Impact of Potassium Fertilizer Application Rate and Method on Cotton Lint Yield and Quality.

The increased yield potential of modern cotton varieties has pushed lint yields to three to four bales acre^‑1 and possibly 5 under subsurface drip irrigation, and as a result greater demands are being placed on cotton root systems to take up sufficient water and nutrients, with potassium (K) uptake being of particular concern. Potassium plays a major role in several critical plant processes, including photosynthesis, activation of protein enzymes, disease and drought resistance, and cotton fiber development and maturity. As K demands have increased, deep-profile soil sampling has indicated decreasing levels of plant available K in the soil of some production areas. Even though K levels are decreasing, most Texas soils are considered close to or greater than the critical level of K (150 ppm), and as a result, K is not included in nutrient management plans. Possibly a consequence of this, K deficiency symptoms in cotton have become more prevalent and severe over the past decade. Insufficient plant K during cotton’s reproductive stage may decrease lint yields and fiber quality and subsequently decrease grower profits. The objective of this research was to evaluate the impact of application methods (broadcast and and rates of K on cotton yield, quality, and return on investment. Results will focus on lint yield, fiber quality, and return on investment for two locations in Texas (Dawson County and Williamson County). In 2015 at the Dawson County location, lint yield increased as the rate of knife-injected K fertilizer increased; however, yield differences did not exist with broadcast applied K. The yield response at this location was not expected with soil test levels of K (250 to 390 mg/kg) greater than the critical level. A possible explanation may be the inability of the soil to replenish available K at a rate to meet the demands of the plant without the addition of K fertilizer.