Soil microbial biomass carbon and nitrogen dynamics under different cropping systems and nutrient management

Abstract

Feeding sub-Saharan Africa’s growing population demands intensification, yet soil biological health the engine of nutrient cycling is rarely monitored. This research examined microbial biomass carbon (MBC) and nitrogen (MBN) dynamics under three cropping systems (rice-rice, rice-legume, maize-wheat) and four nutrient management strategies at the University of Ghana research farm, Accra, during 2019-2022. MBC ranged from 148 µg g⁻¹ (maize-wheat, inorganic only) to 421 µg g⁻¹ (rice-legume, INM). MBC correlated positively with grain yield across all systems (r = 0.78-0.84). Stepwise regression showed MBC alone explained 31.4% of yield variation, with MBN, dehydrogenase activity, and available N contributing a further 34% (Figure 2). Rice-legume rotation with integrated nutrient management maintained the highest biological activity and sustained the steepest yield trajectory over eight consecutive seasons.