Organic and chemical fertilizer input management on maize and soil productivity in two agro-ecological zones of Ghana

In a two-season study, six treatments comprising three organic resources (ORs) [ Centrosema pubsecens (CENT), Crotalaria juncea (CROT), and Zea mays (MZE)], two conventional chemical fertilizer (CF) applications plus control were tested at Nyankpala (Guinea savannah) and Kade (Deciduous forest) to identify suitable conditions to optimize their effects on maize yield and soil chemical and microbial biomass. Aboveground biomasses of each OR were applied to respective plots at 4 Mg ha −1 season −1 , followed by basal NPK 15:15:15 and subsequent topdressing with [(NH 4 ) 2 SO 4 ] at 40 kg ha −1 and 30 kg N ha −1 , respectively. Maize yield response was significant in Nyankpala compared to Kade. Average maize grain yield increased from 1.2 to 1.7 t ha −1 at Nyankpala versus 1.1 to 1.4 t ha −1 at Kade. Additionally, MZE plus CF consistently showed high average grain yield at both sites. On average, agronomic N use efficiency (AE N ) increased from 4.9 to 18.3 kg grain kg −1 N applied at Nyankpala against a reduction from 13.0 to 12.3 kg grain kg −1 N applied at Kade. Moreover, AE N increased with year of cultivation in the sole CF and MZE plus CF treatments. However, CROT plus CF treatment enhanced microbial biomass compared to sole CFs at both sites. Overall, while the effects of MZE with CF application on maize yield appeared suitable at both sites, inconsistent responses were observed in CENT and CROT amendments. We conclude that soil fertility and climate are essential variables in regulating the effects of OR and CF inputs on yield and AE N in maize production systems.