About Crop Water-Use Charts
<click here for crop code key>
AgriMet uses site specific weather data estimate evapotranspiration (ET, or crop water use) for crops grown in the vicinity of each weather station. AgriMet uses the 1982 Kimberly-Penman ET model developed by the USDA Agricultural Research Service in Kimberly, Idaho to compute daily reference ET at each station, and uses alfalfa as the reference crop. Specific crop coefficients are then used to compute crop specific ET based on the alfalfa reference ET.
These crop coefficients vary throughout the growing season based on the plant growth stage. The crop coefficients are tied to the actual plant growth stage by three dates: Start, Cover, and Terminate dates.
Start dates are the beginning of vegetative growth in the spring for perennial crops or the emergence date for row crops. Cover dates are typically when plants reach full foliage. Terminate dates are defined by harvest, frost, or dormancy. Following is an explanation of the columns displayed in an AgriMet crop water use chart, followed by a key to the crop codes. This same key is offered as a pop-up window on the individual station pages. AgriMet crop water use charts are updated each morning at approximately 6:00 Mountain Time, and reflect ET based on the weather conditions for the previous day. There is also a tabular ET Summary Table daily crop water use for each crop for the entire growing season.
Explanation of Terms:
- Crop: Abbreviated identifier for the crop being modeled. See Key for an explanation of crop codes.
- Start Date: Typically the crop emergence date or beginning of vegetative growth for perennials.
- Daily ET: The previous 4 days of crop specific ET
- Daily Forecast: Average of the last 3 days ET
- Cover Date: Typically when the plant reaches full foliage.
- Term Date: Terminate date (frost, harvest, dormancy, etc.)
- Sum ET: Total crop water use to date by crop, since the start date.
- 7 Day Use: Total crop water for the last 7 days.
- 14 Day Use: Total crop water use for the last 14 days.
Key to Crop Codes
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|*Note: Peak chart values represent the maximum daily consumptive use for mature (uncut) stages of alfalfa growth. Mean values represent an "average" daily use that takes seasonal cuttings into consideration.These codes are applicable to both the ET Summary and Crop Water Use Charts.|
|Chart Code||Crop||Chart Code||Crop|
|ETr||Reference ET rate||ONYN||Onion|
|ALFN||Alfalfa (New Plant)||PAST||Pasture|
|ALFS||Alfalfa for seed||PEAS||Peas|
|ASPA||Asparagus||POP1||First Year Poplar Trees|
|BEAN||Dry Beans||POP2||Second Year Poplar Trees|
|BEET||Sugar Beet||POP3||Third Year Poplar Trees|
|BLGR||Blue Grass Seed||POTA||Potatoes|
For further information about AgriMet, contact: Tim Grove, GP Regional Office.
Last Updated: March 18, 2013