Concentrations of phenolic acids (µg·pot−1) in root exudates from different treatments at the flowering stage as detected by HPLC.

Note: LP, 15 µM P; HP, 500 µM P. MS, soybean monoculture; MC, maize monoculture; ISC, maize/soybean intercropping. -, not detectable. All the data are the mean of four replicates ± SE. Data with the same letter represent no significant differences among the different cultivation modes at the same P level as determined by Duncan's multiple range test or a t-test (P