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Water and N management play a vital role in rice (Oryza sativa L.) production; however, limited information is available on the options to increase rice yield in rice-ratoon rice systems, including an appropriate combination of water regime (W), N application rate (N AR ) and N application method (N AM ). To address this question, field experiments were conducted with two Ws [simplified alternate wetting and drying (SAWD) and continuous flooding (CF)], four N ARs (control, N 0 ; 180 kg N ha -1 , N 180 ; 255 kg N ha -1 , N 255 ; and330 kg N ha -1 , N 330 ) and two N AMs [45% of fertilizer pre-plant, 15% of fertilizer at tilling, 40% of fertilizer at bud (BTB) and 45% of fertilizer preplant, 15% of fertilizer at boot, 40% of fertilizer during grain filling (BPG)]. On average, the grain yields of the main crop, the ratoon crop, and their total for SAWD were 3.7%, 6.8%, and 4.4% higher than for CF, respectively. The relationships between N AR and the main crop, ratoon crop, and total yields were well fitted by quadratic equations. The rice yields of the main crop, ratoon rice, and their total under BPG were equal to or slightly higher than those under BTB. The interactive effect of W×N AR was significant on the main rice crop yield and total rice yield, but W×N AM , N AR ×N AM and W×N AR ×N AM were all related to the soil-based yield. The use of integrated water and N management practices could achieve high yields and reduce water and N inputs in rice-ratoon rice systems. core Ideas• The relationships between N AR and the main crop, ratoon crop, and total yields were well fitted by quadratic equations. • The interactive effect of W×N AR was significant on the main rice crop yield and total rice yield, but W×N AM , N AR ×N AM and W×N AR ×N AM were all related to the soil-based yield. • The use of the SAWD-N 180 -BPG treatment could achieve high yields and reduce water and N inputs in rice-ratoon rice systems.

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Simplified cultivation methods for rice production offer considerable social, economic, and environmental benefits. However, limited information is available on yield components of rice grown using simplified cultivation methods in a rice-ratoon rice cropping system. A field experiment using two hybrid and two inbred rice cultivars was conducted to compare four cultivation methods (conventional tillage and transplanting, CTTP; conventional tillage and direct seeding, CTDS; no-tillage and transplanting, NTTP; no-tillage and direct seeding, NTDS) in a rice-ratoon rice system from 2017 to 2020. Main season yields for CTDS and NTDS were higher than for CTTP by 6.1% and 2.8%, respectively; whereas ratoon season yields for CTDS and NTDS were equal to or higher than for CTTP. Annual grain yields for CTDS and NTDS were higher than for CTTP by 4.4% and 3.2%, respectively. The higher CTDS and NTDS yields were associated with higher panicle numbers per m2 and biomass production. Rice hybrids had higher yields than inbred cultivars by 15.8–19.3% for main season and by 15.6–19.4% for ratoon season, which was attributed to long growth duration, high grain weight and biomass production. Our results suggest that CTTP can be replaced by CTDS and NTDS to maintain high grain yields and save labor costs. Developing cultivars with high grain weight could be a feasible approach to achieve high rice yields in the rice-ratoon rice cropping system in southwest China.

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