Short-term effect of tillage, bradyrhizobium inoculation and nitrogen fertilizer application on carbon stock and soil nitrogen in maize-soybean cropping systems in Nigeria Alfisol

The role of soil carbon and nutrients conservation and management is gaining more attention in mitigating climate change, while enhancing sustainable food production. To such, short-term experiments (2011 and 2012) were conducted at the Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria to assess the role of some integrated soil management on soil health under maize-soybean cropping systems. Split-split plot design was used for establishment of the research with three replications using TGX-1448-2E and SAMMAZ 14 as test crops. The treatments were reduced and conventional tillage as main plot, rhizobium inoculated soybean-maize intercrop, rhizobium uninoculated soybean-maize intercrop, rhizobium inoculated soybean-maize rotation and rhizobium uninoculated soybean-maize rotation as sub plot and 0, 40, 80 and 120 kg N ha-1 application rates as sub-sub plot. The soil samples taken from each experimental plot were analysed. The results showed that organic carbon (OC) and nitrogen (TN) were consistently higher in reduced tillage (RT) (6.59 and 1.11 g/kg) than under conventional tillage (CT) (6.32 and 1.06 g/kg) respectively. Carbon stock obtained was 11.42 % higher in RT treatment. The values of OC, TN and carbon stock obtained under rhizobium inoculated soybean-maize rotation was significantly higher, followed by rhizobium inoculated soybean-maize intercrop and rhizobium uninoculated soybeanmaize intercrop. Significant difference was found among effects of N rates on carbon stock and total nitrogen, which were consistently lower in control plots. The study demonstrated that integration of rhizobium inoculation in maize-soybean cropping systems under tillage practices; especially reduced tillage in combination with 80 kg N ha-1 improved soil productivity for mitigating climate change and global warming.Keywords: Tillage, Rhizobium inoculation, Nitrogen fertilizer, carbon stock and nitrogen status