POTASSIUM ACCUMULATION AND CORN YIELD RELATED TO POTASSIUM FERTILIZER RATE AND PLACEMENT

Sandy Coastal Plain soils have relatively low reserves of K and may not be able to supply adequate K for intensive corn (Zea mays L.) production. Field experiments were conducted on Dothan loamy sand (fine-loamy, siliceous, thermic Plinthic Paleudult) for 3 y to determine K fertilizer rate and placement effects on corn growth and seasonal K accumulation. Treatments were 0, 56, 112, 168, and 224 kg K ha-1 broadcast and 56 kg K ha-1 banded plus 0, 56, 112, and 168 kg K ha-1 broadcast. Total K accumulation was increased by K fertilization rate each year. Method of application had a significant effect in a relatively dry year when the broadcast-plus-banded treatments resulted in greater K accumulation. Stover dry matter was increased in two of three years with 56 kg K ha-1, but grain yield was increased in only one year. Yield increased linearly with K rates up to 112 kg K ha-1 when the initial exchangeable-K level was 0.21 cmol L-1. Critical exchangeable-K level was 0.35 cmol L-1 and the critical soil solution K concentration was 0.48 mmol L-1 for dry-matter yield. When corn is grown with intensive production practices, there is little benefit in applying banded K with broadcast K on sandy soils testing high in K.