The earliest sign of winter injury to forage crops is at first green-up in the spring. While this occurs most years in late March through mid-April, recovery this year is approximately 1015 days later than normal.

The first reports of winterkill this year are from south central Iowa, with heaving damage in late summer/autumn 1995 plantings. Alfalfa stand recovery across most of central, north central, and northeast Iowa generally has been good due to a more consistent winter snow cover. I have received many reports of winterkilled and winter-injured alfalfa, orchardgrass, and some 1995 autumn mixed forage and grass plantings from the western third of the state. Western Iowa had little or no snow cover, resulting in cold exposure injury and winterkill. There also have been scattered areas of extended ice cover in parts of western Iowa, which can be directly linked to winterkill in some areas of northwest Iowa and are suspect in others.

To evaluate fields for winterkill, count plants per square foot at several locations in each two-acre portion of the field. Dig representative plants at these sites to assess the health and vigor of the crown and taproot. Slowly recovering areas may have buds just breaking dormancy and are still vigorous, potentially productive stands. Others that have had sufficient late-winter cold injury may show declining vigor, or the taproot and crown may be starting to die.

Inspect split taproots for indications of root health. A healthy taproot is creamy-white and has a firm texture. Cold-injured plants have tan or yellow taproots and a soft, watery texture, and may degrade into a stringy yellow or brown color. Pay close attention to the top 1 to 11/2 inches of the taproot below the crown. A second check 7 to 10 days later in the field will show you whether development is advancing or declining.

Old stands (three or more years) often have an increasing degree of crown rota dark brown disease that develops in the taproot and crown and causes normal thinning of stands over time. The number of plants per square foot and the general health of their taproots are two major factors in assessing stand adequacy.

More information about how to evaluate forage stands is available in two Iowa State University Extension publications: Evaluating Hay and Pasture Stands for Winter Injury, Pm-1362; and the Alfalfa Management Guide, NCR-547.