Irrigating alfalfa a little less frequently with a little more water each time can result in cleaner, healthier, more productive stands, says Bruce Anderson, University of Nebraska Extension forage agronomist.
To keep up with alfalfa’s high summertime water needs, a typical grower often starts irrigating as soon as a cutting is removed and continues until the next one is ready, he says. But constant watering can stimulate weeds, promote root diseases and reduce soil oxygen content, weakening alfalfa plants.
Alfalfa growers should manage irrigation to encourage deep rooting, Anderson urges.
“Stop irrigating a couple days before harvest so the soil surface will dry out and become firm. Then don’t irrigate after harvest until regrowth is 3-4” tall. Shallow-rooted weeds like foxtail and bluegrass then won’t be able to grow until alfalfa already has a head start. And your alfalfa will regrow more rapidly because the roots will find more of the oxygen they need in soil that has not been saturated with water. Of course, this assumes you have been deep watering when you do irrigate so there is water available that alfalfa roots can get to that the weeds can't reach.”