THE ROLE OF SODIUM AND GYPSUM FOR MAINTAINING BERMUDAGRASS TURF ON SAND SOILS

Sports turf managers in Florida who primarily deal with bermudagrass turf on sand soils often express concern about the content of sodium (Na) in soils, especially when it exceeds that of potassium (K), even though the soils are not sodic. Gypsum (calcium sulfate) applications frequently are used to address the situation. Several studies were conducted on sand soils to investigate the role of Na and gypsum for maintaining bermudagrass turf on sand soils. In one study, the turf was fertilized with various rates of K and Na. Sodium fertilization did not adversely affect bermudagrass visual ratings or clipping weights. Sodium uptake was relatively great only in the absence of K fertilization, and tissue Na was not affected by Na fertilization. In a second study which was conducted at a location using irrigation water with up to 700 mg Na L^-1, gypsum applications up to 50 g m^-2 month^-1 did not affect turfgrass visual ratings or clipping weights. Gypsum application reduced soil-test magnesium, but did not affect other soil-test chemical values, nor did it meaningfully affect physical analyses such as saturated hydraulic conductivity, pore space, or water holding capacity. For these non-sodic sand soils, Na did not adversely affect bermudagrass performance, and the use of gypsum appeared unwarranted.