Interference by living plant roots is usually found in decomposition studies with no labelled plant materials carried out under field conditions.It has been found that this interference can be completely eliminated by using porous carborundum tubes with mainly of 140μ×70μ,as the containers for soil and plant material being and the hydro-thermal conditions of the soil inside the tube was identical with or approximate to that outside the tube under submerged and upland conditions respectively.