Integrated mucuna-inorganic fertilizer management for sustainable maize production on the vertisols in the Accra plains of Ghana

Studies were conducted at the University of Ghana, Soil and Irrigation Research Centre between March and December, 2007, using the randomised complete block design, with 8 treatments, 4 replications and plot size, 4.0 m x 6.0 m. The treatments included: no fertilization - control (T1); mucuna only (T2); mucuna + 60 kg P2O4 ha-1 + 40 kg K2O ha-1 (T3); mucuna + 50 kg N ha-1 (T4) mucuna + 25 kg N ha-1 (T5); 100 kg N ha-1 (T6); 50 kg N ha-1 (T7) and 25 kg N ha-1 (T8). Apart from (T1) and (T8), all others were given a basal application of 60 kg P2O4 ha-1 + 40 kg K2O ha-1. At harvest, the maize crop in the mucuna plus 50 kg N ha-1 treatment had total dry weight and grain yield that were higher than values observed in the mucuna only and control treatments. Total dry weights were 3.02, 1.67 and 0.86 t ha-1, respectively; and grain yields were 1.30, 0.59 and 0.22 t ha-1, respectively. The treatments with mucuna incorporated into the soil had lower bulk densities than the others; bulk densities in the mucuna only and control treatments were 1.53 g cm-3 and 1.65 g cm-3, respectively. The organic carbon and total N of soil, after harvest of the maize crop, were greater in the mucuna only treatment than the control; organic carbon in the mucuna only treatment was 1.1 % and in the control, 0.7 %, while total N values were 0.23 % and 0.16 %, respectively. The mucuna plus 50 kg N ha-1 treatment gave the lowest cost:benefit ratio, as a result of its comparatively higher grain yield and income. Cost:benefit ratios were 0.56 and 1.31 in the mucuna plus 50 kg N ha-1 and control treatments, respectively.