Nutritional optimization of hydroponic green fodder using dairy farm wastewater

This study evaluates the reuse of dairy farm wastewater (DFW) as an alternative irrigation and fertigation source for winter hydroponic green fodder (barley and oats), with a focus on nutritional optimization. The wastewater was characterized (pH, TS/TFS/TVS, TN, TP, K, COD, turbidity, and coliforms/E. coli) and disinfected using hydrogen peroxide (H2O2; 0.05, 0.2, and 0.4 M; 10, 30, and 60 min), with and without UV radiation (254 nm). A factorial experiment compared fresh water, commercial fertilizer (Triple 18), and five DFW dilution levels (0, 25, 50, 75, and 100%) in terms of biomass production, plant height, root development, dry matter, ash content, crude protein, fiber fractions, and microbial safety. Hydroponic green fodder irrigated with disinfected DFW showed no detectable coliforms or E. coli after growth, confirming the effectiveness of the disinfection process. Productivity indicators were comparable to conventional treatments at intermediate dilution levels. However, the use of DFW significantly influenced the nutritional composition of the fodder, with distinct responses between barley and oats. Intermediate dilutions (DFW-25 to DFW-75) consistently provided the most favorable balance between crude protein and structural fiber fractions, whereas full-strength effluent (DFW-100) tended to reduce yield or increase fiber content, depending on the species. These findings demonstrate that diluted dairy farm wastewater can be effectively integrated into hydroponic systems as a partial substitute for freshwater and synthetic fertilizers. This approach enhances resource use efficiency and supports the development of circular and sustainable livestock production systems, particularly in regions facing water scarcity and limited arable land.