Abstract: Wheat straw contains water soluble toxic substances,which inhibit seed germination and seedling growth of corn. In this paper,the allelopathic effect of wheat straw mulching on corn seedling growth at different time with different quantities is presented. The results show that mulching with different amounts os wheat straw has different effects on corn seedling growth,4.5ton per hactare of wheat straw yields the best growth of corn seedlings. When the straw is mulched after 5 days of planting,the biggest inhibition on corn seedling growth would happen.When the straw is mulched at the day or after 15 days of planting, the best positive effects would be obained.

Key words: Lancang River Basin, ecosystem services, soil erosion, soil conservation.