CO2 efflux and microbial activities in undisturbed soil columns in different nitrogen management

The surface carbon dioxide (CO2) fluxes together with the soil microbial biomass and activity in undisturbed soil columns were studied in three growing seasons. Soil columns had six treatments: (1) control without plants; (2) mineral fertilized without plants; (3) no fertilizer and maize plants; (4) mineral fertilized and maize plants; (5) manure and maize plants; (6) mineral fertilized plus manure and maize plants. Soil microbial biomass was measured by substrate-induced respiration (SIR) and microbial activity as fluorescein-diacetate hydrolysing activity (FDA). Treatments had a significant effect (P < 0.001) on CO2 fluxes, SIR and FDA. The presence of maize increased CO2 efflux, SIR and FDA compared to unplanted column. Fertilizer + manure treatment resulted in the greatest plant biomass and the greatest CO2 efflux. Significant correlation (r = 0.680; r = 0.586 in two consecutive years) between SIR and FDA was found.