The use of prohexadione calcium in cotton topping primarily aims to control plant growth, shape an ideal plant structure, and increase yield. Its mechanism of action, combined with traditional topping methods (manual or chemical), more effectively optimizes nutrient allocation in cotton.
Its specific effects are manifested in the following aspects:
1. Inhibiting main stem elongation and promoting fruit branch development:
Prohexadione calcium effectively inhibits the excessive growth of the cotton main stem, controlling plant height while promoting the elongation and increase in the number of fruit branches. This results in a more rational plant structure, facilitating ventilation, light penetration, and mechanized harvesting.
2. Promoting nutrient transfer to reproductive organs:
By inhibiting the later stages of gibberellin synthesis, prohexadione calcium reduces nutrient consumption by vegetative growth (such as excessive stem and leaf growth), promoting the transfer of photosynthetic products to reproductive organs such as buds and bolls, thereby increasing the number of bolls per plant and yield.
3. Enhancing stress resistance and disease resistance: Prohexadione calcium can improve the stress resistance of cotton plants, helping to alleviate physiological stress caused by topping, and has a certain control effect on some diseases (such as leaf spot).
4. Environmentally friendly and low residue: Compared with traditional triazole retardants (such as chlormequat chloride), prohexadione calcium degrades rapidly in the environment, has a short half-life, and has no residual toxicity to rotational crops, making it a more environmentally friendly plant growth regulator.
Studies have shown that applying prohexadione calcium in stages during the budding, initial flowering, before topping, and after topping stages of cotton can significantly increase biomass accumulation and yield. The treatment with 1950 g/hm² (T3) showed particularly outstanding results, increasing bud and boll biomass by more than 35% compared to the control, without significantly affecting single boll weight or lint percentage, but significantly increasing the number of bolls per plant.
