| The calibration of SMS2 Soil Moisture Probe and HH2 Meter (HH2) was studied in surface stratum of Heilu soil in the tableland and gully region of Loess Plateau, and the veracity of HH2 and the precisions and sensitivities of different calibration curves were analyzed. The results demonstrate that the CV of voltage by HH2 under different soil densities is less than 6%, and the measurements by HH2 are credible. The slope a of linear regression is increased with the accretion of soil densities, but the constant b is reverse. The calibration curves cannot be discriminated by a0 and a1. The difference of calibration curves is minimum when soil water content is 18%19%. |