Evaluating the long-term effects of reclaimed wastewater irrigation on mango (Mangifera indica L.) cultivation: Soil quality, fruit yield, and fruit quality

Research on the long-term effects of reclaimed wastewater irrigation on mango productivity and fruit quality remains limited. To address this gap, we irrigated a mango (Mangifera indica L.) crop in a semi-arid region of Spain with reclaimed wastewater over a 13 year period using three irrigation treatments—100 % potable water, 50:50 mix of potable water and reclaimed wastewater, and 100 % reclaimed wastewater. During the final four crop cycles, fruit yield, weight, number, and quality (e.g., maturity, soluble solids, dry matter, pulp colour, and soft pulp) were monitored. Additionally, wastewater parameters were analysed on a monthly and annual basis to assess soil and leaf conditions, and determine nutritional changes and potential phytotoxic effects. The results indicated increased nutrient availability (N, P, K, Ca, Mg, Na, and B), reducing the need for fertilisation. Prolonged irrigation increased NO₃⁻, P, Na, B, and Zn accumulation in soil, while reducing Fe and Cu levels. Na and B reached potentially toxic levels in soil. Na levels increased in the leaves, raising concerns about salinisation. Fruit yield and numbers were improved, while the average fruit weight decreased due to internal nutrient competition. Further, fruit quality improved through reduced weight loss and increased soluble solid and dry matter content. Ripening accelerated and soft pulp incidence rose while maintaining the fruit colour. These findings highlight the benefits of reclaimed wastewater in conserving freshwater resources and sustaining crop production in water-scarce regions, if salt accumulation is managed.