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.

Forty-one factorial experiments on rates and forms of the three major elements and rates of some minor and trace elements were carried out over the period 1954–1962 in Iringa, as part of a project to introduce Virginian-type tobacco varieties into the area. There were major responses to nitrogen and phosphate, and a close relationship between their effects, but no responses to other elements. Nitrogen raised yield, particularly in wet seasons, but generally tended to reduce quality, severely above 44 lb N per acre and at lower levels in dry years. Phosphate raised yield and quality, and in some instances crop failures occurred in its absence. Data suggested the optimal N : P2O5 ratio in fertilizer mixtures to be 1 : 15. Despite lack of response to potassium a small amount was recommended, to cover requirements for leaf characteristics which were not measured. The programme amply succeeded in its aim of establishing ‘average’ fertilizer recommendations, which were fundamentally sound, for the whole of the Iringa tobacco growing area. These recommendations are summarized.

On-farm experiments were used for assessing the processing and food value of four promising sorghum cultivars and the willingness of farmers to pay for the herbicide 2,4-D for controlling the parasitic weed Striga hermonlhica in coarse grains. The active participation of farmers in these experiments was useful in determining the conditions under which the improved sorghum cultivars and the herbicide would be most likely to he adopted by smallholder farmers in southern Mali.

Observations on the relative degree of root nodulation were made for three successive years on tall and short cultivars of Pisum sativum and Phaseolus vulgaris sown at dates appropriate to each cultivar and grown under conditions of ordinary horticultural practice. In P. sativum, it was found that the shorter the cultivar, the greater were the number and weight of nodules per plant and the weight of nodules as a percentage of plant weight; dwarf cultivars also produced a greater weight of nodules per square metre of ground occupied and per square metre per day of crop growth. In Ph. vulgaris, differences in number and weight of nodules per plant between dwarf and climbing cultivars were not consistent between years. In a single comparison between Ph. uulgaris and Ph. multiflorus (scarlet runner beans), numbers and weights of nodules per plant were almost identical. Some agronomic implications of these findings are discussed.

Four depth of tillage treatments were given by ploughing to 7 cm. depth by bullock-drawn plough and 14, 21 and 28 cm. depth with a tractor-drawn mouldboard plough in 1962–63. A significant decrease in bulk density was observed with the 21 and 28 cm. ploughing, negatively correlated with dry matter of crop roots and yield of grain. The effectiveness of 28 cm. tillage in reducing the population and dry matter of weeds was significant when compared to tillage at 7 and 14 cm. and there were significant relations between dry matter of weeds and yield of grain. Crop roots under tractor tillage were significantly greater than with 7 cm. tillage. Grain yield was maximum under 28 cm. tillage followed by 21, 14 and 7 cm. deep tillage in that order. The higher grain yields were associated with a greater number of fertile tillers per metre of row and higher yields per tiller.

Inoculation of symbiotic N2-fixing rhizobacteria (rhizobia) in legumes is an alternative to reduce synthetic N fertiliser input to crops. Even though common bean benefits from the biological N2 fixation carried out by native rhizobia isolates, the low efficiency of this process highlights the importance of screening new strains for plant inoculation. Two rhizobial strains (SEMIA 4108 and SEMIA 4107) previously showed great potential to improve the growth of common beans under greenhouse conditions. Thus, this study evaluated the growth and grain yield of common bean plants inoculated with those strains in field experiments. The rhizobial identification was performed by 16S rRNA sequencing and the phylogeny showed that SEMIA 4108 and SEMIA 4107 are closely related to Rhizobium phaseoli, within a clade containing other 18 Rhizobium spp. type strains. Common bean plants inoculated with SEMIA 4107 showed similar productivity to N-fertilised (N+) plants in the first experiment (2016/17) and higher productivity in the second experiment (2018/19). The development of inoculated plants was different from that observed for N+. Nonetheless, comparing inoculated treatments with N-fertilised control, no yield or productivity losses at the end of the growing process were detected. Our results showed that inoculation of the rhizobial isolates SEMIA 4108 and SEMIA 4107 improved the growth and grain yield of common bean plants. The observed agronomical performance confirms that both strains were effective and can sustain common bean growth without nitrogen fertilisation under the edaphoclimatic conditions of this study.