Potassium management effects on cotton yield, nutrition, and soil potassium level

A three-year field experiment was conducted on an alluvial Morganfield silt soil (coarse silty, mixed, non-acid, thermic, Typic Udifluvent) to determine potassium (K) fertilizer rate and placement effects on cotton lint yield and soil K levels. The experiment was arranged in a randomized complete block design with four replications. An incomplete factorial arrangement of treatments (including 0, 68, 136, and 204 kg K ha(-1) broadcast, 0, 34, and 68 kg K ha(-1) banded in factorial combination with 0, 68, and 136 kg K ha(-1) broadcast, and 204 kg K ha(-1) broadcast with zero banded and 102 kg K ha(-1) banded with 0 kg K ha(-1) broadcast) was used. Cotton lint yield increased linearly with band application of K only in a relatively dry growing season possibly due to enhanced K uptake especially early in the season. Combination of band and broadcast application of K fertilizer was more effective in increasing cotton lint yield than either method alone. Maximum lint yield was obtained with the application of 34 kg K ha(-1) banded plus 136 kg K ha(-1) broadcast. This combined treatment resulted in greater leaf K concentration and total K uptake than either broadcast or band application alone. A linear increase in petiole and leaf K at early flowering resulted from broadcast incorporated K rates. Extractable soil K increased linearly in the 0 to 15 cm depth with increasing broadcast application of K fertilizer. Maximum lint yield was predicted at a soil K level near 160 mg kg(-1). The Morganfield (CEC = 11.1 cmol(c) kg(-1)) soil required approximately 2.2 to 2.3 kg fertilizer K ha(-1) to increase soil K by 1 kg ha(-1) in the 0 to 15 cm depth.