Compost Impacts on Sodicity and Salinity In a Sandy Loam Turf Grass Soil

Abstract

Compost application to turf grass may influence soil sodicity and salinity and eventually the establishment and growth of turf grass. The objectives of this study were to determine effects of compost source and application rate on soil sodicity and salinity during 29 months after a one-time application to Saint Augustine grass and Bermuda grass turf grown on a sandy loam soil. Extractable soil Na, electrical conductivity (EC), and pH did not differ among compost sources having variable Na and nutrient levels. However, compost application decreased soil Na, EC, and pH compared to unamended soil likely due to high applications of Ca, Mg, and K, which occupied cation-exchange sites on soil particles, minimizing adsorption of Na and enhancing Na leaching losses during precipitation events. Furthermore, high application of composts increased soil dissolved organic C (DOC) levels, which may have coated soil particles and limited adsorption of Na. Complexation of extractable cations with DOC, followed by potential leaching of DOC-associated cations, tended to decrease soil EC. Thus, composts may actually serve to alleviate soil sodicity and salinity problems. Seasonal variation of extractable soil Na and EC were related to growth stages of turf grass, which influenced DOC levels, and precipitation patterns, which influenced vertical movement of DOC-associated cations.