Biological Nitrogen Fixation and Productivity of Soybean in Maize-Soybean Intercrop under Tillage and Bradyrhizobium Inoculation on Alfisols of Northern Guinea Savanna, Nigeria

Abstract

A field study was conducted in the 2011 cropping season to investigate the effect of tillage and bradyrhizobium inoculation of soybean on biological nitrogen fixation (BNF) and yield components in maize-soybean intercropping systems. Treatments comprised of two tillage practices (conventional tillage (CT) and reduced tillage (RT)) as the main plot and bradyrhizobium inoculation at four levels (inoculated sole soybean, inoculated soybean/maize intercrop, uninoculated sole soybean, and uninoculated soybean/maize intercrop) as sub-plot. The treatments were laid in a split-plot under a randomized complete block design with three replications. Results showed that BNF and nitrogen derived from atmospheric (Ndfa) were significantly higher under RT than CT by 4.18 and 0.10 %, respectively. The BNF was consistently higher in the maize-soybean intercropping system with soybean inoculated with bradyrhizobium than in the uninoculated. BNF was 28.0 % higher in inoculated sole soybean and 80.2 % higher in inoculated maize-soybean intercrop than the uninoculated sole and intercropping system. Similarly, grain yield was 31.0 % higher in the inoculated sole soybean than the uninoculated sole and 33.7 % higher in inoculated maize/soybean intercrop than in the uninoculated intercrop. Biomass yields under inoculatedsole soybean and maize-soybean intercrop, respectively, were significantly higher than in uninoculated sole soybean and maize-soybean intercrop by 30.99and 33.66% for inoculated and uninoculated soybean sole and 34.44 and 30.40 % for inoculated and uninoculated intercrop. The results demonstrated that integrating bradyrhizobium inoculants and tillage will improve N fixation and productivity in maize-soybeanbased intercropping systems in Alfisols of Northern savannah.