Figure 1. Root interactions between soybean and maize plants in the field.

Root interactions were measured as the total root length in the upper 20: 80 kg P₂O₅ ha⁻¹ added as calcium superphosphate, LP: no P fertilizer added. ISC1: maize/soybean intercropping with 20 cm spacing; ISC2: maize/soybean intercropping with 5 cm spacing. All the data are the mean of four replicates ± SE. F value from Two-way ANOVA: 8.35 for P treatment (P<0.05), 159.08 for cultivation mode (P<0.001), 1.99 for interaction (not significant). Bars with different letter(s) vary significantly among treatments as determined by Duncan's multiple range test (P<0.05).