Yield components and quality of intercropped cotton in response to mepiquat chloride and plant density

Cotton yield is greatly improved by moderately increasing plant density and modifying the cotton plants to have a compact structure, which is also required by the increasing demand for mechanized harvest. However, in cotton strip intercropped with wheat, only limited knowledge on yield response to plant density and plant growth regulator i.e. mepiquat chloride (MC) exists. Here we quantified MC and plant density effects on cotton yield components and quality in wheat-cotton relay intercropping by three field experiments in 2010-2012 in Anyang, China. Four plant densities and four MC treatments were applied in different times and dosages. Lint yield significantly increased 40.7% when plant density increased from 3.0 to 7.5plantsm^-2, and enhanced 7.9% by applying MC four times compared to MC free control. High densities increased the number of bolls per m² but decreased single boll weight. Conversely, applying MC generally slightly decreased number of bolls, with the exception of a significant increase by applying MC four times, and increased boll weight. Lint percentage was decreased by applying MC. The yearly climate significantly impacted the effects of applying MC and plant density. Application of MC did not significantly affect cotton fiber length and micronaire, but increased fiber strength. Applying MC in combination with increasing plant density led to harvestable bolls to be located more at low and middle positions on the plant. The increase of boll weight by applying MC was partly resulted from the optimal distribution of harvestable bolls within the canopy. The results help farmers to optimize plant density and MC application in the intercropped cotton.