Biochar-based pelletized seed enhances the yield of late-sown rapeseed by improving the relative growth rate and cold resistance of seedlings

The primary factors limiting the yield of late-sown rapeseed are poor germination, restricted seedling growth and weak cold resistance of seedlings. Seed pelletization is known for its convenience of carrying functional agents to improve seed germination and growth, but little research has been reported on late-sown rapeseed pelletization. Therefore, the rapeseed Huayouza-137 was used to pelletize with biochar and functional agents including 6-benzylaminopurine (6-BA), abscisic acid (ABA), salicylic acid (SA) and trehalose (Tre). Then these seeds were subjected to low-temperature incubator tests and 2-years late-sowing field experiment to study the effects on germination, seedling growth, cold resistance and yield. The results showed that: (1) Compared to the control, the highest yield was observed in Tre1 (DSR=1:50), which increased by 9.75 % in 2021–2022 and 5.88 % in 2022–2023. The 6-BA3 (DSR=1:300), ABA3 (DSR=1:150), SA3 (DSR=1:150) increased yield by 2.75 % ∼ 9.01 % in two growing season. (2) The 6-BA3, ABA3, SA3, Tre1 showed significant improvement in emergence and germination and the relative growth rate of seedlings was significantly higher. (3) Compared with TX0, the pelletizing treatments (6-BA3, ABA3, SA3, Tre1) significantly increased osmoregulatory capacity and enzymatic antioxidant capacity, and reduced membrane lipid damage and reactive oxygen species damage in seedlings during overwintering. (4) The redundancy analysis and correlation network analysis revealed the late-sown rapeseed yield was significantly and positively correlated with the relative growth rate and the cold resistance of seedlings during the overwintering. Overall, this study provides a innovative approach to improve late-sown rapeseed yield by biochar-based seed pelletizing.