EFFECTS OF SOIL TEXTURE AND ORGANIC MATTER ON EVAPORATIVE LOSS OF SOIL MOISTURE

Moisture stress has a major influence on the yield of agricultural crops. The primary source of moisture loss in agricultural soils is evaporation. This study was carried out to ascertain the effects of soil texture and organic matter on soil evaporation and also to establish a relationship between soil moisture diffusivity and water content of a finite soil core resulting from evaporation. The experiment was carried out at the Soil Science laboratory of the Faculty of Agriculture, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana. The University is located at 6.6849° N, 1.5705° W. Soils of various textures were collected from fields under different land uses or management practices at a depth of 0-5cm. Laboratory evaporation was effected using a standing electric fan as a source of power for inducing evaporation. Textural classes for the sampled plots were cocoa farm (Sandy loam), Uprooted/Harvested Oil palm plot (Loamy sand), Grass ley (Loamy sand) and Vegetable plot (Sand). Organic matter content for the sampled plots were 4.80%, 3.71%, 2.55% and 1.69% for the cocoa field, uprooted oil palm, grass ley and vegetable plot respectively. Diffusivity was highest in soils with high organic matter and clay content whereas desorptivity was lower in coarse-textured soils. In general, however, where organic matter and clay content were high, soil water conservation was more effective.