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).