Effects of increased seeding density on seedling characteristics, mechanical transplantation quality, and yields of rice with crop straw boards for seedling cultivation

The high labor demand during rice seedling cultivation and transplantation poses a significant challenge in advancing machine-transplanted rice cultivation. This problem may be solved by increasing the seeding rate during seedling production while reducing the number of seedling trays. This study conducted field experiments from 2021 to 2022, using transplanting seedling ages of 10 and 15 days to explore the effects of 250,300, and 350 g/tray on the seedling quality, mechanical transplantation quality, yields, and economic benefits of rice. The commonly used combination of 150 g/tray with a 20-day seedling age in rice production was used as CK. The cultivation of seedlings under a high seeding rate and short seedling age significantly affected seedling characteristics, but there was no significant difference in seedling vitality compared to CK. The minimum number of rice trays used in the experiment was observed in the treatment of 350–10 (300 g/tray and 10-day seedling age), only 152–155 trays ha^–1, resulting in a 62% reduction in the number of trays needed. By increasing the seeding rate of rice, missed holes during mechanical transplantation decreased by 2.8 to 4%. The treatment of 300–15 (300 g/tray and 15-day seedling age) achieved the highest yields and economic gains. These results indicated that using crop straw boards can reduce the application of seedling trays. On that basis, rice yields can be increased by raising the seeding rate and shortening the seedling age of rice without compromising seedling quality.