Optimizing nitrogen management can improve stem lodging resistance and stabilize the grain yield of japonica rice in rice-crayfish coculture systems

Nitrogen(N)significantly affects rice yield and lodging resistance.Previous studies have primarily investigated the impact of N management on rice lodging in conventional rice monoculture(RM);however,few studies have performed such investigations in rice-crayfish coculture(RC).We hypothesized that RC would increase rice lodging risk and that optimizing N application practices would improve rice lodging resistance without affecting food security.We conducted a two-factor(rice farming mode and N management practice)field experiment from2021 to 2022 to test our hypothesis.The rice farming modes included RM and RC,and the N management practices included no nitrogen fertilizer,conventional N application,and optimized N treatment.The rice yield and lodging resistance characteristics,such as morphology,mechanical and chemical characteristics,anatomic structure,and gene expression levels,were analyzed and compared among the treatments.Under the same N application practice,RC decreased the rice yield by 11.1-24.4% and increased the lodging index by 19.6-45.6% compared with the values yielded in RM.In RC,optimized N application decreased the plant height,panicle neck node height,center of gravity height,bending stress,and lodging index by 4.0-4.8%,5.2-7.8%,0.5-4.5%,5.5-10.5%,and 1.8-19.5%,respectively,compared with those in the conventional N application practice.Furthermore,it increased the culm diameter,culm wall thickness,breaking strength,and non-structural and structural carbohydrate content by 0.8-4.9%,2.2-53.1%,13.5-19.2%,2.2-24.7%,and 31.3-87.2%,respectively.Optimized N application increased sclerenchymal and parenchymal tissue areas of the vascular bundle at the culm wall of the base second internode.Furthermore,optimized N application upregulated genes involved in lignin and cellulose synthesis,thereby promoting lower internodes on the rice stem and enhancing lodging resistance.Optimized N application in RC significantly reduced the lodging index by 1.8-19.5%and stabilized the rice yield(>8,570 kg ha~(-1)on average).This study systematically analyzed and compared the differences in lodging characteristics between RM and RC.The findings will aid in the development of more efficient practices for RC that will reduce N fertilizer application.