LAUSR

We evaluate the application of treated sanitary wastewater (TSW) to provide potassium (K) for crops and reduce demand for fresh water and mineral nutrients. The field experiment was arranged in randomized block design with four replications and five treatments: 50, 100, 150 and 200% of K requirements and one control with conventional K fertilizer. The TSW was applied to maize (November 2012 to February 2013), cotton (June to November 2013) and bean (April to June 2014). After bean, soil chemical properties were evaluated until 0.8 m depth. Fertigation with TSW to K fertilization provides about 50% of water, nitrogen (N) and phosphorus (P) to the bean. The soil nutrient availability and soil organic matter (SOM) did not increase, whereas sodium (Na) had linear increased with TSW levels in investigated soil depth. Soil pH showed same behavior that Na, with the highest pH level of 6.5 in 0-0.2 soil layer. Soil nutrients and organic matter do not increase with TSW doses up to 0.8 m depth. Soil pH and exchangeable Na have linear increasing with TSW doses, respectively up to 0.6 and 0.8 m soil depth. Fertigation with K recommendation also provided a high content of Na, threatening the balance of soil-plant system with continuous use. Na should be the first reference to permanent wastewater reuse in agriculture.