Abstract: To clarify the effects of water management on soil ecological stoichiometric ratios and rice yield, we analyzed soil nutrients, stoichiometric ratios, microbial communities, and rice yield in paddy soils under flooding-rainfed (F-RF), flooding-midseason drying-flooding (F-D-F), and continuous flooding (CF) in a subtropical region, during the early and late rice seasons. The results showed that: (1) The highest soil dissolved organic carbon (DOC) content and DOC/available phosphorus (AP) were observed in the F-D-F. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and AP contents in the CF were lower than those in the F-RF and F-D-F. (2) Soil bacterial Shannon (6.4) and Chao1 (3549.9) indices as well as rice yield (6727 kg·hm^-2) were significantly higher (P<0.05) in the F-D-F than in the FRF during the late rice season. (3) Rice yield was positively correlated with soil DOC, DOC/available nitrogen (AN) and DOC/AP (P<0.05). Soil DOC, DOC/AN, and DOC/AP were significantly correlated with bacterial alpha diversity and the relative abundances of Clostridiales and Rhizobiales. (4) Structural equation modeling indicated that increased soil bacterial alpha diversity and relative abundances of Clostridiales and Rhizobiales stimulated soil DOC accumulation, which in turn increased DOC/AN and DOC/AP and ultimately increased rice yield. In conclusion, the F-D-F treatment increased soil bacterial alpha diversity, DOC content, and DOC/AN, DOC/AP, and thus resulted in higher rice yield.

Key words: paddy field, water management, ecological stoichiometric ratio, soil microorganisms, rice yield