Subsoil incorporation of crop residues enhances humic acid accumulation and its carbohydrates enrichment

摘要

Can subsoil incorporation of crop residues promote soil C sequestration? Soil organic matter(SOM)fractions were separated from four depths in three fields that were managed under either conventional incorporation of crop residues to 15 cm,subsoil incorporation to 35 cm,and no-tillage.The light fraction(LF),53 umparticulate organic matter(POM),mobile humic acid(MHA)fraction,and Ca-bound humid acid(CaHA)fraction were separated and characterized for their amounts and carbohydrate content.Results showed that SOM fractional masses were greater with subsoil incorporation than with conventional tillage or no-tillage.Moreover,results showed an enrichment of carbohydrates in soil and SOM fractions.The carbohydrates ratio of(galactose + mannose)/(arabinose + xylose)indicated a major contribution of plant derived carbohydrates to soil,the MHA and the CaHA.Subsoil incorporation of crop residues seems to enhance the accumulation of SOM fractions and their carbohydrate enrichment.