Effects of Two Sowing Methods on the Growth, Yield, and Quality of Hybrid Rice under Mechanical Transplantation

Poor adaptability of hybrid-rice (Oryza sativa L.) mechanical transplanting is one of the main factors limiting hybrid-rice production. Mixed sowing ensured stronger seedlings and better mechanical transplanting quality than conventional sowing in mechanical transplanting hybrid rice. Field experiments were conducted to identify the effects of mixed and conventional sowing of hybrid rice on rice growth, yield, and quality under mechanical transplantation in Yangzhou City, Jiangsu Province, China in 2021 and 2022. Two hybrid-rice varieties, japonica rice Changyou 4 and indica rice Yuanliangyou, and two conventional rice varieties, japonica rice Nanjing 5055 and indica rice Yangdao 6 were included in this study. Both japonica and indica rice showed the following results. There were no significant differences in biomass and leaf-area index of rice under different sowing methods at the heading and maturity stages. The basic seedling and spike rate was 38.27% and 16.24% higher, respectively, in mixed sowing than those averages in conventional sowing. In addition, the spikelets per panicle of hybrid rice in mixed sowing was 10.88% greater than the average in conventional sowing, indicating better heterosis. Compared to conventional sowing, mixed sowing increased the average gel consistency and taste value by 15.86% and 28.21%, respectively, while chalkiness degree, amylose content, and protein content decreased by an average of 60.47%, 44.89%, and 36.63%, respectively. Our study showed that similar biomass and leaf-area index, large basal seedling and spike rate, and large spikelets per panicle of hybrid rice are the keys to ensuring high yield in mixed sowing. At the same time, mixed sowing improved the appearance, nutrition, and cooking/eating qualities of the rice.