Light fraction organic matter in soil - effect of pasture species, management and arable cropping

Abstract

The light fraction organic matter (LF-OM) is primarily composed of partially decomposed plant and animal residues. A relatively high carbon (C) : nitrogen (N) ratio, a rapid turnover rate and a considerably lower specific gravity than that of soil minerals are general characteristics of LF-OM (Christensen, 1992). The LF-OM is a labile source of C in soil (Biederbeck et al., 1994) and a significant pool for SOM turnover. The LF-OM is sensitive to management practices (Janzen, 1987; Biederbeck et al., 1994). Soil fertility management has been reported to have a clear effect on the quantity of LF-OM in the surface soil (Gregorich et al., 1997). Accumulation of LF-OM is considered to be favoured in continuously vegetated soils with a high return of plant residues such as forests and permanent grassland (Whitehead et al., 1975). This paper reports the effects of different pasture types and management on the LF-OM yield and its C N and sulphur (S) status in soils under short-term pasture, and changes in LF-OM following 3 years arable cropping.