High rates of potassium (K) are often applied in an attempt to increase stress tolerance of hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy] turfs. Two field-grown bermudagrass cultivars,‘Tifdwarf’and ‘Tifway’, were used to determine the influence of applied K on plant nutrient content and nutrient retention in two soils. Six rates of K ranging from 0 to 390 kg· ha–1 were applied twice per month each growing season from 1992 to 1994. The cultivars were established on both a sand-peat (9: 1 by volume) and loamy sand. Potassium chloride and K2SO4 were compared as sources of K, and were applied simultaneously with N applications. Extractable soil K and leaf tissue K concentrations increased with increasing K rates. There was a critical K fertilization level (74 to 84 kg· ha–1) for each cultivar and medium combination beyond which no increase in tissue concentration was observed. Increasing K fertilization resulted in a decrease in extractable Ca and Mg in both media with corresponding decreases in tissue Ca and Mg concentrations. High K rates appear to increase the potential for Ca and Mg deficiencies in bermudagrass, indicating that rates higher than those that provide sufficient K levels for normal growth should not be used.

Received for publication 28 Mar. 1998. Accepted for publication 13 July 1998. Journal Paper no. R-06224, Univ. of Florida Agricultural Experiment Station. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.