Abstract:

This study aimed to investigate the relationship between bolting yield and seed yield in vegetable and oilseed dual purpose rape, determine the optimal bolting harvest level, and establish efficient agronomic practices for dual purpose rape. Field experiments were conducted during 2024-2025 in Wuxue City and Shayang County, Hubei Province. A gradient control method was used, with 11 treatments of bolting yield levels ranging from 0 (no bolting yield) to 7.50 t/hm². The response patterns of key indicators were analyzed, including bolting biomass, seed yield, harvest index, and seed yield components. The results showed that seed yield initially increased slightly but subsequently declined continuously with increasing bolting yield. When the bolting yield was 0.75 t/hm², seed yields peaked at 3269 kg/hm² in Wuxue and 3095 kg/hm² in Shayang, which were increased by 5.3% and 3.8%, respectively, compared to the non-harvested control. However, when bolting yield exceeded 4.50 t/hm², seed yields decreased by 13.8%-43.9% in Wuxue and 11.3%-43.5% in Shayang compared to the control. The primary reason was a reduction in pods per plant which decreased by an average of 35.7% and 34.3% at the two sites, respectively. Yield component analysis revealed that pods per plant was the dominant factor influencing seed yield, with relative contribution rates of 46.3% (Wuxue) and 42.9% (Shayang), followed by plant density (24.8% and 31.3%) and seeds per pod (20.2% and 16.2%), while 1000-seed weight had minimal impact. Quadratic regression models between bolting yield and seed yield identified two critical thresholds: a yield-neutral bolting yield threshold (1.76 t/hm² for Wuxue and 2.18 t/hm² for Shayang), below which seed yield remained unaffected, and an economically optimal threshold (4.02 t/hm² for Wuxue and 4.27 t/hm² for Shayang) that balanced economic benefits with seed yield (achieving 90% of non-harvested yield). These findings suggest that a bolting yield of approximately 2 t/hm² maximizes dual-purpose productivity without compromising seed yield, and bolting yield should be controlled below 4t/hm² to balance economic returns and seed production. Field practices should select appropriate bolting yields based on targeted seed yield goals and economic priorities.

Key words: oilseed rape, vegetable and oilseed dual purpose rape, bolting yield, yield, yield components