Root and Shoot Interactions Between Barley and Field Beans When Intercropped

(1) Barley (Hordeum sativum) and field beans (Viciafaba) were grown alone and with either their roots or their shoots, or both roots and shoots, intermixed. The nitrogen supply, total density and relative time of planting were also varied. (2) The Relative Yield Totals (RYTs) of mixtures were significantly greater than 1.0 only when the root systems intermixed, and RYTs were reduced when N fertilizer was applied. We therefore conclude that the yield advantage of intercropping was due mainly to beans and barley using different N sources. (3) The competitive ability of barley was greater than that of beans. Sowing barley before beans further increased its competitive ability. (4) Root competition had a much greater effect on the relative performance of the two species than did shoot competition. There was evidence that the two species competed for both P and K.