Ojeda, Nadezda (2016-01). Effects of Deficit Irrigation, Fertilization, and Wetting Agent on Runoff Nutrient Concentrations and Exports from St. Augustine Lawns. Master's Thesis.
The need for water conservation and water quality preservation has become essential in the management of residential turfgrass through the United States as urban and suburban populations increase. In many urban areas, a considerable amount of water and fertilizers are used for lawn and landscaping needs, much of which may runoff and contribute to the degradation of receiving surface waters and turfgrass quality. This thesis examines runoff of DOC, DON, and PO4-P concentrations and exports from fertilized and unfertilized simulated St. Augustine grass under deficit irrigation and fertilization or application of wetting agent. A strong and significant relationship (p < 0.001) was observed between DOC, DON, and PO4-P exports and Na^+, K^+, Mg^2+, and Ca^2+ exports during the first year of the study. The results suggest that in years with average rainfall, homeowners can maintain an aesthetic and functional St. Augustine turfgrass lawn and minimize nutrient exports in runoff by applying fertilizer twice a year and irrigating at a 30% ETo rate. Due to limiting water supplies, expanding the use of wetting agents to residential lawns has become of interest. This study also investigated the effects of the application of a wetting agent on fertilized and unfertilized simulated lawns under deficit irrigation for 16 weeks. The application of wetting agent had no effect on the percent of retained water volume in the soil or the percent of water runoff after rain or forced irrigation events. More research is needed to determine whether wetting agents affect water retention and water runoff of residential lawns.