PROMOTED AMINO SUGAR ACCUMULATION IN THE RHIZOSPHERE AND BULK SOIL OF A PADDY FIELD UNDER STRAW APPLICATION

Effects of straw application on amino sugars (a significant soil organic matter pool) in upland fields have received much attention, however, those in paddy fields remain unknown. We conducted a three-year experiment including three treatments: one without straw application (CK) and straw application at rates of 2500 (SA1) and 5000 (SA2) kg ha(-1) yr(-1). SA2 stimulated a higher increase in glucosamine (GluN), muramic acid (MurA), galactosamine (GalN), fungal-derived GluN (GluN(F)), and total amino sugars than SA1 in the rhizosphere and bulk soil in the first year. Generally, the positive effects of SA1 and SA2 on amino sugars did not differ in the last two years. Rhizosphere soil maintained a significantly higher content of MurA at 10.95%-16.35% than bulk soil. In total, rhizosphere soil accumulated insignificantly more GluN, GluNF, and total amino sugars than the bulk soil, indicating a limited positive effect of the rhizosphere on microbial-derived carbon. SA1 and SA2 notably increased the ratio of GluN(F)/MurA in bulk soil, implying that straw application increased the relative contribution of fungal-derived residues to soil organic carbon. This work may contribute to understanding the effect of straw applications on microbial residues and their contribution to soil organic carbon in paddy fields.