Tifway Bermudagrass Response To Potassium Fertilization

Potassium fertilization rates used for ‘Tifway’ bermudagrass [ Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] vary greatly among turfgrass managers and there is no consensus as to the actual quantity required or as to the best Potassium (K) source to use. Effects of K source and rate on Tifway bermudagrass shoot and root growth, quality and tissue K concentration were studied in a 3‐yr field study in Central Florida. Turf was grown on an Arredondo fine sand (loamy, siliceous, hyperthermic, Grossarenic Paleudult). Two K sources (KCl and K 2 SO 4 ) were applied at 8 rates (0, 3.7, 7.4, 9.8, 14.7, 22, 29.4, and 36.8 g K m −2 90 d −1 ) in conjunction with N applied monthly at 4.9 g m −2 Potassium chloride produced a more rapid shoot growth than did K 2 SO 4 , but this effect may be linked to the N source. Bermudagrass shoot growth rate and tissue K concentrations were increased by K fertilization up to 7.4 g K m −2 90 d −1 There was no additional increases in either of the aforementioned parameters, regardless of the K level applied. Turfgrass quality and root weight were not influenced by K application. Greater root weight was observed during May, June, and July than August, September, and October. Observed turfgrass growth responses to Mehlich‐1 extractable K levels suggest that 30 mg K kg −1 soil may be adequate for optimum growth. For an N application rate of 4.9 g m −2 mo −1 , K fertilization levels above 9.8 g K m −2 90 d −1 probably will not enhance Tifway bermudagrass shoot and root growth, quality, or tissue K concentration.