Multiple irrigation levels affect boll distribution, yield, and fiber micronaire in cotton

The boll distribution characteristics of upland cotton (Gossypium hirsutum L.) cultivars are related to cotton maturity and can interact with environment and management practices to determine yield and fiber quality. The boll distributions of six cotton cultivars under four irrigation levels were compared in 2011 and 2012 on the Texas High Plains. In 2011, a year of severe drought and heat, all cultivars had relatively compact fruiting patterns and increases in irrigation affected both boll accumulations up the plant and second-position fruiting sites. In 2012, which was less hot and dry than 2011, all cultivars produced more fruit on higher sympodial branches; however many cultivars followed unique patterns of boll accumulation with increased irrigation. Later-maturing cultivars significantly increased boll production at higher portions of the plant while early maturing cultivars retained more bolls at the bottom of the plant. One cultivar, DP1311, increased yield at the second position as irrigation increased. Micronaire was also compared among the cultivars and irrigation treatments. In 2011, micronaire increased with increasing irrigation, while in 2012, micronaire decreased with increasing irrigation. There was a strong irrigation by cultivar interaction for micronaire in both years, which may have been related to boll accumulation patterns for the cultivars. These findings suggest that the cultivars compensate for yield differently in response to increased irrigation, and the choice of a specific cultivar should also take into account fruiting habits and their potential effect on micronaire in respect to environmental and management factors, particularly water availability.