: ash remained constant at 79:21 for Merinos and 81:19 for Cross-breds.

There was a trend towards ewes being fatter than wethers, but this was only significant with Merinos. Other sex differences in body composition, body growth and wool growth were not significant.

Dry weight per unit area was related to plant density differences and leaf area duration (LAD) up to pod-setting (late June). Total dry weight and seed dry weight at maturity were not related to total LAD or LAD after pod setting. Seed yield at a node was closely correlated with leaf area at the same node (r = 0·67 to 0·94).

Differences in net assimilation rate (NAR) between varieties were not significant. A substantial rise in NAR in July-early August was attributed to additional photosynthesis by pods.

The project involved two breeds of Indian goats – Barbari and Jamunapari, three levels of energy and three levels of protein, making a total of 18 treatments. There being no specific recommendations for goats, the high, medium and low levels of energy (T.D.N.) and protein (D.C.P.) represented 125, 100 and 75% of Morrison's standard for sheep, respectively. A total of 97 Barbari and 87 Jamunapari does were allocated to the nine ration treatments and were bred within the breed naturally. The rations comprised a concentrate mixture (linseed cake and/or barley grain), dry roughage (gram bhusa), greens, mineral and trace-element mixtures and common salt. The effect of nutrition on reproductive performance, as revealed by the five and four kiddings completed in the Barbari and Jamunapari was as follows:

While the first kiddings did not indicate a sizeable effect, the subsequent ones showed a significant effect of nutrition. Almost all the does in the low-energy groups, irrespective of the protein levels, did not kid for the last kidding under reference.

The maximum percentage of twins was noted in high-energy-cum-high-protein (47·5%)and high-energy-cum-medium-protein (45·3%) groups of Barbari and Jamunapari respectively. The average twin-birth percentages, irrespective of nutrition, were 14·8, 37·3, 38·0 and 40·2 in Barbari and 9·0, 20·5 and 23·0 in Jamunapari respectively. Triplets, although rare, occurred within the Barbari but only one case occurred within the Jamunapari.

On average Barbari and Jamunapari had 2·0 and 1·5 kids per doe per year in the high-energy-cum-medium-protein group compared with 1·0 and 0·4 in the low-energy ones, respectively. Furthermore, high- and medium-energy groups had shorter intervals between kiddings compared with the low-energy ones.

Scottish Blackface ewes were used to investigate the effect of protein deficiency during pregnancy on serum albumin, globulin, transferrin and plasma urea concentrations. Twenty-eight sheep were offered one of two iso-caloric diets in amounts which maintained energy intake at levels comparable to those found in hill sheep during winter. For half of the sheep (HP group) the crude-protein concentration was 11·8% and for the remainder (LP group) 6·0% in the dry matter. A further six sheep (group CL) were offered a diet containing 16·0% crude protein in amounts which prevented undernutrition. Concurrent changes in plasma volume and in certain serum proteins during pregnancy were determined in a second experiment.

Serum globulins were not affected by protein intake and fell from 44·5 to 30·7 mg/ml during pregnancy. This was attributed mainly to a 30% increase in plasma volume which occurred during pregnancy.

Serum albumin concentrations at the end of pregnancy were 29·3, 22·0 and 17'7 mg/ml and serum transferrin concentrations 400, 307 and 300 mg/100 ml in the CL, HP and LP groups respectively. Initial mean albumin and transferrin concentrations were 28·0 mg/ml and 383 mg/100 ml respectively. The usefulness of the parameters as indices of the protein status of pregnant ewes was discussed.

Plasma urea N concentrations were related to the current protein intake of the animal. Mean values during late pregnancy were 26·0, 7'4 and 4·0 mg urea N/100 ml in the CL, HP, and LP) groups respectively. Limitations as to its usefulness were discussed.

Comparative slaughter was used to assess the effects of body-weight loss on Brahman cross (BX) and Africander cross (AX) steers of the F3 generation with respect to the empty body weight, the hot carcass weight and various offal components. Animals were slaughtered at design weights of 325, 341, 358, 374 and 390 kg, some while during positive body-weight growth (Group A) and others during weight loss from 390 kg at a rate of 0·5 kg per day (Group B).

AX animals had less empty body weight (B. B. W.) and dressed carcass weight (H. C. W.) at the same fasted body weight. Weight loss also reduced the amount of E. B. W. at the same fasted body weight but the effect on H. C. E. was not significant.

The breeds were very similar with respect to the various components of the offal, except that the AX had heavier heads. The weight loss treatment increased the proportion of the head, tail and feet, because these comparatively bony structures lost relatively little during the weight loss period. The heart was also relatively increased by the weight loss treatment. The liver, gall bladder, kidneys, total gut tissue, spleen and thymus were reduced relative to E. B. W. in Group B animals. The liver showed its most rapid weight loss in the early period of body-weight loss, being the only organ to show any variation in its rate of change during body-weight loss.

Body-weight loss caused changes in the distribution of the gut tissue, with a relative loss in the rumen-reticulum and a relative gain in the hind gut.

Four growth regulators were tested: N-dimethylaminosuccinamic acid (aminozide); N-pyrrolidinosuccinamic acid (F529); 2-chloroethyldimethyldodecylammonium chloride (JF2579); potassium 2(3-chlorophenylcarbamoyloxy) propionate (JF3072); all shortened stems. JF2579 and JF3072 were phytotoxic and lessened yield. Aminozide and F529 (tested in 1970 only) did not affect yield in 1970 but aminozide increased yield by 28% in 1971. Seed rates and row spacings had small effects on yield which varied with season. Growth regulators did not interact with seed rates or row spacing. Plant density and growth regulators had effects on yield via the number of stems and pods per stem. The effects of season on yield were greater and were caused via 100 grain weight. Speculative hypotheses are suggested to explain the different actions of season and treatments.

The relationships between joint and carcass specific gravities and composition are examined and the prediction efficiency of equations relating these parameters tabulated. The problems of assessing carcass composition in large abattoirs are indicated. The use of the tenth rib sample joint in conjunction with a specific gravity estimation technique is recommended.

In some plants the roots have been shown to be major sites of cytokinin production. The part they play in controlling growth and development of cereals was studied by spraying barley with kinetin solution and by changing the size of the root system. Two varieties of barley were grown in culture solution and kinetin was applied and root sexcised at the second-, third- or fifth-leaf stage. The kinetin in aqueous solution was sprayed on the leaves, and either most of the root-tips, or an equivalent weight of entire root strands, were removed. Kinetin increased both shoot apex development and the final ear size. The weights of the main shoot and the whole plant also wore increased, particularly by the later treatments. Removing entire root strands decreased the whole plant dry weight more than removing most of the root apices, but the main shoot weight was less affected. Kinetin interacted with root removal, though neither the interaction nor the main effect of root removal showed unequivocally that cereal roots are the site of cytokinin synthesis, possibly because new root tips were regenerated.

Forty merino sheep of mixed ages including lambs, ewes, wethers and rams were slaughtered and dissected. The chemical fat content often muscle groups in each sheep was measured directly and the mean value for the musculature of the whole carcass calculated.

A characteristic pattern of chemical fat deposition was shown with the intercostal muscle group and the abdominal group being consistently highest in fat content, the shin and hind-limb muscles lowest and other intermediate. The pattern of growth of intramviscular fat was consistent with differences in activity of the muscle groups in the maintenance of posture. It was postulated that variations in fat content in muscle groups are affected by differences in blood flow.

A highly significant relationship was established between dry matter and chemical fat content for each of the muscle groups. The regression was characteristic for each muscle group, and differed for most groups.

Regressions between individual muscle group fat and that of total musculature fat revealed that no group was consistently the best predictor of the total carcass musculature fat though there was considerable difference between the groups. It was concluded there is no group which could be used for prediction purposes commercially.

In a group of 14 other ewes subjected to weight loss up to 30%, and half of which were implanted with resorcylic acid lactone, no discernible effects on muscle group fat content were revealed.

Experiments were conducted on 12 male growing calves of zebu cattle (Bos indicus) and buffalo (Bos bubalis) to study the effect of feeding wheat straw presoaked with water on the voluntary feed intake, digestibility coefficients of nutrients and volatile fatty acid concentration and production. The feed intake was improved significantly (P < 0·05) in both the species as a result of soaking. The digestibility of crude protein and crude fibre was depressed (P < 0·05), whereas the nitrogen-free extract utilization increased significantly (P < 0·01) on soaking of straw. The availability of digestible energy and metabolizable energy was also more as a result of water treatment of wheat straw. The production rates of total volatile fatty acids and acetic acid were higher in both the species fed on water-soaked wheat straw. It is concluded that pre-soaking of wheat straw for 1–2 h with ordinary tap water may give an overall beneficial effect in both zebu and buffalo calves.

Several alternative statistical approaches to the analysis of genotype-environment interactions are summarized, and their inter-relationships are presented mathematically and graphically. An experiment was designed to test the ability of these analyses to satisfactorily describe genotype-environment interactions and to locate genotypes causing or contributing significantly to such interactions in a situation where environments differed in only one factor, i.e. soil nitrogen status.

Twenty-five lines of wheat were grown at each of 5 levels of applied nitrogen (0–270 kg N/ha) in a sandy, nitrogen-deficient soil, and their grain yields and yield components (ears per unit area, grains per ear, weight per grain) were determined. Designating the nitrogen levels as ‘environments’, linear yield responses, and deviations from linear responses, of individual wheat entries to environment mean yield were calculated according to the various statistical procedures previously outlined. The results suggested that the linear response to environment mean yield was similar for all wheat entries. However, further inspection of the data revealed that the responses of eight entries to environment mean yield departed significantly from linearity. Although several analyses satisfactorily identified these aberrant entries, classifying them as ‘unstable’, it was concluded that the degree of departure from linearity of response was not an adequate measure of instability. Furthermore, as previously suggested by Knight (1970), it was confirmed that the relative ranking of an entry for yield stability according to such a concept varied according to the average response of the group of entries with which it was being compared.

The general effects of applied nitrogen on yield components were to increase the number of ears and the number of grains per ear, and to decrease grain weight. However, only the first of these effects occurred consistently for all entries. The number and weight of individual grains per ear varied with the nitrogen treatment, often unpredictably, in a complex pattern which differed significantly between entries.

An experiment comparing six-course rotations which included 1-, 2- and 3-year leys of pure grass, pure legume and grass/legume mixture is described, and the results from the fifth and sixth phases of the first cycle and first and second phases of the second cycle are discussed.

Compared with all-arable cropping, the inclusion of leys increased the yield of barley grown as the second and third crops after the leys were ploughed up, although the difference was less when 58 kg N/ha had been applied. Neither length nor type of ley affected yield in the second crop after ploughing the leys, but in the third crop 2- and 3-year leys led to greater yield than 1-year leys.

Only rotations containing 1-year leys were compared with all-arable cropping in the fourth and fifth crops after ley, but some effects of these were still apparent in that both Italian ryegrass and broad red clover leys led to an increased sugar percentage of sugar beet grown as the fourth crop when no nitrogen was applied, and broad red clover leys led to a greater response to nitrogen in barley grown as the fifth crop after ley.

Photosynthetic electron transport, osmotic volume changes and protein loss on osmotic shock were measured in isolated pea chloroplasts after treatment with a range of aldehyde concentrations at various temperatures and times. ADP+Pi-stimulated oxygen production was the most sensitive to inhibition by the aldehyde treatment. With suitable conditions, osmotic volume changes could be prevented and protein losses on osmotic shock reduced to about 1% of the control value, whilst NH3-uncoupled electron transport retained about 40% of its activity. Results showed that basal, ADP + Pi-stimulated and NH3-stimulated O2 production could be used together to indicate the extent of chloroplast fixation thus providing a way of assessing fixation in preparations where osmotic changes are difficult to measure.

Glutaraldehyde (M.W. 100) was found to be 60–80 times as effective as formaldehyde (M.W. 30), on a molar basis, in preventing osmotic volume changes and protein loss on osmotic shock.

The application of this work for the production of large amounts of glutaraldehyde fixed chloroplasts and of fixed herbage for use as a tool in nutritional studies in ruminant animals is discussed.