Abstract: In order to investigate the effects of soybean varieties with different kin relationships on the growth and nitrogen utilization efficiency, three soybean (Glycine max) varieties with different kin relationships were selected for this intercropping experiment. Soybean variety Huaxia 3 (A) was the target variety which was intercropped separately with Huaxia 3 (A), Guizao 1 (B) which was one parent variety of Huaxia 3, or Zhonghuang 24 (C) with no close phylogenetic relationship with Huaxia 3. The experiment was conducted under low nitrogen level (LN, 0.6 mg·L^-1) and high nitrogen level (HN, 60 mg·L^-1) by using sand culture method. There were 4 soybean plants in each pot with two plants of A and two plants of variety A, B, or C, forming treatments LN-AA, LN-AB, LN-AC, HN-AA, HN-AB, HN-AC with four replicates for each treatment. The result showed that the plant biomass, total root length, root volume of variety A intercropped with variety C were higher than with variety B. The total root length and root volume of A increased by 50% and 57% under LN-AC than under LN-AB, and by 46% and 50% under HN-AC than under HN-AB, respectively. The nitrate reductase activity (NRA) of A was higher when intercropping with C than with B. NRA was 56% higher in LN-AC than in LN-AB and was 49% higher in HN-AC than in HN-AB. There were no significant differences among treatments in total nitrogen content of leaf and stem (NCLS) at the fullbloom stage. However, NCLS of A variety in HN-AB was significantly higher than in HN-AC at the podfilling stage. The same trend of kinship influence was observed under LN treatment at the podfilling stage. In general, kin recognition exists in soybean and the recognition ability is affected by its growth stage.

Key words: Radermachera sinica, Karst, Triadica rotundifolia, sap flow density, transpirationwater consumption.