Effect of tillage, rhizobium inoculation in maize-soybean based cropping systems and nitrogen fertilizer application on chemical fertility status of savanna Alfisol, Nigeria

Field experiment was conducted at Research Farm of Institute for Agricultural Research, Ahmadu Bello University, Samaru, Nigeria, to investigate the effect of tillage, rhizobium inoculation in maize-soybeanbased cropping systems and nitrogen fertilizer application on chemical fertility status of a savanna Alfisol. The study was split-split plot design with three replications using improved soybean variety (TGX-1448-2E) and maize (SAMMAZ 14). The treatments were two tillage practices (reduced and conventional tillage) as main plot, four rhizobium inoculation in soybean-maize-based cropping systems (inoculated soybean-maize intercrop, uninoculated soybean-maize intercrop, inoculated soybean-maize rotation and uninoculated soybean-maize rotation) as sub-plot and four nitrogen fertilizer rates (0, 40, 80 and 120 kg N ha-1) as sub-sub plot. At harvest, soil samples were taken from each of the experimental plots and analyzed for selected soil chemical properties. Soil organic carbon, total nitrogen, soil pH, available phosphorus and exchangeable bases were consistently higher under reduced tillage (RT) than under conventional tillage (CT). Soil organic carbon, total nitrogen, soil pH, available phosphorus and exchangeable bases were significantly higher under rhizobium inoculated soybean-maize rotation compared to other cropping systems. A significant difference was found among the effect of nitrogen rates on soil organic carbon, total nitrogen, soil pH, available phosphorus and exchangeable potassium which were significantly lower under 0 kg N ha-1. The study demonstrated that integration of rhizobium inoculated soybean in soybean-maize-based cropping systems under tillage practices, especially RT would improves chemical fertility status of the soil and subsequently reduced N application rate from 120 to 80 kg N ha-1.Key words: tillage, rhizobium inoculation, cropping systems, Nitrogen fertilizer, chemical fertility, Alfiso