ABSTRACT

Two studies were conducted in the San Joaquin Valley of California to evaluate the effect of foliar applied K on cotton yields. A third test was conducted to determine the effect of Applying KCl in the first irrigation with and without subsequent foliar applications of K as KCl, KNO₃, and Supersol U-K. The two foliar timing studies resulted in significantly higher yields when KNO3 was applied in two applications at 3 and 4 weeks after flowering rather than earlier or later in the season. The water run/foliar K test did not have significant differences among the yield means. However, petiole K levels showed clearly that the crop took up K which was applied in the irrigation water. It was absorbed late in the season, and even though soil exchangeable K was low, did not increase lint yields. Results were similar for both 1991 and 1992 tests.