The relationship between boll retention and defoliation of cotton at the fruiting site level

Abstract

Defoliation is used to ease mechanical harvest and reduce lint staining of cotton (Gossypium hirsutum L.). Crop conditions are important determinants of its efficiency, but their effects have not been fully examined. We performed a multiple-site field study during 2018-2020 (under 17 environmental conditions, covering three cotton regions in China) to explore the relationship between boll retention and defoliation at the fruiting site level. The hormonal defoliant, thidiazuron and boll opener, ethephon, were tank-mixed or their combination product was used in this study. There was a positive Spearman ranking correlation between boll retention and defoliation in most experimental sites, with correlation coefficients (r) ranging from .275 to .725 at 7 d after application of harvest aids, suggesting that the leaves at fruiting sites bear-