摘要
Field studies were conducted over 2 years to determine the response of soil microbial biomass pool to biochar and N fertilizer combinations in a rain-fed rice cropping system.Biochar was applied at four doses:0 t ha^(−1),3 t ha^(−1),6 t ha^(−1) and 12 t ha^(−1) in combination with N fertilizer at four rates:0 kg ha^(−1),30 kg ha^(−1),60 kg ha^(−1) and 90 kg ha^(−1) to a Typic Paleustalf Alfisol.Soil samples from two depths(0-10 and 10-20 cm)were collected to determine microbial biomass C(MBC),N(MBN),P(MBP),MBC/N ratio,MBC/P ratio,soil CO_(2) flux,microbial qCO_(2),cultivable bacterial and fungal abundance.Biochar and N fertilizer combination effects on MBC,MBN and MBP pools were dependent on biochar doses,N fertilizer rates and soil depth.MBC/N and MBC/P ratios were decreased after 2 years.Soil CO_(2) flux was maximum at post-seeding stage of rice plant,while decreasing trends occurred at active tillering and harvest stage.Increasing doses of biochar irrespective of its combination with N fertilizer rates decreased CO_(2) flux and microbial qCO_(2).Combinations of biochar and N fertilizer increased fungal/bacterial ratio and induced a shift to a more fungal-dominated population after 2 years.Our results sug-gest that combination of biochar doses(3-12 t ha^(−1))with N fertilizer rates had stimulatory effects on microbial biomass pools and activity with positive implications for organic carbon accumulation,nitrogen(N)and phosphorus(P)retention in tropical soils.
