With the present understanding that decomposing straw may not only affect soil properties, but pos-sibly greenhouse gas emissions as well, focus among environmental researchers has gradually expanded toinclude understanding of decomposition rate and stability of straw of different plants in different soils underdifferent management conditions. Against such a background, a short-term (60 days) greenhouse simulationexperiment was carried out to study the effects of straw placement, external mineral N source and tillageon straw decomposition of maize and cotton in two contrasting soils, a red soil (Ferrasol) and a black soil(Acrisol). The treatments included straw addition only (T1); straw addition + mineral N (T2); and strawaddition + tillage (T3). Straw was either buried in the soil or placed on the surface. Sampling was doneevery 15 days. Placement, addition of external mineral N sources (urea, 46% N), straw type, soil type andexposure duration (15, 30, 45 and 60 days) affected straw decomposition. Decomposition was more in buriedstraw than in surface-placed straw at all sampling dates in red soil. The addition of an external N sourcesignificantly increased decomposition. The study could not, however, fully account for the effect of tillageon straw decomposition because of the limited effect of our tillage method due to the artificial barrier tomechanical interference supplied by the mesh bags.