Treated Wastewater and Fertigation Applied for Greenhouse Tomato Cultivation Grown in Municipal Solid Waste Compost and Soil Mixtures

Low-fertility soil and the use of brackish water for irrigation act as obstacles and limit crop production. The utilization of municipal solid waste (MSW), compost (C), and treated wastewater (TWW) is receiving attention nowadays not only to overcome the above limitations but also as an efficient way for waste management and reuse of raw materials. In the present study, MSW compost in different ratios (5%, 10%, 20%, and 40%), fertigation and/or irrigation with TWW were studied in tomato plants (Solanum lycopersicum L.). The addition of compost increased organic content, pH, electrical conductivity (EC), and mineral content of the growing media, while fertigation and TWW supported the mineral status of the growing media, and this was reflected in the increase of N, K, and Na in tomato leaves. Plants grown in compost-based media with fertigation produced more leaves, compared to the control, while irrigation with TWW did not increase the number of leaves. Plant biomass increased with the application of ≥20% C, fertigation, and/or TWW applications. Plant yield increased in 40% C, while fertigation increased yield in case of lower (5%-10% C) compost ratios, but TWW application did not change the yield. The combination of high C ratios and fertigation and/or TWW decreased tomato fresh weight. Different levels of C did not affect leaf photosynthesis, stomatal conductance, internal CO2 concentration, and chlorophyll fluorescence, but, in general, the combination of compost with fertigation and/or TWW affected them negatively. Fruit total soluble solids, acidity, ascorbic acid, firmness, and total phenolics were increased with the high ratios of compost and/or fertigation and TWW applications, but marketability did not. Bacteria (total coliform and Escherichia coli) units increased in growing media subjected to TWW, but lower levels were counted on the fruit, mainly due to splashing or fruit contact with the soil. The results indicate that up to 40% C can be added into the substrate, as increased plant growth and maintained plant yield for greenhouse tomato cultivation is observed, while fertigation and TWW could be used in a controlled manner as alternative means for nutrient and irrigation in vegetables following safety aspects.