Potassium Application Timing and Cotton Yield in Texas' Southern High Plains

Cotton is a major cash crop cultivated mainly for its fiber and seed oil. Cotton is very sensitive to K deficiency compared to most other field crops. Potassium is required in photosynthesis, metabolism, osmotic potential maintenance, and water uptake during fiber development. The nutrient is required at rates of about 2.2 to 5.0 kg ha^-1 day^-1 during boll fill period. Studies were conducted in 2016 and 2017 in Lubbock and Lamesa in the Texas Southern High Plains to determine K timing application rates effect on the yield and fiber quality of two cotton varieties, DP 1518 B2XF and DP 1612 B2XF. The treatments were K applied at 0, 90, and 180 kg K ha^-1 pre-plant, side-dress, and split application at low and high irrigation levels. Leaf tissues and under the plant canopy soil samples (0 - 15cm and 15 - 30 cm soil depths) were collected at the first bloom. Cotton was harvested at the end of the season to determine yield, and fiber quality response to K rates. The in-season soil K concentrations were quantified using the Mehlich III (M3) extraction method. Harvest results determined that side-dressed K application produced significantly greater lint yields in cotton variety DP 1518 B2XF in both locations. There was no significant difference between treatments in terms of fiber quality and tissue K uptake. The 180 kg K ha^-1 rate consistently produced greater soil K concentrations at the 0 – 15 cm depth across location, although response to timing was different across location which were irrigated using different methods. Responses to treatment was not determined in the 15 - 30 cm depth across location.