Application of organic and inorganic fertilizer for sustainable maize and cowpea yields in Nigeria

A pot experiment evaluating the influence of five rates each of compost, inorganic fertilizer (MFert), and combination of both fertilizers (OBF) on maize (Zea mays L.), performance was conducted in the greenhouse using three cropping cycle. This was followed by a field trial lasting four cropping seasons at Ilora in the derived savanna and at Ibadan in the forest zones of Nigeria. Maize followed by cowpea was used as test crops on the field. Application of the fertilizers led to increases in maize and cowpea grain yields and improved the nutrient element concentrations in maize leaf tissue. Agronomic effectiveness of compost and OBF on maize relative to MFert was 88 and 118%, at Ilora and 81 and 97% at Ibadan. There was an increase of 56 and 89% Relative Agronomic Effectiveness (RAE), for compost and OBF over MFert in the residual study on cowpea. Also, the soil macro and micro nutrient status was highly improved in comparison with the MFert at postharvest period. The optimum rates of the organic fertilizers for sustainable maize and cowpea yield were between 5 and 10 t ha(-1). The agronomic effectiveness of the residual organic fertilizers was higher than that of MFert. Optimum rate of OBF was 5 t ha(-1). Application of compost significantly increased total microbial biomass in the soil. Also, compost and OBF application led to a fairly high population of Azotobacter (N-fixing bacteria) and thus its biomass. The MFert, however caused a sharp reduction in microbial biomass in the soil. The organic fertilizer improved aggregate stability index and permeability of the soil. On the whole, the positive effects obtained from OBF and compost in this study favor the recycling of farm wastes for sustainable crop production.