Evaluation of porous cup soil-water extractors: Physical factors

Abstract

The performance and characteristics of small, porous cup, soil-water extractors, installed in a soil with known water-transmission properties, are described. Cup conductivities decreased sharply during an 8 week period and, in the absence of other flux limiting factors, would limit water entry in the permeable topsoil but not in the slowly permeable subsoil. Measured cup water uptake however was much less than that predicted from either cup conductivity or soil water transmission properties. This is attributed to flow impedance near the cup walls. Under these conditions flow distribution in a soil with extractor cups would be much closer to that of an unextracted soil than is predicted from soil water flow theory.