Sustainable Greenhouse Production of Hydroponic Tomato Under Treated Wastewater Irrigation

Water reuse is increasingly recognized as a valuable strategy for sustainable water resource management and for strengthening agricultural resilience to water scarcity. This study demonstrates that treated municipal wastewater can serve as an alternative irrigation resource for substrate-based greenhouse tomato production over a six-month production cycle, while focusing on crop performance, plant adaptation, and management constraints associated with effluent quality. Plants were irrigated either with treated wastewater (WW) or standard nutrient solution (SW), while grafting and Trichoderma application were assessed as potential mitigation strategies against mild salinity-related stress. The WW exhibited elevated electrical conductivity (5.71 mS cm−1), driven by high Na+ and Cl− concentrations. Although yield in WW was reduced by 37–45% compared to SW treatments, plants remained productive. Yield decline was associated with impaired fruit set, linked to salinity stress, reduced nutrient acquisition, and carbon assimilation. Foliar nutrient analysis revealed significant deficiencies under WW irrigation, as well as accumulation of Na+ and Mg2+. Grafting partially improved yield under both water management regimes, whereas Trichoderma application had no significant effect under the present conditions. Despite reduced productivity, tomato plants exhibited adaptive responses over time, with partial recovery of fruit set, suggesting a degree of acclimation to saline irrigation. This study highlights that treated wastewater represents a promising alternative irrigation resource, even in intensive production systems, particularly in regions where freshwater availability is increasingly constrained by climate change and seasonal drought.