An improved method for the isolation and the quantitative measurement of crop roots.

The isolation of crop roots from soil samples, making use of the dispersing action of carbon dioxide gas evolved by the reaction of added oxalic acid on carbonates in the soil has been described. The roots are photographed in a thin layer of water against a matt black back­ ground, resulting in sharp negative pictures that can be used by a 'Quantimet' image analyser to measure length or other properties embodied in the photographs. The methods are applied in a study of the rooting characteristics of potato crops in a rotation experiment.