Monday, April 21, 2014

Winter Injury in Perennial Forages

Two weeks ago Rory Lewandowski described in this blog how to evaluate forage stands for winter injury. So our question is, “Have you walked out into your forage stands yet this spring?” If not, you may be in for a rude surprise.
The hard freeze lst week was cause enough for concern for us to check a few fields. There is some frost dieback of the top leaves, particularly in orchardgrass (see photo).

Notice the yellowish tinge to the orchardgrass in the foreground compared with darker green tall fescue in the background that suffered less frost injury.
But the more serious problem we observed when looking around was severe heaving damage in alfalfa, particularly in the Wayne county, OH area. Some fields showed heaving of 70% of the stand.
Plants with crowns heaved up 2 or more inches out of the ground are probably already dead like in the photo above.
Heaving is usually more severe in areas with less than ideal internal and surface soil drainage and on soils with high shrink/swell potential. Tiling will likely help improve the alfalfa production potential of those soils, but heaving can still occur on certain soil types even when with tiling.

Heaving is also more likely where a mid to late fall harvest was taken. Fall harvesting can weaken plants and the removal of plant residue late in the fall can dramatically increase the potential for heaving, because the residue serves to moderate soil temperature fluctuations and catch snow that also insulates against wild temperature swings during the winter.

Plants heaved 1.5 inches.
 Some plants will be heaved 1 to 1.5 inches above the soil surface or less. These plants may on casual inspection appear normal and be greening up. But closer inspection will reveal crowns above the soil surface, which will likely limit the productive life of the plant.

Heaved plants will desiccate more quickly, be injured by wheel traffic, and crowns may break or be cut off at the first harvest. Some of those plants may survive through the first harvest, but their yield potential is compromised and they will likely disappear from the stand at some point during the growing season.
Plants heaved to varying degrees, starting to greenup.

Can anything be done to help heaved stands? Dan Undersander has written a very useful fact sheet about heaving that can be found here. He suggested that if the majority of plants are heaved an inch or less, that the taproot may not be broken and the stand has a better chance of being salvageable for this year. In this fields, delay the first harvest to allow more recovery time and raise the cutter bar sufficiently to avoid scalping the crowns. He also states that the stand should not be rolled or cultipacked, as this will only damage the crowns.

We also observed severe winter injury in some perennial ryegrass varieties and even in some white clover varieties in our trials. Time will tell how much they will recover, but the winter damage was quite substantial in some varieties, including an older perennial ryegrass check variety we use in our trials.

Literature Cited
Undersander, D. 2009. Heaving in alfalfa fields. Agronomy Advice. Agronomy Dept., University of Wisconsin. Available online at