Subsurface Imaging of Tillage Systems Effects On Soil Physical Properties Using Electrical Resistivity Tomography.

In this study we seek to demonstrate through the use of electrical resistivity (rho) imaging the effects of different tillage systems on the spatial variation of soil resistance to penetration and soil porosity. Two-dimensional DC resistivity tomography was performed on a long term conventional tillage, (CT), minimum tillage (MT), no tillage (NT) and on no tilled plot just tilled NTT plots on 11.75 m transects with an Iris Syscal Pro ten-channel receiver resistivity meter and 48 electrodes in dipole-Dipole configuration, with inter-electrode spacing of —0.10 meters. Soil penetration resistance and bulk density were spatially measured along each transect at 10 horizontal positions and at 0.05 m depth increments up to 0.4 m depth. Gravimetric soil moisture and dry bulk density values by the cylinder method with 98.125 cm3 internal volume brass cylinders were measured on triplicates for each plot at 0.05 m depth increments up to 0.5 m depth. Volumetric soil water was obtained by multiplying gravimetric value by bulk density A total of 1505 resistivity values were obtained for each transect. Total variation in soil resistivity was highly significantly explained by tillage treatment and soil depth and by their interaction. High values were found above 20 cm layers of the tilled treatments, and the largest differences between treatments were found between 5 and 15 cm of depth. The response of soil resistivity to soil tillage was able to significantly discern between tilled and untilled soil, and between a freshly tilled soil layer (NTT at 10 cm of depth) and soil tilled in the past (CT and MT at the same depth).Soil bulk density, penetration resistance and water content were also correlated with soil resistivity.