Plant growth regulators used to prevent excessive vegetative growth and increase pod formation in soybeans work by inhibiting unproductive vegetative growth, thereby concentrating nutrients on flowers and pods. This achieves growth control without sacrificing yield, ultimately boosting pod set rates and total production. Specific strategies are outlined below:
Commonly Used Regulators and Their Effects
Prohexadione-calcium:A mild growth-control agent that inhibits excessive stem elongation without affecting leaf or pod development. It shortens internodes, thickens stems, and significantly improves lodging resistance. It also promotes flower bud differentiation, leading to increased flowering and pod formation, making it a preferred choice for soybean growth control. The 5% suspension concentrate (SC) formulation is suitable for field spraying; it disperses evenly, providing a gentle growth-control effect that does not cause crop growth to stall completely.
Paclobutrazol:By inhibiting gibberellin biosynthesis, this agent shortens internodes and promotes root development. It directs dry matter toward the pods, effectively increasing the pod set rate. It is a commonly used, Ministry of Agriculture and Rural Affairs-approved agent for soybean growth control, suitable for major soybean-producing regions such as Northeast China and the Huang-Huai-Hai Plain.
Compound Growth-Control Agents:Examples include 30% Paclobutrazol + Mepiquat Chloride (SC) and 30% Uniconazole + Mepiquat Chloride (micro-emulsion). Spraying these during the 4–6 trifoliate leaf stage (branch formation stage) helps shape a compact plant structure, reduces flower and pod drop, and improves ventilation and light penetration within the crop canopy.
(Yield-Boosting Agent): Spraying once during the seedling stage and once during the flowering stage—with optional follow-up sprays during the pod-setting stage—promotes nutrient transport to the pods. This reduces the incidence of empty pods and shriveled grains while increasing the number of pods per plant.
Brassinosteroids and 14-Hydroxy-brassinosteroid + Thidiazuron:These are key regulators recommended for the "one spray, multiple benefits" (integrated growth promotion) strategy. When applied with foliar fertilizers during the pod-setting and grain-filling stages, they prevent premature senescence and promote grain filling, further increasing grain weight and solidifying yield gains.
