In sixteen factorial field trials with N, P, K, Mg, trace element and farmyard manure treatments, yields declined during the first four years of cropping following a resting period under grass, responses to K and farmyard manure increased, and other treatments showed no significant changes. After a few years of continuous cropping potassium deficiency may seriously limit yields, especially of sweet potatoes. N, P and K fertilizers maintained yields as well as the farmyard manure treatment.

In many instances measures developed for the control of coffee berry disease in East Africa have become less effective since 1961. Changes in the flowering and fruiting patterns of the coffee tree have recently become evident, ascribed in part to the onset of a wetter and cooler climatic cycle in 1961–62, and in part to the effect of the disease itself which, by removing crop, stimulates out-of-season flowering. Consequently, instead of a single main crop in which susceptible and highly infective ripe berries are present for a short time only, a series of over-lapping crops results in ripe berries being on the trees for most of the year. This has changed the disease epidemiology: formerly the main source of infection was conidia from the maturing wood, but now conidia from the berries are often predominant. This has greatly affected the efficiency of control measures, and means are suggested for restoring the previous situation.

Sisal was grown in double rows with broad-interrow covers of Pueraria phaseoloides, controlled volunteer vegetation or clean weeding. Clean weeding gave the best yield over one cycle, but Pueraria cover was best in the second cycle. Pueraria was better than volunteer vegetation in all trials, with the greatest margin on soils low in nitrogen, or where there were pernicious weeds. On an exhausted soil, sisal with a Pueraria cover responded to fertilizer nitrogen applied in the early or late part of the cycle. Manuring sisal growing with a volunteer vegetation cover with 50 tons sisal waste/ha. improved growth to the same extent as replacing the cover with one of Pueraria. In the absence of manures, yields declined from cycle to cycle with all the covers. At the level of manuring which maintained yields with a volunteer vegetation cover, yields declined slightly with clean cultivation, and improved considerably with a Pueraria cover.

The range, mean, genotypic and phenotypic coefficients of variation, heritability and genetic advance for various characters, of forty-seven varieties of ragi (Eleusine coracana) showed a wide range of variation and highly significant varietal differences. The genetic advance was highest for yield of straw and genotypic coefficients were higher than phenotypic coefficients for most characters. Path coefficient analysis indicated that the number of productive tillers and grain weight of main ears were the major components for seed yield.

Analyses of total N and P in coffee leaves from different geographic areas have been compared. The levels of these nutrients are correlated with each other and the quadratic regression equation for leaf N on leaf P has been derived. The value of N/P ratio in the coffee leaf for diagnosing nutritional status is assessed. No correlations were observed between Mg and either N or P. Irrigation of coffee in Kenya on latosolic soils raises leaf P but not N levels, in the absence of organic mulch and fertilizers. Effects of organic mulch, N and P fertilizers on leaf levels of N or P are discussed.

Potassium, calcium and magnesium in coffee leaves are presented as total K + Ca + Mg in dry matter and as percentages (proportions) of this sum. Brazilian coffee and leaf samples collected in different parts of Kenya generally fell within the normal ranges of values reported from the Kivu area in the Congo Republic. Data for Kenya coffee leaves are examined for the influence of season, cultural treatments such as organic mulch and fertilizers, and cropping level, on the concentration and balance of the nutrients.

Fifteen Australian and exotic wheat varieties revealed genotypic differences in their patterns of root development and drought tolerance. Earliness in plant maturity, which accounted for 40 to go per cent of the observed variation in drought tolerance, appeared to be by far the most important characteristic of tolerant genotypes, but there nevertheless appeared to be a measurable relationship between some parameters of root development, water use efficiency and drought tolerance. The impact of study of this kind on the problem of breeding for drought tolerance is briefly discussed.

Field trials were carried out using an aerial spray of Magniosan 55 (55 per cent magnesium nitrate) for the correction of severe magnesium deficiency in a Valencia orange orchard. Two treatments were applied, in autumn and spring respectively, each containing 50 l. Magniosan 55 solution in 200 l. water per hectare. The spray did not cause damage to fruit or leaves, penetrated satisfactorily into the lower and interior part of the canopy, and increased the Mg content of the leaves of treated trees from 0·095 to 0·190 per cent.