Figure 2.
The shoot N concentration and accumulation of summer maize at V6, V12, R1, R3, and R6 growth stages as affected by N application rates in the field in 2009 (A, C) and 2010 (B, D), respectively. The error bars represent the standard error of the mean (n = 4 in 2009 and n = 3 in 2010). For each stage, bars with same lowercase letters are not significantly different in different N treatments (P < 0.05). ns indicates no significant difference. * and *** indicate significant difference at P < 0.05, and < 0.001, respectively.