Long-term amendment of soils with compost and pig manure: effects on soil function, production and health risk assessment

Organic amendments are frequently used in agriculture to enhance soil quality and, simultaneously, to contribute to a sustainable way of waste management. This study was aimed at evaluating the effects on the terrestrial environment after long-term application of organic amendments on agricultural soil. A multi-approach analysis was performed of the systematic and long-term (13 years) use of compost and pig manure as agricultural fertilizers in Mediterranean soils. The impact on physical-chemical properties and functions of soil, as well as on vegetable growth, was also studied. The concentrations of heavy metals accumulated in soil and plants, both wheat straw and grain, were also determined. Moreover, the health risks of exposure to potentially toxic elements through a number of pathways were assessed for farmers in direct contact with soil and consumers of vegetable/meat products. In general terms, the long-term input of pig manure and compost increased the organic matter content, soil levels of phosphorous and potassium and microbial activity. It also improved the mineralization processes of carbon and nitrogen, as well as some enzymatic functions and crop yield. Furthermore, the application of neither compost, nor pig manure, was associated with human health risks due to heavy metal exposure.