2005 Year in Review

From the Fields

Is ice sheeting a risk to the successful over wintering of alfalfa and other perennial forages? The weather conditions in parts of northern Illinois have prompted producers to ask that question.

Even though dormant, the crown and root system of perennial forages continue to “breathe” (respire) during the winter months. During this respiration, forages use oxygen and release carbon dioxide and other gases. As long as there is open porosity in the soil, these gases are exchanged during the winter months.

A persistent, continuous layer of ice can block the exchange of gases. This condition is similar to the physiological injury caused by extended periods of saturated soils and water logging. In other words, ice sheeting can smother plants and can result in winterkill.

Very low temperatures following ice sheeting can result in rapid killing of plants as cold temperatures are easily transferred through ice to the plants. When alfalfa plants are covered with ice in laboratory studies, plants start dying after about a week, and most are dead in 30 to 40 days.

Ice damage is rather unpredictable. If there is a snow layer between the ice and soil, chances of alfalfa survival are increased. Ice sheets formed on frozen soils with low soil moisture, followed shortly by snow cover on the ice are less likely to do damage. The porosity or density of the ice will also affect plant survival.

Alfalfa varieties with a higher degree of winter dormancy will have a better chance of survival. The age of the stand and the relationship of the alfalfa crown to the soil level will also affect survival. The more harvests (and less number of days between harvests) taken the previous season, the more prone the stand is to winter injury.

One way to reduce damage from ice sheeting is the recommended practice of leaving 6 to 8 inches of stubble in the fall. This will also increase the chances of snow cover.

It appears that grasses are more tolerant than legumes to smothering (from ice sheeting) and can withstand injury for up to 10 to 14 weeks. Prior to spring, about the only way to estimate the damage due to smothering from ice is to dig up frozen plants and put them in a sunny, warm room. Plants will green up in a week or less, if alive.

by  Editor, theCity1.com
February 11, 2005