The problem to be considered arose in connexion with applications for plant breeder's rights. An applicant has to submit material for scrutiny by the authority, one aspect considered being uniformity. The applicant may wish to conduct a preliminary test, of the same type as the authority's, to allow a calculation of the probability of passing the regulation test. In both tests only a sample is examined and the population frequency of off-types remains unknown. It is assumed here that the authority sets a critical frequency (e. g. 0–01) and specifies a size of sample (e.g. 300). The result is regarded as a failure if the observed frequency exceeds the critical frequency (e.g. if more than three off-types are observed in a total of 300). Given that this is the test procedure it is possible to calculate the conditional probability of passing the regulation test, knowing the result of a preliminary test.

Crosses between nine inbred lines of diploid doublecut red clover were measured for corolla tube length and nectar height, caged with honey-bees, and observations made on the number of bee visits and seed yield. There was evidence of additive genetic variation in nectar height, corolla tube length, bee visits and seed yield. The possibilities for improvement in these characters by selection are discussed. Attention is drawn to a remarkable discriminating behaviour of honey-bees, in that they could apparently recognize plants which had only one parent in common. A cage with a strong colony of honey-bees produced more than twice as much seed as a cage with a weak colony, and plants near to hives gave significantly more seed than plants distant from hives. Plants of English origin tended to have higher and more accessible nectar, more bee visits and greater seed yield than plants of continental origin.

An experiment examined the interaction between nitrogen and irrigation on a sward of Lolium multiflorum (Italian ryegrass). Between rates of 100 and 200 units of nitrogen per acre, the response to nitrogen over the whole season was not increased by irrigation. Positive and negative interactions occurring in different periods cancelled each other out. Between rates of 200 and 400 units of nitrogen per acre, irrigation substantially increased the response to nitrogen, negative interactions being small relative to positive interactions. The results suggest that the moisture status of the upper few inches of the soil is an important factor in determining response to applied nitrogen. Response to nitrogen was increased when irrigation improved the moisture status of this zone.

Three sampling experiments were conducted to examine the effect of sample size and sampling intensity on the precision of dry-matter content and botanical composition estimates of perennial rye-grass-white clover herbage. One of these experiments examined the between-sample variability of these attributes and of dry-matter yield in relation to other sources of experimental error in a small-plot sward trial. The sample sizes examined were 800 g, 400 g, 200 g, 100 g, 50 g and 25 g green weight. In general the accuracy of dry-matter content and botanical composition estimates decreased with decreasing sample size. The between-sample variabilities of 25 g and 50g samples were high in relation to their between-plot variabilities. Single 100 g samples provided reasonably good estimates of these attributes and of dry-matter yield, but single 200 g samples provided a more satisfactory margin for error. Samples larger than 200 g appeared to be unnecessary. When weight-for-weight comparisons of single and duplicate samples were made there appeared to be little advantage in duplicate sampling. A theoretical examination of measurement inaccuracies inherent in the techniques used in small-plot sward trialssuggested that variation in plot length measurements in particular may make an undesirable contribution to the variability of such trials. A procedure for the conduct of small-plot trials is recommended. It is concluded that, where plot size and replication are limited, further improvement in the precision of such trials will not be readily attainable.

Carcass measurements were made on 24 Rambouillet lambs of different live weights but of the same age, and the lambs divided into 3 groups of 8 according to live weight. Group I, with the lowest mean live weight, had the lowest dressing percentage, relatively heaviest head and feet and lightest pelt, while group III, with the highest mean live weight, had the highest dressing percentage, the relatively lightest head and feet and the heaviest pelt of the three groups.

Group I contained the lowest percentage, and group II, of medium live weight, the highest percentage of muscle, while the relative weights of bone and fat tissue were similar. Group III contained the highest percentage of fat tissue and the lowest percentage of bone. The differences in the relative weights of the edible internal organs between the three groups were not significant.

Testis weight was relatively much greater in Group III than in the lighter animals. While dressing-out percentage increased with body weight, the increase was not equally distributed between fore and hindquarters. Hindquarters were relatively larger in group II than in group I; but the forequarters accounted for the greater part of the differences between groups II and III.

The amount of labile phosphate released in two soils from incorporated sheep dung (of two phosphate levels) was determined in a pot experiment. The inorganic phosphate in dung was initially highly available but it diminished in value after a period of contact with soil. The organic fraction of the phosphate had only small availability. A further pot experiment where dung was applied to the surface of the two soils indicated that, although dung phosphate may be readily available, its value for grass depends on the extent of dung/root contact.

Field and pot experiments were carried out to determine how copper deficiency can be corrected on some soils in north-east Scotland. Spring-sown oats and barley are more susceptible to this deficiency than mixed herbage, while potatoes and swedes have not responded to Cu. The deficiency can be corrected by applying 10–20 lb CuSO4.5H2O per acre to the soil. Both field and pot experiments show that such treatments have large residual effects and under field conditions are effective for at least 8 years. A foliar spray supplying 1 lb CuSO4. 5H2O per acre is usually less effective than a soil dressing.

Using soil undiluted with sand, the increase in grain yield produced by Cu treatment in pots was appreciably greater than in the field. The Cu content of mature oats and barley was practically unaffected by soil dressings but foliar spraying produced a considerable increase.

Significant correlation coefficients have been obtained between soil Cu, extracted by 0·05 M EDTA, and the increase in grain yield produced by Cu applications in both field and pot experiments. In field experiments in north-east Scotland, cereal yields were not restricted by a deficiency if the EDTA-extractable Cu was above 1·1 ppm. With soil contents below 0–75 ppm Cu, the grain yields from spring-sown oats and barley were usually increased considerably; small responses were possible with contents between 0·75 and 1·1 ppm.

Nitro-chalk was applied to S.23 ryegrass swards, at approximately monthly intervals, at two contrasting levels in 1961 and three levels in 1962. Steer calves, 3–6 months old, grazed in rotation round a series of four paddocks on each treatment. Paddocks were trimmed and fertilizer applied after each grazing. The herbage intakes of the calves were determined on three occasions in 1961 and four occasions in 1962. Faecal output was estimated by chromic oxide dilution. In vitro digestibility determinations were carried out on samples of herbage clipped from the swards.

There was a close linear relationship between the digestibility of the herbage and the amount eaten, over the full range of digestibility encountered (68–82%). Regression equations calculated within seasons and fertilizer levels, and within years, did not differ significantly. The regressions of faecal output on herbage digestibility were not significantly different from zero.

The observed relationship between herbage digestibility and herbage intake may reflect (a) the greater sensitivity of young ruminants than adult stock to changes in the digestibility of the diet, and (b) the reduced importance of the chemostatic control of food intake, except at very high levels of digestibility, in young rapidly growing animals.

An experiment begun in 1956 and using a five-course rotation of barley, grass-clover ley, potatoes, wheat and kale and a block of permanent grass was continued.

N decreased yields of the rotation ley, slightly increased yields of potatoes (after the ley), but greatly increased yields of wheat, barley and kale and permanent grass. P increased the yields of all arable crops, of kale dramatically, but not of permanent grass. K greatly increased yields of wheat and the rotation ley and even more of potatoes, but it increased yields of barley, kale and permanent grass little.

F.Y.M. increased the yields of all crops; potatoes responded most. Applying fertilizers with the F.Y.M. diminished its effects, but except for wheat and barley grain a combination of the two produced the largest yields.

Mean yields from all combinations of N, P and K were a little smaller between 1961 and 1965 than between 1956 and 1960, and the yields were maintained best by applying F.Y.M. and fertilizers together. Responses to N and to K were similar in both rotations, but responses to P became larger with time.

Yields and quality of herbage from a cocksfoot/white clover sward were compared over a 3-year period when cut repeatedly with a reeiprocating-blade mower to either 1 in or 2½ in from ground level or with a cylinder lawnmower to 1 in from ground level. The comparisons were made under two frequencies of cutting, namely five times per season at the ‘grazing’ stage, or three times at the ‘silage’ stage.

Cutting to 1 in from ground level with the reciprocating-blade mower gave a greater total yield of dry matter and crude protein than did cutting to 2½ in with the same mower in the first year, when the average dry-matter yield difference was 10·7 %, but no significant differences were recorded in subsequent years. It is suggested that the difference noted in the first year was due mainly to the harvesting at the first cut in the season of the layer of herbage between 1 and 2½ in from ground level, and not to any differential effects of the treatments on stem and leaf development of the cocksfoot.

Cutting to 1 in from ground level with the lawnmower gave smaller dry-matter yields than did cutting to 1 in with the reciprocating-blade mower at both stages of growth in the first year, but a slightly greater yield at the ‘grazing’ stage in the third year. The type of mower used affected the botanical composition of the sward.

Samples of a Colombian criollo breed of cattle, the Blanco Orejinegro, and contemporary onequarter Jersey crossbreds were kept on a farm in the Andes. Records were included of all calvings which occurred over an 8-year period, giving totals of 1357 lactations from 514 purebreds and 424 lactations from 137 crossbreds.

Age at first calving was about 41 months for both breed groups. Cattle were milked twice daily by hand without calf at foot. Mean lactation yields were 220 kg (purebreds) and 612 kg (crossbreds). The repeatability and heritability of milk yield are estimated. Statistics are also given for lactation length, daily yield, calving interval and butterfat percentage. The effects on yield of age at first calving and calving year were negligible, but month of calving was important.

It is concluded that the low level of performance was partly due to failure to eject milk without calf at foot, at least in the case of the purebreds, and that this was itself mainly due to genetic causes. The improvement in yield due to crossbreeding was not accompanied by a loss of other desirable traits. The development of the local cattle industry is discussed in the light of these results and the general characteristics of the region.

Differences in fatty acid composition and other body components were studied in two inbred lines of mice and crosses between them (reciprocals). The two inbred lines differed significantly (P < 0·05) in percentage moisture and percentage fat in the carcass, but there was no difference between the two kinds of crossbreds. Percentage protein of the carcass did not differ among the lines. Seven fatty acids were identified and considerable variation in the amount of each was found in the mice. About 65 % of the fatty acids identified was composed of palmitic and oleic. The two inbred lines differed significantly (P < 0·05) from each other for four of the seven fatty acids. The crossbred mice also differed for four of the seven fatty acids, but not necessarily the same acids as for the parental lines. Heterosis (crossbreds exceeding the mean of the parents) was observed for several traits. Crossbreds had a larger percentage protein and less fat in their carcasses than the inbreds. Crossbreds exceeded the inbreds for percentage lauric and percentage myristic acids, but had less palmitoleic acid than the inbreds. In general crossbreds had a higher percentage of saturated fatty acids than the inbreds.

Oestrogenic activity was recorded by teat length extension in wether lambs grazing red clover S. 123 in September and October 1965 and between 21 April and the end of October 1966. The number of lambs born alive to ewes grazing red clover (S. 123) for the 2 weeks prior to mating and for 4 weeks after mating was reduced. Oestrogenic activity was also recorded in wether lambs on lucerne var. Eynsford and on white clover S. 100 from mid-June to mid-October 1966.

Oestrogenic activity was confirmed in red clover, but not in lucerne, by mouse bioassay. Slight oestrogenic activity was shown in one white clover sample only.

Soil aggregates of different sizes, separated by sieving, and artificial aggregates stabilized by a chemical conditioner were used to study the effect of particle size on the uptake of nitrogen and phosphorus by plants growing in pots. Phosphate uptake was consistently less from the coarser than from the finer fractions of soil. The uptake of nitrate was also greater from smaller than from larger aggregates, despite its mobility in soil moisture.

Data collected from mid-pregnancy until the 5th week of lactation were used to select three nearly uniform groups each of nine ewes suckling single lambs. After 4 weeks of lactation, experimental treatments were applied to these selected groups as follows: Group I. Both ewes and lambs fed ad lib.throughout. Group II. Ewes fed ad lib. throughout. Lambs offered one-third the quantity of solid food being consumed by group I lambs. Group III. Food intake of ewes restricted to 9·2 g D.o.M./kg, based on their mid-pregnancy live weights. Lambs fed ad lib. throughout. The effects of these treatments were assessed in terms of milk production, food intakes and live-weight changes of ewes, and the solid food intake and growth rates of lambs. Mean total milk production of ewes of groups I and II remained similar until the 8th lactation week, but during the 8–12 week period milk production of the ewes in group II was 6·17 kg greater than that of ewes in group I. The data suggest this difference was due to a reduced intake of milk by the lambs suckling the ewes in group I during the weaning process. From week 4 the milk yield of group III ewes declined rapidly and though these ewes drew on body reserves for milk production, this process could not sustain milk yields. The average daily live-weight gains of lambs of groups I and III were both significantly greater than that of group II, and the gain of group I lambs was significantly greater than that of group III. All groups of ewes made similar live-weight gains during early lactation and after 4 weeks each group had attained a mean value of about 60 kg. Groups I and II continued to gain weight and during week 12 their respective mean weights were 67 and 65 kg. This difference was not statistically significant. The mean live weight of group III ewes declined rapidly after week 4, reaching a minimum value of 41·5 kg. The mean daily intake of dry matter by ewes of all groups reached a maximum value of about 2·9 kg/ewe in lactation week 3 and declined to about 2·6 kg in week 4. Intakes by ewes in groups I and II were almost identical throughout. During the period of restricted feeding the mean daily intake of group III ewes was 0·58 kg dry matter/ewe. During week 5 the mean daily intakes of solid food dry matter by lambs of groups I, II and III were 44, 32 and 158 g respectively. These increased to 1230, 418 and 1537 g respectively during week 12.

The incidence and distribution of haemoglobin types and potassium and sodium concentrations in whole blood of 411 Sudan Desert sheep and 11 Merino sheep were determined. Haemoglobin types were distinguished by electrophoresis in starch gel and blood potassium and sodium levels by flame photometry.

Of the 411 animals examined, 396 possessed haemoglobin B in the homozygous state while only 15 possessed haemoglobin AB. The homozygous AA haemoglobin was not detected. No bimodality was found in whole blood potassium and sodium levels and the distributions were normal.

Diallel crosses, without reciprocals, were made between two strains resistant to leaf curl and two susceptible strains as part of a breeding programme for leaf curl resistance. F1, F2, F3 and backcross progenies were studied. Results revealed that leaf curl resistance, previously described as polygenic, is controlled by a major dominant gene designated as Vr1. The presence of minor modifier genes was also indicated.