The paper examines the statistical properties of criteria currently used to determine the distinctness of herbage varieties and suggests alternatives.

Investigations were carried out during 1976–80 on the alkaline alluvial soils of Daurala and Jullundur and on the acid hill soils of Simla and Shillong to study the effect of soaking non-dormant mother seed tubers in a solution of single superphosphate alone and in combination with urea, KCl, gum acacia and agromin (micro-nutrient mixture) on the tuber yield and P economy of the subsequent potato crop. On the alluvial soils, soaking increased the yield of daughter tubers but only on P-deficient soil. Increasing the period of soaking above 6 h and the concentration of superphosphate above 1·5% in the solution tended to reduce the emergence and tuber yield. On the acid hill soils soaking tubers for 4 h in a solution of 0·5% urea + 1·5% single superphosphate + 0·2% Dithane M-45 increased the yield of daughter tubers. Inclusion of KCl, agromin or gum acacia in the soaking solution had little effect. The increase in yield due to soaking was produced by an increase in number and size of daughter tubers and was equivalent to about 22 kg P/ha applied to soil.

A missing value technique for the analysis of data where repeated measurements are taken on each experimental unit is proposed. The method suggested, which is a natural multivariate analogue of the well-known technique for univariate analyses, fits those missing values which minimize the determinant of the sums of squares and products matrix and provides the necessary downward adjustment to the residual degrees of freedom. A simulation exercise provides evidence that the method is fairly reliable.

The relative importance of some sources of plant-to-plant root-weight variation in a field-grown carrot crop was investigated in two experiments sown in contrasting soil conditions but using the same seed lot and experimental design. In each experiment the following possible causes of root-weight variation were recorded on an individual plant basis: umbel order and size of seed, sowing depth, time taken for seedling emergence, length of cotyledons at emergence, distance to nearest neighbours within a row and row position within the seed bed. The relative importance of these differing sources of root-weight variation was assessed by determining how much of the variation in In (root dry weight) they accounted for at two harvests in each experiment.

In the first experiment, carrot seeds were sown in warm, moist conditions in May. These conditions gave a near-ideal emergence, 82% of seedlings emerging over only 5 days. Thirteen days after sowing, the most important source of root-weight variation, out of the variables measured, was position of the row within the bed. However, approximately two-thirds of the root-weight variation could not be attributed to any of the measured variables.

In the second experiment carrot seeds were sown in hot, drying conditions in July. The subsequent spread of seedling emergence extended over approximately 40 days. The total sum of squares of In (root dry weight) in this experiment was six times greater than the sum of squares in the first experiment. At 105 days, 61% of the rootweight variation in Expt 2 was accounted for by differences in time of seedling emergence. Differences in cotyledon length, measured when fully expanded, accounted for 24% and sowing depth differences accounted for 19% of the root-weight variation. Differences in umbel order, seed size and distance to the nearest neighbouring plants within a row never accounted for more than 8% of the sum of squares of In (root dry weight) in either experiment. Thus these variables were not important sources of rootweight variation. In contrast variables which affected the time of seedling emergence, such as sowing depth and physical conditions around the seed, were major sources of root-weight variation.

A simple technique to evaluate accurately the effect of mechanical stress on root growth has been developed. The roots are allowed to grow against a predetermined pressure in the chamber of a pressure-plate apparatus. The root growth was studied against the applied pressures of 0, 2, 4, 6, 8 and 10 bar. A relationship of the form Y = aXb was observed between the rate of root elongation (Y) and applied pressure (X).

This paper provides estimates of varieties × environments and plot error variances based on more than 1000 trials of varieties of oats, barley, wheat, perennial and Italian ryegrass, timothy, cocksfoot, potato, sugar beet, swedes, autumn kale, forage maize and field beans. Tables of critical differences and acceptance probabilities are presented to guide in planning future series of trials.

Calcium metabolism in dairy sheep was studied using radioisotope and balance techniques. The rate of calcium absorption increased, but the efficiency of calcium absorption decreased, with increasing calcium intake in dry sheep. Endogenous faecal and urinary calcium losses, and the rate of calcium absorption, decreased, but the efficiency of calcium absorption increased in pregnant sheep given a calcium-deficient diet. The rate and the efficiency of calcium absorption and the calcium balance of lactating ewes were not influenced by the prepartum level of calcium intake, when calcium intake in early lactation was high. Endogenous faecal calcium loss was related to dry-matter intake, and total faecal calcium loss was related to calcium intake.

Resistance to insects in cow peas was studied in a diallel cross and in a test cross. Number of pods and seed yield under unsprayed conditions, expressed as a percentage of their values under sprayed conditions, were confirmed as reliable characters for the assessment of resistance and as suitable for diallel analysis. Non-allelic interaction was not detected for these ratios despite its presence in yields. Resistance to flower damage by Maruca and resistance to all damage by post-flowering pests were both highly heritable and were controlled polygenically by alleles showing partial dominance.

The test cross was not as informative as the diallel cross in the analysis of the genetic control of resistance in a group of moderately resistant lines, but was useful in selecting the best of these for future crosses. The results from both schemes suggested that resistance should be accumulated by intercrossing resistant lines before attempting to transfer it to agronomically-preferred susceptible lines.

Response of rainfed barley to different methods of nitrogen application was studied on a loamy sand soil in 1974–5 and 1975–6. The nitrogen fertilizer was applied by broadcasting, side drilling, drilling below the seed and in solution. In a year of lower rainfall, applying the fertilizer below the seed or in solution produced significantly more grain yield than broadcasting or side drilling. In a year of higher and well-distributed rainfall, applying the fertilizer below the seed was significantly better than other methods of nitrogen application. The magnitude of the response to applied nitrogen increased with increase of crop season rainfall and its better distribution. Placing N below the seed improved water use. It was followed in order by applying in solution, side drilling and broadcasting in both the years.

The effects of including monensin in the diet on the dynamics of protozoa in the rumen of sheep were investigated using injections of protozoa labelled with 14C-choline.

The half time of rumen fluid was higher in sheep receiving monensin but neither the pool size nor the composition of protozoa species (mainly smaller entodiniomorph ciliates) was significantly affected.

More protozoa passed out of the rumen as liquid outflow rate increased and there was a tendency for the apparent production rate of protozoa to be higher with the resulting increase in washout of protozoa.

Various population improvement methods were applied to the spring-sown bulb onion crop. Synthetic populations were developed by recurrent selection, basing this selection on the performance of inbred lines per se for improved yield, bulb quality and storage performance. From the synthetic populations, partially inbred populations were also developed by half-sib selection methods. Results showed that gains, primarily in storage performance and marketable yield, were obtained in many of the synthetics. The mean gain in yield per cycle was of a similar magnitude to gains reported for maize using similar selection procedures although individual onion synthetic populations varied considerably in their achieved gains. Further gains in quality and storage performance, with no reduction in yield, were obtained by the development of partially inbred populations from the synthetics. These results are discussed in relation to the breeding of improved onion cultivars in the U.K.

A field trial of five contrasting types of white clover grown in monoculture was established in August 1978. Measurements commenced in October and continued for 12 months during which time no additional treatments were applied.

Seasonal trends of dry-matter accumulation and distribution were recorded and particular reference was made to the components of harvestable yields, which showed a strong seasonal trend. During the summer the density of growing points decreased in all types except D while the number of leaves per growing point and mean dry weight per leaf increased. The principal component of yield, mean dry weight per leaf, increased later than number of leaves per growing point. Stolons did not show the same cyclical pattern and produced an overall increase during the experiment. The five genotypes also showed large variation in the distribution of dry matter between leaves, flowers, stolons and roots.

The development of spring and winter barley sown in both the spring and autumn has been followed in two seasons. The rates of development were similar in both types for autumn sowings but the spring types developed faster in spring sowings. Differences in the rate of development were related to photoperiod and temperature although soil water stress modified variety response. Yields were higher from autumn and early spring sowings. Sowing in April resulted in a considerable reduction in yield. The significance of these results for barley breeders is discussed.

Selection for high-(H) and low-(L) drought-induced abscisic acid (ABA) accumulation in spring wheat was made from a cross between parents which contrasted in the character. By the F5 generation H and L selections were homozygous for ABA accumulation, which differed between the classes by 80%. The selections were evaluated in field experiments in which the amount of available water was varied.

In one experiment, in which plots were automatically sheltered from rain, H selections outyielded L selections by an average 0·36 t/ha both when fully irrigated and when water was withheld between anthesis and maturity. The extra grain yield of the H selections was not produced at the expense of additional water requirement in either treatment. When water was withheld during the 4 weeks preceding anthesis, the grain yields of H and L selections were similar, but H selections used less water between 1 May and maturity. Averaged over all treatments the ratio of grain yield to water use was greater for H selections than for L selections by 0·12 t/ha/100 mm. Withholding water caused a reduction in water use and a corresponding reduction in biomass production in both sets of selections.

In two trials in which plots were either irrigated weekly or received natural rainfall only, the ratio of grain yield to water use was again greater for H than for L selections, by an average 0·10 t/ha/100 mm.

It is concluded that in spring wheat, selection for high levels of ABA accumulation in response to water stress may provide an opportunity of increasing grain yield and water-use efficiency.

Two experiments were undertaken with maize silage, which had been sterilized by subjecting it to a 6 Mrad dose of γ radiation, inoculated with micro-organisms implicated in the aerobic deterioration of silage and subsequently exposed to air. The inocula employed comprised mixed strains of yeasts, bacilli and lactic acid bacteria and combinations of these. The changes which accompanied aerobic deterioration were observed. The major losses of fermentation acids, ethanol, ammonia and dry matter, and increases in total nitrogen and temperature were associated with inocula in which yeasts were represented. Similar changes of a lower magnitude were also observed in silage treated with inocula containing bacteria only, although these were not always accompanied by the growth of these organisms or loss of dry matter. However, when employed in mixed inocula with yeasts, the bacteria proliferated and tended in some instances to increase losses further, suggesting an association between the groups of micro-organisms in the aerobic deterioration process. Losses were also sustained in sterile silage which received no inoculum and the possible reasons for this are discussed.

The relationship between structure and the ability of piglet intestine to transport alanine has been determined during the first few weeks of postnatal life.

Villus length halved without change in crypt depth during the 3rd week of postnatal life. A similar shortening of villi, accompanied by an increase in crypt depth, took place when 2-week-old piglets were weaned on to a solid diet. Weaning piglets at 3 weeks increased crypt depth without causing further shortening of villi.

Alanine transport was shown, by quantitative autoradiography, to be largely confined to enterocytes in the region of the villus tip. The way in which this transport function developed was analysed further by fitting logistic growth curves to measurements of intra-enterocyte alanine concentration. The ability of enterocytes to transport alanine occurred earlier and alanine was accumulated to higher concentrations in enterocytes studied in 21- compared with 15-day-old unweaned piglets. Weaning piglets on day15 or 21 and measuring alanine transport 5 days later produced a pattern of development similar to that reported previously for adult animals.

Transport of alanine throughout postnatal development showed sodium dependency. Effects of alanine on intestinal short-circuit current of weaned piglets were again similar to those recorded in adult animals.

These results are discussed in terms of intestinal adaptation to a changing environment and in relation to the ‘notional capacity’ of a pig villus to transport amino acids during the early postnatal period of development.

Kale of normal and low S-methyl-L-cysteine sulphoxide (SMCO) content was produced by growing the same cultivar in soils of normal (20–30 mg/kg) and low (5–10 mg/ kg) soil sulphate-S concentration. Compared with normal S plots, kale grown in low S plots showed little or no reduction in D.M. yield or total N content, but contained lower concentrations of inorganic sulphate, SMCO and glucosinolates.

Replicated plots of normal and low SMCO kale were grazed by lambs for 12-week periods in two consecutive years, using a fixed crop allowance of 2·5 kg D.M./animal/ day. All animals were given injections of copper and iodine, and oral supplements of selenium, to ensure that effects upon animal performance could largely be attributed to differences in kale SMCO concentration.

SMCO concentration in the diet consumed by lambs grazing normal and low SMCO kale was respectively 0·60 and 0·35% D.M. Following the onset of kale feeding, all animals developed subclinical haemolytic anaemia which stabilized by week 6, and was more marked during weeks 1–6 than during weeks 7–12. Animals grazing low SMCO kale showed a less severe anaemia than those grazing normal SMCO kale, which was associated with lower blood concentrations of dimethyl disulphide and Heinz bodies, and higher reduced glutathione (GSH) and packed cell volume (PCV) levels. Liveweight gain and wool growth were greater for lambs grazing low than normal SMCO kale during weeks 1–6, corresponding to the period of most severe haemolytic anaemia, but during weeks 7–12 there were no differences between the two groups.

It was concluded that SMCO content depressed kale feeding value, with most of the depression occurring in the first 6 weeks of grazing, and that in these experiments the lambs were able to adapt to kale containing 0·6% D.M. as SMCO after 6 weeks of feeding. Endocrine factors involved in this adaptation are discussed.

Over a period of 3 years 18 autumn-calving, single suckled, April-weaned cows were stocked at three rates at pasture to gain 132, 70 or 25 kg (H, M and L respectively) between April and August and fed to lose 100, 54 or – 13 kg (H, M and L respectively) while housed between November and April, the relative total energy intake over winter being 0·64, 0·83 and 1·00 respectively. Milk yield was reduced by 2·68 kg/day on the H and 1·25 kg/day on the M treatment and as a result calves gained 37 and 10 kg less respectively over winter than on the L treatment. However, despite poorer calf performance economic considerations would indicate a preference for high weight gain during the grazing season and a corresponding loss over winter.

Wool growth rates (WGR) of individual sheep were measured by a patch-sampling technique, during periods of developmental growth, body-weight loss (which ranged from 21 to 34% of original body weight, at rates between 60 and 150g/day) and subsequent compensatory growth under ad libitum feeding.

There was a ‘lag phase’ of about 30 days before WGR appeared to be affected by changes in direction of the animals' growth paths.

During body-weight loss WGR declined about 300% more than the percentage change in body weight, with the duration of nutritional stress exerting a greater influence than the rate of body-weight loss.

During compensatory growth in body weight, the relationship between WGR and rate of body-weight change was initially negative. Sheep required between 11 and 14 weeks to reach the WGR of 21 g/day found during developmental growth. Compensatory growth of wool did not occur.

Duration of the nutritional stress, rather than its severity (as indicated by rate of body-weight loss), was the more important determinant of the time taken for the sheep to regain normal levels of wool growth after the commencement of ad libitum feeding.

Chaffed lucerne hay of 64% apparent organic matter (OM) digestibility was fed to wether sheep under four feeding regimens: two levels of dry matter (D.M.) intake (700 (L) and 1050 (H) g/day) and within each level two feeding frequencies (once a day (daily) and once an hour (hourly)). Three separate groups of sheep were used concurrently: a slaughter group was used to obtain feeding behaviour data and to measure pool sizes and obtain samples from the reticulo-rumen; a digestion group, in which each sheep was prepared with a rumen and a duodenal cannula, was used to measure duodenal digesta flow, rumen microbial growth and reticulo-rumen motility; a balance group was used to measure digestibility and nutrient balances.

High D.M. intake increased reticulo-rumen pool sizes and flow rates but it did not affect apparent digestibilities or the proportions of OM, fibre, cellulose, hemicellulose, lipid and nitrogen digested in the stomach and intestines. Increased feeding frequency had a major effect on reticulo-rumen pool sizes but did not affect apparent digestibilities or partition of digestion of non-nitrogenous constituents. Daily feeding resulted in increased total-N flow to the duodenum; however, N retention was significantly greater with frequent feeding. It is suggested that this was due to a more efficient tissue utilization of N.

The kinetics of digesta flow within the reticulo-rumen, expressed as fractional flow rates, were studied with data from sheep fed hourly. The fractional inflow, outflow and disappearance rates for OM, fibre, cellulose and hemicellulose did not change with an increase in intake because of an equivalent increase in reticulo-rumen volume. Increasing D.M. intake by 50% resulted in a 24% increase in water intake, a 19% increase in reticulo-rumen water volume, and a 49% increase in water outflow rate. The data suggest that the increased outflow of water was achieved by increasing the net flow of water across the mucosa into the reticulo-rumen, rather than by increasing salivation.

There was no difference between treatments in the frequency of reticulo-rumen contractions. It was calculated that for each A sequence contraction, OM flow was 0·26 and 0·37 g and water flow was 4·38 and 0·36 g on L and H intakes respectively. A 50% increase in intake resulted in a 42% increase in OM passage per A sequence contraction. This increased passage with intake was not accompanied by an increase in reticulorumen contraction frequency.