Physiochemical variation within the storage of separated dairy cattle solids as amended by polyaluminium chloride and polyacrylamide

The increased utility of separation technologies on dairy farms is proposed to relieve nutrient management issues associated with storage capacity and environmental pollution. However, potential effect upon nutrient composition and physical parameters during storage is not yet well established. The aims of this study were to (i) determine any physiochemical differences between solid slurry fractions produced by chemical and/or mechanical means of separation; (ii) evaluate the effect of short-term storage on separated solids and raw feedstock; and (iii) compare the proportional changes relative to pre-storage values. This investigation utilised a chemical coagulation-flocculation process prior to separation via decanter centrifuge. Samples were analysed for N, P, K, C, Mg, Ca, and S, in addition to other nutrient and physical characteristics. Findings indicate the interactive effects of separation type on relative storage-mediated changes including chemical amendment reducing the amount of plant available nitrogen (as NH₄⁺) although providing savings in terms of volumetric storage capacity through increased bulk density. Further farm-scale measurements are needed across other store types to substantiate the differences recorded. • Coagulation-flocculation initially produced solids which were denser and higher in plant available N. • Irrespective of treatment storage-mediated differences were noted for TP, TK, NH 4+ , Zn, S, bulk density, WHC, and pH. • Storage losses of NH 4+ were 94% for amended and 83% for non-amended solids.