Cultural standards and the husbandry techniques used on small farmers' fields are seldom the same as those practised on research and experimental Stations in the developing countries. The need for extensive agronomic experiments to be sited on small farmers' fields is emphasized. This method has been quite widely used with annual crops, but could with advantage be more generally adopted in perennial crops. Some of the advantages of this approach in agronomic investigations are illustrated by examples from work carried out in East Africa.

Effects of N, P and K on yields of cotton were investigated using data obtained over an 18-year period from a factorial experiment comparing various combinations of the three nutrients. The results clearly indicated a significant and fairly consistent response of cotton to the application of fertilizer nitrogen, but the rate of increase in yield with increased N gradually diminished. The response to P was erratic and to K was negligible. The response to N did not vary with levels of P or K. Whether lack of response to P on the alkaline soils of the Gezira was due to sufficient already available in the soil, or because the added fertilizer was fixed and rendered unavailable to the plant needs further investigation. Lack of response to added K was attributed to the high content of available K already in the Gezira soil.

Poor emergence of crops is common during the rainy season on the clay soils of the central Sudan. Arachis hypogaea, Sesamum indicum, Hibiscus cannabinus and Gossypium hirsutum were studied under a range of soil water and air-filled pore space conditions by sowing on earth ramps; these were covered with water which was subsequently drained either completely or so as to leave water standing. Air-filled pore space was estimated by air-picnometer and water content by oven drying. The conditions in the sloping beds were related to those normally found in experimental plots (using Triticum aestivum). When the effective air-filled pore space was as low as 10 per cent all crops emerged poorly. Sesame emerged well at 40 per cent and all others at 20 per cent. The best emergence was found when water was drained completely at the shortest interval included in the experiments, i.e. on the day after covering the beds.

Winter wheat seeds were grown on compressed soil (a) with and without smearing, (b) with surface horizontal or at 45°, and (c) with and without a sand cover. Germination was not affected. At a soil suction of 0·1 bar, root penetration of the horizontal surface was decreased by smearing and by absence of an overburden; on a surface of 45° smearing had very little effect. As a general summary of the limited information, root penetration is decreased by 50 per cent for a ten-fold increase in suction above 0·1 bar; the effect of smearing is equivalent to a five-fold increase; and the effect of slope is equivalent to a four-fold decrease.

In Queensland it is standard practice to burn sugar cane before harvest, but incomplete burns are common, due to the lush condition of the crop and the occurrence of weeds. Experiments conducted over seven seasons to dry out foliage of both weeds and cane, using bipyridylium desiccants, showed that paraquat was consistently more effective than diquat. After treatment of cane foliage, several days were necessary for fully effective desiccation, during which time a slight drop in sugar content could usually be detected. It is practical to spray cane leaves in the outside rows, adjacent to headlands (where weeds normally thrive). Treatment of this peripheral zone could affect no more than 10 per cent of a cane stand, and any loss of sugar would usually be more than offset by the benefits of desiccation, viz: a cleaner burn, quicker cutting, less trash, and fewer penalties.

Univariate analyses of variance of mineral nutrient contents of samples of first and third leaves from seven fertilizer experiments in East Africa gave only limited information. Principal component analyses were then carried out on the nutrient contents of the third leaves. The most important component represented a balance between nitrogen and the basic nutrients potassium, calcium and magnesium, the variation of which was often related to yield. The results suggest that yield responses are likely to follow fertilizer applications only when the ratio of nitrogen to basic nutrients is within a defined range.

In a 20 plot experiment with central composite second-order rotatable design, basal non-chlorophyllous sections of “D” leaves of Sugarloaf pineapples were sampled at harvest and analysed for N, P, K. Maximum yield of 17·8 tons per acre of good quality Sugarloaf pineapples and maximum fruit length of 27·4 cm. were associated with the nutrient combination of 36–42–32 lb/acre N P K applied at 4, 6, 11 and 12 months. The nutrient levels in the basal sections of “D” leaves corresponding to maximum fruit yield were 0·35–0·40% N; 0·04% P; 0·44% K; K/P 11·2–11·5: 1. K/P ratio for maximum fruit length was 10·4–11·5: 1. N/K ratio was associated with lodging.

In an oil palm uniformity trial in West Malaysia leaf samples were analysed and fruit type was recorded. Significant differences were found in foliar composition according to fruit type and it is suggested that this factor should be taken into account, together with other genotypic differences, in using leaf analysis as a guide to the fertilizer requirements of palms.

The rapid loss of viability in extracted cacao beans prevents long storage or long periods of shipment of selected seeds. Beans partially dried in a stream of carbon dioxide or nitrogen and stored at 25 to 28°C remained viable up to 60 days whereas those dried in air lost viability within 45 days. Storage of artificially dried beans in the absence of air was detrimental to their viability. A moisture content of about 50 per cent gave a high percentage germination within 30 days and reduced deterioration of beans.

Initial results of long-term trials in northern Nigeria indicate that deficiencies of potassium and trace elements, and soil acidity, may become important under continuous cultivation on some soils, in addition to the more common deficiencies of nitrogen and phosphorus.

Heritability of four quantitative characters in two crosses of Brassica campestris L. was found to be high. Dominance was detected only for plant height at heading time in both the crosses, and for sowing-to-heading period in Toria-TP × Toria-7. Transgressive segregation was expected in the segregating progenies for all the characters. Epistasis was complementary in all characters except in plant height at ripening time, where it was of the duplicate type. Additive × dominance type of epistasis was most significant and was present in most of the characters. Genes for most of the characters were linked with a major gene for seed colour (Rr). Yield was genetically correlated with the four quantitative characters studied.

The results are presented of an investigation into the use of very small plots for experimental work on maize (Zea mays) and groundnut (Arachis hypogaea), for the first three harvests of a project which is continuing. Despite the diminutive plot size, the random variation was quite low, resulting in a fairly sensitive experiment. The yield responses to increasing plant density were pronounced for both maize and groundnut, giving optimal spacings of 30 × 6 in. and 12 × 4 in. respectively.