Potassium application reduces calcium and magnesium levels in bermudagrassleaf tissue and soil

High rates of potassium (K) are often applied in an attempt to increase str ess tolerance of hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. tran svaalensis Burtt Davy] turfs. Two field-grown bermudagrass cultivars,'Tifdw arf' and 'Tifway', were used to determine the influence of applied K on pla nt nutrient content and nutrient retention in two soils. Six rates of Krang ing from 0 to 390 kg . ha(-1) were applied twice per month each growing sea son 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 a s sources of K, and were applied simultaneously with N applications. Extrac table soil K and leaf tissue K concentrations increased with increasing K r ates. 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 co ncentration was observed. Increasing K fertilization resulted in a decrease in extractable Ca and Mg in both media with corresponding decreases in tis sue Ca and Mg concentrations. High K rates appear to increase the potential for Ca and Mg deficiencies in bermudagrass, indicating that rates higher t han those that provide sufficient K levels for normal growth should not be used.