Response to deficit irrigation of morphological, yield and fiber quality traits of upland (Gossypium hirsutum L.) and Pima (G. barbadense L.) cotton in the Texas High Plains

Cotton (Gossypium spp.) production around the world often occurs in water limiting environments. Although Upland (G. hirsutum) and Pima (G. barbadense) cottons have been evaluated under conditions of water stress before; these two species are rarely compared to each other. This may be due to differences in irrigation management and environmental constraints (i.e. season length). In 2014 and 2015, two Upland cultivars and two Pima germplasm lines were evaluated at Lubbock, TX, USA. Plant architecture, boll retention, lint yield and fiber quality were assessed under three deficit subsurface drip irrigation levels. Crop water use was evaluated using soil water balance in conjunction with neutron probe soil water content measurements. In 2014 during flowering at the high irrigation rate, Upland cultivars extracted significantly (p < 0.01) more water from the soil profile compared with Pima lines resulting in 30 mm greater water use during this period. However, in 2015 water use did not vary significantly between species. In both years the Pima species had greater boll retention, especially at nodes eight and above, and higher fiber quality compared to Upland, confirming previous reported quality differences between these two species. In addition, Pima's fiber traits were observed to be less impacted by water deficit, and in some instances slight increases in quality were observed. While Uplands had negative impact to deficit irrigation especially for fiber length, strength, and uniformity under the highest water deficit. The Upland cultivars produced significantly greater lint yields compared with Pima with differences averaged across years of 1154 kg ha(-1) and 504 kg ha(-1) at the high and low irrigation levels, respectively. New, high yield-Pima cultivars are needed to create premium cotton lint to encourage producers evaluating Pima cotton as an alternative to Upland cotton production, as water availability declines.