Jump to Main Content
Carbon availability and microbial biomass in soil under an irrigated wheat-maize cropping system receiving different fertilizer treatments
- Mahmood, T., Azam, F., Hussain, F., Malik, K.A.
- Biology and fertility of soils 1997 v.25 no.1 pp. 63-68
- soil microorganisms, biomass, carbon, nutrient availability, wheat soils, nitrogen fertilizers, urea, mineralization, biological activity in soil, biogeochemical cycles, seasonal variation, animal manures, application rate, semiarid zones, soil respiration, corn soils
- Seasonal changes in carbon availability and microbial biomass were studied in soil under an irrigated wheat-maize cropping system receiving different fertilizer treatments over the past 10 years. Treatments included N-100 and N-200 (urea at 100 and 200 kg N ha-1 year-1, respectively), FYM-16 and FYM-32 (farmyard manure at 16 and 32 t ha-1 year-1, respectively) and a control (unfertilized). Aerobically mineralizable carbon (AMC; C mineralized after 10 days aerobic incubation at 30 degrees C) increased (13-16%) under wheat at both rates of urea whereas under maize it increased (22%) only with the lower rate of urea. Farmyard manure also increased the content of soil AMC under both crops, the effect being two- to threefold higher under wheat than under maize. Urea application caused an 32-78% increase in the specific respiratory activity (SRA) under wheat but caused an 11-50% decrease during the maize season. Farmyard manure also resulted in a higher SRA under both crops but only at the higher application rate. Under wheat, microbial biomass C (MBC) decreased in urea-treated plots but showed a slight increase at the higher rate of FYM. During the maize season, MBC was higher under both urea (42-46%) and FYM (36-47%) treatments as compared to the control. Microbial biomass turnover rate was highest for FYM-32 (2.08), followed by FYM-16 and urea treatments (1.35-1.49); control plots showed a turnover rate of 0.82. The higher AMC and SRA during the active growth period of wheat than that of maize indicated that root-derived C from wheat was higher in amount and more easily degradable.