Estimated Crop Water Use (ET)

Instructions: To determine amount to irrigate; add daily ET for each day since your last irrigation or significant rainfall…..(look below in link for more info).

Weather Data from SLV Research Center Extension Office

For the latest recorded message, call 754-3494 extension 40 (Center), Ext 38 for LaJara and Ext 36 for Center #2. Use the crop maturity and planting date closest to your own.

The Internet address is:

Evapo-Transpiration (ET) Crop Reports

This information provided by

Andrew Houser,
SLV Research Ctr
Colorado State University

For information on using the data, call 754-3496 x26 or e-mail:ahouser@colostate.edu

Notes:

  • Weather stations used for ET calculations are located at Center (SLV Research Center), Center02 (7 mi NE of Center), Blanca and La Jara. Use the weather station closest to the field for which you want the ET (crop water use).
  • To determine amount to irrigate; add daily ET for each day since your last irrigation or significant rainfall..
  • Add daily evapotranspiration (ET) for each day since your last irrigation. This is the amount of water the crop has used. This amount plus 10-20% for efficiency must be added.
  • Totals for two, three, four, five, and 7-days are added for you.
  • Rainfall is not included. Subtract effective rainfall for each individual field.
  • What is presented is the net amount of irrigation needed. Add 10 to 20% for irrigation inefficiency. You might add 20% for high pressure overhead sprinklers and add at least 10% for low pressure drop nozzles. In the early season, do not irrigate until the amount needed is at least 0.50 inches unless you are trying to keep the surface wet for emergence. Irrigating with small amounts wastes water as most of the water is lost to soil evaporation.

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