Soil legacy phosphorus (P) activation is critical for enhancing P use efficiency, while how reduced P fertilization on legacy P recovery under intercropping soil remains elusive. This study investigated the impact of fertilizer P reduction on the fertilizer P use efficiency (PUE), crop biomass, legacy P recovery, transformation and the underlying biogeochemical driving mechanisms under the maize-soybean intercropping system using a combination of sequential fractionation (SF), solution 31P nuclear magnetic resonance (P-NMR) spectroscopy and Illumina MiSeq sequencing. Four P fertilizer application rates, including conventional fertilization rate (CF), P fertilization reduction by 15 % (P15), 25 % (P25) and 50 % (P50), were conducted in the pot experiment using an Ultisol with maize-soybean intercropping. The result showed that the P15 treatment significantly increased P uptake, biomass and PUE of the maize relative to the CF treatment, but insignificantly for the soybean. The SF and P-NMR analysis revealed the depletion of total organic P (Po), while enrichment of liable Po, i.e. orthophosphate diesters in the maize rhizosphere, which probably resulted from the rhizospheric enhancement of acid phosphomonoesterase and microbial activities, and enrichment of specific bacterial communities (Candida- tus_Koribacter, Ramlibacter and Noviherbaspirillum). This study provides a theoretical basis for the P fertilization reduction to enhance PUE and legacy P recovery, thus facilitate pursuing soil health and green crop production under maize-soybean intercropping system.
