Phosphorus fertilization reduction enhanced legacy P recovery in an Ultisol under maize-soybean intercropping system: Implication for soil health and green crop production

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 (P_o), while enrichment of liable P_o, 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 (Candidatus_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.