Abstract: 【Objective】The decomposition characteristics and nutrient releasing patterns of rapeseed and wheat straws were studied under different rice cultivations and straw mulching models in 2007 and 2008 growing seasons, respectively.【Method】Wheat and rapeseed straws were wrapped in net nylon bags and put on the surface or embedded into the soil under conventional cultivation and water-saving cultivation models.【Result】The results showed that the decomposition rate of straw was faster in the first 30 days and then slowed down until the end of the experiment. Under water-saving cultivation model, 90 days after straws were embedded into soil, the decomposition rate was high up to 61.06%. The cumulative decomposition rates of wheat and rapeseed straw were 48.88%-59.95% and 50.88%-61.06%, respectively. Under conventional cultivation model, the straws that were mulched decomposed faster than the straws that were embedded into the soil did. With straw mulching, there was no obvious difference in decomposition rates between the two cultivation models. When straws were embedded into the soil, the straw under water-saving cultivation model decomposed faster than the straw under the conventional cultivation model. The sequence of nutrients releasing rates were K＞P＞N≈C. C releasing rates of wheat straw and rapeseed straw were up to 48.29-63.79% and 50.29-66.55%, and N were up to 48.35-52.83% and 46.48%-57.67%, and P were up to 54.83%-67.49% and 56.44%-75.64%, and K were up to 91.98%-95.99% and 92.31%-96.24% after 90 days of decomposition, respectively. The effect of cultivation model and incorporation method on N, P and C releasing patterns had almost the same trend with the decomposition of straw. K release rate was more than 90% after 30 days of decomposition. 【Conclusion】 It is concluded that on the basis of straw mulching, the water-saving cultivation model can promote the straw to decompose and to release the nutrients.

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