Assessing Forage Stands for Winter Survival
Winter can be one of the most challenging periods for forage stands, especially alfalfa. Conditions such as fluctuating temperatures, excess moisture, and ice can weaken or kill plants long before spring growth begins. That’s why early-stand assessment is critical. The sooner you evaluate winter survival, the more options you have to protect yield potential and make informed management decisions for the season ahead.
When Should You Start Scouting for Winterkill?
Spring is the right time to begin evaluating forage stands. As soon as the frost is out of the ground and alfalfa begins to come out of dormancy, growers should start checking fields for signs of winter injury or winterkill. Early scouting allows you to identify problem areas before they significantly impact first cut yield and overall stand productivity.
What Causes Alfalfa Winterkill?
Alfalfa winterkill rarely results from a single factor. More often, it’s a combination of environmental stresses that weaken plants over time. Common contributors include:
- Frequent freeze–thaw cycles, which can damage crowns and roots.
- Flooding and ice sheeting, which may deprive plants of oxygen.
- Heaving, where plants are physically pushed out of the soil, exposing crowns and roots to cold, dry air.
Fields with poor drainage or minimal snow cover are often at higher risk for winter injury.
Key Ways to Assess Forage Stands for Winter Survival
A thorough stand assessment involves more than just a visual check. Two simple but effective methods – plant health evaluation and stem counts – can provide a clear picture of stand viability.
1. Check Whether Plants Are Alive
Begin assessing plant health as soon as soils are workable. This root evaluation helps distinguish between plants that are slow to green up and those that will not recover.
- Dig several plants from different areas of the field, going 4–6 inches deep.
- Examine the taproot:
- A turgid, firm taproot indicates a live, healthy plant.
- A taproot that is brown, dehydrated, or ropelike suggests the plant is dead or dying.
2. Conduct Stem Counts
Once there is enough top growth (typically 4–6 inches), stem counts provide one of the most reliable indicators of yield potential. They’re often more accurate than plant counts because alfalfa compensates by producing more stems as plant density declines—up to a point.
- Count all stems within a square foot area.
- Take multiple counts across the field and calculate an average.
- As a general guideline:
- 55 or more stems per square foot indicate full yield potential.
- 40–50 stems per square foot may result in moderate yield reduction.
- Fewer than 40 stems per square foot typically leads to at least a 25% yield reduction, and the stand should be considered for rotation or replacement.
Can You Interseed Alfalfa into an Existing Stand?
Interseeding decisions depend heavily on the age of the stand.
- Stands more than one year old should not be interseeded with alfalfa. Auto-toxic compounds released by established alfalfa plants can prevent new seedlings from surviving.
- However, grasses can be interseeded to help increase forage tonnage and improve stand uniformity.
- Stands less than one year old can be reseeded with alfalfa, but only if the field is disked and reseeded immediately. This is the only effective way to avoid autotoxicity in young stands.
Planning Next Steps: Reseeding or Rotating
If a stand is too thin to justify keeping, early identification gives you flexibility.
- Direct seeding a new forage stand is often the preferred option.
- Fields following soybeans typically work well for reseeding because minimal residue allows for good seed-to-soil contact.
- If rotating out of alfalfa, fields more than a year old often provide enough nitrogen credit to support a grain or silage corn crop with only modest starter fertilizer.
READY TO GET STARTED?
Contact your local DLF dealer to select the best forage or turfgrass species for your operation and region.