Inhibition of apical dominance affects boll spatial distribution, yield and fiber quality of field-grown cotton

Apical dominance inhibition is important in cotton (Gossypium hirsutum L.) production due to its indeterminate growth habit. Apical dominance can be inhibited physically by the manual removal of apical buds or chemically by the application of plant growth regulators. However, knowledge of the yield and boll distribution of cotton under different methods of apical dominance inhibition remains limited. Thus, an experiment was conducted to evaluate the effects of different methods of apical dominance inhibition (physical inhibition, chemical inhibition and no inhibition) on the plant growth, within-plant boll distribution, crop maturity, yield and fiber quality of cotton from 2016 to 2018. Compared with no inhibition, chemical inhibition and especially physical inhibition reduced plant height, whereas only physical inhibition promoted the ratio of fruiting sites to fruiting branches, which indicated that chemical inhibition resulted in a more compact plant type than physical inhibition. Earlier crop maturity was observed with both physical and chemical inhibition methods than without inhibition, and this finding was attributed to a higher number of inner bolls at lower and middle nodes. The lint yield response to the different inhibition methods varied among years and between varieties. The lint yield of XIN4 was significantly enhanced by physical inhibition and chemical inhibition in 2 of the 3 years, by an average of 11.5 % and 8.7 %, respectively. An effect of inhibition method on the lint yield of CRI60 was observed only in 2016, in which physical inhibition significantly improved the lint yield by 14.0 % compared with that obtained without inhibition. Chemical inhibition achieved a similar lint yield to physical inhibition in all three years. Fiber quality was slightly reduced under chemical inhibition compared to physical inhibition, but the values were within the acceptable range regarding grade standards. Overall, although apical dominance inhibition did not consistently improve lint yield, it remains a desirable management tool for achieving a favorable cotton architecture for mechanical harvest. Additionally, chemical inhibition appears to be a promising alternative to physical inhibition in cotton production due to its simplicity as a management tool.