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Extension > Local Extension Offices > Meeker > County Agriculture Educator > Articles > Time for spring assessment of alfalfa fields

Time for spring assessment of alfalfa fields

Source: Karen Johnson, University of Minnesota Extension

With the variability in weather we have experienced this winter, farmers and agronomy advisors have been questioning how the alfalfa will survive the winter. Reports have come into the office with mixed results as to the health of our alfalfa fields. Now is the time to walk your fields and dig some plants to evaluate your alfalfa stands.

There are a number of factors that contribute to the survival of an alfalfa field. Mother Nature has the final say whether a field will survive the winter or not. This past winter, we experienced a variety of weather conditions including little to no snow cover, temperatures below 15F over a period of time, ice sheeting, and late season temperature fluctuations. Other factors that contribute to potential winter injury include:

  • Stand age (older stands are more likely to winterkill than younger stands)
  • Variety genetics (winter hardiness and disease tolerant varieties are less likely to winterkill)
  • Field fertility (pH is above 6.6 is less likely to winterkill, high fertility less likely to winterkill than low fertility fields)
  • Fall harvest schedule (an aggressive harvest schedule prevents the plant from storing carbohydrates in its root structure which it will need to maintain health as it regrows. Stands in which last cutting is taken between September 1 and the middle of October are at greatest risk, as plants did not have enough time to accumulate adequate carbohydrate levels in the root system before winter.)

How does your field look? Are there thin spots in the field? Do a stem count. University of Wisconsin Extension research has shown that stem count is a much more accurate method of estimating the yield potential of an alfalfa field than plant count. To estimate stem count, select 3 or 4 representative areas of the field for evaluation. Count all the living stems (over 2 inches tall) within a 2-square-foot section in the field. Remember to divide the count by 2 to get the stems/square foot. Alfalfa stands with greater than 55 stems/sq. ft. are in excellent condition. Stands with 40-55 stems/sq. ft. are in good condition with slight yield reduction expected. Stands with less than 39 stems/sq. ft. are in poor condition and termination of stand is recommended.

How healthy is your field? Now until green up occurs is an excellent time to evaluate crown health. Please note that if the field is experiencing winter injury it may be slow to green up. Dig up plants from 3 or 4 representative areas in the field. Make sure to dig down 4 in. to 6 in. to include the root of the plant. Evaluate crown size, symmetry, and number of living stems present. Split the root in half to view the color and texture of the root interior. Pictures to help evaluate this are available on the University of Minnesota Forage Production website or by viewing the “Alfalfa stand assessment: Is this stand good enough to keep?” prepared by University of Wisconsin Extension. Healthy plants will have a large crown, symmetrical shape with many shoots. The color of the root will be off-white with few signs of discoloration. Poor quality plants will look brown and dehydrated with few shoots if any present.  If the field has poor stand quality, but is needed for feed this year, consider interseeding annual forage such as oats or ryegrass to help increase yield for this year. Contact your nutritionist to discuss how this may work in your dairy ration.

Now is the time to evaluate your alfalfa fields for stand count and overall plant health. The earlier you can make an accurate decision about your field, the more options you will have to plant a new alfalfa seeding, interseed into an existing stand or purchase additional hay if needed.  Have a question or comment? Feel free to contact the McLeod County Extension office at 320-484-4334 or email at ande9495@umn.edu.

Contacts

Karen Johnson
Extension Educator, Ag Production Systems
(320) 484-4303
ande9495@umn.edu
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