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.

The effects of part, age and species of plant and some soil characteristics on the relationships between (a) sum of the cations (Σ cations)–% total N and (b) ratio of sum of the cations sum of the anions (R)–% organic N relationships in crops were tested in four experiments in the glasshouse. Crops were grown in soil and given four or five amounts of N03-N and sometimes a uniform dressing of other nutrients.

Results confirmed that there was a positive linear relationship between S cations in plants and their % total N when N03-N was supplied and the proportions of cations and anions entering roots from the soil solution (R values) were not constant but were in some way related to the elaborated nitrogen status of the plant, suggesting they may be linked with nitrogen metabolism. The cation-anion relationships were of the same general type regardless of the part of the plant that was analysed, its age or species, or of the type of soil in which it was grown. Analysis of leaves adequately reflects relationships in whole plants. Although the relationships had the same form with all species, dicotyledons had greater Σ cations and R values than monocotyledons at equal % total N and organic N respectively. Within the group of relationship curves obtained with different soils, at equal % total and organic N, 2 cations and R values were greater in grass grown in alkaline than in acid soil. Soil properties that affect the proportions of NH4-N and N03-N presented to plant roots probably have an important influence on the relationships. These cation–anion relationships in crops were not changed when yields varied greatly.

Two uniformity trials were carried out, one using S. 22 and the other Irish Italian ryegrass. In both trials the plants were grown at 6 in spacing and were harvested in basic units of 1 yd. If no allowance was made for guard rows the smallest plots were the most efficient in that they required a smaller total area of ground and fewer plants to detect a specified difference. For comparative purposes, the size of trial required to detect a difference of 7% of the mean was used. Allowing for 1 guard row round each plot, 2 yd plots were as efficient as those of 1 yd and had the advantage of requiring fewer replications. The effects of plot and block shape were considerable. In general long narrow plots in short wide blocks were more efficient. The choice of plot and block shape is most important. For a given plot size a poor shape may be less than half as efficient as a good one.

Data from 692 daughters of 38 Red Danish bulls, tested as heifers in the Danish cattle progeny testing stations 1963–64, were analysed to provide information on the efficiency of feed utilization by dairy cows. The results showed that because of, the feeding system adopted, efficiency measured as FCM per food unit was automatically closely related to FCM yield.

Analysis based on pooled, within-bull, values showed that (a) both efficiency and FCM were negatively associated with body-weight gain during lactation, suggesting that feed allowances per unit FCM were low in relation to those for maintenance, (b) weight measured after calving was positively associated with efficiency and FCM yield whereas the association of these latter variables with weight at the end of the winter period was negative, and (c) the gain in weight during lactation was much lower in cows heavy at calving and higher in those heavy at the end of the winter.

The between-bull correlations, although less reliable than the within-bull values, clearly indicated that the selection for FCM yield would result in increased cow weight.

It is suggested that the selection of dairy cattle should not be based solely on milk yield but that suitable adjustments should be made so that selection for efficiency is safeguarded. Quantitative assessment of such adjustments would necessitate changing feeding procedures at central testing stations.

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.

Groups of Awassi lambs, aged 7–13 months at start of the trial, were fed for 100 days on four different rations. A ‘control’ ration contained ground barley: the others contained different proportions of dried sugar-beet pulp, and no barley.

Male lambs were initially heavier, and gave better weight gains than the females. Groups on beet pulp grew better than the ‘control’. The most economical weight gains were obtained in the group in which beet pulp constituted 40 % of the ‘concentrate’ portion of the diet.

Sulphur content, expressed as a percentage of clean dry wool weight, was measured at monthly intervals in two breeds of sheep, Cheviot and Merino x Cheviot backcross (¾ Merino, ¼ Cheviot), offered an equivalent annual amount of feed in three ways—constant level, natural grazing cycle and reversed grazing cycle. The relationships between S content and wool growth rate or nutrient intake differed with both breed and nutrient cycle, but all the results could be explained satisfactorily on the basis of a constant optimum composition for each individual with sulphur impoverishment related to lack of balance between follicle activity rate and high-S substrate availability.

The difference in mean maximum S content between breeds (3·87% and 3·81% for Cheviot and ‘Merino’ respectively) was much smaller than the difference between individuals within the breeds (4·05·3·72% and 3·92·3·66%). The seasonal depression within individuals varied with nutrition and wool growth rate, Cheviot sheep showing the greatest depression and lowest values (2·89 and 3·28% for Cheviot and 'Merino, respectively in the reversed cycle group). There was no consistent seasonal trend in the relationship between clean and unscoured wool weight.

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.

Four barley varieties were grown in a greenhouse with varying levels of nitrogen fertilizer in two experiments. One experiment was sown in late September and received supplementary light, the other in March without supplementary light.

Varietal responses to nitrogen were essentially the same in both experiments. At low levels, differences in yield and protein content between varieties were small and inconsistent; at high levels, differences were pronounced and consistent. Betzes and Hannchen were highest in yield and lowest in protein, Palliser was intermediate in both, and Compana was lowest in yield and highest in protein. The results correspond with the known behaviourof these varieties under field conditions in Canada, except that Betzes yields more than Hannchen.

We suggest that relative potential yields of genotypes can be estimated under similarly controlled conditions.

Three years' data on a herd of Sudanese cattle were used to study the influence of sex and sire on their growth from birth to 1 year of age. The traits studied included body weights at birth, weaning and yearling ages, and body measurements at birth and weaning age. Analysis of variance indicated no significant sex by sire interactions. Male calves had significantly (P < 0.01) heavier birth, weaning and yearling weights and faster pre-weaning average daily gain than female calves. There were no statistically significant differences between sexes in post-weaning gain or body measurements. The sire effects were highly significant (P < 0.01) for birth and yearling weights and postweaning average daily gain, but not for weaning weight and pre-weaning average daily gain. Sire effects were also significant (P < 0.05) for height at withers and heart girth at birth and weaning age and for body length at weaning age. The heritability estimates of birth and yearling weights and post-weaning gain were relatively high, whereas the heritability estimates of weaning weight and pre-weaning gain were low.

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.

The interactions between nitrogen fertilizer and crop rotations in their effects on the yield of cotton in the Sudan were studied by superimposing fertilizer treatments on a rotation experiment which was already more than 30 years old. This experiment compared ten rotations comprising various combinations of cotton with fallow and an alternating crop of dura (a sorghum millet) and lubia (Dolichos lablab. L.). The results support the concept that low basic yields in the absence of a nitrogen dressing are primarily due to nitrogen deficiency. In general the response to nitrogen was greater on rotations which led to low yields of cotton so that rotational effects were greatly reduced or eliminated when a nitrogen dressing was given. Although in some cases cotton following fallow out-yielded cotton following dura, in general rotations containing dura and lubia gave higher yields of cotton than rotations with the same intensity of cotton cropping combined with fallows only. These beneficial effects of other crops instead of fallows in the rotation, although not in agreement with the long-term averages wereto be expected from the long-term trends in yields with time. Combined with the finding that even the most adverse effects of dura could be largely compensated for by a fertilizer dressing, this indicates that cropping in the Gezira could be considerably intensified without loss of cotton yield per acre per year. The difficulties of such intensification would centre around weed, disease and pest control rather than soil fertility. Further experiments are required to determine the fertilizer nitrogen requirements of cotton following different crops.

Two experiments designed to provide data for the estimation of functional relationships, which may be used to determine economically optimum plant populations and planting patterns in Desire'e potatoes, are described. Functional relationships between the number of main stems per acre and yield per acre were estimated from the results of experiment (i). Experiment (ii) investigated the relationship between stem number per tuber and seed tuber weight. ‘Square root’ functions estimated for seed yield and ware yield from the results of Exp. (i) were used to calculate a total Financial Returns curve. This returns curve, together with the Cobb-Douglas function estimated from the results of Exp. (ii), was used to calculate the stem numbers per acre, which would give maximum returns per acre and economically optimum returns in different cost/price situations.

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.

In a pot experiment providing for rapid growth of sorghum plants in the red clay loam soils of the Cotton Research Station, Namulonge, in the Buganda Province of Uganda, large yield increases were obtained from added phosphate. In an uncultivated soil which had carried undisturbed natural vegetation (Pennisetum purpureurn)for at least 10 years the response curve had negative curvature throughout. In an arable soil, yields without added phosphate were very poor and the response curve was sigmoid in form. With the arable soil, liming did not modify the form of the response curve for added phosphate but at the heaviest dressing lime decreased yield.

A sigmoid curve for response to superphosphate has been demonstrated in field experiments in a Buganda red clay loam. There was evidence that the curve was abnormal; with small dressings of triple superphosphate yield of cotton and beans, and their phosphorus uptake, were decreased, but these characters were increased with larger dressings. Heavy dressings, from 4 to 16 cwt triple superphosphate, increased yield of these crops. Similar effects were observed with maize during growth and maturity was advanced, but final yield of grain was not affected by applied phosphate. The suggestion is made that in a long growing period the maize was able to absorb adequate phosphorus, even though the phosphate intensity in the soil was low, to achieve its potential yield.

Three granular nitrophosphates containing 5, 26 and 50 % of their total phosphorus in a water-soluble form, granular potassium metaphosphate, Gafsa rock phosphate and basic slag (both as powders) were compared with granular superphosphate and powdered dicalcium phosphate as standards in two annual experiments with ryegrass and in three experiments with barley.

In 1960 total yields of ryegrass during a whole season were similar with all fertilizers. Nitrophosphate-5, Gafsa rock phosphate and basic slag acted more slowly than granular superphosphate and grass grew less well and took up less phosphorus during the first 12 weeks. Over the whole growing season more phosphorus was taken up by grass from powdered dicalcium phosphate and from granular potassium metaphosphate (0.5–2.0 mm) than from granular superphosphate (1.0–4.0 mm).

Powdered dicalcium phosphate was equivalent to about 60% as much phosphorus applied as superphosphate to barley. Rock phosphate was almost inert and percentage granular superphosphate equivalents of basic slag and potassium metaphosphate were 22 and 23% respectively. Percentage superphosphate equivalents of the granular nitrophosphates were 1, 25 and 53% and almost equal to the water-soluble phosphate they contained.

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.

The residual value of three nitrophosphates, potassium metaphosphate, basic slag and rock phosphate was compared with that of superphosphate in two experiments with potatoes, barley and swedes grown in rotation. The residual value of the fertilizers was also compared with that of (a) six cumulative annual dressings of superphosphate supplying either one-half or the same total amounts of phosphate and (b) single fresh applications of superphosphate applied once in each rotation. Yields and phosphorus uptakes are discussed in relation to the amounts of soil phosphate soluble in 0·5 M-NaHCO3.

In the first rotation residues of rock phosphate produced about 1 ton/acre less potato tubers than residues of other fertilizers and cumulative annual applications of superphosphate produced 0·6–0·9 tons/acre less tubers than all residues except rock phosphate. In the second rotation residues of fertilizers increased tuber yields less than cumulative dressings of superphosphate. Over two rotations mean yields from residues and from cumulative dressings were the same. Mean yields of barley over two rotations were 1–3 cwt/acre greater from residues than from cumulative annual dressings; the residual value of the different phosphates was the same. For swedes residues from the alternative phosphates, including basic slag and rock phosphate, were equivalent to those from superphosphate and gave the same mean yields as six cumulative dressings of superphosphate broadcast at planting.

Average residual values of alternative phosphate fertilizers, calculated from (a) yield response, (b) P uptake, and (c) soil analysis were: superphosphate, 100; nitrophosphates, 100–102; potassium metaphosphate, 95; basic slag, 94; Gafsa rock phosphate, 92. Mean percentage ‘fresh’ superphosphate equivalents of residues from all fertilizers were 17 and 26% after the first rotation and 11 and 15% after the second rotation for potatoes and swedes respectively.

The percentage of the total variance in crop yields accounted for by linear regression on NaHCO3-soluble P ranged from 38 to 70% for potatoes, 9 to 28% for barley grain and 42 to 92% for swedes. Mean yields of the crops increased by 0·24 ± 0·037 tons/acre (potatoes), 0·22 ± 0·08 cwt/acre (barley) and 1·16 ±0·148 tons/acre (swedes) for each ppm NaHCO3-soluble phosphorus in the soil at harvest.

Solubility products (pKsp) for iron and aluminium hydroxides and phosphates have been determined in a Buganda acid clay loam. Significantly greater values, i.e. lower solubility products occurred when determined at a soil:solution ratio of 0·4 than at 0–8. In the most acid soils, pH 4·8–5·0, values of pKsp) were consistent with the possibility that iron and aluminium concentrations were controlled by goethite and gibbsite. Above pH 5 the data indicated that these minerals were not effective. The maximum pKsp) value for iron phosphate was too small to be consistent with that for strengite, indicating that this mineral did not affect phosphate concentration in the soil; the maximum value for aluminium phosphate was consistent with that for variscite but the occurrence of this mineral cannot be deduced from the data. Triple superphosphate applied at 8 cwt per acre or less was converted within 2 years to a very insoluble form, having a solubility similar to that of variscite; with 16 cwt per acre the phosphate concentration was much greater than with the smaller dressings after this period and the soils appeared supersaturated with variscite.