Effects of side-deep fertilization on yield formation and nitrogen absorption of high-quality early indica rice under precision sowing in line and machine planting

As a major grain crop in China, the efficient cultivation of rice is essential to ensure national food security. Side-deep fertilization and precision drill sowing technology are key measures to improve the efficiency of mechanized rice cultivation. This study aims to elucidate the effects of side-deep fertilization on rice yield formation, rice quality, and nitrogen absorption under precision drill sowing and machine planting, providing a theoretical basis for mechanized high-quality rice cultivation in the southern rice region. In 2022-2023, field experiments were conducted using the Wufengyou 286 rice cultivar. The experiments included two factors: mechanical seeding and raising (precision drill sowing (PS) and broadcast sowing (BS)), and fertilization method (side-deep fertilization (SF) and conventional surface fertilization (CK)). The effects of different treatments on seedling quality, machine transplanting quality, yield formation, nitrogen absorption, and rice quality of high-quality early indica rice were investigated. (1) The yield of precision drill sowing with side-deep fertilization was significantly the highest. Compared with conventional surface fertilization, side-deep fertilization increased rice grain yield by 9.97%-19.62%. Compared with broadcast sowing, precision drill sowing increased rice grain yield by 4.32%-6.29%, primarily due to improvements in the effective panicle number and uniformity of the machine-transplanted population. (2) Precision drill sowing significantly improved the quality of seedlings, reducing the missing hill percentage of machine transplanting by 5.6%-6.0%, and improving the uniformity of seedling number transplanted per hill by 22.0%-33.0%. (3) Both side-deep fertilization and precision drill sowing improved the number of tillers at the tillering peak stage. These methods also increased dry matter accumulation and leaf area index during the rice growing period.Side-deep fertilization, compared with conventional fertilization, increased dry matter accumulation at maturity by 15.71%-18.08% and leaf area index by 19.15%-20.78%. Precision drill sowing, compared with broadcast sowing, increased dry matter accumulation at maturity by 4.56%-7.42% and leaf area index by 8.08%-9.88%. (4) During the middle and late rice growth stages (panicle initiation to maturity), precision drill sowing with side-deep fertilization increased nitrogen accumulation. Side-deep fertilization, compared with conventional fertilization, increased nitrogen accumulation at maturity by 22.66%-28.24%. Precision drill sowing, compared with broadcast sowing, increased nitrogen accumulation at maturity by 7.97%-11.76%. (5) Compared with conventional fertilization, side-deep fertilization significantly reduced the chalky grain rate by 10.63%-20.41%, chalkiness by 13.63%-19.62%, and amylose content by 8.08%-10.42%, but increased protein content by 10.98%-11.25%. In conclusion, side-deep fertilization under precision drill sowing and machine planting can improve seedling quality, machine transplanting quality, rice tillering and panicle formation, growth and development, and nitrogen absorption, thereby increasing the yield of high-quality early indica rice. Additionally, while the appearance quality of rice was improved, the protein content of rice was also increased.