Captions
Fig. 1. Effect of topsoil depth on grain yields of maize and soybean in 2016, 2017 and 2018. The main effects of topsoil depth, crop species and cropping year, and their interactions are all highly significant (P < 0.001). Values with means ± standard error (n=3). Within a growing season of each panel, values with a same letter are not significantly different (P > 0.05).
Fig. 2. Effect of topsoil depth on root and shoot biomass of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages in 2017. Values with means ± standard error (n=3). Within a growth stage of each panel, values with a same letter are not significantly different (P> 0.05).
Fig. 3. Effect of topsoil depth on N, P and K uptake in shoot of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages in 2017. Values with means ± standard error (n=3). Within a growth stage of each panel, values with a same letter are not significantly different at (P> 0.05).
Fig. 4. Effect of topsoil depth on N, P and K uptake per unit root length of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages in 2017. Values with means ± standard error (n=3). Within a growth stage of each panel, values with a same letter are not significantly different at (P > 0.05).
Fig. 5. Effect of topsoil depth on the concentrations of available N, P and K in the rhizosphere soil of maize at the milk stage (R3), and of soybean at the seed-filling stage (R6) in 2017. Values with means ± standard error (n=3). Within each panel, values with a same letter are not significantly different at P > 0.05 among treatments in two crops (2-way ANOVA).
Fig. 6. Effect of topsoil depth on enzyme activities in the rhizosphere of maize at the milk stage (R3), and of soybean at the seed-filling stage (R6) in 2017. Values with means ± standard error (n=3). Within each panel, values with a same letter are not significantly different at P > 0.05 among treatments in two crops (2-way ANOVA).
Table 1. Significant level (P ) of main effects and interactions of topsoil depth and crop species on grain yield (2016, 2017, 2018), growth parameters (2017), nutrient uptake (2017), and concentrations of available nutrients (N, P and K) and activities of enzymes in the rhizosphere soil (2017) of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages.
Fig. S1. Effect of topsoil depth on N, P and K uptake in root of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages in 2017. Values with means ± standard error (n=3). Within a growth stage of each panel, values with a same letter are not significantly different (P> 0.05).
Fig. S2. Effect of topsoil depth on total root length of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages in the top 30 cm of soil profile in 2017. Values with means ± standard error (n=3). Within a growth stage of each panel, values with a same letter are not significantly different (P > 0.05).
Table S1. The effect of topsoil depth on the concentrations of N, P and K in root, stem and leaves of maize at the jointing (V7) and milk (R3) stages, and of soybean at the initial flowering (R1) and seed-filling (R6) stages in 2017. Values with means ± standard error (n=3). Values with a same letter are not significantly different between topsoil depths (P > 0.05).