Crop Water Use Update

By Jerry Wright, Extension Engineer, West-Central Research and Outreach Center, Morris, MN

Water is a very important component of crop production. Over the growing season an annual crop may require 15 to 20 inches of soil water to enable healthy plant growth and nutrient uptake. This soil water amount needs to come from in-season rainfall and pre-season stored soil water in the rooting zone.

Daily crop water usage (also known as evapotranspiration or ET) is very dependent on the stage of plant growth, soil water status and the day's weather, especially air temperature and solar radiation (sun energy). Daily ET will very from less than 0.05 inches to over 0.30" depending on the plant size, canopy cover and the weather.

Evapotranspiration (ET) is the combination of water that is evaporated from the soil surface and the leaf area by transpiration. When plants are small much of a crop's daily ET (0.05 to .10 inch per day) comes from soil surface evaporation. As the crop canopy cover increases the daily crop ET increases to typically 0.15 to 0.30 inches per day during full canopy and good soil moisture conditions. The ET during this time period comes mostly from transpiration from the plant leaves. If the soil moisture content in the active root zone is less than 50 percent of capacity, the daily ET of a crop can be significantly reduced during these times. This will cause some degree of stress to plant growth and yield reduction depending on the length of time this soil moisture shortage occurs and the weather conditions at the time. Daily crop water usage (ET) estimations for full canopy crops across Minnesota can be observed at the following address: http://bob.soils.wisc.edu/wimnext/water.html

Co-Editors:Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Cindy Tong, Department of Horticulture, University of Minnesota, ctong@extension.umn.edu
Production Editor: Suzanne Wold, Research Specialist, University of Minnesota, woldx018@tc.umn.edu

Disclaimer
Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current directions of the manufacturer

Last Revised May 4, 2000.
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