The TDR probe method is much faster than the gravimetric measurement, but it needs to be calibrated regularly.
In 2008 and 2009 a number of points were sampled using both methods, for comparison.
Fig. 3 shows the results obtainedwhen comparing measured soil moisture (MSM) values at two depths (0–5 and 5–10 cm) by the gravimetric method and the TDR probe.
The MSM values presented in this analysis vary from 5 to35%.
The root mean square error (RMSE) for mean value per field is 3.4% and 4.3% for individual sample points.
Furthermore, analysis of the two methods reveals a slight overestimation of the moisture measurement
when using the probe, compared with the gravimetric method