Influence of Soil Water Status and Meteorological Conditions on Evaporation from a Corn Canopy1

Author:
  • JRJ. T. Ritchie
    J. T. Ritchie
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Abstract
In predicting evaporation rates for field crops, it is important to consider the influence of soil water status on the actual evaporation rate relative to the potential rate. This study was conducted to determine actual evaporation rates of corn (Zea mays L.) as influenced by soil water status and potential evaporation rate. Actual evaporation rates were measured during the 1972 growing season with a weighing lysimeter. Evaporation rates were found to be practically independent of the soil water status for all existing conditions of potential evaporation. During the season more than 20 cm of soil water was removed from the 120‐cm deep profile.Leaf diffusion resistance and leaf water potential measurements indicated that at least 80% of the extractable soil water was freely available to plant roots. These findings differ from those of Denmead and Shaw (Agron J. 54:385–390, 1962) who found that evaporation reduction in container grown corn plants started when about 20% of the extractable water was removed from the soil for potential evaporation rates above 6 mm/day. The difference between the results from the experiment reported by Denmead and Shaw and this experiment point out that serious errors are possible when using their results for predicting evaporation from corn plants growing under field conditions.