Abstract: In order to explore the soil ecological effects of intereropping winter forage crops in young citrus plantation and its influenee on growth of the trees, rye grass, Chinese milkvetch and mixture of the two were intercropped into newly planted citrus plantation in red soil on hilly area of central Zhejiang Province. The results showed that intercropping could enhance soil temperature during winter and effectively reduce soil and water erosion, which were very important to protect the trees from cold injury and the soil environment;however, intereropping would retard increase of soil temperature during spring and had some negative effects on growth of the trees during spring and summer; the influence of intereropping on soil fertility was not obvious during the two year experiment. When the technique of intereropping was to be extended in practice, euhivation and management measures of the intereropped citrus plantation must be strengthened and the relationship between utilization of the forage and the amount of biomass direetly returned to the soil should be well coordinated so that the integrated efficiency could be enhanced.

Key words: arbuscular mycorrhizal fungus, watermelon, graft, defensive enzyme, continuous cropping.