Enhanced strategies for water and fertilizer management to optimize yields and promote environmental sustainability in the mechanized harvesting of ratoon rice in Southeast China

Ratoon rice utilizes the axillary buds sprouting from the remaining stubble of the main crop after harvest to form panicles, enabling a second harvest. However, mechanized harvesting often resulted in damage to the rice stubbles in the rolling zone, potentially leading to reduced yield. Enhancing the number of tillers in the rolling zone through optimized agronomic measures was crucial for achieving higher yield. However, research on water and fertilizer management corresponding to low stubble ratoon rice under mechanized harvesting was limited. A two-factor experiment was conducted to assess the impacts of water regimes (flooded; alternate wetting and drying) and nitrogen fertilizer management (0 kg N ha−1; Tiller promotion fertilizer 90 kg N ha−1; Split nitrogen application: Tiller promotion fertilizer 60 kg N ha−1 + Booting stage fertilizer 30 kg N ha−1) on the yield formation, greenhouse gas emissions, and carbon footprint of low stubble ratoon rice. The results indicated significant effects of water regimes and nitrogen fertilizer on yield. Compared to single application of tiller-promoting fertilizer coupled with continuous flooding (N-FL), Split application of tiller-promoting fertilizer coupled with alternate wetting and drying (SN-AWD) significantly increased average annual yield by 25.4 %. SN-AWD significantly increased the ratoon ability of the basal first and second nodes compared to N-FL. The soil quality index and ecosystem multifunctionality under SN-AWD increased by an average of 32.37 % and 10.16 times, respectively, compared to N-FL. This increase resulted in significant enhancements in root length and root surface area, consequently improving pre-anthesis and post-anthesis dry matter accumulation and ultimately enhancing yield. Although N2O emissions increased under SN-AWD compared to N-FL, CH4 cumulative emissions decreased significantly by 37.86 % on average over two years, leading to a 23.02 % reduction in total greenhouse gas emissions and a 38.62 % reduction in carbon footprint per unit grain. SN-AWD attained maximum net ecosystem economic benefit (NEEB), increasing by 35.42 % compared to N-FL. Overall, the comprehensive analysis suggested that SN-AWD was a sustainable water and fertilizer management approach beneficial for balancing ratoon season yields, environmental footprint, and economic benefits.