Dynamics of biomass (A), shoot Zn accumulation (B), shoot Fe accumulation (C), shoot Mn accumulation (D) and shoot Cu accumulation (E) of summer maize at V6 (six-leaf stage), V12 (12-leaf stage), R1 (silk emerging), R3 (milk stage) and R6 (physiological maturity) stages, respectively, with different N levels.

<p>The number of observations was shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093895#pone.0093895.s004" target="_blank">Table S2</a>.The bars represent the standard error of the mean. Bars with different lowercase letters are significantly different at different N levels (P<0.05).