In straw return rice regions of Northeast China, the insufficient effective panicles and low nitrogen(N) use efficiency (NUE) are the primary factors limiting yield. To address this issue, field experiments were conducted during 2023-2024 on rice paddies that had undergone continuous straw return for six consecutive years. This study aimed to explore cultivation models that synergistically enhance yield, NUE, and economic benefits under straw return. The experiment included two planting densities (D) of D1 (30 cm×13.3 cm) and D2 (30 cm×10 cm), two N fertilizer types of conventional urea (U) and blended controlled-release N fertilizer (CRU), and four N levels of 0 kg/ha (N0), 105 kg/ha (N1), 140 kg/ha (N2), and 175 kg/ha (N3, traditional N level). The results showed that D2CRUN2 achieved the highest yield, with an increase of 16.43% compared with D1UN3. This yield increase was primarily attributable to a 16.07% increase in panicles per m 2 . Further analysis revealed that the interaction among D, N fertilizer type and N level significantly affected crop growth rate (CGR), net assimilation rate (NAR), transport ratio of biomass per stem-sheath (TRBS), and export ratio of biomass per stem-sheath (ERBS). D2 and CRU increased CGR (16.64% and 24.56%, respectively) and NAR (9.89% and 9.63%, respectively) but decreased TRBS (7.62% and 12.86%) and ERBS (7.50% and 12.93%). N application exhibited similar trends. Compared with D1UN3, the optimal model D2CRUN2 significantly increased CGR (23.16%) and NAR (11.13%) but decreased TRBS (12.48%) and ERBS (12.58%), thereby optimizing dry matter accumulation and transport. Simultaneously, D2CRUN2 increased NUE, soil organic carbon (SOC), and NO 3 - -N by 54.03%, 6.79%, and 5.25%, respectively, compared to D1UN3, which facilitated yield formation and significantly boosted net profit by 38.05%. Therefore, under long-term straw return, D2CRUN2 improves soil fertility, plant population structure, yield, NUE, and economic benefits. ig. 1. The partial least squares path models (PLS-PM) describes the relationships among different factors. D, planting density; T, type of N; NL, N level. • The synergistic optimization of density and CRU achieves dual improvements in yield and efficiency. • D2CRUN2 was revealed to improve the physiological mechanism of photosynthesis and matter transport. • It has resolved the challenge of reconciling increased yields with enhanced efficiency under straw return.
Wu et al. (Sun,) studied this question.