Daily water usage for most agricultural and horticultural crops is at its full potential in early August. Water usage varies from 0.15 to 0.3 inches per day, depending on temperature and cloud cover. “This will continue for at least the next two-to-four weeks,” says Jerry Wright, engineer with the University of Minnesota Extension Service. For irrigators, keeping track of daily crop water usage (ET) for the past two-to-five days is a big help in deciding when to start up with the next irrigation. For crops in full seed/produce development, it’s generally best to start irrigating when the soil water in the rooting zone has depleted no more than one-half to three-quarters of an inch of water. This depends on the crop’s rooting depth and the water-holding capacity of the soil, Wright says. The daily crop ET potential estimations at different locations across the state are available at www.soils.wisc.edu/ wimnext. Daily estimates for a site-specific location can be sent free via e-mail if you place a request on the contact address listed on the above Web site. Regular in-field soil moisture checking and keeping track of a crop’s daily ET use can go a long way in helping an operator optimize the crop’s growth. It also reduces the potential for leaching of crop inputs – such as nitrogen- into the groundwater. Information on how to use daily crop ET information is reviewed in the Extension Service’s irrigation scheduling bulletin, number 1322, at www.extension.umn.edu/distribution/cropsystems/DC1322.html. Other information can be obtained from Jerry Wright, at jwright@umn.edu or by calling the West Central Research and Outreach Center in Morris, at (320) 589-1711.
