Fig. 3. The wavelengths that contributed to significant regression coefficients (P 0.05) in the prediction of clay content are shown for field-moist and air-dry in situ and air-dry ground models. The relative magnitude of each regression coefficient indicates the strength of the correlation. The upper graph shows the mean of the regression coefficients common in all three models. All plots are on the same x axis. Values of the y axis are not shown, but all y axes are on the same scale.