NO-TILL CORN PRODUCTION AS AFFECTED BY MULCH, POTASSIUM PLACEMENT, AND SOIL EXCHANGEABLE POTASSIUM

Optimizing the yield of no-till corn (Zea mays L.) requires an understanding of corn response to K fertilization practices in no-tillage systems. This study was conducted to determine the effects of mulch rate, K-fertilizer placement method, and soil exchangeable K (SEK) concentration on corn grain yield, ear leaf K concentration (ELKC), and root SEK distribution in a no-tillage system. There were five initial SEK concentrations (54, 59, 78, 95, and 122 mg K kg-1), three mulch rates (zero, normal, and double), and two methods of K-fertilizer placement, broadcast and banded, at a rate of 46 kg K ha-1. A Crosby silt loam soil (fine, mixed, mesic Aeric Ochraqualf) was used. Increasing mulch rate increased ELKC at all SEK concentrations and yield at SEK below 90 mg K kg-1. Increasing SEK increased yield in the zero and normal mulch treatments but not in the double mulch treatments. Banding K increased ELKC and yield only at low SEK concentrations; the effect of banding on yield was observed only in the zero mulch treatments. The lack of yield increase with banding in the mulched treatments was attributed to greater root growth in the 0- to 5-cm depth, which may have allowed for more efficient use of broadcast K fertilizer. The SEK concentration decreased with depth and distance from the row in all treatments. Results indicate that the yield benefit of banding K, increasing SEK concentration, or both decreases with increasing rate of mulch.