The difference between the N dilution curve for 478 and Wu312 and the critical N dilution curve could be explained by the
differences in plant shoot dry weights and plant densities between the experiments. In our experiment, two maize inbred lines 478 and Wu312 had smaller shoot dry weight, and the plant density (60,000 plants ha1) was also lower than that in Ple´net and Lemaire’s experiments. As a result, the shoot dry weights of the both inbred lines in our experiments were obvious lower than that in Ple´ net and Lemaire’s experiments at a given time, while the shoot N concentrations were almost the same between the experiments