IRRIGATION EFFECTS OF COOLING TOWER EFFLUENT ON SOIL CHEMISTRY AND ALFALFA IN THE RIO GRANDE RIVER BASIN
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Development of alternative sources through wastewater reuse is important to meet water demands in arid regions. However, effects of wastewater irrigation on soil properties and crop performance must be evaluated before advocating its widespread use. Objectives of this study were to evaluate: (i) effects of prior evaporative disposal of saline-sodic blowdown water (BW) on soil (fine-loamy, mixed, and thermic Typic Calciorthods) properties in the disposal area, and (ii) effects of flood irrigation with three water qualities (control, BW 1X, and BW 2X) on soil salinity and alfalfa performance using a greenhouse soil column study (soil collected from same study area as objective (i)). Results indicated that although prior land disposal of BW had increased salinity and sodicity of soil, they were within the tolerance limits of the intended crop, alfalfa. Mass balance calculations indicated measured (156Mgha -1) and calculated (132Mgha -1) salt accumulation at the test site used for evaporative disposal were similar. Alfalfa grown using BW under greenhouse conditions produced prime quality hay and biomass yield similar to the control treatment (83gcolumn -1 vs. 105gcolumn -1 in control). Although 36 years equivalent of flood irrigation with BW 1X did not result in saline soil (BW 1X irrigated soils EC ranged from 22 to 35 dSm -1), BW 2X irrigation resulted in saline soils. Sodicities of irrigated soils were greater in fine textured deep soils than coarse textured surface soils (e.g., SAR of 61 at 0-5cm vs. 195mmol 1/2L -1/2 at 30-60cm in BW 1X), indicating the need for high solubility Ca amendments for long-term irrigation with BW on fine texture soils within the soil profile. 2010 John Wiley & Sons, Ltd.
