In recent years, the massive exploitation of agricultural land intended to meet growing food demand has led to a reduction in soil fertility through the depletion of nutrients and organic matter. To implement sustainable agriculture, it is necessary to reduce soil tillage and use residual biomasses that are easily available in the region as soil amendments. Furthermore, it is important to test these residual biomasses in order to exclude a possible increase of heavy metals in soils due to the incorporation of the aforementioned biomasses. The current study aimed to evaluate the effects on soil fertility and health following the application of organic fertilizers combined with different soil tillage practices and the agronomic response of Brassica carinata A. (Braun). The soil tillage treatments consisted of conventional (CT) and minimum tillage (MT), whereas the fertilization treatments were mineral fertilizer (Nmin), municipal solid waste compost (Ncomp), mixed compost and mineral fertilizer (Nmix), and sewage sludge (Nss). These treatments were compared with an unfertilized control (N0). The Ncomp and Nss treatments enhanced soil fertility, increasing the organic carbon and available phosphorus concentrations compared with N0 and Nmin, whereas no significant difference was showed between the soil tillage treatments in terms of soil fertility. In addition, Nss did not show any significant difference compared to Nmin in terms of crop biomass, whereas this parameter appeared higher in CT compared with MT. A principal component analysis showed that the concentrations of toxic elements applied by the organic amendments did not change the dynamic equilibrium of the soil-plant system. Over the short term, the replacement of CT and Nmin with MT and Nss can be achieved, thus guaranteeing the sustainable cultivation of Brassica, without significant changes in heavy metal concentration in soil.
Keywords: Brassica production; Compost; Heavy metals; Sewage sludge; Soil quality; Sustainable agriculture.