Carbon accumulation efficiency of granulated straw incorporation and its response to nutrient supplement in infertile agricultural soils: Evidence from biomarkers

Granulating fluffy straw into high-density particles is an innovative approach for uniformly incorporating straw into plough layers. However, massive granulated straw incorporation probably causes microbial nutrient limitation, decreasing straw-C accrual and crop yield. Whether nutrient supplement increases straw-C accumulation remains unclear. In this study, we conducted one-year of micro-plot experiments incorporating massive granulated straw with initial C:N ratio (GS) and adjusted the C:N ratio by nutrient supplement (GSN) in infertile upland and paddy. After one year, GS incorporation greatly improved the surface (0–20 cm layer) soil organic C by 91% and 80% in upland and paddy, respectively, compared to their control. In upland, GS led to lower lignin phenols but higher amino sugars than paddy owing to its stronger microbial anabolism. In upland, GSN incorporation decreased soil organic C by 11.3% than GS by reducing lignin phenols and amino sugars. However, GSN incorporation increased organic C by 2.2% in paddy, via promoting microbial necromass accumulation. GSN incorporation improved crop yield by 26.6% in upland and 12.0% in paddy than GS. Collectively, granulated straw incorporation effectively enhances organic C and crop yield but that responses to nutrient supplement depend on soil properties. Tailored nutrient management is crucial to optimizing C sequestration and productivity in diverse soils.