Synergic Effect of Nutrient-Enriched Biochar and Zeolite on Soil-Tomato System Irrigated with Urban Treated Wastewater

This study investigates the impact of nutrient-enriched biochar and zeolite amendments, combined with irrigation with treated wastewater (TWW), on soil fertility and tomato plant growth at the Water Resource Recovery Facility of Palermo University. We conducted a pot experiment with tomato plants to test the combined effect of PO43−-enriched biochar and NH4+-enriched zeolite, with or without using TWW for irrigation. Tomato plants irrigated with TWW matched the growth rates of those irrigated with tap water. The enriched amendments improved total nitrogen and phosphorus in the soil (23.2 and 9.3%, respectively). They seemed to promote a more salinity-tolerant microbial community, as indicated by the slight increase of microbial biomass carbon (MBC) in the combined treatment. The enriched amendments and the irrigation with TWW also led to a higher amount of metagenomic DNA extracted from soil microbiota parallel to the increase of MBC. Electrical conductivity levels suggested that TWW increased soil salinity; however, biochar and zeolite amendments effectively counteracted this effect. These results support the integrated use of TWW and nutrient-enriched amendments as a sustainable agricultural practice, offering a strategy to improve crop productivity while maintaining ecological balance. Future research should focus on the long-term results of these treatments and their influence on the soil microbiome.