Integrated Soil Fertility Management for Increased Maize Production in the Degraded Farmlands of the Guinea Savanna Zone of Ghana Using Devil-Bean (Crotalaria retusa) and Fertilizer Nitrogen

Abstract

The native N and P of soils of the Guinea Savanna Zone of northern Ghana are only about 20 and 10% of the crops’ requirements, respectively, and organic matter content is usually below 1%. Hence, cereal yields without soil amendments are usually below 500 kg/ha. Organic residue and mineral fertilizer combinations are necessary to increase nutrient use efficiency. Devil-bean is a very promising leguminous cover crop for this agro-ecology. The best time to intercrop devil-bean in maize, effect of P on the maize, and the effect of incorporated devil-bean biomass on grain yield of N-fertilized maize were investigated. In 2003, devil-bean was drilled in maize at 1, 3, and 4 weeks after planting (WAP) the maize which received 0, 20, and 40 kg P/ha. Phosphorus enhanced maize growth and yield. The devil-bean biomass was incorporated into the soil in the 2004 growing season. Maize was planted, fertilized with 0, 20, and 40 kg N/ha, and intercropped again with devil-bean as before. About 40 kg N/ha fertilized maize grown on incorporated devil-bean intercropped at 1 WAP in 2003 had the highest grain yield of 1.59 t/ha. In 2005, the devil-bean intercropped in the 2004 40 kg N/ha maize at 3 WAP produced the highest biomass containing 42–88, 4–11, and 25–52 kg/ha of N, P, and K, respectively. Maize grain yield significantly increased with incorporated biomass with the highest biomass producing the highest grain yield. The cumulative effect of the biomass applications was significant in this study.