Effects of Density and Miantaijin Chemical Control on Boll Characteristics and Physiological Activity of Direct-Seeded Cotton after Wheat Harvest

[Objective] The aim of this research is to study the effects of planting density and Miantaijin(diethyl aminoethyl hexanoate·mepiquat chloride of mass fraction 27.5%) chemical control on physiological leaf characteristics and boll setting characteristics of direct-seeded cotton after wheat harvest. [Method] In 2011―2012, the early-maturing variety Guoxinzao 11-1 was used as the experimental material. The study was conducted in Yangzhou University in 2011―2012 under the direct-seeded after wheat harvest cropping system, and the randomized complete block design was arranged with planting densities and Miantaijin rates. [Result] Under the density 105 000 plant·hm^－2 combined with 1 170 mL·hm^－2 Miantaijin, the boll setting was mainly concentrated before August 31. The SPAD value, soluble sugar content, soluble protein content, free amino acid content on July 15, July 30, August 15 of direct-seeded cotton after wheat harvest showed significant or extremely significant open-down parabola relationship with the number of bolls before August 31. It indicates that keeping the appropriate level of carbon and nitrogen physiological activity in cotton leaves is beneficial to high-quality bolls. [Conclusion] High density (105 000 plant·hm^－2) combined with proper Miantaijin control (1 170 mL·hm^－2) would contribute to forming quality bolls of direct-seeded cotton after wheat harvest, and the physiological activities of leaf carbon and nitrogen are suitable.