Proportion, composition and potential N mineralisation of particle size fractions obtained by mechanical separation of animal slurry

Mechanical slurry separation is a useful technology for slurry management on farms. The characteristics of the fractions obtained depend on the separation efficiency and on the characteristics of the original slurry. In the present work, three types of slurry – pig, cow and duck – were separated into 4 particle size fractions. The proportion, composition in terms of carbon and nutrients as nitrogen (N) phosphorus (P) and potassium (K) was evaluated. The potential of N mineralisation of whole slurries, and each fraction after soil application, was assessed. Results of the study showed that the characteristics of the slurry fractions obtained depend strongly on the slurry type considered, namely on its dry matter (DM) content. A positive value of PNM was observed with the 3 slurry types and 4 fractions considered, indicating that no N immobilisation occurred. Nevertheless, results showed that the value of PNM vary significantly (P < 0.05) with slurry types and slurry particle size fractions.