Competition was studied among four varieties of jute, one cultivated and one wild type of each of C. capsularis and C. olitorius. Varieties exposed to competition showed significant effects on different characters at species and variety level for all the characters. Variety competition, average competition except for base diameter, and specific competition except for node number and base diameter, were significant for all the characters. Wild forms were less effective than cultivated ones as competitors, and the action of one species on the other did not affect all growth parameters in the same way.

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.

Three methods of applying four fungicides were tested for controlling powdery mildew on roses. Best results were obtained by air blast application, with high-volume sprays providing better control than low-volume sprays. The former, unassisted by air blast, failed to give adequate control. Fluorescent tracers showed that performance of various modes of application depended on their ability to provide a satisfactory fungicide deposit on the lower leaf surface, which was particularly susceptible to the disease.

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.

To assess the potentialities of Ph. vulgaris for haricot type bean production in Britain, a large collection of types was surveyed. One hundred varieties, mostly but not exclusively bush types, were grown both in the greenhouse and in the field. Characters of agronomic importance were evaluated. The morphological basis of the difference between the climbing and the bush habit was shown to be the interaction between two character contrasts, indeterminate versus determinate vegetative growth, and long versus short internodes. The four classes resulting from this interaction were identified and are described. Flowering habit, pod type and seed size were surveyed. Among the bush beans, wide variation in day length sensitivity in flowering was shown, and it is clear that day length neutral types can easily be selected. Among the determinate dwarfs, pods are either leathery or fleshy. Leathery types dry out readily, and do not dehisce freely in the field, and are therefore agronomically desirable in dry bean production. Fleshy pods are used for culinary purposes. The indeterminate bush types included in this survey have parchmented pods, which tend to dehisce when dry, and hence are subject to crop loss in the field. A wide range of seed size and seed colour is available for selection according to requirement. Two small variety trials yielded evidence that Colombian determinate bush types grow and crop satisfactorily within the limits of the growing season in eastern England. From two spacing trials, optimum within-row spacing was deduced.

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.

Soil acidity, incipient potassium deficiency, and a deficiency of one or more trace elements were limiting factors in three trials of long-term soil fertility changes under continuous cultivation in the Sudan Savanna zone of Nigeria. The effectiveness of organic manures is explained largely or wholly in terms of these factors, since no evidence has yet been found to suggest that the addition of organic matter as such is of value.

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.

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.

Shifting cultivation of dry rice on steep hill-sides continues to be widely practised in Sarawak, Malaysia. Fertilizer experiments have shown that economic increases in yield can be obtained by mixing 0·9 kg. (2 lb) of mono-ammonium phosphate pellets (11 per cent N: 21 per cent P) with 2·4 kg. (5·3 lb) of seed just before dibbling. In certain areas additional increases might be gained by further increasing the rate of application of phosphorus, from the use of potassium, and from top-dressing with nitrogen. Closer spacing (30·5 cm. or 12 in. square) than that traditionally used should also increase yields per unit area.

A three-year study of the effects of sowing date, nitrogen application and seed rate on wheat showed that sowing in mid-October gave consistently greater grain yields than sowing in mid-September or mid-November because grains were larger and more numerous per head. Nitrogen increased yields but the effect decreased with later sowing. Nitrogen probably increased grain yield by increasing the number of ears, but this effect diminished with higher levels of nitrogen. Grain yield was only slightly influenced by seed rate, and the interaction of seed rate with sowing date or nitrogen was unimportant.

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.

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.

The quality of bean pods was influenced to a large degree by the variety, season of planting and the precise time of harvesting. The varieties Tenderette, Executive and Bush Blue Lake 274 were outstanding in their concentrated yield and pod quality. The development of seeds in the pods was faster in beans planted during the spring than in the autumn. Thickening of the pods during ripening was more rapid in the autumn than in the spring season. Outstanding differences were found between varieties with regard to the speed of seed development during pod ripening. As opposed to the outstanding differences between varieties with regard to quality characteristics, the differences with regard to yield were generally small and without economic importance.

Nitrate content in the petiole of sugar beet (var. Polygrave) reaches its maximum three months after emergence of the seedling. There is a linear correlation between the final yields and the nitrate content of the petiole at the maximum stage. Nitrogen fertilization should be given in the first three months of the beet growth.

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.

CCC applied to bread wheat, in 1967 and 1968 as a foliar spray at 1·40 and 2·28 kg./ha. a.i., prevented and/or delayed lodging to some extent. However, this effect was small and complete control of lodging seems to be unlikely, even when using large amounts. CCC increased grain yields, by 1·5 to 10·9 qu./ha., depending on the extent to which lodging was reduced. Significant depressions in yield were obtained, presumably owing to an observed increase incidence in ear diseases, particularly Septoria nodorum. The increase in grain yield was due mainly to an increase in 1000 grain weight and grains per ear, whereas the effect on tillers per unit area was slightly negative. Where no lodging occurred, there was a slight but non-significant tendency for increasing grain yields after CCC treatment.

In Kenya, coffee growing east of the Great Rift Valley has its main flowering either in February–March or in October–November. These flowerings are mainly initiated from approximately August to December and June to September, respectively. Changes from an early to a late flowering rhythm and vice versa can be caused by (a) pruning, (b) the condition of the tree, and (c) the weather pattern, but more information is needed for a complete understanding of this problem.

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.