Rapidly improving infertile croplands and enhancing their soil organic carbon (SOC) pool necessitate substantial organic materials incorporation. Converting loose crop straw into granulated form facilitates uniform incorporation within the plough soil layer. As an innovative soil amelioration approach, the efficiency and patterns of SOC accumulation remain unclear. Two field experiments were conducted in infertile subtropical upland and paddy soils with 0, 30, 60, and 90Mg ha⁻¹granulated straw incorporation. After one year, SOC accumulation efficiency from straw input remained stable in upland (30.8–37.5%) with increasing amounts of straw incorporation, while declined from 60.0 to 38.3% in paddy. In both croplands, the contributions of lignin phenols to SOC increased with increasing straw incorporation, while the contributions from amino sugars remained constant at higher straw input levels. Subsequently, the ratios of lignin phenols to amino sugars increased with increasing straw incorporation, indicating faster plant residue accumulation compared to microbial necromass, as the granulation approach limited microbial involvement in straw transformation. Thus, single-time incorporation of substantial granulated straw presents an effective agricultural strategy for rapid amelioration of infertile croplands.

Japanese Andosols  /  different soil layers  /  organic rice farming  /  reconstructed fields  /  rice yield