Facilitated Phosphorus Acquisition of Maize Is Dependent on the Root Traits of Associated Faba Bean in Intercropping Systems.

Plants deal with phosphorus deficiency by changing the root morphology or strengthening the rhizosphere processes. How does these strategies affect adjacent plants in intercropping? Previous studies have proved that faba bean roots can release proton, acid phosphatase and organic acid to mobilize the insoluble phosphorus in soil. To our knowledge, however, there is still lack of study on how morphological parameters of faba bean roots affect the phosphorus acquisition of maize. The objectives of the present study is to investigate the root morphological and rhizosphere differences among faba bean varieties and their effects on the growth and phosphorus uptake of associated maize, and to identify the mechanisms of efficient phosphorus acquisition in faba bean/maize intercropping. We designed a greenhouse experiment with three factors, the first factor is faba bean cultivars (Lincan, Kangleniutabian, Zhangye and Mingqin) with large variation to mobilize sparingly soluble P in soil, and the second factor is root barriers (solid barrier, nylon mesh barrier and no barrier) with 5 replications for each treatment. Results showed that acid phosphatase in rhizosphere soil of cultivar Lincan was 18.4% and 18.7% higher than that of cultivars Minqing and Zhangye. The citrate concentration in rhizosphere soil for cultivar Kangleniutabian was 2.1 times and 2.3 times as much as that of Minqin and Zhangye, and the malic acid concentration was 2.32 times and 2.31 times as much as those of Mingqin and Zhangye. The root length, root surface area and root volume of Lincan are all significantly higher than other cultivars. The rhizosphere processes of faba bean was positively correlated with not only P acquisition of faba bean itself, but also P acquisition of associated maize. The morphological parameters of faba bean roots was negatively correlated with P acquisition of associated maize. The finding has shed a light on understanding the mechanism behind interspecific facilitation on P acquisition, but also have an importance in selecting a reasonable cultivar in intercropping.