Reading Crop Water Use Tables Tutorial

Listed at the Crop Water Use link is the crop water use information for several weather stations in northeast and north central Nebraska. Each table has lines of information about a specific crop (corn, soybeans, alfalfa, potato, and lawns) and specific emergence date (month day). We are trying to update these tables daily Monday through Friday, however, on occasion the server in Lincoln or at Norfolk may fail making it impossible for us to update the information.

The estimated crop water use is calculated based on local weather information collected at the weather station location and is for a well watered crop. If you tend to under-irrigate, these values will be higher than you might experience when monitoring your soil water levels.

Emergence date and relative maturity selections were made based on local input about when each crop was planted in the area around the weather station location. We have tried to bracket the planting season for corn and soybeans in an effort to provide information to a broad group of producers. The other crops have a single emergence date.

    1. Page down until you find the weather station closest to your field.
    2. The date when the data was updated is provided on the top left side of each table. The date when the data were collected is presented a few lines down and is centered on the page.
    3. Find the line of information that is closest to your field situation

      4. (Example: soybeans emerged on 5 20 ) in columns 2 and 3.

    4. Read the accumulated growing degree days based on that emergence date in column 4.
    5. Read the calculated crop water use for the previous week, the past 3 days, and yesterday in columns 5, 6, and 7.
    6. Read the estimated crop water use for the next three days and next week in columns 8 and 9.
    7. Read the estimated stage of crop development based on the growing degrees accumulated and the relative maturity of the crop. The crop water estimate is the same for all relative maturities until the grain fill period. Late in the season, varieties with higher relative maturites will maintain a high crop water use rate for several days longer than low relative maturity varieties.
    8. The last column provides the estimated growing degree days required for the crop to reach physiological maturity. Perennial crops like alfalfa and lawns give unrealistically high estimated growing degree days to maturity values.

If you have any questions or comments about these data tables, feel free to call Bill Kranz at 402-370-4012.