Manage your fall alfalfa for winter injury
With Texas’ record number of 100-degree-plus days and historic drought this year, it has been so hot for so long it’s hard to even imagine cooler temperatures finally will return. But they will — eventually.
And as the super-hot days of summer finally give way to cooler temperatures this fall, alfalfa growers in Texas, Oklahoma and New Mexico are encouraged to consider winter injury risk when considering late fall cutting. That can be risky when bumping up against winter.
“Growers really need to assess the risk vs. the gain when it comes to fall cutting of alfalfa,” says Charles Scovill, Syngenta field agronomist. “While it may be tempting to take a final cutting late in fall, you could be ultimately risking winter stand injury.”
• Alfalfa fall management should include concerns over winter injury.
• Growers should avoid alfalfa cuttings too late in the fall.
• Winter-tolerant varieties help minimize damage risk.
To increase their potential for winter survival, alfalfa plants should get five to six weeks of growth to accumulate root carbohydrates and proteins before going dormant for the winter.
A killing freeze can vary greatly in the Southwest; it’s generally not until mid-November on the Rolling Plains, but earlier on the High Plains, compared with September to Oct. 15 in Northern states. Nevertheless, freezes don’t always wait until mid-November in Southern states — the first freeze can swing earlier or later.
It is important to look at your probable window for a first freeze and manage your fall harvest of alfalfa to give the plants the best chance for a strong winter survival.
Fall management guidelines
When considering fall cutting, Scovill suggests the following management tips:
• Select winter-tolerant varieties. Work with your agronomist to determine what varieties have strong winter survival and persistence ratings, and are best for your region and field.
• Know your field and your soil. Soil fertility management is vitally important for maintaining productive alfalfa stands. Potassium (potash) is especially important for developing plants that have good winter survival.
• Assess need for feed. Growers should weigh the need for additional hay against the risk for winter damage. If forage is absolutely needed, prolong cutting until after hard frost so stored energy is not lost with alfalfa regrowth.
“Growers should always try to allow at least five to six weeks of uninterrupted growth in September and October,” says Scovill. “There needs to be a period of continued cool temperatures for stands to develop resistance to cold temperatures to store energy for winter.”
He adds you should keep in mind that even with the best management practices, that acts of nature can impact your alfalfa crop.
Sudden changes from warm to cold will reduce hardening; excessively wet soil predisposes alfalfa to winter injury; and midwinter thaws break dormancy and make plants more vulnerable.
Syngenta offers a range of winterhardy alfalfas including industry-leading 6422Q, which has a winterhardy score of 0.9, something rare for a fall-dormancy 4.5.
Alfalfa growers can contact their Garst, Golden Harvest or NK representative to determine the best products for their specific alfalfa needs.
This article published in the October, 2011 edition of THE FARMER-STOCKMAN.