Long-Term Effects of Effluent Water Irrigation on Soil Chemical Properties of Sand-Based Putting Greens

The increase of the world's population and the decrease of freshwater resources have led to increased use of alternate water resources to meet the water need. Using treated wastewater (effluent water) for urban landscape irrigation has become a common practice to alleviate freshwater shortage. Golf courses are the leading urban landscape users of effluent water, because intensively managed turf can use nutrients in the wastewater efficiently. The objectives of this study were to assess changes in soil chemical properties of sand-based putting greens, following conversion from freshwater irrigation to effluent water irrigation, and identify potential concerns related to long-term use of effluent water on sand-based greens. Soil samples were collected and analyzed from greens at the Heritage Golf Course in Westminster, Colorado. The course started to use effluent water for irrigation in 2000. Nine out of eighteen (1, 3, 5, 7, 9, 11, 13, 15, 17) greens were selected for soil sample collection. Soil samples (0-10 cm below soil surface) were collected in September of 1999, 2003, and 2009. Soil test data showed that the soil's chemical characteristics changed over time. Soil organic matter (SOM) increased from 0.12 to 1.5%, and cation exchange capacity (CEC) is increased by as much as double over nine years. Extracted phosphates increased by 388% after nine years of effluent water use. Exchangeable calcium, magnesium, potassium, and sodium also increased, by 198, 116, 148, and 452%, respectively, over nine years of effluent water irrigation. In addition, increases over time were found for extractable iron, manganese, copper, zinc, and aluminum. In conclusion, using effluent water for irrigation has both benefits and risks. Increased salinity (EC) and sodium levels are the greatest risks when using effluent water; however, to a certain degree, these can be managed through appropriate cultural practices such as leaching and adding gypsum. Supplemental nutrients and decreased fertilizer costs are the greatest benefits of using effluent water for irrigation. Our results showed that released nitrogen, phosphorus, potassium, and magnesium levels increased in the soil after using effluent water, which would be beneficial for the grass and lowering the fertilizer's cost.