[Quantitative analysis of root morphology and phosphorus absorption in wheat and faba bean intercropping system.]

The intercropping of legume and cereal crops could affect crop roots growth. The relationship among intercropping, root morphology and phosphorus (P) acquisition under different P levels is still unclear. With field experiments and a rhizo-box experiment, we examined the changes of yield, biomass, P acquisition and root morphology of wheat and faba bean under different planting patterns (monocropped wheat, MW; monocropped faba bean, MF; and wheat and faba bean intercropping, W//F) and different P levels. In the rhizo-box experiment, both root weight and root-shoot ratio were increased by 21.2% and 61.5%, respectively, but shoot weight was decreased by 14.6% when wheat intercropped with faba bean. Root P content and P uptake of intercropping wheat (IW) increased by 23.8% and 12.1% when compared to MW. Both shoot and root weight, root-shoot ratio, total root length, and root volume of intercropping faba bean (IF) increased by 16.5%, 47.3%, 24.0%, 3.5%, and 8.4% as compared to MF, respectively, which resulted in higher shoot and root P content and P acquisition of IF. In the field experiment, P uptake by IW decreased by 8.7% at tillering stage, but P acquisition increased by 40.6%, 19.7%, 7.8% and 12.4% at join-ting, heading, filling, and maturity stages as compared to MW. By contrast, P acquisition of IF decreased by 9.8%, 9.0% and 5.2% at flowering, podding, and maturity stages as compared to MF. Partial least squares (PLS) regression analysis showed that root surface area and total volume of wheat and root surface area of faba bean had the greatest contribution to crop P acquisition. Intercropping induced higher root volume and root surface area which resulted in higher P acquisition under low P stress. In conclusion, interspecific interaction amplified the root-soil interface zone and increased P uptake at seedling stage under low P stress, which could contribute to the intercropping advantages at later stage.