TILLAGE EFFECTS ON THE RADAR BACKSCATTERING COEFFICIENT OF GRAIN STUBBLE FIELDS

The effect of different tillage on the microwave backscatter from grain stubble plots was investigated as a function of frequency. polarization, row direction and type of tillage implement. The Canada Centre for Remote Sensing (CCRS) truck-mounted FM-CW scatterometer was used to make the radar backscattering coefficient (sigma-degrees) measurements. Factorial analysis found the effects of row direction to be as significant as the differences between tillage implements on sigma-degrees of like polarized data. The cross-polarized data were less sensitive to row direction effects. There were no significant differences between the HH and VV polarizations at any frequency investigated. An airborne SAR image of an area close to the experiment site was qualitatively used to demonstrate the effects of tillage and row direction. The scatterometer results and airborne SAR interpretations indicate the necessity of accounting for row direction, as well as surface roughness, when using SAR data for soil mapping applications. Techniques are identified which may allow estimation of these roughness effects. Radarsat, and other Earth observation satellites will view agricultural fields with many row aspects and thus research needs to be conducted to determine the effects of row direction on sigma-degrees at the anticipated azimuth view angles.