In 11 profiles of alluvial soils of the V Region, Chile, different chemical indicators of soil K (K-CaCl2, K-NH4Ac, K-HNO3, K at equilibrium, labil K, specific K adsorption sites, K retention, buffer capacity and potential buffer capacity of K) were evaluated as biological indicators of K deficiency. To this end, ryegrass (Lolium perenne) growing in pots with or without K and vines (Vitis vinifera L.) growing under field conditions. The pot experiments indicated that K-NH4Ac y K-HNO3, were the parameters that best correlated with total K extraction and foliar K concentration. A positive biological response to the addition of K, in terms of dry matter production, occurred with soil values between 0.09-0.26 cmol+ kg-1 of K-NH4Ac and 0.25-0.50 cmol+ kg-1 of K-HNO3. Vines under field conditions showed K deficiency with values under 0.26 cmol+ kg-1 of K-NH4Ac or 0.50 cmol+ kg-1 of K-HNO3. The K sufficiency level (without visible symptoms in the foliage and foliar K concentration of 1.5% or higher) was 0.54 cmol+ kg-1 for K-NH4Ac and 1.13 cmol+ kg-1 for K-HNO3. Potassium fertilization and the irrigation method (furrow or drip) affected the different chemical forms of K throughout the soil profile, so a soil serie naturally K deficient became well supplied after 3 years of K fertilization.