Field evaluation of polished desalinated produced water for alfalfa irrigation in a semi-arid environment

Abstract

Water scarcity is a critical challenge in West Texas, where agriculture and the oil and gas industry compete for limited water resources. The oil and gas industry generates approximately 32% of the nation’s produced water, presenting significant opportunities for beneficial reuse. This study evaluated polished desalinated produced water (PDPW) as a supplemental irrigation source for field-grown alfalfa in a semi-arid region, with conventional groundwater serving as the reference irrigation source. Soil chemistry, heavy metal accumulation, plant physiology, forage quality, and microbial community dynamics were assessed under both irrigation treatments at two growth stages. Polished desalinated produced water met most irrigation water quality standards, although strontium concentrations exceeded recommended thresholds, highlighting the need for continued monitoring. Exceedances in soil macronutrients and organic compounds were primarily attributed to historical soil conditions rather than PDPW application. Interpretation of sodium accumulation was limited because PDPW was blended with groundwater during part of the study period. No significant differences ( p > 0.05) were observed in plant growth or biomass between PDPW and control treatments. Forage quality was comparable and, in some cases, improved under PDPW irrigation through lower fiber concentrations. Microbial community profiling using 16 S and ITS rRNA sequencing revealed stable alpha and beta diversity, with variation driven primarily by sample type and growth stage rather than irrigation source. Dominant bacterial and fungal taxa remained consistent across treatments. These findings suggest that, with appropriate treatment and monitoring, PDPW has the potential to serve as an alternative irrigation source for alfalfa production in semi-arid regions. However, long-term studies are needed to evaluate sustainability and potential cumulative impacts on soil, plants, and microbial communities.

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