N and P fertilizers applied to maize had considerable effects over a five-year period, especially when both were given. Initial applications of 47 lb/acre/P2O5 with annual dressings of 58 lb N, produced a mean yield increase of 55 per cent above the control. K gave little response in the first three years, but thereafter became more important. 1120 lb ammonium sulphate nitrate caused striking reductions in soil pH, Ca, Mg, K, total and organic P but increases in exch. Mn and soluble P. 112 lb double superphosphate increased the total and organic P and 65 lb K2O reduced organic P. Organic carbon suffered a mean loss of 33 per cent over five years. Recommendations are made regarding P2O5, N and K on this soil.

Nodule and plant dry weight of five photoperiodically different cowpea varieties increased with increasing day-length. There were no effective nodules on any varieties in 8-hour days and the response of nodulation to day-length was greater than plant dry weight. Nodule and plant dry weight also increased with increasing availability of water, but at the highest watering rate nodule weight was significantly lower under long than short days. Cowpea should nodulate well under tropical day-lengths provided enough water is available.

Visual symptoms of deficiencies of nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and boron on pyrethrum are described, and compared with those observed previously on other species of chrysanthemum.

In 90 local sesame types there was some association between seed coat colour and seed size, stem height, number of branches, number of pods, yield per plant and earliness. Forty-five coefficients show the degree of correlation between ten agronomic characters. Yield was significantly and positively correlated with all characters except the number of days to first flowering and to first maturity. Stem height, number of pods per plant and seed size seem to be the best criteria for selection in sesame.

Cocoa leaves were analysed for potassium, calcium, magnesium, manganese, iron, copper and zinc to assess the nutritional status of this crop in Papua–New Guinea, as part of a study into a dieback disease. Potassium and manganese contents of the leaves were generally high, whilst magnesium, iron and copper were often low. Some exchangeable cation data from soils is presented. Nutrient imbalances, toxicities and deficiencies, may make cocoa more susceptible to dieback.

The development of the first group of short-statured, late-maturing sorghum lines and hybrids and their initial testing for the Northern Guinea and sub-Sudan Savanna zones in Nigeria is described. The necessity of developing such types of sorghum is discussed, together with some of the problems encountered when breeding the new types.

Monthly and annual totals for the Penman estimate of potential evaporation have been reliably determined, for periods varying from 7 to 11 years, at 14 East African observatories. At each site, these annual and monthly totals are normally distributed, with coefficients of variation of the order of 5 and 10 per cent, respectively. Meteorological stations established for the sole purpose of supporting evaporation surveys should therefore be relocated at 5- or 6-year intervals so as to derive maximum benefit from the valuable instruments. The results of these variability analyses were applied in the evaluation of confidence limits for monthly and annual potential evaporation rates, and reference is made to recent compilations of such limits for 137 sites in Kenya and Tanzania.

Growth and flowering studies were made for three years on the mango varieties Dashehari Langra and Nisar Pasand. The main growth periods were March July, March July and February-November respectively, with a peak in June for Dashehari and May for Langra, but Nisar Pasand showed no such peak. Flowering on shoots within one year of the previous flowering was recorded on 73 per cent of Nisar Pasand shoots, 38 per cent with Langra and 6 per cent with Dashehari. Nisar Pasand was shown to be a regular bearer.

Trials on cotton in Uganda show that four DDT sprays give substantial increases in yields and a reduction in percentage of stained cotton. Benefits were obtained from early ploughing prior to sowing and there were positive interactions between time of ploughing and spraying. Fertilizer applications of superphosphate and sulphate of ammonia generally produced marginal benefits but more cotton was obtained from fertilized plots if they were sprayed, though not if unsprayed. The effect of fertilizer on the pest complex was slight, though one pest appeared to be attracted to lush fertilized cotton. Spraying gave excellent control of bollworms and mirids.