GNGTS 2014 - Atti del 33° Convegno Nazionale

with which the average velocity of the radar waves propagation through the media for the our soil was determined as v = 0.07 m/nsec (Daniels, 2004). Soil moisture monitoring. Fig. 1 shows the soil moisture monitoring measured with TDR, outcomes in the first 40 cm of soil profile estimated through the integrated geophysical techniques. The peak of soil moisture is obtained three hours after the start of irrigation and the 0-20 cm soil moisture shows a larger variability compared to the 20–40 cm one, after with the pass of the hours the water is distributed into the soil. Fig. 1 – Soil moisture content in the first 40 cm of soil profile measured with TDR probes before, during and after irrigation. The peak was obtained three hours after the start of irrigation, and compared to the 20–40 cm , the 0-20 cm soil moisture profile shows a larger variability. ERT and GPR surveys was performed to characterize soil horizon and soil water movement before and after an irrigation stage, as well as to determine the groundwater level and to assess its influence on crop. Soil images obtained were carried out before and after irrigation, so different images with a different soil moisture permit to gain information about the water diffusion trough the soil. ERT application permitted to point out the electrical resistivity changes in relation to soil moisture variations as a result of irrigation. ERT images are reported in Fig. 2 and refer to the situations before irrigation (higher panel) and 24 hours after the irrigation (middle panel); while, the lower panel depicts the change of the electrical resistivity corresponding to the two above cases. The ERT1 survey carried out before the irrigation permitted to point out that the layer between the soil surface and 0.4 m depth exhibits resistive structures with values above 100 Ω m and an average moderate resistivity between 20 and 70 Ω m. Such a layer corresponds to the zone with higher root density and thus an increased root uptake, and a high porosity due to soil shallow tillage, as confirmed by GPR surveys shown below (see Fig. 3a). On the basis of granulometric analysis, the first layer between 0 and 0.3 m was characterized by a content of silt and clay on the fine fraction of 55.0% and 29.0% , respectively. For the layer 0.3-0.6 m depth, the content of silt and clay was about 44.0% and 41.0% , respectively, and ERT1 image exhibited lowest resistivity values (ρ < 20 Ω m). The higher clay content of this horizon and a lower root density with a more limited water uptake by bean roots is the cause of the soil electrical resistivity reduction (Michot et al. , 2003). ERT2 survey was carried out 24 hours after the application of 38 mm of irrigation water in the experimental field. As can be seen, the water distribution during the moistening phase 230 GNGTS 2014 S essione 3.3