Irrigation of Urban Turf Grass: Effect of Sodium on Carbon, Nitrogen, and Phosphate Leaching from Soil.

The use of sodium compounds to increase the carbon extracted from soil is common in extraction procedures   However, relatively few studies have investigated the effects irrigation with high sodium adsorption ratio (SAR) has on the amount of carbon, nitrogen, and phosphate leached from soil and no known studies focus on soil under urban grass lawns and parks. This study has two objectives; 1) determine the leaching potential of dissolved organic carbon, nitrogen, and phosphate from soil at various levels of SAR and subsequent precipitation; 2) determine the levels of proteins, aromaticity, and glomalin-like compounds in leachate.  Intact soil cores (0 to 7 cm) were collected from 4 turf park areas in College Station, Texas.  Two of the areas have been under irrigation with municipal drinking water; two have had precipitation only.  Each core was leached with water at one of 7 SAR levels, ranging from 0 to 48, or municipal tap water.  This was repeated two times, after which rain water was added in a similar manner and the leachate collected.  Conductivity and pH was recorded for each leachate sample. Subsamples of leachate were analyzed to quantify total suspended solids, while the remainder of the leachate was filtered through a 0.7 µm ashed GF/G filter.    By determining the rate of organic carbon and nutrient release from soil at various SAR levels, this study may help the development of urban irrigation policies for protection of drinking water sources and soil quality based on SAR levels in municipal water sources in Texas.