Digestate Application on Two Different Soils: Agricultural Benefit and Risk

In order to valorize the use of digestate, the purposes of this study was to discriminate the fertilizing potential of solid and liquid fractions of digestate using two soils that differed for chemical characteristics, to expand the digestate use reducing its environmental impact. The two fractions did not contain toxic compounds and differed in chemical compositions. The two soils responded differently to the addition of the two-digestate fractions and the benefit depended mainly on soil characteristics rather than on quantity and quality of the organic material applied. In the soil with neutral pH, the highest intrinsic amount of organic matter, microbial biomass (MBC), fungi, bacteria and cation exchange capacity were observed; all these properties increased the most over time, in presence of both solid and liquid fractions. Differently, in the soil with alkaline pH and minor amount of intrinsic organic matter, MBC, fungi and bacteria, only few properties such as oxidative soil activity, bacteria colonies, and organic matter amount were improved by the addition of digestate fractions. The use of both fractions showed more agricultural advantages in respect to the relative risks, and the solid fraction was the most effective. Even if the effects of digestate on soil ecosystem can differ in extent, we can expect economic benefit deriving from the reduction of the costs for its disposal, agricultural benefit for their high supply of nutrients to the soil and environmental advantages for the decrement in the use of manufactured fertilizers.