Simple mathematical models to predict leaching fractions and mean displacement depths of salts either uniformly distributed in the soil profile or surface applied have been derived from the solution of Peck's differential equation of salt balance. Predictions from these models are comparable with those obtained from Burns' equation and fit published data well.

Field experiments were carried out in the early and late growing seasons in the rainforest zone of Nigeria to find out the relationship between lodging, morphological characters and yield of maize.

Morphological characters associated with lodging were plant height, ear height and length of basal internode. There was a negative correlation between lodging and yield. Much of the lodging recorded, especially in the early growing season, was due to weak stems. Earliness, diameter of stem and leaf area had no relationship with lodging.

The effect of 96 h water deprivation on plasma proteins, blood and urinary electrolyte concentrations were studied in Barmer goats of the Rajasthan desert. The total plasma proteins, particularly albumin, increased significantly by water deprivation. Plasma potassium concentrations remained unchanged. The urinary K/Nu ratio increased considerably. There was a decrease in urinary sodium concentration after the 4th day of water deprivation.

A dry-block digestion system suitable for the estimation of total protein nitrogen in plant material has been evaluated. The method was found to be as accurate as Kjeldahl flask digestion, required much less fume cupboard space and enabled samples to be dealt with in large batches through weighing, digestion and analysis. The batch size can be designed to be compatible with the autoanalyser capacity. These advantages result in more rapid analysis with less chance of errors and accidents. A 45 min digestion period was found suitable for several crop species of widely different protein content, only field bean seeds required longer digestion time. Using the technique described samples are digested at a relatively low temperature (330 °C) for a short time and digests do not solidify on cooling. The autoanalyser method for determining ammonia concentrations in barley and malt digests (Micheson & Stowell, 1970) has been slightly modified for use with the plant materials studied. The dry-block and autoanalyser system is rapid, precise and compact, requires small amounts of tissue and is suited to the routine analysis of breeding material.

supplements of protected soya-bean–tallow were incorporated at 0, 1·7, 3·0 or 5·0 kg/day into a hay–concentrate diet and fed ad libitum to Friesian cows during the first 13 weeks of lactation.

Intakes of supplement during weeks 1–6 were 0,1·34, 2·25 and 3·18 kg/day and during weeks 7–13, 0, 1·64, 3·10 and 4·24 kg/day on each of the respective treatments.

As the lipid supplement increased there was a reduced intake of hay and concentrates, giving rise to reduced intakes of total, protein, and particularly ‘carbohydrate’ (non-protein, non-fatty-acid) energy. Apparent digestibilities, particularly of fibre, decreased as fatty-acid intake increased. After correcting for endogenous losses, true digestibilities of organic matter, carbohydrate, protein, non-fatty-acid lipid, total energy, calcium, magnesium and phosphorus were unaffected by the amount of supplement given, whereas fibre digestibility was reduced by increasing the supplement. Fatty acid digestibility was little affected up to an intake of 1·4 kg/day but above this there was a sharp reduction.

Yields of milk, milk energy, protein, fat and lactose were increased at low lipid supplementation but reduced at the highest supplementation when amounts of protein and carbohydrate digested were lowest.

Lipid supplementation reduced concentrations of rumen total volatile fatty acids in association with reduced, proportions of butyrate and. increased proportions of propionat. Plasma β-hydroxybutyrate and magnesium were reduced and plasma free fatty acids increased in cows given lipid supplemented diets.

There were no differences between treatments in plasma glucose, lactate or calcium nor in live-weight changes.

During the period 1962–73, the majority of the 92 lactations of imported British Friesian animals were initiated during the dry season (October–March). The following average values were obtained: lifetime number of lactations, 4·5; lifetime milk production, 9392 kg; age at producing first live calf, 39·6 months; milk yield of nine lactations, 2159 kg; lactation length, 336·5 days; daily milk yield, 6·3 kg; 305-day milk yield, 2012 kg; dry period, 173 days.

Milk production was highest in the fourth lactation when the animals averaged 7 years old. Differences in milk yield among lactations were small. Peak daily milk yield was greatest in the third lactation and was reached within the first 21 days of each of the first four lactations. A second but lower peak with the highest milk production persistencies at a later stage of lactation apparently depended on feed availability. The 305-day milk yield was reasonably predicted from the 100- and 200-day yields.

Lactations subsequent to abortions and stillbirths were slightly longer, gave less milk (P > 0·05) and were followed by longer dry periods than those initiated by normal births.

During the first 13 weeks of lactation, four groups of seven cows were given hay and a basal concentrate mix containing 0, 1·7, 3·3 or 5·0 kg/day of a protected lipid supplement (320 g long-chain fatty acid/kg D.M.). The proportion of hay to total concentrate was maintained at 25:75 and cows were fed to appetite.

The total amount of energy digested corrected for endogenous loss (DEc) was partitioned into crude protein energy (CPEc), fatty-acid energy (FAEc), ‘carbohydrate’ (non-protein non-fatty acid) energy (CEC) and non-fatty-acid energy (NFAEc = CPEc + CEc).

Partial efficiency of milk production and live-weight gain was curvilinearly related to FAEc, maximum efficiency occurring at about 30 MJ/day of FAEc.

Net energy utilized was significantly related to DE0c for both of the periods considered, Weeks 2–6 and weeks 7–13. In addition, a curvilinear effect of the ratio of fatty acid energy to non-fatty-acid energy was established. At fixed intakes of digestibl energy, net energy utilized was maximal for ratios of FAEc/NFAEc of 0·14 and 0·18 for weeks 2–6 and 7–13 respectively.

Milk yield was significantly related to DEc for weeks 1–6 and 7–13; milk energy yield was significantly related to DEc for weeks 7–13. The multiple regression relationships between milk yield or milk energy yield and CPEc, FAEc and CEc gave a negative effect of crude protein, possibly indicating that the proportion of total energy supplied as crude protein (18–26% of DEc) was above the optimum requirement.

At fixed intakes of digestible energy, outputs of milk and milk energy were maximal at ratios of FAEc/NFAEc of 0·16 and 0·15 for weeks 1–6 and 7–13 respectively. The inclusion of a curvilinear effect of total energy (DEc2) gave some indication that utilization of energy for milk production for weeks 7–13 diminished at the highest digestible energy intakes whilst energy utilized for live-weight gain increased.

Five experiments were made to observe the effect on nitrogen (N) utilization by young cattle of supplements of sucrose, glucose monohydrate (dextrose), and maize starch when added to basal diets of concentrates and straw. The supplements provided about 12% of the total intake of air-dry food. Twenty-four yearling Friesian heifers were used in each of two randomized block experiments to measure live-weight gain, and 6, 10 and 10 yearling Friesian steers in three changeover design experiments to measure N retention.

Rates of live-weight gain and N retention were increased by all the supplements amongst which no order of superiority in benefit conferred could be established. The improvement in N retention was associated with a marked reduction in urinary N and a small increase in faecal N with supplemented rations.

The proportions of volatile fatty acids (VFA) in rumen fluid were not affected by starch supplementation. Both sugars, but glucose more than sucrose, decreased the ratio of acetic to propionic acid, measured 2 h after feeding.

Statistically significant multiple linear regression equations were observed between N retained and intakes of N and digestible organic matter (DOM), both as absolute amounts with live weight as a further independent variate, and as intakes/unit metabolic body size. N2 and DOM × N as additional variates did not benefit the fit of the equations over the range of intakes studied.

Agricultural research now has a long tradition of being served by statisticians, both those who are professionally trained and others who (in no derogatory sense) may be described as amateurs because their primary scientific training is in some other discipline. This paper urges that, as part of good research management, more attention be given to the numbers of statisticians needed and the responsibilities they should undertake.

Questions to be considered include not only ‘Who should analyse specified bodies of data?’ but also ‘Which data require full statistical treatment?’. Poor judgement here can mean that the pattern of statistical activity is governed by the forceful approaches of other scientists more than by the scientific content of a problem; moreover, statisticians may be left with no time for the vital tasks of collaborating with others in the planning of research and displaying initiative in new approaches to quantitative problems. Not all research institutes have yet made their statisticians collaborators and partners in research rather than technicians with sharply delimited duties.

Agricultural statisticians today should be deeply involved in research in cooperation with other disciplines, as innovators in statistical technique, and to some extent in development of statistical theory. They must be encouraged to publish, as partners in research teams and individually, to produce and document computer programs that implement methods required in agricultural research, and to improve statistical understanding among their colleagues in other disciplines. They are scientists whose responsibilities and rights are equivalent to those of other disciplines but need to be interpreted in relation to the research role of their subject. This paper asks for their proper integration into agricultural research, and not for special privilege.

Three field experiments in 2 years were made in S.E. Scotland to investigate the effect of water (normal rainfall or irrigation to maintain soil moisture tension between pF 2·0 and 2·5) on the response of the potato crop to nitrogen fertilizer (0, 100, 200 or 300 kg N/ha).

Final tuber yield was closely related to leaf area duration. Addition of water reduced the delay in early haulm growth resulting from fertilizer nitrogen application. The beneficial effect of reducing moisture tension could not be related to water per se, nitrate, ammonium or conductivity levels in the fertilizer band or nitrogen uptake. Accumulation of nitrate in the roots and stems + petioles early in the season indicated that the rate of protein synthesis was reduced at high soil moisture tension in the presence of fertilizer nitrogen.

In a long growing season (1971, 153 days) there was a significant response of tuber yield to nitrogen, with an increase in yield even at the highest rate tested (300 kg N/ha) and irrigation enhanced this response.

In a normal season (1970, ca.130 days) there was a significant irrigation x nitrogen interaction on tuber yield. Irrigation increased the optimum rate of nitrogen from 100 to 200 kg N/ha in one experiment and from nil to 200 kg N/ha in another.

Addition of water increased the number of tubers at harvest but the effect of nitrogen was less consistent. Yield increases resulting from application of nitrogen or reduction in soil moisture tension were mainly due to increases in the proportion of large tubers.

Four hay-fed cows were used to study the effects on chewing behaviour of daily supplements of 3 kg whole barley grains, 3 kg whole oat grains or 2·2 kg rolled oats. Both whole grains increased the total time spent chewing by a similar small extent, probably due to a direct physical effect of the grain. The quantity of whole oat grains voided in faeces was lower than that of barley and it is concluded that the quality of chewing is more important than duration in breaking grains and ensuring their subsequent digestion.

The responses of Stylosanthes guyanensis (Stylo) to frequency and height of cutting and the effects of feeding increasing amounts of stylo meal on egg production, yolk vitamin A, yolk colour and percentage hatchability were studied. In the agronomic study, the higher the cutting height, the higher the total yield of dry matter, yield of crude protein, yield of carotene, percentage of crude fibre and the lower the carotene and crude-protein content. A highly significant correlation between the carotene content and crude-protein content (r = +0·91) was obtained.

The addition of stylo meal as more than 10% of the feed significantly (P < 0·01) depressed egg production. On the other hand, yolk colour, yolk vitamin A status and percentage hatchability were significantly improved with the feeding of stylo meal.

Data are presented from 104 sheep from three separate sources (batches) in which variation in the degree of maternal body protein loss was induced by nutritional means. The change in body protein content during pregnancy was calculated as the difference between body protein content in early pregnancy, predicted from the relationship with body weight in control sheep killed in early pregnancy, and actual content on slaughter at parturition. Serum albumin and globulin concentrations and body weight were measured at intervals during pregnancy and examined for relationships with body protein change.

Highly significant linear relationships were found between the change (%) in albumin concentration during pregnancy or albumin concentration in late pregnancy and the calculated change (%) in maternal body protein content (P < 0·001 in both cases) though fitting separate intercepts for each batoh of sheep led to improvements in fit.

Equations for prediction of loss (%) of body protein from change in body weight or maternal body weight during pregnancy though significant, were also improved by fitting separate intercepts for batches. The relative value of the relationships for predicting body protein loss is discussed.

Serum globulin concentration was not affected by protein status of the animal.

An analysis of variance is developed for data from an incomplete mixture diallel experiment, where one subset w of the p genotypes are not grown together in mixtures. Estimation procedures and tests of hypotheses concerning relative yield totals and aggressivities are discussed, and an example is presented.

The production of flowers in perennial ryegrass (Lolium perenne) has been associated with a reduction in root relative to shoot growth and the post-flowering period with the death of roots. Any effect that reproductive development has upon the root system does not appear to adversely affect subsequent shoot growth. In the present experiments, vernalized plants restricted to root axes present prior to flowering showed little difference in herbage production and length of life compared with unvernalized plants similarly restricted. Flower production did, however, limit the ability of plants to initiate main root axes. It would seem unlikely that the mid-summer depression of herbage growth is due to the effect of reproductive development upon the root system.

The least-squares means for first lactation milk yield, yield per 100 kg of body weight at first calving, yield per day of first lactation length, yield per day of first calving interval and yield per day of age at second calving were 1692 ± 28·2, 339·8 ± 7·30, 5·51 ± 0·97, 3·37 ± 0·81 and 1·07 ± 0·03 kg and the heritabilities of those traits were 0·192 ± 0·086, 0·078 ± 0·078, 0·287 ± 0·096, 0·192 ± 0·086 and 0·305 ± 0·097 respectively. The genetic correlations of first lactation milk yield with various measures of efficiency of milk production (except with yield per 100 kg of body weight) were positive and high (> 0·80). These results indicate that milk yield per day of age at second calving may be used for the selection of buffaloes.

In t h e four production areas studied the gross energy contents of the biomass of the U.K. and Californian sugar beet crops were about 222 GJ/ha/year, while those for the Queensland and Transvaal sugar cane crops were about 682 GJ/ha/year. Recoverable sucrose constituted about 45% of the gross energy yield in the sugar beet crops but only about 29% in t he sugar cane crops, largely due to the bagasse (fibre) present in the cane. Since the sugar cane bagasse was used as fuel it provided nearly all the energy for the production of raw sugar from the sugar cane crops, but sugar beet by-products supplied no energy for t he production of sugar from sugar beet. This difference between the two species was the main reason why the support energy required for sugar production from beet, 28·8 GJ/t sugar, was greater than for production from sugar cane, 10·5 GJ/t sugar. The ratios, energy in refined sucrose:support energy required for its production, were 0·60 for sugar beet and 1·60 for sugar cane.

The efficiencies of conversion of the photosynthetically active solar radiation incident on the crops into energy in biomass (excluding fibrous roots) were 1·2% for sugar beet and 2·0% for sugar cane. This difference in efficiency did not appear to be due to a consistent species difference in the proportion of t he radiation intercepted by the crops, and may have been a consequence of the more efficient photosynthetic carbon fixation mechanism in sugar cane than in sugar beet. The efficiencies of conversion of incident photosynthetically active radiation into energy as sucrose recovered from the plants showed no consistent difference between species and averaged 0·56%.

Tri-w-butyl phosphate has previously been shown to increase the drying rate of cut grass leaves. It also markedly inhibited respiration and thus reduced loss of dry matter during drying. In the work reported here, some other commercially available phosphate esters were tested for the same effects, except for the inhibition of respiration. Four mixtures of ethoxylated phosphate esters increased the drying rate of excised S. 24 perennial ryegrass leaves, and three of these also reduced the loss of dry matter during drying.

The results suggest the possibility of devising single chemical treatments for both increasing the drying rate and reducing the respiration rate of forage crops conserved by drying in the field. The potential advantages of such treatments, together with the difficulties of realizing these advantages in practice, are briefly discussed.

External balances of water, sodium and potassium were examined in carpet wool Chokla sheep given water once in 24, 48 and 72 h during the hot months. There was a significant decline (P < 0·01) in feed intake on the third day of dehydration. The water intake of this group approached 30% of body weight and there was also a significant (P < 0·05) decrease in urine volume after 2 days of water deprivation. There was a large balance for potassium in all treatments and most especially when the sheep were given water every 72 h. It is argued that this unusually high balance of potassium was probably a characteristic of sheep adapted to a hot climate.

Evidence was sought for genetic differences in the absorption or systemic use of copper by comparing responses in plasma Cu concentration to oral and intravenous Cu repletion. Lambs of the North Ronaldsay (Orkney), Scottish Blackface and Welsh Mountain breeds and crosses of these with the North Ronaldsay were used.

In two oral repletion phases average Cu intakes/kg live weight were 0·87 and 0·63 mg/week and similar for all breed groups. Plasma Cu concentrations of Scottish Blackface lambs showed little or no increase while those of North Ronaldsay lambs increased rapidly, and those of Welsh Mountain lambs increased moderately. The plasma Cu concentrations of the cross-breds increased more rapidly in the first than in the second phase; their rate of change lay between the pure breeds but was closer to that of the North Ronaldsay in the first phase.

The rates of increase in plasma Cu concentration during intravenous repletion were relatively uniform for the different breeds and crosses except the Blackface which showed a lower rate. It was concluded that the large differences between groups in response to oral Cu repletion were largely attributable to differences in the efficiency of Cu absorption.