Abstract:

The weedy rapeseed (volunteer rapeseed) in the direct seeding area of rice-rape rotation is serious, which competes fiercely with cultivated rapeseed and reduces the yield and quality. The existing prevention and control technology is difficult to adapt to mechanized production. To elucidate the effects of tillage practices and pre-germination gibberellic acid (GA₃) application on the occurrence of volunteer rapeseed and the yield and quality of cultivated rapeseed in rice- rapeseed rotation fields, thereby providing a basis for developing effective control strategies, the study was conducted in a long-term rice-rapeseed rotation field. Employing two tillage methods(rotary tillage and no-tillage) combined with varying rates of pre-emergence GA₃ application (0, 2.25, 4.5, 9.0, 13.5, and 18.0 L/hm²), density of volunteer rapeseed, the yield and quality parameters of cultivated rapeseed, were measured. Results showed that volunteer rapeseed density significantly exceeded that of the cultivated crop, being 7.6-8.1 times and 5.0-6.1 times higher under tillage and no-tillage conditions, respectively. Emergence surveys indicated that tillage increased volunteer emergence by 176.9% and 131.7% compared to no-tillage. Under no-tillage, the GA₃ treatment at 18.0 L/hm² increased volunteer emergence by 192.3%-240.3% relative to the control (0 L/hm²). Regarding yield, cultivated rapeseed yields under all treatments were lower than those of volunteer plants, reaching only 48.61% and 60.23% of volunteer rape yields under tillage and no-tillage, respectively. In terms of quality, cultivated rapeseed exhibited an oil content (mean 43.14%) that was 16.5% higher than that of volunteer rape, while its glucosinolate content was 34.45% lower. High-concentration GA₃ (e.g., 18.0 L/hm²) significantly increased cultivated rapeseed yield under no-tillage conditions (up to 1171.03 kg/hm²) and moderately reduced seed glucosinolate content. Combining tillage with pre-germination gibberellic acid regulation effectively suppresses volunteer rapeseed occurrence while enhancing the yield, oil content, and fatty acid composition of the cultivated crop. When integrated with irrigation-induced germination and crop rotation measures, this approach enables sustainable pest management in rapeseed production. In the future, the research on the activation mechanism of dormant seeds in different soil layers and the integrated prevention and control technology of agricultural machinery and agronomy can be further carried out to provide support for the green, high-yield and high-efficiency production of rapeseed in the rice-rape rotation area of Southwest China.

Key words: rapeseed, rice-rape rotation, weedy rapeseed, tillage practices, pre-sowing germination regulation, gibberellic acid (GA₃), seed dormancy, yield, quality