Predicted and observed finger diameters in field soils

Wetting front instability resulting in fingered flow has been found in both wettable and non-wettable soils. Laboratory research has resulted in a number of expressions for finger diameter. The applicability of one of these equations was tested for three soils where detailed soil moisture contents were measured. Information needed for finger prediction, such as the main wetting and drying loops of the soil moisture characteristic curves, were measured as well. Predicted finger diameters for the two sandy soils agreed well with the observed moisture patterns, whereas for the loess soil the wetting front was flat as predicted. The finger diameters in dry soil were based on the main wetting loop and in the wet soils they were dependent on the main drying loop.