Two groundnut varieties, the small-seeded, early-maturing Natal Common and the large-seeded, late maturing ‘pops’-susceptible Makulu Red, were cultivated in nutrient solution, Application of calcium, labelled with 45Ca, to the roots and the fruit-medium respectively, showed that both varieties absorbed most of their seed-Ca from the fruit-medium. The translocation of calcium from the shells to the nuts was greater in the small-seeded variety Natal Common, which showed less susceptibility to ‘pops’. Calcium absorbed by pods and gynophores also migrated to a certain extent into the vegetative parts.

The yield, variability and quality of 16 sweet potato cultivars, harvested after 21 weeks growth, were evaluated in sub-tropical Australia. The coloured-flesh cultivars L8-92, Centennial, HAC-Pink, Copperskin Goldrush and Nemagold produced yields of marketable storage roots in excess of 19,000 kg ha−1, which was three to four times the yield of the local commercial cultivar, White Maltese. The high variability in mean yield per plant of all cultivars offers scope for selection within cultivars. Those with a deep orange flesh and high soluble solids content, i.e. L8-92, Copperskin Goldrush and Centennial, were preferred by members of a taste panel. A high carotene cultivar L8-92 has the greatest commercial potential because it produced the highest yield of marketable storage roots and had the highest taste panel rating for eating quality of stored roots.

Temperature effects on coleoptile development were studied in 18 genotypes of spring and semi-winter wheats, illustrating a simple experimental approach for choosing genotypes and management practices that would minimize genotype–environment interactions for stand establishment.

In field experiments at Pantnagar, India during 1968–70, evapo-transpiration (ET) in wheat was significantly correlated with U.S.W.B. class A pan evaporation (E0) when the crop was in an active stage of growth and moisture was non-limiting (50 or 25% depletion of available moisture). The estimated ET was higher than E0, probably due to ‘oasis’ and ‘clothesline’ effects. When ET measurements were made at varying distances from the upwind side during the subsequent three years, it was found that ET decreased with increasing distance downwind with a conspicuous border effect up to about 25 m distance. In the absence of advective heating, i.e. in extreme downwind locations, the actual ET was 480, 533 and 530 mm during 1970–71, 1971–72 and 1972–73 respectively.

The magnitude of heterosis for 15 characters was studied in ten sorghum hybrids, produced by crossing ten restorer varieties with male-sterile Combine Kafir 60 as a common female parent. The most evident expressions of heterosis were higher yield and increased vegetative growth, often associated with delay in flowering. The increase in yield of the hybrids over their superior parents, ranging from 35 to 238%, resulted mainly from an increase in number of grains per head, rather than from an increase in the weight of individual grains. The regressions of hybrids on male parents, and the correlations of yield with other characters were studied, and the prospects of producing adapted hybrids for the Sudan are briefly discussed.

Four tomato varieties (Harvester, Pusa Early Dwarf, Ife No. 1 and Ibadan Local) were grown in three ecological zones of Western Nigeria, at a range of densities from 10,000 to 40,000 plants/ha. The highest yield of fruits was obtained at a plant population of 30,000 plants/ha. Pusa out-yielded the three other varieties. Fruit number per plant declined as plant density increased.

Annual applications of calcium, potassium and nitrogen (as urea) over three years caused significant differences in soil exchangeable cation ratios and in the yields of subsequent groundnut and maize crops. High rates of potassium and nitrogen, combined with low rates of calcium, lowered groundnut yields, and high rates of potassium, enhanced by ploughing in crop-residue ash, seriously reduced the exchangeable Mg: K cation ratio and maize magnesium status. Maize yields were significantly negatively correlated with soil potassium status. The balance between exchangeable cations in these soils is very easily upset by injudicious combinations of fertilizers and management practices.

Variety, spacing and harvesting date trials with fodder beet were carried out in Cyprus under rainfed conditions. The variety Polyrossa gave the highest dry matter (DM) yield, 12,906 kg/ha. Yield of DM increased linearly with population density to an optimum spacing of 45 × 20 cm. Yields of beet decreased slightly when harvested after 15 June and significantly when harvested after 29 August. Irrigation with saline water increased DM yields.

Changes in soil moisture and nitrate content in the top 75 cm of soil in bare and cropped plots were followed throughout the growing season in a Ferruginous savanna soil. A low leaching efficiency, of 0.38–0.66 cm/cm rainfall, was related to very slow wetting of the subsoil, a phenomenon which could be explained satisfactorily only by assuming that part of the rain passed through the profile relatively quickly in the larger pores. However, losses of fertilizer nitrate to deep drainage by this rapid percolation were only 25% of that applied, at most, the greater part remaining in the top 45 cm of soil for almost the whole growing season, thus explaining why only small responses have been obtained at this site to delayed or split applications of nitrogen.

Three systemic insecticide granules, viz. carbofuran, phorate and disulfoton, were applied at 1·0, 1·5 and 2·0 kg ai/ha on 16 January, 16 February and 16 March 1973 against Brevicoryne brassicae Linn. on Indian rape plants (Brassica campestris var. sarson) in the Kulu valley, Himachal Pradesh, India. The results showed that phorate at 2·0 kg/ha, followed by disulfoton, applied on 16 February, gave effective control of the pest and were reasonably persistent. None of the granules were phytotoxic but these treatments increased crop yields.

The effects of frequency of potash fertilizer application and of different rates on sweet potato yields were studied in three different cropping systems on Njala upland soils. Fertilizers containing higher K rates (448 kg/ha sulphate of potash) and an N/K ratio of 3:4, gave maximum tuber and low vine yields with low vine/tuber ratios on intensively cropped areas, whereas fertilizers containing lower K rates (112 kg/ha sulphate of potash) and an N/K ratio of 3:1 gave maximum but relatively low tuber and relatively high vine yields, with relatively high vine/tuber ratios on newly cropped areas after seven years bush fallow. Two equal split applications of fertilizer is recommended under the weather conditions prevailing in this part of Sierra Leone.