Improving cropping systems may be an important step in providing a more stable food supply in sub-Saharan Africa. We examined the effects of three cropping systems in a two-year study: continuous maize (Zea mays L.), maize-mucuna (Mucuna pruriens var. utilis), and maize-pigeon pea (Cajanus cajan). Nitrogen (N) and phosphorus (P) fertilizer rates were imposed on maize in each system and the budgets of each nutrient were measured. Seeding mucuna and pigeon pea crops after the maize crop in the first year did not result in maize grain yield increases from N and P fertilizers in the subsequent year. Mucuna-based and pigeon pea-based cropping systems also increased maize grain yield by 37.5 and 32.1 %, respectively, in the second year. Two-year cumulative economic returns on maize production were generally equivalent or better for cropping systems that included legume cover crops in the second growing season of the first year, compared to continuous maize or those including annual cover crop plantings. The April 2002-December 2003 N budget showed a gain of N (> 400 kg ha-1) under all cropping systems presumably from soil N mineralization and atmospheric N inputs. Phosphorus losses occurred for all budget periods, presumably through the process of chemical precipitation. The mucuna-based cropping system appeared to have a significant potential for soil P replenishment. The relay of mucuna into maize in one out of two years cropping system was most economical in sustaining high maize yields and improving soil N and P status without commercial fertilizers.
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