Results from the fitting of dynamics of SPAD readings to a piecewise function.

The letters a1, c, and a2 represent function coefficients as shown in Fig. 6. N1, N2, N3, N4, N5, and N6 indicate N application rates of 0, 75, 150, 225, 300, and 375 kg N ha−1, respectively.

***P <0.001.