Chemical weed control in six root crops and fourteen vegetable crops, commonly grown in the tropics, is reviewed.

The general principles of leaf analysis as a diagnostic method and as a guide to plant nutritional status are outlined and discussed. Factors, other than nutrient supply, that affect leaf composition are mentioned and methods of leaf sampling, preparation and storage are described. The practical application of leaf analysis to fruit, flower, vegetable, tree and miscellaneous economic crops is reviewed and suggestions are made for its use as an advisory aid.

The weights of the branches, stems and roots of two or three year old arabica coffee trees were compared with the diameters of the stumps or stems and with the heights of the trees. No formula could be derived, relating the weight of the plants to one or more non-destructive observations, which was valid for all three treatments to which the trees had been subjected, i.e. stripped of crop when two years old, cropping when two years old, and bearing a crop when three years old. Bearing a crop when two years old resulted in thin, light stems and a poor root system.

Although bambara groundnut (Voandzeia subterranea) is an important pulse crop in Africa and particularly in Ghana, information on the crop is not only very limited but conflicting, especially as regards flowering and mode of pollination. Both self- and cross-pollination can take place in varying degrees, depending on variety or strain, and this is brought about by two species of ants, Pheidole megacephala and Monomorium pharaonis, without which pollination might be severely limited or prevented altogether. The extent of cross pollination may be greater in varieties or strains with a more open habit, i.e.. varieties resembling the wild uncultivated ancestors, whereas the bunch cultivated types are more likely to be self-pollinated. It is suggested that varieties or strains may show differences in their ability to cross with one another.

In 1963 and 1964 a total of 290 cotton trials, 78 groundnut trials and 51 finger millet trials were conducted on small farms in Uganda to determine the effects and profitability of applying ammonium sulphate and single superphosphate under local conditions. The organization and methods of these trials are described and their results discussed. Ammonium sulphate gave highly significant increases in millet and cotton yields, whilst superphosphate produced similar results on groundnuts but was less effective on cotton and unprofitable on millet. Recommendations are made for groundnuts and millet, but a further season's results are thought necessary before recommending fertilizer treatments for cotton. Soil and leaf samples were taken from the trials and analysed, and relevant agronomic field data were recorded. The correlations of these factors with trial yields and responses are discussed. In general, soil and leaf analyses have been disappointing in assessing responses to fertilizers, but these responses tend to be greater where better farming is practised.

Castor beans grew well in sandy soils in U.A.R. where field crops had previously failed to produce good yields. Calcium nitrate up to 300 kg. per feddan resulted in increased yields of seeds and oil in a two-year experiment. Better yields were obtained by increasing the number of plants up to 3 per hill at distances of 45 cm. apart. The oil percentage and other properties were not influenced by nitrogen fertilizers or plant density.

The yield and soil data are presented of four long-term experiments on sugarcane at Muzaffarnagar (Uttar Pradesh), Anakapalle (Andhra Pradesh), Padegaon (Maharashtra) and Shahjahanpur (Uttar Pradesh). On soils where phosphorus and potash were not limiting, application of ammonium sulphate over 14 years at Muzaffarnagar and Anakapalle gave higher yields than those obtained by application of farmyard manure, and the fertility status of ammonium sulphate plots was in no way inferior to plots treated with farmyard manure. When phosphorus was also limiting, the application of a basal dose of compost on black cotton soil maintained yield levels. There was a steady decline in yields of cane in plots which received a dressing of ammonium sulphate without any basal dose of compost, but when N.P.K. equivalent to the compost were added the yields were equal to those from plots receiving compost. Thus the effect of compost is explanable on its nutrient content rather than on its effect on physical properties of the soil. In Shahjahanpur there was a decrease in cane yield as the experiment progressed, but the decline in yield in ammonium sulphate treated plots was of the same magnitude as from the plots receiving no dressing of ammonium sulphate. By changing the cane variety and the rotation simultaneously, the yield from all plots went up but subsequently showed a declining tendency.

Cocoa was used as a test crop to compare the use of nine plant species and natural regeneration as ground covers in plantations. The nine species were Tephrosia hookeriana and villosa mixtures, Indigofera sumatrana, Flemingia congesta, Desmodium asperum, Cassia tora, Indigofera spicata, Crotalaria longithyrsa, Mimosa invisa, and Tithonia diversifolia. F. congesta and T. diversifolia gave the best and most persistent ground cover. Significant differences appeared in the effects of the covers on cocoa jorquetting, heights of jorquette, stem diameter and yields. T. diversifolia retarded cocoa development (to as low as 34% of control) while the others appeared to improve it. Yields in plots of Tephrosia mixture, I. sumatrana, and F. congesta were respectively 72, 59 and 54 per cent higher than under natural regeneration.

A two-year field investigation was conducted to evaluate the response of two varieties of Guinea grass and two leguminous species, grown alone and in mixtures, to fertilizer treatments. Styloxanthes gracilis and a Guinea grass variety ‘Liconi’ were observed to be superior to others in their yielding ability. Styloxanthes and the Liconi Guinea grass appeared to be mutually compatible at particular seeding rates. Sabi Guinea grass and Centrosema pubescens were the poorest performers under all conditions. Findings also suggested that the adapted and mutually-compatible legumes and grasses could be grown in mixture under tropical conditions, and high yields obtained without the use of expensive nitrogenous fertilizers.

Four standard Nigerian varieties of sorghum were grown in trials together with local varieties representative of sorghums from each of the five main ecological zones. Analysis of the data showed a relation within each zone between mean yield and time of heading. When the standard varieties and the local varieties flowered simultaneously, yields were similar. When the standard varieties flowered later—or in some cases earlier—than the local varieties, the local varieties out-yielded them.