Effects of Graywater Irrigation for Cotton Production on Soil Chemical Properties.

Rapid urbanization and economic growth along the Texas-Mexico border has resulted in a significant increase in freshwater demands for drinking and agricultural/urban landscape irrigation.  It is projected that urban water demand will double in the near future and consequently, future urban water demands will have to be met using Rio Grande water, currently being used for agricultural irrigation. Therefore, it is important to develop alternative sources through water reuse to meet agricultural/urban landscape irrigation needs and to extend the availability of freshwater sources in the region. Cotton growers will have to increasingly rely on alternative water sources for irrigation such as graywater or reclaimed water as more freshwater is diverted for domestic and municipal uses.  However, potential impacts of irrigation with these waters with elevated salinity on soil salinity and cotton performance needs to be evaluated before advocating their use on a large scale. This three year project evaluated effects of graywater irrigation for cotton production with and without organic mulching on coarse texture soil salinity. Results of the study indicated salinity (EC) and sodicity (SAR) of soil doubled top 12” depth in graywater irrigated soils although values were much lower to classify soil as saline and sodic. Concentrations of N, P, K, Ca, Mg, Na, Zn, Fe, Cu, B, were greater in soils that received graywater irrigation compared to those irrigated with freshwater. Results indicated no significant cotton growth, cotton seed and lint yield differences between freshwater and graywater irrigated soils conditioned by mulching. Significant differences in cotton performance were observed between mulched and non mulched treatments. Cotton irrigated with graywater irrigation on soil conditioned with mulch produced approximately 70% more lint than that without mulch conditioning.  Study results show promising potential for cotton production with graywater irrigation on well drained soils.