Wool-growth rates were measured at monthly intervals on eight free-grazing Cheviot wethers. Nutrient intakes provided by the upland environment were measured at the same intervals during the 2½ years. Analysis of periodic regression disclosed that both intake and wool growth had similar seasonal cycles but were slightly out of phase. It was concluded that the similarity was largely due to the relationship of both characters with some independent seasonal variable. The seasonal cycle of efficiency of wool growth depends on the time relationship between its two components, but it was found that variation amongst sheep in wool production was greater in the summer months and this depended more on variation in overall efficiency than on variation in grazing intake.

Three tests—two winter and one summer—involving 134 growing-finishing pigs showed no response to germicidal ultraviolet radiation. The pigs received no direct sunlight and were irradiated nearly continuously for periods of 54–70 days. Lamps with a 2537 Å output of 5·2 W were provided at rates of one lamp per 11·1 m2 in two tests and one lamp per 3·35 m2 in one test.

1. Data on the fresh weight, mineral and fat composition of foetuses from Border Leicester / Cheviot ewes were obtained for seven singletons, fourteen sets of twins and four sets of triplets. The age of the foetuses ranged from 80 to 144 days. The foetuses were dissolved individually in concentrated nitric acid and the mineral composition of the resultant solution determined.

Introductions of red clover indigenous to the Atlas mountains of North Africa were shown to have a high degree of resistance to Sclerotinia trifoliorum when a natural attack occurred in field trials at Cambridge. Differences between the two classes of clover varieties: (1) North African populations, and (2) the British varieties Essex broad red and S. 123, were highly significant for the proportion of row affected, the number of affected areas and the average length of affected area. The North African material is expected to be a useful source of resistance to Sclerotinia trifoliorum, in breeding programmes.

We are indebted to Mr H. H. Rogers for his guidance and for collecting the red clover plants during the 1962 North African expedition which was supported by the Agricultural Research Council. We also acknowledge valuable criticism of the manuscript and provision of a computer programme by Mr J. L. Fyfe and help with field records by Mr M. Pope and Mrs H. E. Pape.

1. The nitrogen content of an arable soil to 15 cm depth, sown to a ryegrass/white clover sward increased on average by 0·005 % N each year.

2. Under a grass sward without clover and without fertilizer nitrogen, there was an increase of 0·017 % N in 3 yeais in the top 7·5 cm of soil; an annual addition of about 70 kg N/ha.

3. Including white clover in grass swards not receiving nitrogen fertilizer resulted in an increase over 3 years of 0·026% N to 7·5 cm depth in one experiment, and 0·014% N to 15 cm depth in another, an annual increment of 100–110 kg N/ha.

4. The increase was greater under ryegrass/white clover swards than under cocksfoot/white clover swards. A similar difference was found both in accumulation of organic carbon and in clover content. In an experiment comparing many different grasses it was not possible to distinguish differences in the level of soil nitrogen, after 4 years under grass, which could be ascribed to species or strains.

There was no significant effect of nitrogen fertilizer applied at rates of up to 314 kg N/ha per year for 3 consecutive years.

In a factorial experiment on a mixed grass/clover sward, continued over 13 years, D.M. yields were strongly affected by N and K, which showed a marked interaction. P had very little effect on yield. There was evidence of a depressing effect on yield of continued application of KC1 at low rates of N input: this is thought to be due to excess Cl. It may be associated with the effect of Cl on clover growth, since it did not occur in predominantly grassy swards heavily dressed with N, in spite of high Cl content in the herbage.

The botanical composition of the herbage was strongly affected by the fertilizer treatments.

Urea nitrate, urea phosphate, and a mixture of urea phosphate and urea were tested as nitrogen fertilizers to find whether the presence of the anion decreases the damage urea causes to germinating seeds and seedlings and increases the efficiency of urea by preventing loss of ammonia.

Urea nitrate was compared with ammonium sulphate for grass grown in pots in the glasshouse and with ammonium nitrate for permanent grassland in the field. In the glasshouse, a large dressing of urea nitrate damaged the early growth of grass in sandy-loam soil. On average of sandy-loam and clay-loam soils with a small dressing of fertilizers, grass recovered similar amounts of N from urea nitrate and ammonium sulphate; with the large dressing it recovered less from urea nitrate.

In the field, 100 and 200 lb N/acre were applied to permanent grassland which was cut twice. The herbage was ‘scorched’ by the urea nitrate because its solution is very acid. Urea nitrate at 200 lb N/acre produced less dry matter containing less nitrogen than did ammonium nitrate.

Urea nitrate, urea phosphate and urea phosphateurea mixture were compared with ammonium nitrate for barley and grass grown in clay-loam and sandyloam soils. Tests were made of 33, 67 and 100 lb N/acre for barley and 100, 200 and 300 lb N/acre for ryegrass; the fertilizers were applied immediately before sowing. On the light Woburn soil early growth of barley was least good with urea nitrate, which also damaged the early growth of grass.

1. Data from eleven forages fed in digestibility trials were used to obtain statistical relations between organic matter intake (I), faecal dry matter output (F) and the concentration of nitrogen (N), copper (Cu), magnesium (Mg) and silicon (Si) in faecal dry matter.

2. Exploration of multiple regressions using all variables, and their products, gave a prediction relationship with four variables that was slightly better than that for nitrogen alone, as obtained by Arnold & Dudzinski (1963). FN and the products of(FN × FCu) and (FN × FSi) were the contributing variables. The eleven forages could not be brought into a single expression.

(1) In a 3×2 factorial experiment sixty Large White type weaner pigs (30 hogs and 30 gilts) were individually and restrictedly fed to 200 lb live weight, six diets (as wet mashes) containing 70 % of either maize, sorghum or barley, each cereal having been processed by either crimping or grinding prior to inclusion in its respective diet. A further two groups of six litter-mate hog pigs per group were used to measured the digestibility of and the nitrogen retention from these six diets at approximately 50, 110 and 190 lb live weight.

2. Grinding gave significantly better digestibility than crimping, the ground diets having significantly higher digestible energy contents than the crimped. Between cereals the order of significant decreasing digestible energy content was from maize to sorghum to barley dietary treatments.

3. There were no significant differences between cereals in nitrogen retention. Between processing treatments grinding, in terms of g. retained per kg live weight per day, gave a significantly higher value than crimping, at 107 lb live weight.

The effects of Nitro-chalk, superphosphate and potassium fertilizers on the chemical composition of grassland herbage and the removal of major plant nutrients have been traced over 14 years.

Without fertilizer N, but with adequate K, clover supplied a yearly average of up to 87 lb Nsol;acre. With an annual application of 348 lb N and adequate K, 237 lb of N was recovered annually.

Without applied P, herbage P concentration fell with time especially under heavy N treatment. When P was applied, herbage P concentration did not fall, irrespective of N treatment: K depressed P concentration irrespective of P application. Maximum removal of P occurred with annual applications of 348 lb N, 43 lb P and 280 lb K: at these rates gain and loss of P approximately balanced.

Herbage K concentration was greatly increased by K fertilizer. It was reduced by N when no K was applied but applying K counteracted this effect. Removal of K slightly exceeded the 280 lb of K applied when 348 lb N was also applied.

1. In experiments on potatoes and sugar beet, interplant competition for light was varied by altering the spacing distance between plants grown in containers, while competition for water and nutrients was eliminated.

2. In both experiments the relative growth rate was 10 % less in closely spaced plants because net assimilation rate was greatly decreased; leaf area ratio was increased. Increasing competition for light decreased mineral nutrient uptake.

3. It was considered that differences between the treatments in the intensity of competition for light was greater in these experiments than it normally in the field because differences in leaf area index were greater. The leaf area of widely spaced plants was smaller in these experiments than in the field; this was thought to be due to a more limited supply mineral nutrients in the former.

4. In both species, the greatest crop growth rates were observed at leaf-area indices well below the maxima attained. The likelihood that observed crop growth rates were near maximal under the prevailing environmental conditions is discussed.

1. The lengths and weights of 241 pig embryos, aged 26–109 days, were recorded; the pregnant sows were from a mixed herd of Landrace, Large White and Wessex stock and some of their crosses.

2. An empirical linear regression of length on age was estimated (equation 1); the relation between weight and age was represented by a polynomial weight and age was represented by a polynomial (equation 2).

We thank Mr A. S. Cray and the other directors of Unigate Ltd. for giving us the pigs; Mr P. Sedgewick of that Company gave us excellent co-operation. Prof. C. W. Ottaway and Dr P. Radford helped us throughout the investigation.

In crosses segregating 1:1 for normal: variegated inflorescences there was a consistent and statistically significant tendency for individuals with variegated inflorescences to be less erect than those with normal.

(1) Nine Scottish Blackface and four Merino × Cheviot ewes were shorn and given an acute cold exposure (at approximately −18 °C) in climate chambers. Individual exposures lasted up to 10 h. Because they were shorn, the sheep subsequently received 4 weeks of mild cold exposure, although kept indoors at an ambient temperature between + 8 °C and +15 °C. Skin and wool samples were taken before and after treatment. Twelve unshorn control ewes were also sampled.

(2) Wool production in the Blackface sheep was depressed following the treatment, and this was accounted for by a reduction in both the mean length and the mean diameter of the wool fibres.

A mean of 27·137( ± 2·634) × 109 sperm were found in ten epididymides from six Suffolk rams. This is substantially fewer than has been reported previously because fewer spermatozoa were found in the cauda. However, the total number is similar to that calculated on the basis of daily sperm production and testis weight.

1. Investigations of individual soyabean families over a 5-year period showed in some famines that the strain compounded in the F5 generation had a more stable environment × genotype interaction than the daughter strains compounded in the F6 generation.

2. Regression of each strain yield on an ‘environmental’ mean gave values for the slope of the regression line (bi), and the mean square of the regression (s2d) gave a value of deviations from the regression line. The values bi and s2d were used as estimates of stability.

3. Groups of F5 and F6 compounded strains were compared. Analysis of variance for yield over 5 years for twenty-four F5 compounded strains and twentyfour F6 compounded strains gave s2d value of 166·4 for the former and 289·1 for the latter. With 72 degrees of freedom for each group they differed from each other at the 1 % level of P.

4. Multiple correlation analyses were also done on the two groups of strains. It was concluded, all else being equal, that the F5 strains over a period of years would be less liable to give low yields in a bad year than the F6 strains.

1. Forty-five Friesian first calf heifers were used in an experiment to study the effect on milk production of two levels of feeding in the last 6 months of pregnancy and two levels of feeding in the first 8 weeks of lactation.

2. In each of two years herbage was rationed daily at different rates to two groups of pregnant heifers from late April until they calved in the autumn. The mean daily rations were 3·5 lb herbage dry matter and 2·4 lb herbage dry matter per 100 lb live weight for the two groups. The mean daily amounts consumed were 2·1 and 1·8 lb herbage dry matter per 100 lb live weight respectively.

3. The rates of gross live-weight gain during the period April to August were 2·2 and 1·7 lb/day for the two groups respectively. Estimated as the net gain of the dam alone, the rates of live-weight increase during the experimental period were 0·89 and 0·49 lb/day respectively, amounting to a mean difference in live weight after calving of 57 lb between the groups.

1. The infusion into the rumen via a cannula of 11. of aqueous solutions containing formic acid and/or histamine had no influence on the time sheep took to eat their food offered immediately after the infusion.

2. The infusion of formic acid solutions containing histamine into the rumen via stomach tube had variable effects when the length of stomach tube introduced was random. When they were introduced through 72 cm of stomach tube (measured from the incisor teeth), so that the end of the tube was at the cardia, one sheep consistently refused food or ate only a little but another sheep was only occasionally affected in this way.

3. Solutions marked with phenol red passed rapidly to the abomasum when introduced into the region of the cardia via a stomach tube. Only insignificant quantities of phenol red were detected within the same time in the abomasum when the solution was introduced into the rumen via a rumen cannula.