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This article in SSSAJ

  1. Vol. 51 No. 5, p. 1113-1121
     
    Received: Nov 10, 1986
    Published: Sept, 1987


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doi:10.2136/sssaj1987.03615995005100050004x

Energy and Water Balance of a Sparse Crop: Simulated and Measured Soil and Crop Evaporation1

  1. R. J. Lascano,
  2. C. H. M. van Bavel,
  3. J. L. Hatfield and
  4. D. R. Upchurch2

Abstract

Abstract

Dryland crops grown in semiarid environments often do not completely cover the soil, leaving a portion of the soil surface exposed to a condition of rapid soil-water evaporation. Quantitative separation of soil evaporation and crop transpiration is important if cultural practices or cultivars are to be evaluated. This study was designed to evaluate a combined energy and water balance model, ENWATBAL, to describe the concurrent heat and water fluxes in a row crop. Inputs to the model include soil and plant variables and daily weather data. Measurements were made for a period of 74 d over a cotton (Gossypium hirsutum L.) canopy during 1985 on an Olton soil (fine, mixed, thermic Aridic Paleustolls) at Lubbock, TX. Data collected included soil-water content, soil temperature, root distribution, soil evaporation with microlysimeters, and leaf area index, for both an irrigated and a dryland plot. The values for daily evaporation and evapotranspiration calculated with the model were within 1 standard deviation of the measured values. Cumulative evaporation and evapotranspiration from the model agreed with measured values within 7% for the dryland and 8% for the irrigated plot. Estimated soil-water and temperature profiles also agreed closely to measured values. Soil evaporation was found to be 30% of evapotranspiration, for both the irrigated and the dryland plot. The ENWATBAL model provides a reliable method of evaluating the effects of management practices and crop selection on the water-use efficiency of crop production in a semiarid area.

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