Enhancing soil productivity in the rain-fed upland ecology through rotational cropping of NERICA (new rice for Africa) and cowpea (Vigna unguiculata)

The NERICA 1 rice variety was grown in rotation with indeterminate cowpea (Adidome mottled), in the Hohoe and Kwaebibirem Districts of Ghana, from 2007-2010, in a randomised complete block experiment, with three replications. Soil and cowpea samples were analysed for nitrogen (N) and organic carbon (OC) contents. Socioeconomic surveys were also conducted before and after the agronomic experiments. The treatments included: Cowpea + P 2O5 + K 2O (T 1), Cowpea only (T 2), Cowpea plus 50 % recommended inorganic N fertilizer, using sulphate of ammonia + P 2O5 + K 2O (T 3), Recommended N, i.e. 90 kg N ha -1 + P 2O5 + K 2O (T 4), 75 % N + P 2O5 + K 2O (T 5), 50 % N + P 2O5 + K 2O (T 6), 25 % N + P 2O5 + K 2O (T 7) and no fertilization, control (T 8). The P 2O5 and K 2O fertilizers (triple super phosphate and potassium sulphate, respectively) were applied basally, at rates of 45 kg P 2O5 ha -1 and -1