干旱区生态环境知识资源中心

Land application of wastewater conserves fresh water and recycles nutrients, but little is known of its impacts on arid and semiarid landscapes.. Lagoon treated saline-sodic industrial effluent was applied from 2002-2005 to a 0.4-ha Chihuahuan Desert shrubland to assess the deposition and recovery of effluent components and changes in soil quality vis-a-vis non-irrigated area. Effluent irrigation supplied 26% of the average annual nonstressed evapotranspiration (ET) of the native shrubs [Larrea tridentata (DC.) Coville and Prosopis glandulosa Torr. var. glandulosa], and increased both soil stress factors (sodicity, salinity, and pH) and :soil fertility (N, P. and K). After 3 yr, the soil saturation extract electrical conductivity (ECe) reached as high as 6.1 dS m(-1) and Cl- 76 mol(e) m(-3) at 105 cm depth under irrigated L. tridentata. After 4 yr, saturation extract sodium adsorption ratio (SAR(e)) readied 25-35 at 7.5 cm under the irrigated shrubs and intershrub spaces. There were 27 Mg ha(-1) of cumulative ionic deposits to the site comprised mostly of Na+, Cl-, and CaCO3 equivalent alkalinity, with soil analysis recovering most of the deposits (>57%) except for K+ and Na+ (8% to 13%). Subsurface leaching of NO3- - N and P was detected within the upper 1 m soil depth after 4 yr, and a high downward mobility of Cl- revealed the potential for deeper NO3- - N leaching at higher N loading rates. While long-term effects on the natural vegetation are unknown, results contribute to a limited scientific database for sustainable wastewater land application in semiarid regions.