Hydraulic Conductivity and Diffusivity Relations of the Mollisols of Tarai*

Phoolbagh clay loam, Beni silty clay loam and Haldi loam soils of Pantnagar farm were studied for moisture characteristics. A major portion of water from the soils was released when the soils were subjected to 1/3 bar suction. The maximum height of rise of water due to capillarity occurred in Beni silty clay loam (109.6 cm) followed by Phoolbagh clay loam (100.2 cm) and Haldi loam (89.0 cm). Capillary fringe in the three soils was 20 cm.

Hydraulic conductivity and soil-moisture suction relation in a form similar to that observed by Gardner (1958) fitted the experimental values. Soil-water diffusivity variations at saturation in the three soils ranged from 1002 to 1898 cm²/day. However, the differences are not large from just below saturation to field capacity. The maximum variation in the hydraulic conductivity of the three soils occurred at saturation and lower water contents. In the region between 10 to 1000 mbar all the soils have about the same hydraulic conductivity.