Soil Layering and Compaction Effects on Unsaturated Moisture Movement

Abstract

AbstractMeasurements of the velocity of flow and hydraulic gradients were obtained in the suction range of 0 to 700 cm. of water across the plane of contact for three different soil textural pairs, two of which were sampled from naturally occurring textural breaks in alluvial soil profiles. The hydraulic conductivity values across the textural breaks indicated that the soil properties were favorable for moisture transfer from large pores to smaller pores, but that a barrier existed for water movement from smaller pores to large pores. The barrier developed as the suction increased in a coarse layer in contact with finer material. With water removal from the larger pores at moderately low suctions, flow from the fine soil layer into the coarse material was reduced. In the naturally occurring breaks in soil texture it was found that the compaction of the different soil layers determined the degree of expression of the barrier to water movement.