Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2020
Publication Date: 2/24/2020
Citation: Witt, T.W., Ulloa, M., Schwartz, R.C., Ritchie, G.L. 2020. 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. Field Crops Research. 249:107759. https://doi.org/10.1016/j.fcr.2020.107759.
Interpretive Summary: Cotton production often occurs in water limiting environments. Historically, in the U.S., most cotton producers grow the higher yielding but lower quality Upland cotton. In some areas of the U.S., producers can grow the lower yielding but higher quality Pima cotton. There is little information comparing these two species in water limited environments. In 2014 and 2015, the yield, fiber quality, and crop water use of these two cotton species were evaluated at Lubbock, TX under three deficit subsurface drip irrigation levels. In 2014, the Upland species used more water (1.18 inches). However, in 2015 there was no difference in soil water use. The Pima species had greater boll retention with higher fiber quality, however, the Upland species had higher yields. For both years, fiber length and fiber uniformity increased with increasing irrigation across species while other fiber traits were not affected. Declines in fiber quality were especially important for the Upland species at the lowest irrigation level, because the fiber quality was in the discount range. However, the Upland species produced greater than 446 pounds per acre more yield than the Pima species. The Pima species showed less of a reduction in yield and fiber quality between the highest and lowest irrigation rates. The higher premium for Pima cotton lint may encourage producers to evaluate Pima cotton as an alternative to Upland cotton production as fresh water availability declines globally.
Technical Abstract: 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.