There is wide variation in the morphological characteristics of sweet potato leaf tips which are acceptable as a vegetable for human consumption. Thus many cultivars are available from which further selections can be made for yield, palatability, tenderness, flavour, and nutritional quality. A list is given of some cultivars which combine a number of desirable traits.

Yields of sweet potato tips varied from 10 to 16 t/ha in weight and 61 to 352/m2 in number, whilst yields of marketable roots varied from 1 to 16 t/ha. Cultivar differences in dry matter, fibre, ash, vitamin B2 and oxalate were also observed. The tips appeared to provide an excellent source of vitamin B2 which is important for Asian diets deficient in this vitamin. Application of 120 kg N/ha gave higher tip yields than no nitrogen, primarily due to increases in their number and size. Among the leaf types evaluated, Kinangkong (a fine leaf cultivar) produced the highest yield, and had the highest amount of protein, lowest oxalate, and fairly high dry matter, which makes it a very desirable leafy vegetable.

Blanched leaf tips of ten sweet potato cultivars were evaluated for eating qualities such as tenderness, flavour, stem and leaf colour, and hairiness to determine selection criteria. Some cultivars compared favourably with the control in most quality attributes, with a general agreement on the acceptability ranking of three cultivars. Stepwise multiple regression analysis suggested that all the quality attributes studied are important in predicting general acceptability of blanched tips, but the use of stem colour and hairiness for initial selection should be sufficient to reduce the number of lines prior to further evaluation.

In dryland areas, where rains recede much earlier than the time of sowing of crops, moisture in the seed zone becomes limiting for stand establishment. Mulches are known to conserve moisture in the upper soil layers, so we studied the effect of mulching a standing maize or fallow on the yield of the maize and on following wheat. Mulching maize with green twigs of ‘basooti’ a few weeks before harvest increased its yield by 16%. Both in maize and on fallow mulching increased water storage, particularly in the upper soil layers, and increased wheat yields from 19.0 to 22.5 q/ha after maize and 29.1 to 33.3 q/ha after fallow. It also led to increased water use and water use efficiency of wheat.

The potential was demonstrated of using sodium chloride and sodium metabisulphite as chemical preservatives during pre-drying storage of wet cassava chips, and during slow sun-drying under adverse weather conditions. Both chemicals permitted chips to maintain a good colour and texture and prevented gross microbial deterioration.

Insects cause serious problems during the storage of cassava chips, when quality may be reduced and significant quantities of the product consumed. The major species naturally infesting chips were Rhizopertha dominica, Lasioderma serricorne and Araecerus fasciculatus. Infestation occurs during the sun-drying process, and up to 16% reduction in chip weight due to insect feeding was recorded after 2 months storage. Chips that had not received any pre-drying storage, but contained salt as a preservative, were infested by fewer insects than chips without salt. The poorest quality chips had significantly more insects than better quality ones.

Five fire-cured tobacco varieties were grown under different fertilizer levels and environments, to investigate their effects upon quality of the cured leaf. Environment exerted the greatest effect, and the best quality of leaf was produced from virgin soils. Fertilizer responses were greatest in environments where traditional agricultural methods operated, but even heavy applications of fertilizer under these conditions did not compensate for lack of good initial soil conditions. Although variety affected the style of tobacco produced, varietal differences were small compared with the effects of environment and fertilizer.

Irrigated and unirrigated crops of pearl millet were grown in Hyderabad, India, during the post-monsoon season of 1977. Irrigation increased both the dry weight of roots and the number of root axes, but because the additional axes were thick and unbranched the total length of roots was unaffected. However, irrigation did cause more of the root length to be in the top 20 cm of soil. Yield of the irrigated crop was higher than that of the dry crop, mainly because more tillers survived to produce grain. Grain growth of the dry crop occurred when the net growth of the crop was zero, probably because of movement of assimilate from stems to panicles. Possible strategies for improving yields are examined in the light of the growth data.

Yields of pearl millet were significantly increased when grown after legume crops such as groundnut (22·6%), cowpea (24·2%) or pigeonpea (12·1%) instead of after pearl millet. A previous crop of short-duration mung did not affect the yield of pearl millet. Benefits from previous crops of groundnut and cowpea were equivalent to about 60 kg N/ha applied to a pearl millet crop following a previous crop of pearl millet.

Banana packing systems rely on floating the fruit in water in order to remove latex produced at the cut surfaces of the crown. At some periods of the year up to 5% of the fruit sinks and rolls along the bottom of the tanks, resulting in heavy scarring of the peel. Potassium content of buoyant fruit exceeded 1·3% dry weight in the pulp and 6·0% in the peel, but in one investigation the sinker fruit had 36 and 20% less than these levels respectively. Application of potassium fertilizer in the field greatly reduced the amount of sinker fruit.

Experiments were carried out in which injuries caused by Diopsis macrophthalma larvae were simulated. The results show that these larvae can have negative or positive effects on rice (number of stems, height, maturation time, number of ears and yield), depending on time and level of attack, growing conditions and variety. The results suggest that under normal conditions the effect on number of stems, height, number of ears and yield is positive, and only becomes negative if poor growing conditions are combined with a late, heavy attack. An experiment with Diopsids was carried out to evaluate the simulation experiments.

Measurements indicate that the tea crop—which consists of young shoots—is sink-limited and that the plucking of immature shoots, essential for quality tea, is a major factor limiting yields of the crop. The importance of this aspect in selecting for high-yielding plant material is discussed.

Trials on ferrallitic soils in Uganda showed that crops responded to lime after the first year of cropping on soils which had a pH up to 6·0, and to potassium on soils which had an extractable K level up to 18 mg 100 g−1. Soil and leaf analyses indicated that responses to lime on soils of pH above 5·2 were due to an increase in phosphate availability. Low yields at several sites in the first year were apparently due to immobilization of nutrients during rapid mineralization of soil organic matter. In later years soil organic matter did not decline appreciably, and yields dropped only at sites where potassium or minor element deficiencies apparently developed.