Nitrogen derived from promiscous soyabean in maize-based cropping system in the moist savanna of Nigeria

Abstract

Promiscuously nodulating soybeans were developed by IITA, Ibadan, and introduced in the moist savanna region of Nigeria to encourage smallholder farmers to cultivate the crop since it has no requirement for artificial rhizobial inoculation. The anticipated benefits include increased income and quality of livelihoods to farmers and improved soil fertility management strategy. Studies conducted by collaborating scientists within the moist savanna of Nigeria have shown promiscuous soybeans to respond to rhizobial inoculation, which is often accompanied by increases in arbuscular mycorrhizal fungal (AMF) infection of plant roots and P uptake. The actual amount of N₂ fixed by the promiscuous soybean cultivars in this environment ranges from 30 – 130 kg N ha^-1, representing 25 – 60% of N₂ derived from fixation. Cultivation of these soybean cultivars either as an intercrop or in rotation with maize often results in significant increases in the maize crop. However, results have shown that these increases cannot be due solely to the carry-over of N from soybean residue.

Nigerian Journal of Soil Science Vol. 15 2005: 109-115