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Little attention has been paid to root distribution in combined perennial legume and annual cereal crops.The main objectives of this study were to explore the regularity of root distribution and the influence on nitrogen (N) acquisition in different alfalfa (Medicago sativa I.) and corn (Zea mays L)intercropping patterns.A three year (2007-2009) field experiment studied four intercropping patterns of alternating alfalfa and corn rows with alfalfa: corn rows sown at 2 ∶ 2, 3 ∶ 2, 4∶ 2, and 5 ∶ 2.Sole crops of corn and alfalfa were used as controls.Roots were sampled over 3 consecutive years by auger sampling method in the prime filling stage of corn from different soil depth, and the root length density (RLD) was used to describe the root spatial distribution of intercropped alfalfa and corn.The results showed that the al falfa/corn intercropping system had the greater RLD values compared to the sole cropped alfalfa or com.In addition, the root mass centre of intercropped alfalfa descended into deeper soil layers with advancing stand age, and likewise proliferated laterally towards associated corn rows.Whereas the corn root mass spread at relative shallow soil profile, and also more deployed laterally to neighboring alfalfa root zone.The gap between alfalfa and corn rows was the highest colonized area with greater intermingling and the highest RLD of both species root.The complementary and compatibility of the root spatial distribution of component crops in alfalfa/corn community were the essential cause for better biomass yield.