a1 Department of Agricultural and Food Chemistry, Queen's University of Belfast, and Department of Agriculture for Northern Ireland, Newforge Lane, Belfast, BT9 5PX
The C and N in the biomass of soils from eight grassland field experiments where lime had been applied was determined by the chloroform fumigation method. Lime application increased C and N in the biomass by approximately 30% overall, although there was no effect at two sites. In the unlimed plots basal CO2 production, biomass C, and flush of mineral N production (FN) increased with soil pH. Biomass C and FN were correlated with total N content but not with organic C.
Differences in the apparent C/N ratio of the biomass were found in unlimed soils of pH ≤ 4·5 and in those of pH > 4·5, the ratios being 4·2 and 5·8 respectively. For limed soils the ratio was 5·2. It is probable that the chloroform fumigation method is not suited to soils of very low pH, and that the C/N ratio obtained in soils of pH < 4·5 is artificially low.
(Received February 26 1983)
p1 Present address: Soils and Plant Nutrition Department Rothamsted Experimental Station, Harpenden, Hertfordshire, AL5 2JQ.