INFLUENCE OF SURFACE SOIL CONDITIONS ON DRYING IN EARLY SPRING

Abstract

Changes in water content of adjacent plowed and unplowed surface soils were measured in early spring in the field. The plowed plots on sand and clay soils lost more water than unplowed plots. The major decrease in water content of the clay soil was in the 0–7-cm layer, whereas the sand lost as much water from the 7–15-cm layer as from the 0–7-cm layer. The medium-grained soil showed greater drying from the unplowed than from the plowed surface. The higher bulk density of this soil may account for this observation. Differences in net radiation measured above plowed and unplowed surfaces were too small to account for the measured differences in water loss. There was evidence that the drier surface was due to lower hydraulic conductivity of the plowed surface, but increased turbulent transfer from the rougher surface could also be involved.