At the 12-leaf collar stage (V12) of maize in 2018, the following analyses were performed: (i) analysis of acid phosphatase (ACP) and ALP activity in the collected samples of fresh root and rhizosphere soil by using an ELISA Kit (Shanghai HengYuan Biological Technology Co., Ltd., Shanghai, China); (ii) analysis of ADP-glucose pyrophosphorylase (AGpase) of photosynthetic enzymes through enzyme-linked immunosorbent assay in the largest functional leaf samples collected; and (iii) determination of the net photosynthesis (Pn) rate of the largest functional leaf by using the LI-6400XT Portable Photosynthesis System (LI-Cor, Lincoln, NE, USA). After the harvest of each crop, the grain and straw were separated for the analysis of dry weight and total P (TP) content.
