Protect alfalfa from winter injury

As the hot days of summer give way to cool fall temperatures, alfalfa growers are encouraged to consider winter injury risk when thinking about fall cutting.

“Growers really need to assess the risk versus the gain when it comes to fall cutting of alfalfa,” said Charles Scovill, Syngenta field agronomist. “While it may be tempting to take a final cutting late in the fall, you could be ultimately risking winter stand injury.”

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, or the temperature that will stop further top growth for the season, normally occurs between September 1 and October 15 in northern states. Therefore, it is important to manage fall harvests to give the plants the best chance for strong winter survival.

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 particularly important for developing plants that have good winter survival.

·         Assess need for feed. Growers should weigh the need for additional hay against the risk of winter damage. If forage is 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,” Scovill said. “There needs to be a period of continued cool temperatures for stands to develop resistance to cold temperatures and to store energy for the winter.”

Keep in mind, even with the best management practices, acts of nature can impact your alfalfa crop. Sudden changes from warm to cold will reduce hardening, excessively wet soil in the fall predisposes alfalfa to winter injury and midwinter thaws may break dormancy and make plants more vulnerable.

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