After a longer than average winter in the Midwest, assessing spring stands will be particularly important to a successful alfalfa crop this year. Here are a few important steps to take that will help you gauge levels of winterkill and winter injury, assess damage accurately and take the proper steps forward.
Roots Tell All
As you walk your field, excavate several alfalfa plants with a spade or shovel aiming to retrieve at least six inches of root tissue. When examining the roots, look for the following:
• Normal roots should be creamy white to tannish brown with very few scars or lesions.
• Moderate to slight damage is harder to assess but is usually manifested by slight discoloration (yellowing), a corky feel and very slow or no re-growth occurring after the soil has warmed up.
• Severely damaged roots will be discolored and possibly have a water soaked or mushy feel to the crown region.
If certain parts of the field look healthier than others, be sure to take root samplings from each area. This will allow you to get a better understanding of your field’s health overall.
Take Counts at the Right Time
Wait until your crop is growing vigorously to take your stand counts; the recommended time is typically when alfalfa is two- to four-inches tall. To get an accurate assessment, throw an alfalfa square and count the number of plants and stems that fall within the border of the square.
If your field is relatively consistent, take one count per acre otherwise take two per acre. Remember to only count plants that are healthy and will survive. Any winterkilled plants should not be counted as to avoid an inaccurate reading and plan for your crop moving forward. A good rule of thumb is that plants with only one to three stems growing out of one side should not be counted.
Newer recommendations for measuring yield potential for an existing stand use the stems per square foot as a more accurate measure of yield potential for an existing stand.
• > 55 stems—Yield not limited
• 40 – 55 stems—Expect some yield reduction
• < 40 stems—Significant yield reduction; replace as soon as possible
Winter Injury Management
If you do need to keep winter-injured crops for the coming season, you’ll want to be sure to pay special attention to them.
• It is recommended to delay first cutting until first flower, giving the crop more time to recover.
• Top dress these stands with potash and/or phosphorus according to soil test.
• Do not treat winter-injured crops with spring herbicides that are known to stress or stunt plant growth.
Not all crop injury can be avoided, but taking these steps to assess damage and establish a plan to move forward will help you get the most out of your crop heading into summer.
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