Establishing desirable cropping systems with higher fertilizer-use efficiency and lower risk of environmental pollution is a promising approach for a more sustainable agriculture development. Intercropping may facilitate phosphorus (P) uptake and reduce P-fertilizer application rates. However, how root-root interactions mediate enhanced P-fertilizer use efficiency in intercropping remains poorly understood. Using a long-term field experiment established in 2009, where there have been three P-fertilizer application rates (0, 40, and 80 kg P ha-1) and nine cropping systems (four intercropping combinations and corresponding monocultures), we calculated aboveground P content, the apparent recovery efficiency of P fertilizer (AREP, reflecting P-use efficiency), and diversity effects, i.e. selection effect (SEP) and complementarity effect (CEP). We also investigated the P-related physiological and morphological traits of crop species and linked root traits with AREP. We found that long-term intercropping significantly increased shoot P content and AREP in all combinations compared with corresponding monocultures; intercropping with 40 kg P ha-1 application showed a relatively high P uptake and AREP. The P-uptake advantage in intercropping was mainly related to the positive CEP. The paired crop species (i.e. faba bean, oilseed rape, chickpea, and soybean) exhibited greater P-mobilizing capacity than sole maize. Intercropped maize exhibited greater root physiological, e.g., rhizosheath phosphatase activity and carboxylates (proxied by leaf manganese concentration), and morphological traits (e.g., specific root length) than sole maize, partly related to facilitation by efficient P-mobilizing neighbors. The greater AREP was mainly contributed by morphological traits of maize, rather than traits of paired crop species. We highlight that interspecific facilitation mediated by trait plasticity can meet P requirements and save P-fertilizer input in intercropping which probably decreases environmental costs and improves the sustainability of P management globally.