Effect of Different Irrigation Patterns on Soil Dissolved Organic Carbon and Microbial Biomass Carbon in Protected Field

Objective The objective of this study was to research the distribution characteristics in the profile of dissolved organic carbon(DOC),microbial biomass carbon(MBC) in protected field under three irrigation patterns(subsurface irrigation,drip irrigation and furrow irrigation).MethodThe modes of irrigation are subsurface irrigation,drip irrigation and furrow irrigation.The same irrigation experiments were conducted for ten years.Soil samples at different depths within 0-100 cm were collected and the contents of soil total organic carbon(TOC),dissolved organic carbon(DOC),microbial biomass carbon(MBC) and their profile distribution were determined.Result The results showed that the content of soil total organic carbon,dissolved organic carbon,and microbial biomass carbon were all showed the biggest amount in the soil surface and their content increased with layers' depth,but there were significant differences within irrigation methods.Soil total organic carbon content in 0-10 cm and 80-100 cm soil layers were furrow irrigationsubsurface irrigationdrip irrigation and in 10-80 cm soil layers was subsurface irrigationfurrow irrigationdrip irrigation.In 0-100 cm profile layers,DOC content showed furrow irrigationdrip irrigation subsurface irrigation.MBC content showed drip irrigationfurrow irrigationsubsurface irrigation.The content of DOC and MBC accounted for 4.98%-12.87% and 1.48%-2.82% of the total organic carbon,respectively.Their ratios were all showed drip irrigation furrow irrigationsubsurface irrigation.There were significant positive correlation between the content of soil dissolved organic carbon,the microbial biomass carbon and the soil total organic carbon content.Conclusion Furrow irrigation is conducive to accumulation of SOC and DOC;drip irrigation is conducive to an increase in MBC;subsurface irrigation is the least conducive to the accumulation of soil organic matter comparison,not only the content of TOC is low but also the content of DOC in the ratio of TOC is small.