Variation in amounts of carbon and nitrogen associated with particle size fractions of soils from the Palace Leas meadow hay plots

An increase in carbon (C) content of one of the more acid Palace Leas meadow hay plots (pH 4.0) is shown to occur in the >63 pm size fraction, while there is a reduction in organic matter associated with clay size fraction relative to a less acid plot (pH 5.8). Total nitrogen (N) content also is higher on the more acid plot, but the increase is smaller than for carbon, and leads to a wider overall C:N ratio in the acid plot. The lower N accumulation in the more acid plot is due to the relative increase in coarse (> 2 mm) organic matter, with a high C:N ratio. The technique used for separation of the particle size fractions does not involve removal of coarse organic matter (> 2 mm) or drying of the soil. In the grassland soils studied, coarse organic matter is a significant component (up to 13%) of total C, yet this fraction is frequently removed before analysis. By not drying the soil, separation into particle size fractions is facilitated.