Minimum tillage and organic fertilization for the sustainable management of Brassica carinata A. (Braun) in the Mediterranean environment

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.