Plant growth, ion dynamics, and microbial communities in soils irrigated with treated produced water for sustainable agriculture

The reuse of treated produced water (tPW) for irrigation is increasingly attractive in water-scarce regions, yet its impacts on plant performance, soil health, ion dynamics, and microbial communities are not fully explored. This study evaluated plant growth and soil response over a nine-month greenhouse experiment in the Permian Basin (Texas), using clay-rich and sandy-loam soils irrigated with tPW at total dissolved solids (TDS) concentrations of 500, 1000, and 1500 mg/L, alongside a desalinated-groundwater as the control. Soil quality index analysis showed that tPW at ≤1000 mg/L maintained and occasionally improved soil health relative to the control, whereas 1500 mg/L caused soil degradation by disrupting ion balance, increasing salinity stress, and shifting microbial communities. Moderate-salinity tPW preserved a balanced ion profile that supported nutrient retention, microbial activity, and soil structure; in contrast, higher TDS led to ion accumulation, salinization, nutrient depletion, and osmotic stress, which diminished water retention and fertility. Alfalfa irrigated with 1000 mg/L tPW produced forage with higher crude protein, lower fiber fractions, and improved digestibility, affirming its suitability for saline forage systems. Microbial analysis illustrated minimal impact on bacterial and fungal diversity at ≤1000 mg/L TDS, whereas 1500 mg/L TDS alters fungal composition in loamy soils, reducing richness and increasing pathogenic fungi in deeper layers. These results underscore the promise of tPW for sustainable irrigation, provided that salinity levels, ion accumulation, and microbial responses are carefully managed to safeguard soil health, optimize nutrient cycling, and sustain long-term productivity.