Buffering foliar K solutions to pH 4 increased K uptake and lint yield of cotton (Gossypium hirsutum L.). Research was conducted (1995-1997) on a Collins silt loam (coarse-silty, mixed, active, acid, thermic Aquic Udifluvents) to evaluate buffering of foliar B and/or K solutions for no-till cotton production. Foliar treatments included 0.11 kg B ha-1 and 4.1 kg K ha-1 applied separately and/or in combination as unbuffered or buffered to pH 6 or 4. Additional treatments included 0.11 kg B ha-1 of an experimental blend of surfactant and boric acid salts (HM 9751; Helena Chemical, Memphis, TN) and an untreated check. A general soil sample showed the research area had a 6.6 pH and 190 kg ha-1 (high level) Mehlich-1 extractable K, which called for recommendations of 0.56 kg B ha-1 and 28 kg K ha-1. Plots were fertilized at 90-15-28 kg N-P-K ha-1, respectively. Foliar K was applied as KNO3 in 1995, but K2SO4 was applied in 1996 and 1997. Foliar B was applied as Solubor DF (Na2O·5B2O3·10H2O; U.S. Borax, Valencia, CA) [17.4% B]. Foliar treatments were applied in 93.3 L H2O ha-1 at bloom and repeated on a 7-d interval for four applications. Solutions were buffered with Buffer Xtra Strength (alkyl aryl polyethoxy ethanol phosphates and organic phosphatic acids; Setre Chemical, Memphis, TN). Foliar K and/or B solutions buffered to pH 4 increased first-harvest and total lint yields more than unbuffered or solutions buffered to pH 6 did. Foliar B + K solutions buffered to pH 4 increased total yields by 15.9%, while foliar K solutions buffered to pH 4 increased yields by 13.8%, and foliar B solutions buffered to pH 4 increased yields 10.3% above the check yields.