Cotton yield response to soil applied potassium across the U. S. Cotton Belt


Across the U.S. Cotton Belt, potassium (K) deficiency symptoms in cotton (Gossypium hirsutum L.) have become more common over the past decade. In 2015-2017, an experiment was conducted in Alabama, Arkansas, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, two regions in Texas, and Virginia for a total of 23 site-years. The objectives were (a) to quantify soil K levels at-depth in representative soils where cotton is commonly grown in major cotton production regions with observed K deficiencies; and (b) to evaluate the effects of application method and K rates on cotton lint yield, loan value, and return on fertilizer investment. Granular and liquid potassium chloride were broadcast or injected, respectively, 2-4 wk prior to planting at 0, 45, 90, 135, and 180 kg K2O ha(-1). Locations other than Texas and Oklahoma generally had soil K levels <less than 150 mg kg(-1), the Mehlich III critical K level, and thus, a yield response to applied K fertilizer was expected. However, among the 23 site-years, a treatment effect was determined at 5 site-years. Two of those, Williamson County, Texas, and Virginia endured severe moisture stress and resulted in low yields (<526 kg lint ha(-1)). A positive lint yield response to knife-injected 0-0-15 was determined in 2015 at the Lubbock County, Texas, location-a location with high yield (>1,653 kg lint ha(-1)). Inconsistent yield responses among locations indicate that K dynamics in the soil-cotton plant system are not well understood and deserve continued investigation.