abstract: Radioactive isotopes are universally measured by instrumental methods. The relative ease with which radioisotopes may be detected, and quantitatively measured, has led to their widespread use as tracers in chemical, physical and biological systems. Radioisotope techniques take place in the study of chemical, physical and microbiological processes in soil. In soil sciences the major applications are to investigate the fate of labelled nutrient ions added to soil, to demonstrate the dynamic nature of the exchange ions equilibrium and to determine the size of the labile pools of various nutrient ions and their interaction with soil materials. Another important application of radioisotopes has been elemental analysis of soil and plant materials. Most radioisotope work with the soil organic matter has involved the use of 14C to study the decomposition or transformation of labelled compounds or plant materials, and the evolution of 14CO2.