Field trials in Northern Nigeria have shown that the yield of introduced varieties of maize can be economically improved with combinations of nitrogen and phosphorus fertilizer. Three response areas have been defined. In the south, where most of the maize is grown, the initial response is to nitrogen. Further north, with the exception of one small area in which the response is almost entirely to phosphorus, phosphorus and nitrogen and equal limiting factors. Estimates of the most profitable combinations of nitrogen and phosphorus to use in each area have been obtained from quadratic response surfaces fitted to the yield data of the experiments.

Sorghum is the principal foodcrop grown in Northern Nigeria. A survey of local varieties grown during the rains was carried out in 1958 and the 821 samples collected were assigned to seven morphologically distinct races, of which four are important. Varieties belonging to the Guinea race, with loose, open panicles, are mainly cultivated in high rainfall areas south of latitude 11°30′N. Further north, three races, Kaura, Farafara and Chad are grown in the dry Sudan Savanna zone. Varieties of these races have compact panicles and bulging grains. Estimates of the contribution made by each of the four major races indicate that the Guinea race accounts for nearly 50 per cent of the total sorghum production in Northern Nigeria.

The importance of carotene supplements in the feeding of White Fulani Zebu cattle has been studied in three experiments. The live weight gains of heifers, with and without carotene on two planes of nutrition, showed 0·2 lb/head/day gain on the ‘high’ plane, but the ‘low’ plane group did not respond to carotene supplement. The association between cottonseed feeding and vitamin A deficiency, studied by comparing the rates of depletion of heifer calves on cottonseed supplements and on a sorghum/groundnut mixture, indicated that cottonseed can enhance the rate of carotene/vitamin A depletion in the liver. Carotene supplements equivalent to 2 oz red palm oil, to cows before and after calving failed to improve the vitamin A potency of milk. The total daily secretion of carotene and vitamin A in the milk was insufficient to maintain adequate liver stores in a suckled calf.

An investigation was undertaken on the relative tolerance to salinity of the olive varieties Manzanillo, Souri and Sigoise in the arid zone of Israel (Negev), in an experimental grove of the Jewish National Fund, using 11-year-old trees that were grown on saline and non-saline soils under irrigation with sewage water. Manzanillo was the most sensitive to salinity, yields and development of trunk, crown and root system all being adversely affected. Sigoise was the most tolerant to salinity and vegetative development was not impaired at all. Souri was intermediate in sensitivity to salinity. In spite of the susceptibility of Manzanillo it is preferred because of its high yield, which was greater even on a saline soil than yields of the other two varieties on non-saline soil.

Thirty Dorset Horn ewes were put to the ram four times in two years; four ewes lambed four times to produce 22 lambs, and 21 ewes lambed three times, producing 100 lambs with satisfactory birthweights. The minimum interval from parturition to conception was 32 days and there was no decline in the liveweight of the ewes. Another 37 ewes were run with a teaser ram from 1 January to 1 August 1964 (when it was replaced by a fertile ram) and from 15 April to 31 August 1965 when it was again replaced by a fertile ram. There was a marked decline in oestrual activity in Flock 2 from the middle of March until the middle of July.

The fixation of nitrogen in root nodules of pigeon pea, Centrosema pubescens and Styloxanthes gracilis were studied, and the transfer of nitrogen to other parts of the plant. Fixation reached a maximum of 14·5, 10·3 and 4·6 mg. per day per plant respectively, and the rate of transfer of nitrogen from the nodules was at a high constant rate throughout the experimental period. With pigeon pea and Centrosema younger plants seem to be more efficient fixers of nitrogen than older on, but the reverse was true with Styloxanthes.

Faeces of different birds and animals were analysed for sulphur and nitrogen. Chick faeces contained the highest amount of sulphur while farmyard manure gave the highest value for mineralized S after incubation. There was a high degree of correlation between the total S and total N.

Twenty strains of Eragrostis curvula, together with E. plana, Chloris gayana and Digitaria smutsii, have been compared on the basis of (a) herbage yields and (b) nitrogen, phosphate and potash composition and yield, from broadcast stands in a randomized block experiment over two seasons. The strains of E. curvula were grouped into types for which the names Curvula, Robusta Blue, Robusta Green, Robusta Intermediate, and Chloromelas were used. Significant differences were demonstrated in herbage yield between certain of these types, but there were no clear differences in nitrogen content. Chloris, Digitaria and the three Robusta types had the highest phosphate and potash content, whereas the Chloromelas type and E. plana were intermediate and the Curvula type was lowest in these constituents. Robusta Green, Robusta Intermediate and Curvula types had the highest nitrogen yield, Robusta Green and Robusta Intermediate types the highest phosphate yield, and Robusta Intermediate and Robusta types the highest yield of potash. The superiority of types other than Curvula (Ermelo and Tanganyika strains), and the need for research on the types, has been demonstrated.

Essential features are described of a computer programme, written in F.A.S., for the evaluation of 1 : 1 and 4 : 1 confidence limits of expected ‘twenty-day’ totals of rainfall. The paper deals briefly with the availability and utility of the programme to agricultural research workers in Africa.

The relations between plants and their water supplies are complex and there is no uniquely critical soil water deficit (i.e. no unique stage in the drying cycle at which growth and/or commercial yield begins to be significantly affected by increasing dryness of the soil). Evidence is presented that different deficits are ‘critical’ according to the type and depth of the soil, and the adequacy of nutritional supplies.

The problems arising in field trials in plant pathology and entomology are considered under five headings: (1) experimental design, (2) conduct of experiments, (3) records, (4) analysis and (5) interpretation. Solutions to the problems are not always given, but it is useful to recognize their existence. Examples are given from a wide range of crops