Sweet Potato Response to K and P Fertilization1

Abstract

AbstractLimited literature is available to provide recommendations of K source and rate and P rate for sweet potato [Ipomoea batatas (L.) Lam.] production. Many growers, therefore, continue to use the more expensive sulfate (SO4) source of K rather than chloride (Cl) and higher than recommended rates of K and P. Accordingly, on‐farm experiments were conducted during 3 years on North Carolina Paleudults to determine effects of K source and rate and Prate on sweet potato yield, grade, and quality. Potassium sources were KCl and K2S04. Fertilization rates of K varied over the five K experiments and depended on initial soil test levels which ranged from 0.04 to 0.12 cmol K L−1 by Mehlich‐I extractant. In the three P experiments, the various P rates were also dependent upon the initial soil test levels which ranged from 11 to 30 mg P L−1 also by Mehlich‐I extractant. As K source had no effect on yield, grade, or quality, it was concluded that the higher Cl concentrations, up to 22.8 g kg−1, in vegetative tissue with increasing KCl rates had no detrimental effect on sweet potato yield, grade, or quality. Total yield response to K applications was obtained where soil test K levels were ≤ 0.08 cmol L−1, although no. 1 yields increased only where soil test K levels were ≤ 0.05 cmol L−1. Phosphorus applications had no effect on yield, grade, or quality of sweet potato.