Shadow analysis field measurements related to soil surface roughness.

The present study aimed to fill the need for a reliable, low-cost and convenient method to measure soil surface roughness. Based on the interpretation of micro-topographic shadows, this procedure is primarily designed for use in the field. The principle underlying shadow analysis is the direct relationship between SSR and the shadows cast by soil structures under fixed sunlight conditions. The results obtained with this method were compared to the statistical indexes used to express field readings recorded by pin meter and chain set methods. The tests were conducted on 4-m 2 sandy clay loam plots divided into 1-m 2 subplots tilled with three different implements: chisel, tiller and roller. The highly significant correlation between the statistical indexes and shadow analysis results proved that both variability (CV) and dispersion (SD) are accommodated by the new method. The method also showed a good proportionality with the chain roughness (CR). The SSR obtained for the different methods is mainly related to the presence of aggregates. The shadow analysis simplifies the interpretation of soil surface roughness and shortens the time involved in field operations by a factor ranging from 4 to 20.