Characterisation of Malian and Belgian solid waste composts with respect to fertility and suitability for land application

Two composts, a Malian (C1) and a Belgian (C2), and a peat substrate (C3) were analyzed for their suitability for land application. The results revealed that the materials can be used in agriculture but only the application of the peat substrate may create N immobilization. Composts had higher P, Ca, and Mg contents and lower C and K contents and C/N ratio than the peat substrate. The available P extracted from the three materials ranged from 15% (for C2) to 48% (for C3) and available K from 36% (in the composts) to 48% (for C3) of the total elements respectively. The fractionation of Mn, Fe, Zn and Cu in operationally defined fractions (water soluble, exchangeable, complexed, organically bound and residual) allows an estimation of the availability of metals for uptake. For example, 16% of the total Mn in the composts (C1 and C2) and 22% in the peat substrate would be plant available. Available Fe in the three materials was less than 2%. Available Zn varied between 10 and 25%. The fractionation allowed an estimation of the potential for contamination of groundwater following the applications of composts to agricultural lands.