Estimating Soil Factors for Nine Kansas Soils Used in an Evapotranspiration Model

Laboratory and greenhouse experiments were performed for 9 Kansas soil types to determine percentage sand, silt and clay, moisture content percentage by weight (0 m) at -1/3 bar and -15 bar water potential, and soil factors that quantify the soil's drying rate: U, the cumulative evaporation during the energy-limiting stage; and c, the least squares slope of evaporation rate versus time /2 during the soil-limiting stage of soil surface evaporation. Hydrometer method for mechanical analysis was used to determine the particle-size distribution, and pressure plate method was used to determine 0 m. U and c were obtained from weight losses from soil columns in a greenhouse experiment. Results of the experiment Indicated that particle size composition and percentage water-holding capacity (WHC) Influenced the values of U and c obtained. U and c were relatively low for sandy soil and soil with low WHC but higher for soil with greater WHC and percentage silt. The values of U ranged from 5 to 18.7 mm; of c, from 1.68 to 3.73 mm day'/2. Trans. Kans. Acad. Sci., Vol. 81 (1), 1978.