Abstract:

In order to clarify the effects of chemical topping on agronomic, yield and quality traits of long-staple cotton, ‘YL39’ with vigorous growth and long internodes and ‘YL62’ with steady growth and short internodes were used as test materials, and a randomized block test was conducted with four spraying doses to analyze the response of different types of long-staple cotton to chemical topping. The results showed that: the increase of plant height, number of fruiting branches, plant height growth and bolls per plant after chemical topping showed a decreasing trend with the increase of spraying dose, and more than 60% of the bolls of the two materials were concentrated in 5-12 fruiting branches; chemical topping had no effect on the boll weight, lint, yield; there was a tendency to increase the micronaire value and maturity after chemical topping. ‘YL62’ had more newborn fruiting branches and effective bolls after chemical topping, which had good yield potential; ‘YL39’ was more sensitive to chemical topping, with limited newborn fruiting branches and less effective bolls at high doses, which affected the final yield. On the whole, the spraying of chemical topping agent 1125 mL/hm² + 150 g/hm² 98% mepiquat soluble powder can replace manual topping, which can control growth and ensure yield and quality.

Key words: long-staple cotton, chemical topping, spray dose, agronomic trait, yield, fiber quality