Effects of subsoil bulk density on rhizospheric soil microbial population, microbial biomass carbon and nitrogen of corn (Zea mays L.) field
下层土壤容重对玉米根际土壤微生物数量及微生物量碳、氮的影响

A mini-plot experiment was conducted to study the impacts of subsoil bulk density on rhizospheric soil microbial population, SMBC, and SMBN in corn field on a sandy loam soil at the Experimental Farm of Henan Agricultural University in 2005 and 2006. The plot was 1 m by 1m in size and was planted with six corns. Five different soil bulk density were included and the experiment was arranged in a randomized complete block design with four blocks. The population of soil bacteria, fungi, and actinomycete decreased with increase in soil bulk density and soil depth. Soil microbial biomass C and N response the same as soil microbial populations to soil bulk density and soil depth. The higher the soil bulk density, the less of soil microorganisms, SMBC and SMBN in the rhizosphere. All selected soil properties were significant differences among soil bulk densities in the same soil layer, and they were also affected by soil bulk density in the adjacent layers. The effects of soil bulk density on selected soil properties were more evident in the 20-40 cm than in the 40-60 cm depth. Furthermore, corn growth had a significant effect on microbial populations, SMBC, SMBN, in soil rhizosphere. The effects of soil bulk density on soil biochemical properties were more apparent at the corn silking stage than other growing stages.