Laboratory study of the availability of nutrients in physical fractions of cattle slurry

Abstract

SummaryThe characteristics of three fractions obtained by physical separation from each of 19 cattle slurries are reported, with the aim of investigating their behaviour in the soil. The fraction retained on a 1 mm sieve (F1) was the poorest in nutrient content. The fraction passing through a 1 mm sieve but retained in Richard's apparatus on a cellulose membrane of 2·4 nm pore radius (F2) contains most of the slurry's organic N and Pand most divalent cations (Ca2+ and Mg2+). F3, which passes through the cellulose membrane, contains most of the slurry's inorganic N and most monovalent cations.The individual fractions are both chemically and physically much more homogeneous than the slurry as a whole, and their relative proportions are well correlated with the slurry's density and dry-matter content (P < 0·001), so that this kind of fractionation may confidently be expected to provide an analytical scheme facilitating research on the behaviour of slurry after its application to soil.