Spatio-temporal Distribution Of Soil Physiochemical And Biological Properties In The Culticated Layer Under Different Tillage Systems

The effects of different tillage systems [conventional tillage (CT), no-tillage (NT), fallow (FF)] on soil physicochemical and biological properties (soil enzyme activities, microbial biomass carbon, soil nematodes), and spatiotemporal distribution of these parameters at different soil depths during the maize growing season were investigated in order to provide useful biological indicators for soil quality assessment in the aquic brown soil.The results showed that significant differences in soil moisture, pH and electronic conductivity were observed in different samping dates and tillage treatments. The concentration of exchangeable K⁺ differed distinctly among different tillage treatments. The contents of soil organic carbon (SOC) decresed with increasing depth, and distributed vertically. SOC was stratified and accumulated in the upper soil layers (0³0 cm) under NT and FF, while distributed uniformly under CT. No significant tillage effect on vertical distribution of SOC was found, and MBC had an evident surface accumulation in soil profiles. Significant differences in soil moisture, total nitrogen and NO₃--N were observed under different tillage treatments.Significant differences in soil enzyme activities, microbial biomass carbon (MBC) and soil nematodes were observed in different samping dates and depths. Except for ripening stage, the contents of MBC were significantly higher under NT than under CT at the 0⁵ cm depth. Significant differences in microbial biomass carbon were only found among different growth stages. Tillage systems had important influences on the MBCand nematode numbers at different depths during the maize growing season. Plant-parasitic nematode group was dominant among the four trophic groups in this study. Significant differences in soil bacterivores, fungivores, plant parasites and omnivores-predators were observed in different sampling dates, depths and tillage treatments. No significant differences in NCR was found among soil depths. Soil enzyme activities were affected by tillage systems at different depths during the maize growing season. Total N and exchangeable K⁺ were positively correlated with MBC, soil nematodes, diphenol oxidase, glucosidase and catalse; while exchangeable Mg²⁺ and pH were negatively correlated with dehydrogenase and glucosidase.The results showed that similar soil biological activities were observed between NT and FF, were higher than those under CT. Soil enzyme activities and nematodes were sensitive to soil environmental changes, which can be used as useful bioindicators for soil quality in the aquic brown soil.