The results of a three-year water conservation trial in the Zambezi Valley of Zambia are reported, for an area characterized by high temperatures and low, often poorly distributed, rainfall, with low infiltration and high evapotranspiration rates. As a result of these conditions local farmers often produce grain crops yielding as little as 200–300 kg./ha., though considerable increases could be obtained by simple water conservation methods. Of four treatments, tieridges made before the start of the first rains consistently gave the heaviest yields. Mean yields of the three crops under trial (maize, sorghum and bulrush millet) were higher on tie-ridges than on conventionally prepared seedbeds by 168, 159 and 17 per cent in the 1968–69 to 1970–71 seasons respectively.

Root measurements on three Malayan varieties of tapioca (high, medium and low-yielding clones) showed that the onset of tuberization brings about a slowing-down or cessation of growth in root length, but no changes in stem growth rate were associated with the onset of tuber growth. High yield was associated with high tuber weight rather than with tuber number, which could be related to the size of storage tissue cells formed by the root cambium. The process of tuberization in tapioca is discussed generally.

The effects of plant population on yield and its components were investigated in three experiments in 1969, 1970 and 1971. Increasing populations from 9000 to 36,000 plants/ha. increased yield linearly. The number of tubers produced per plant was not affected by population, but an increase in plant density decreased average tuber weights. Increasing sett weight from 203 to 608 gm increased tuber yields/ha. and the number of tubers per plant but did not affect average tuber weights in two experiments. In 1971 compound fertilizers increased yield up to the highest rates of 90 kg./ha. each of N, P2O5 and K2O respectively.

The genotypic and phenotypic correlations and path-coefficients were studied in two different environments, using twenty fodder genotypes of cowpeas. Among quantitative characters, leaves/plant, branches/plant and stem girth were highly correlated with both green and dry matter yield, whereas among quality characters, total protein (per cent) showed significant association with digestibility (per cent). Based on path-coefficient analysis, leaves/plant and protein (per cent) were found to be the most important component characters. These two characters were also highly correlated at both the genotypic and phenotypic level and, therefore, selection based on leaves/plant is likely to be useful for simultaneous improvements in yield and quality of fodder in cowpeas.

Effects of cutting lengths on tuber yields and vine production of Missus and Madam sweet potatoes, as influenced by two different fertilizer regimes, were studied on Njala upland soils of Sierra Leone. Cuttings 61 cm. long gave significantly the highest tuber yields for both early-maturing cultivars when fertilized with 336 kg. sulphate of ammonia, 112 kg. basic slag, 448 kg. sulphate of potash, 841 kg. lime and 340 kg. sulphate of magnesium per ha. in two split applications a month apart. Fertilized with 502 kg./ha. sulphate of ammonia per application for 4 applications, 61 cm. long cuttings again gave the highest vine production. The lower the vine/tuber ratio, the higher the tuber yield.

The effect was investigated of seasonal differences between winter and spring on the development of parthenocarpic and fertilized fruits in two squash cultivars, Zucchini Elite F1 and Bushy White. The former had stronger parthenocarpic characteristics than the latter. The effect of night temperature on growth of the parthenocarpic fruits was most pronounced, both rate of growth and final weight increasing with decreasing temperature. Whereas long days inhibited development of parthenocarpic fruits, the heaviest and longest fruits were obtained under normal day-length conditions.

Field experiments conducted in two localities in two growing seasons on the effect of inoculating haricot bean showed that a local strain of Rhizobium significantly improved nodulation and usually increased the nitrogen content of plants. In three out of four experiments, increases in seed yield were obtained ranging from 20–145 Per cent (significant in two cases). Inoculation was better than 43 kg. N/ha. of combined nitrogen but not better than 86 kg. N. Soil inoculation gave better early nodulation than seed inoculation, but the difference diminished in the later stages of plant growth.

The Sudanese local onion cultivar Wad Ramli has a markedly long rest period (60 days) and a long dormant period of up to six months. It has high dry matter (16 per cent), high soluble solids (15 per cent) and strong pungency, factors which contribute to its good storability under conditions that are usually adverse for good storage.

Tall local sorghum and new dwarf varieties were compared, both as sole crops and when intercropped with an early cereal, in a replicated experiment, and at five sites in observation plots. Dwarf varieties were superior both as intercrops and as sole crops, and intercropping was better than sole cropping for all varieties. In the experiment 27 per cent more total grain yield (sorghum + early cereal) was obtained when dwarf varieties were used instead of tall. When the sorghum was intercropped, increased yields per plant came largely because there were more grains per head.

Four sesame varieties were tested at three plant populations to study varietal and population effects on some attributes of vegetative growth. Significant differences between varieties were detected and planting density was found to modify both areas and dry weights of leaves.

Four local sesame varieties were tested at three plant populations. Increase in plant density increased seed yield, which was positively related to number of pods per plant, seeds per pod, 1000-seed weight, heights of main stems and numbers of nodes per plant. Changes in soil moisture did not affect relative turgidity, whereas stomatal openness decreased as the irrigation interval became longer.