Abstract: The method of stratified digging was adopted to study the fine root distribution and underground competition in a walnut-soybean intercropping system in Loess Plateau of western Shanxi, Northwest China, aimed to provide scientific support for the efficient and sustainable management of fruit tree-crop intercropping system in this region. The walnut fine roots in the intercropping system were concentrated in 0-40 cm soil layer, and 55.7% of the roots were mainly distributed within the areas 0.5-1.5 m from walnut tree. Soybean fine roots were mainly distributed in 0-20 cm soil layer, and presented an increasing trend with the increasing distance from walnut tree. The underground interspecies competition between walnut and soybean mainly occurred within the areas 1.0-2.5 m from walnut tree, and was most intense within the areas 1.5-2.0 m from the tree.

Key words: straw amendment, C/N, soil CO₂ emission, black soil, soil carbon sequestration.