By Ben Beckman
As temperatures cool this fall, don’t be too quick to shut irrigation off on alfalfa, especially if the soil profile is dry.
Alfalfa water use drops considerably as temperatures cool. During peak summer growth, plants may use around a third of an inch of water per day, while fall demand may drop closer to 0.10-inch. While that may seem like a reason to stop irrigating, it’s worth a closer look.
Fall irrigation in alfalfa has two benefits, but both depend on having room in the soil profile for additional water. Because alfalfa is a perennial and can continue growing into the fall until a hard freeze, adequate soil moisture can help plants maintain healthy roots and prepare for winter. Fall irrigation can also rebuild soil moisture depleted during the growing season. Alfalfa has a deep root system, and water stored deeper in the profile can provide a valuable reserve when growth and water demand increase again next summer.
Irrigate based on soil moisture, not the calendar. If the profile is already full, adding more water provides little benefit. If soils are dry, fall can be an efficient time to rebuild those reserves before freeze-up.
Also keep soil texture in mind. Coarser soils may take water quickly but hold less, while finer-textured soils generally hold more water but may take it in more slowly. And don’t forget to keep local irrigation restrictions in mind.
For more information, see Nebraska Extension NebGuide G1778, “Irrigation Management and Crop Characteristics of Alfalfa.”
Source : unl.edu