Two weeks ago Rory Lewandowski wrote an article describing 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 this past 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 http://ohioforages.blogspot.com/). But this is not the biggest problem we found.
The more serious problem we observed was severe heaving damage in alfalfa, particularly in the Wayne country area. Some fields showing heaving of 70% of the stand.
Heaving is usually more severe in areas with less than ideal internal and surface soil drainage and on soils with high shrink/swell potential. It is more likely where a mid to late fall harvest was taken. Fall harvesting can weaken plants and it reduces the plant residue that serves to moderate soil temperature fluctuations and catch snow that also insulates against wild temperature swings during the winter.
Plants with crowns heaved up 2 or more inches are probably already dead or in the process of desiccating and will soon die. Plants that are heaved 1 to 1.5 inches above the soil surface or less 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. Such 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.
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.
A careful inspection of all alfalfa and other forage stands at this point in time is very important. A “windshield inspection” is inadequate to accurately assess the health of alfalfa stands this year. Walk your fields and get a broad view to determine whether spring growth appears uniform. If growth is spotty or nonexistent, it is very likely that plants have suffered some injury or heaving.
Visually estimate the ground cover of desirable forage plants as the stand develops 4 to 6 inches of new growth. Stands with more than 80% ground cover and good vigor should produce excellent yields assuming good growing conditions, stands with 60-80% ground cover should produce fair yields, stands with 40 to 60% ground cover will probably produce yields in the 60% range of normal, and stands of 20-40% ground cover will yield less than half their normal potential. Weeds will become a real problem in the thinner stands, and over seeding with Italian ryegrass or with oats will boost first harvest yields. Destroying the stand and rotating out to another crop should also be considered where substantial damage has occurred.