## 5 Results and Discussion
### Effect of Individual Processing Steps on Soil Moisture Estimation
At 0.1 m soil depth, R\({}^{2}\) values between 0.27 and 0.39 with corresponding uRMSE values between 0.059 m\({}^{3}\)/m\({}^{3}\) and 0.067 m\({}^{3}\)/m\({}^{3}\) are achieved. Focusing on the alternating incidence angles, the Fourier Series transformation further reduces its effect on the resulting soil moisture. The minimum and maximum estimated soil moisture values at the CRNP stations in the three vegetation periods range from 0.186 m\({}^{3}\)/m\({}^{3}\) to 0.563 m\({}^{3}\)/m\({}^{3}\), from 0.162 m\({}^{3}\)/m\({}^{3}\) to 0.481 m\({}^{3}\)/m\({}^{3}\), and from 0.145 m\({}^{3}\)/m\({}^{3}\) to 0.412 m\({}^{3}\)/m\({}^{3}\) (Figure 11). While still exceeding the observed range of soil moisture values in the non-vegetation period, there is a clear reduction compared to the range of IA soil moisture estimation. The transformation into the Fourier Series is especially addressing the maximum soil moisture values. Looking at the varying correlation between in-situ measured soil moisture and estimated soil moisture for the individual years at each CRNP station, the additional Fourier Series transformation could reduce the observed range of R\({}^{2}\) during the observation period at each station in the mean by around 16%, compared to the IA soil moisture. At the Apulian Tavoliere site, a similar behavior can be observed, with a decrease in the upper extreme soil moisture values. Figure 10: Comparison between incidence angle normalized soil moisture estimation and in-situ measured soil moisture (SM) from all eight CRNP stations (**A**), and all six capacitance stations at 0.025 m (**B**) and 0.1 m (**C**) soil depth, grouped into the three vegetational periods. The addition of vegetation correction improves soil moisture estimation at the CRNP stations with mean R\({}^{2}\) values ranging between 0.55 and 0.68 and corresponding uRMSE values between 0.041 m\({}^{3}\)/m\({}^{3}\) and 0.046 m\({}^{3}\)/m\({}^{3}\). The improvements in R\({}^{2}\) range from 15% to 105% compared to the previous soil moisture estimations without vegetation correction, and uRMSE is reduced by up to 27%. The soil moisture estimations for the soil depth of 0.025 m and 0.1 m at the Apulian Tavoliere site improved in general as well. For the 0.025 m soil depth, R\({}^{2}\) values range between 0.29 and 0.49, with the corresponding uRMSE between 0.056 m\({}^{3}\)/m\({}^{3}\) and 0.063 m\({}^{3}\)/m\({}^{3}\). For the 0.1 m soil depth, R\({}^{2}\) values range between 0.39 and 0.42, with corresponding uRMSE between 0.057 m\({}^{3}\)/m\({}^{3}\) and 0.066 m\({}^{3}\)/m\({}^{3}\). In this regard, the improvements ranged from 14% to 217% in R\({}^{2}\) and from 1% to 28% in uRMSE compared to the backscatter time series without vegetational correction. Regarding the correlation coefficient at the crop dominated stations, the vegetation correction improved the observed R\({}^{2}\) values in all but one case (Table 5). At station SE_C_001 in 2020, the IA + FS soil moisture estimations are performing better with an R\({}^{2}\) of 0.67 compared to 0.39 from the IA + FS + VA soil moisture estimation. For uRMSE, a similar behavior is present at that station. At the Tavoliere site in Puglia, the increase in performance due to vegetation adaptation is most evident when compared to soil moisture values at 0.025 m depth, while it is not as pronounced at 0.1 m soil depth. Looking at the meadow dominated CRNP stations, the correlations between IA + FS and IA + FS + VA are mostly the same, as the vegetational correction is not applied but for one station. Having a backscatter intensity range greater than 0.10, the vegetation correction was applied and increased the correlation from R\({}^{2}\) = 0.66 to R\({}^{2}\) = 0.73 at station RU_C_007 in 2020. As the footprint of the CRNP stations as well as the 200 m pixels incorporates multiple agricultural fields, a change in the field diversity could be responsible for the change in backscatter range compared to the previous years.