Base irrigation on crop stage and actual crop water use, not the calendar.
As producers and agribusiness industry professionals, we know that no two years are the same in Nebraska. This has probably never been more evident than this year. We had an early, warmer-than-normal spring that looked much like summer and accelerated early crop growth and loss of soil moisture.
Crop evapotranspiration has been almost twice what it usually is for this date, as seen in the ET data from York (Table 1
). These higher cropwater ET rates depleted soil moisture much earlier in the season than normal. For example, in 2011 the crop ET for May 13-20 was 0.07 inch while in 2012 it was 0.29 inches. For June 3-10, 2011, Crop ET was 0.42 inches and for June 4-11, 2012 it was 1.30 inches. With an early start to the irrigation season, especially in areas with below normal soil moisture profiles, effective irrigation management is essential to keep input costs in check.
How to Check ET
Several changes have been made to the NAWMN reporting site to make it even easier to use. Locations that have not been updated in the past week are grey and those that have been updated are red. This should make it easier to quickly identify sites in your area with current reference ET data. In addition, automatic weather station sites are shown in blue and a few sites measuring pasture or grass ET are shown in green.
The changes in crop water use from last season to this season reinforce the point that each year is different and needs to be monitored accordingly. We cannot assume that crop water use will be the same each year or occur at the same point on the calendar. Producers should use tools to estimate both crop ET and soil water status to irrigate according to the needs of their field.
For more information on crop water use in Nebraska and how to incorporate it into your irrigation management program, see articles at cropwatch.unl.edu