Genotypic differences in yield formation, phosphorus utilization and nitrogen fixation by cowpeas in Sierra Leone

Available phosphorus (P) and nitrogen (NP) generally occur in very low amounts in soils of the tropics and subtropics. Under such conditions, most crops would require the addition of N and P fertilizer. This is not possible for small-scale farmers who cannot afford or have limited access to fertilizers, and therefore depend on low-input cropping systems. The selection of cultivars adapted to low soil nutrient conditions would sustain the production levels of subsistence farmers. Experiments were therefore conducted over a five-year period to identify cowpea cultivars with high phosphorus use efficiency and nitrogen fixation. Two of such cultivars-IT86D-1010 and IT86D-719 have been identified. Root morphological characteristics such as root length, root fineness and vesicular-arbuscular mycorrhizae are responsible for high P uptake and use efficiency. Multilocational testing of the cultivars showed that they cannot do well in areas with low rainfall. They have been distributed to farmers through the extension services for large scale production in southern Sierra Leone. (author). 28 refs, 4 figs, 6 tabs