Improving ratoon rice grain yield and soil carbon pools in subtropical regions through integrated crop and soil management practices

Integrated crop and soil management measures have proven effective in enhancing crop yields and resource use efficiency, although the impacts on soil carbon pools and related microbial diversity remain unclear. In this study, we compared rice yield and soil properties between a local ratoon rice farming practice model without organic fertilizer application (FP) with an improved farming practice model (IFP) based on integrated management practices, including a > 20 % increase in planting density, 30 % increase in panicle fertilization, and application of 1.8 t/ha of organic fertilizer, in Hunan Province, China. The 5-year average annual rice grain yield was 32.0 % higher in the IFP (13.3 t/ha) than in the FP. Soil organic carbon (SOC) content was nonsignificantly higher by 9.2 % in the IFP (22.4 g/kg) than in the FP; furthermore, the labile organic carbon and dissolved organic carbon contents were 10.7 g/kg and 45.5 mg/kg, respectively, in the IFP, significantly higher than those of the FP and N-free control. The carbon pool management index in the IFP was 191.4 in 2022 and 132.9 in 2023, and was significantly higher by 95.0 % ( P < 0.05) than in the FP; the carbon pool activity and carbon pool activity index were similarly improved in the IFP. The average microbial biomass carbon in the IFP was 179.3 mg/kg, but did not differ significantly among the IFP, FP, and control. The bacterial and fungal Chao1 indexes were 5.6 % and 13.3 % higher, respectively, in the IFP (Chao1 for bacteria: 5252.5; fungi: 2291.5) than in the FP. The bacterial and fungal abundance-based coverage estimator (ACE) indexes were 7.2 % and 13.3 % higher, respectively, in the IFP (ACE for bacteria: 5871.5; fungi: 2530.4) than in the FP; however, there was no significant difference between the IFP and FP ( P > 0.05). These results support the efficacy of integrated agronomic measures in greatly increasing rice grain yield while supporting soil fertility through enhancing carbon pools and related microbial diversity. As modern ratoon rice production becomes increasingly mechanized, such measures will become easy to adopt. • The IFP with integrated agronomic measures could sharply increase rice grain yield. • The IFP could improve soil fertility through enhancing carbon pools and related microbial diversity. • The IFP involves measures will become easily to adopt on mechanization ratoon rice production.