Department of Plant Sciences

One major limitation in tropical agriculture is the loss of productivity of soils due to continuous cultivation. This is often due to leaching losses of nutrients, erosion or crop removal. There is need to explore improving productivity of soils by using grain legumes complemented with low-use of applied nitrogen. Modern interspecific rice hybrids called New Rice for Africa (NERICA®) are low input cultivars developed to overcome environmental stresses including low soil fertility. The productivity of these NERICAs under legume/rice rotation and low-nitrogen (0 vs. 30 kgN ha-1) was evaluated in farmers’ fields in 2007 and 2008 in rainfed upland in Kasuwa Mangani (10o24’N, 7o42’E; northern Guinea savanna), and lowland at Edozhigi (09º 45′N, 06 º 7′E; southern Guinea savanna) ecologies in West Africa. Preceding plots of incorporated soybean and Mucuna after harvest, gave 33% increments in rice yield over the previous control-fallow plots in the upland ecology. While, in the lowland, plots with previously incorporated grain soybean (cv. TG× 1485 – 1D) and dual-purpose cowpea (cv. IT 98K–131–2) residues gave about 0.8 Mg ha-1 greater rice yield than plots with previous mucuna or dual-purpose soybean. Although NERICA L–42 produced over 25% more tillers and panicles than the farmers’ cultivar, both cultivars had similar yield of 3.6 Mg ha-1, possibly because of the severe effects of iron- toxicity that limited their potentials. Results showed that upland NERICA rice would perform better after soybean or mucuna rotation, and the lowland NERICA after soybean or dual-purpose cowpea cultivation than traditional fallow.