VISUALIZATION AND QUANTIFICATION OF THE EFFECTS OF CEREAL ROOT LODGING ON THREE-DIMENSIONAL SOIL MACROSTRUCTURE USING X-RAY COMPUTED TOMOGRAPHY

Cereal anchorage failure or root lodging represents a significant economic loss to cereal farmers. Current understanding and subsequent attempts to model the mechanisms of root lodging has been based on investigations that disturbed the soil/root system to visualize the process. To date, no studies have observed the effects of lodging on the belowground (subterranean) stem and soil structure in undisturbed soil. Field impregnated samples with soil structure, stem, and root positions preserved for lodged and unlodged wheat and barley plants grown at two population densities were collected from three contrasting soil types. Using X-ray computed tomography, the changes in soil macrostructure were visualized and quantified. Image analysis was used to determine selected soil pore characteristics including pore size distribution. Results from image analysis illustrated that barley can root lodge (previous research has suggested that lodging in this species only occurs from stem buckling). Root lodging created a significant increase in porosity and pore size at the macroscale. Much of this effect seemed to be caused by rotation of the subterranean stem, which has not been considered in models of cereal anchorage. There were no obvious differences in the mechanisms of root lodging between wheat and barley grown at different plant population densities and on different soil types. This was the case despite large differences in the spread of the root plate and in the number of crown roots between these treatments. It was recognized, however, that considerable heterogeneity in soil characteristics prevented any small differences from being detected using this method.