Mitigation of soil water stress by moderately deep sowing and exogenous application of glucosinolates during the early seedling stage in rapeseed

Introduction Determining the optimal sowing depth suitable for different water conditions is a key agronomic factor for crop establishment and yield potential. This study aimed to identify the optimal sowing depth for rapeseed that maximizes seedling vigor under varying water conditions. Methods Seedling emergence and plant growth were evaluated under four water conditions (variable moisture, drought, normal water, and waterlogged) at different sowing depths (1–5 cm). Meanwhile, the hypothesis that seedling vigor under deep sowing conditions could be improved by exogenous application of glucosinolates (GS) was tested. Results Results indicated that the highest seedling emergence percentage (EP) was observed at 3 cm, representing increases of 123.2% (variable moisture), 100% (drought), and 11.1% (normal water) compared with 1 cm. Under waterlogged stress, seedling EP showed no significant differences between 1 and 3 cm for 50% of the 16 cultivars. Moreover, seedling EP was significantly improved at 3 cm after seed priming with GS compared with 1 cm, with increases of 46.4% (drought) and 63.0% (waterlogged), whereas no significant differences were observed under normal water conditions. Furthermore, plant phenotypic performance indices were higher at 3 cm with GS treatment than at 1 cm across all water conditions. Discussion Collectively, a sowing depth of 3 cm combined with exogenous application of GS not only promoted seedling emergence but also benefited subsequent plant growth in direct-sown rapeseed. These results provide practical insights for ensuring reliable seedling establishment in rapeseed.