Effects of straw returning and nitrogen application on yield and quality of hybrid indica rice under different rotation patterns

The effects of straw return and nitrogen fertilizer application on the quality and yield of indica rice were studied using the hybrid strain 'F you 498'. The multiple-straw rotation method was investigated using the straw return of three previous crops vegetable-rice (G), rape-rice (R), and wheat-rice (W). Nitrogen fertilizer was optimized by testing different ratios conventional application of pure nitrogen = 150 kg·hm^-2; base to tiller to panicle fertilizer ratios tested = 4:4:2 (N₁) and 3:3:4 (N₂). The results showed significant effects on the rice quality and yield in all of the straw return types and nitrogen fertilizer applications. Two factors had a large effect on the yield: the chalky grain rate and the grain protein content. The vegetable-straw yield (g) increased by 1.1%-7.8% compared to rape-straw (R), and by 10.5%-19.8% compared to wheat-straw (W). The vegetable-rice straw also improved the whole rice rate, reduced the chalky grain rate, and improved the food quality. Regardless of straw type, the yield increased after nitrogen fertilizer application, and the highest yield was obtained using the N₂ treatment. All straw types reduced the amount of nitrogen applied: N-G treatment by 16.7%, N-R treatment by 30.0%, and N-W treatment by 16.7%. Compared to the N₂ treatment, the yield decreased by 2.6% (N-G), 1.7% (N-R), and 5.8% (N-W). The rice yield was not significantly reduced when the N-G and N-R rotations were used, but the rice chalkiness rate and chalkiness degree were significantly reduced, and the quality improved. Therefore, rice quality was improved and yields were maintained, but nitrogen was saved. Based on the rice quality and yield when using the vegetable-rice straw rotation, the nitrogen fertilizer amount should be reduced to 125 kg·hm^-2, and a base to tiller to ear fertilizer ratio of 3:3:4 was the optimal combination in this study. When using the rape-rice and wheat-rice straw rotations, the nitrogen fertilizer amounts should be 105 kg·hm^-2 and 150 kg·hm^-2, respectively, and the fertilizer ratio remains 3:3:4. This study may provide a theoretical basis for improving the quality and yield of rice when using the straw return rotation method.