Ensuring high yields of late-sown rapeseed plays a crucial role in mitigating the conflict of cropping seasons between rice and rapeseed cultivation, while maximizing the utilization of winter fallow fields in the Yangtze River Basin (YRB). In this study, we focused on the early-maturing rapeseed variety, Huayouza 137. A completely randomized block design was employed, including a control group (CK) with clear water, as well as treatments with different concentrations of gibberellic acid (GA3) at 10, 25, and 50 mg L-1 (G1, G2, G3), 2,4-epibrassinolide (2,4-EBR) at 0.25 mg L-1 and 0.5 mg L-1 (B1, B2), and Diethyl aminoethyl hexanoate (DA-6) at 10 and 20 mg L-1 (D1, D2). The foliar spraying of these regulators was carried out at the 3-leaf stage from 2021 to 2023, and their effects on nitrogen utilization and yield formation of late-sown rapeseed during the overwintering stage were investigated. The results showed that moderate concentrations of GA3, 2,4-EBR, and DA-6 significantly enhanced the yield of late-sown rapeseed compared to CK. However, excessive application of regulators, such as GA3 and B2 treatments, had a negative impact. Notably, G1, B1, and D2 treatments exhibited the highest yield increases. Specifically, compared to CK, they resulted in yield increments of 13.9%, 10.3%, and 6.3% from 2021 to 2022, and 12.5%, 7.2%, and 6.2% from 2022 to 2023, respectively. Foliar spraying regulators also increased the leaf area and leaf dry matter. On one hand, the content of leaf gibberellin (GA3), indoleacetic acid (IAA), and zeatin (Zt) increased, while the abscisic acid (ABA) content decreased, leading to an expansion of the leaf area. On the other hand, the activities of leaf nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthetase (GOGAT) increased, enhancing the nitrogen assimilation capacity of the leaves and resulting in increased leaf dry weight. Correlation analysis revealed that yield was positively correlated with leaf area and leaf dry matter. Leaf area showed a positive correlation with GA3, IAA, and Zt content, while negatively correlating with ABA content. Moreover, NR, GS, and GOGAT activities were positively correlated with GA3, IAA, and Zt content, respectively, while negatively correlated with ABA content. In conclusion, foliar spraying of late-sown rapeseed with appropriate concentrations of GA3, 2,4-EBR, and DA-6 at the 3-leaf stage enhanced the activities of NR, GS, and GOGAT enzymes. This, in turn, improved leaf nitrogen assimilation capacity and nitrogen use efficiency by regulating hormone levels in the leaves. Additionally, it facilitated leaf expansion, resulting in a larger leaf area, increased dry matter accumulation, and ultimately higher yield. Among the treatments, G1 (10 mg L-1 GA3), B1 (0.25 mg L-1 2,4-EBR), and D2 (10 mg L-1 DA-6) demonstrated the most effective outcomes. This study provides important theoretical and technical support for the exogenous regulation of late-sown rapeseed cultivation in the YRB, particularly in terms of pre-winter strong seedling cultivation, and the improvement of winter fallow field utilization.
WeChat
WeChat