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

摘要

Cereal anchorage failure or root lodging represents a significanteconomic loss to cereal farmers. Current understanding and subsequentattempts to model the mechanisms of root lodging has been based oninvestigations that disturbed the soil/root system to visualize the process.To date, no studies have observed the effects of lodging on thebelowground (subterranean) stem and soil structure in undisturbed soil.Field impregnated samples with soil structure, stem, and root positionspreserved for lodged and unlodged wheat and barley plants grown at twopopulation densities were collected from three contrasting soil types.Using X-ray computed tomography, the changes in soil macrostructurewere visualized and quantified. Image analysis was used to determineselected soil pore characteristics including pore size distribution. Resultsfrom image analysis illustrated that barley can root lodge (previousresearch has suggested that lodging in this species only occurs from stembuckling). Root lodging created a significant increase in porosity andpore size at the macroscale. Much of this effect seemed to be caused byrotation of the subterranean stem, which has not been considered inmodels of cereal anchorage. There were no obvious differences in themechanisms of root lodging between wheat and barley grown atdifferent plant population densities and on different soil types. This wasthe case despite large differences in the spread of the root plate and in thenumber 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.