Abstract
Land application of treated wastewater is increasing particularly in areas where water stress is a major concern. The primary objective of this study was to quantify the effect of irrigation with aerated lagoon treated wastewater on soil properties. Core and bulk soil samples were collected from areas under the canopies of mesquite and creosote and intercanopy areas from each of the three plots. Irrigation water quality from 2006 to 2008 showed that average sodium adsorption ratio (SAR), electrical conductivity (EC) and pH of irrigation water were 37.16, 5.32 dS m-1 and 9.7, respectively. The sprinkler uniformity coefficients of irrigated plot-I was 49.34 ± 2.23 % and irrigated plot-II was 61.57 ± 2.11 %. Within irrigated and between irrigated and un-irrigated plots, most soil physical properties remained similar except saturated hydraulic conductivity (Ks) which was significantly higher under mesquite canopies than in the intercanopy areas. Chloride (Cl-) concentrations below 60 cm depth were higher under creosote than mesquite canopies in irrigated plots indicating deeper leaching of Cl-. Nitrate (NO3 -) concentrations below 20 cm depth under canopy and intercanopy areas were low indicating no leaching of NO3 -.The average SAR to 100 cm depth under shrub canopies was 18.46 ± 2.56 in irrigated plots compared to 2.94 ± 0.79 in the un-irrigated plot. The Na+ content of creosote was eleven times higher un-irrigated than un-irrigated plot and Na+ content of herbaceous vegetation was three times higher in the irrigated than unirrigated. Thus irrigation with high sodium wastewater has exacerbated the soil sodicity and plant Na+ content. Since the majority of mesquite roots are found within 100 cm, and creosote and herbaceous vegetation roots are found within 25 cm from soil surface, a further increase in sodicity may threaten the survival of woody and perennial herbaceous vegetation of the study site.
Highlights
Southern New Mexico is characterized as semi-arid region where wastewater reclamation and reuse for irrigation has become important part of water resources planning
The levels of dissolved organic matter (OM) and suspended solids in effluent depend on the quality of the raw sewage water and the degree of treatment [5,6] Suspended solids present in effluents accumulate in soil voids and physically block water-conducting pores leading to a sharp decline in soil hydraulic properties [4,5]
Evaporation losses at the experimental site ranged from 50 to 90% similar to the typical values reported for arid regions, which can result in 2 to 20 fold increases in soluble salt concentrations [23]
Summary
Southern New Mexico is characterized as semi-arid region where wastewater reclamation and reuse for irrigation has become important part of water resources planning This has occurred as a result of the increasing fresh water scarcity, high nutrients in wastewater, and the high cost of advanced treatment required for other wastewater uses. The primary goal of land application of wastewater is to maximize vegetative cover to increase the capacity of the soil to serve as a sink for wastewater contaminants, minimize salt accumulation in the root zone, and avoid NO3- leaching to the groundwater [11,12] In this context application of treated wastewater on common arid and semiarid shrubs could be more
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