Dynamics of organic matter in soil as determined by variations in C-13/C-12 isotopic ratios and fractionation by ease of oxidation

Management of organic matter in soils requires techniques that accurately monitor changes in soil organic matter over the short term and long term. This study was carried out in a glasshouse pot experiment to examine changes in soil carbon under the influence of long-term cropping, plant residue, and fertiliser application, using variations in C-13/C-12 isotopic ratios of organic materials and fractionation by ease of oxidation. The study examines the changes in carbon contents of adjacent soil samples with different cropping histories as affected by application of fertiliser and crop residue and the growth of wheat. Significant increases in soil carbon values were observed with residue application. The effects of the applied fertiliser on soil carbon levels depend on the presence or absence of wheat. A higher amount of labile carbon was found in the native soil than in cultivated soil.