Environmental and agronomic impact of fertilization with composted organic fraction from municipal solid waste: A case study in the region of Naples, Italy

In larger urban agglomeration, composting of organic waste is a possible solution to the long-standing rubbish problem, limiting the amount of waste going to final disposal. Fertilization with composted waste from Naples city was studied with the aim to evaluate the possibility of recycling of waste through the agricultural use of composted waste. The best results from the agronomic (soil fertility, quantity and quality of lettuce yield) and environmental (risk of potentially toxic metal and nitrate pollution, C storage in stable SOM) perspective, were obtained using the 30 Mg ha-1 dose of compost. In compost and soil, total concentrations of Cu, Cr, Pb and Zn were always below European pollutant limits. However, after plant growth and compost fertilization at the highest dose (60 Mg ha-1), the amounts of 'EDTA-extractable' Pb and Zn in soil significantly increased, suggesting a role of composted organics and root exudates in metal bioavailability. Fertilization with composted waste could have positive agronomic and environmental effects if the doses are balanced against the N requirements of crops. However, further researches are needed to assess the long-term effect of repeated compost application to soil and the potential cumulative effects.