Fall Alfalfa Irrigation
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.”
Fall Thistle Control
Did you spray thistles this past spring or summer? If so, it may be worth revisiting those areas. New plants or regrowth may have shown up, and late September through early November can be a good time for thistle control in pastures and hayland.
For biennial thistles like musk, plumeless, bull and Scotch thistle, look for small, flat rosettes close to the ground. Controlling these rosettes now can prevent plants from bolting, flowering and producing seed next year.
Canada thistle is a little different. This creeping perennial spreads through both seed and an extensive root system. Fall is one of our best opportunities for control because actively growing plants are moving nutrients back into their roots for winter, helping systemic herbicides reach that underground system.
Several herbicides are labeled for thistle control, including GrazonNext HL, Milestone, Chaparral, DuraCor, and Tordon 22K. Product effectiveness varies by thistle species, so match the product to the weed and site being treated. For current options, rates and restrictions, check the Nebraska Extension NebGuide EC130, “Guide for Weed, Disease and Insect Management in Nebraska,” and always follow label directions.
Remember: One fall treatment probably won’t eliminate an established problem. Scout again next spring and continue timely control to prevent seed production and reduce the infestation over time.
Late Summer Annual Grasses
Late summer is often when annual grasses like foxtail, sandbur and barnyardgrass become especially noticeable in pastures. They commonly show up where grass stands are thin, animal traffic is heavy, or overgrazing has left open space.
By this time of year, control options are limited. Annual grasses are difficult to selectively remove from established grass pastures, and many plants are already producing seed. If seed has not matured, mowing may help reduce seed production.
Long-term control starts with maintaining a healthy, competitive pasture. Proper stocking rates and adequate recovery between grazing periods help desirable grasses fill open space and reduce opportunities for annual grasses to establish.
Where annual grasses remain a problem, identify the species and plan ahead. For many summer annual grasses, herbicide control means using a labeled preemergence product next spring, timed before germination. Once plants emerge, selective control in a grass pasture becomes much more difficult.
Annual grasses may be easy to notice now, but late summer is often too late for much direct control. Focus on limiting seed production, improving pasture competition and planning for earlier control next year.
