GRAIN-YIELD, KERNEL WEIGHT, AND DISEASE RESPONSES OF WINTER-WHEAT CULTIVARS TO CHLORIDE FERTILIZATION

Wheat yields in the Great Plains are frequently improved by potash (0-0-60 N-P-K) application on soils with seemingly abundant supplies of available K. The Cl component in this fertilizer may cause many of the observed yield responses. Field research was undertaken to determine the effects of Cl on grain yield, plant Cl, kernel weight and growth rate, and foliar disease and/or disease-like symptoms of winter wheat cultivars. Two sites with five Cl levels (0, 22, 45, 90, and 135 kg ha-1) and two cultivars (Redwin, Cree) were used in 1988. Seven sites with two Cl levels (0 and 45 kg ha-1) and six cultivars (Redwin, Cree, Weston, Manning, QT542, Neeley) were used from 1991 to 1992. Chloride increased yield by an average of 267 kg ha-1 (7%) at seven responsive sites. Size of yield response to Cl was generally not affected by cultivar selection, but differed greatly with location. Whole-plant Cl analyses were useful in discriminating between yield responsive (less-than-or-equal-to 3.0 g kg-1) and nonresponsive (>3.0 g kg-1) sites to Cl fertilization. Improved Cl nutrition enhanced plant development, increase immature kernel weights, and accelerated kernel growth during the grain-fill period. Fertilizer Cl increased mature kernel weights, up to 17%, at eight sites. Kernel weight was the most important yield component affected by Cl. Physiological leaf spot in Redwin and Manning, flag leaf sequence in Weston and QT542, powdery mildew (Erysiphe graminis DC. f. sp. tritici Em. Marchal), and leaf rust (Puccinia recondita Roberge ex Desmaz. f. sp. tritici) were suppressed by fertilizer Cl. These phenomena may explain in part the yield responses to Cl; however, yield response to Cl occurred even without foliar disease and disease-like suppression.