Alfalfa

Alfalfa Planting Tips

If you are planning to seed alfalfa this spring, you most likely have most of your plans made. You have chosen the field, conducted the necessary soil tests, selected an alfalfa variety, and finalized those last-minute planting arrangements. Most of you are now at the stage where you are waiting for the weather to cooperate so that you can seed or drill alfalfa. As you wait for the weather to cooperate, check over your seeding plans and see how they compare with some basic guidelines, as recommended by Warren Thompson, a national forage specialist.

  • Choose fields with well-drained soil. Thompson suggests that soils drain well internally and do not puddle or “pond”. He discourages the use of soils with a hardpan near (or shallower than) three feet.
  • Conduct soil tests. Soil pH should be six and a half or above. If lower, Thompson says apply lime, but save the field for another planting. “It takes a minimum of six to eight months to correct or partially correct a pH problem on “open” soils, and around twelve to eighteen months to correct on ‘heavier’ soils,” he says. “This is especially true if you need to elevate the level one full point or more.” (Add phosphorus and potassium as described by soil test results.)
  • Select an alfalfa variety. Take time to research the numerous varieties available from Hoegemeyer's product line. Pay attention to dormancy and disease resistance ratings. Consider whether you are going to hay it or graze it. Ask questions and look at research data. Thompson says this is a very critical step in the overall planting process. “If you get a good stand, the price of seed represents only about five to seven percent of the total stand establishment cost,” he says. “But, if the stand is poor, or the variety you choose is unproductive, those percentages increase in direct proportion to decreased yields.”
  • Finalize planting arrangements. Decide whether conventional tillage or no-till is best for your growing situation. “More farmers each year are seeding no-till alfalfa,” says Thompson. “But, it’s very important that growers follow proven no-till seeding recommendations. Don’t take any shortcuts.”
  • Head for the field. Thompson says you can begin seeding as soon as the frost is out of the ground and you can get into the field. He cautions that precise placement of alfalfa seed is the last crucial step. “More stands of alfalfa are lost during seeding than at any other time in the history of the field,” he says. “Don’t bury the seed! The ideal seed depth in most soils is one-quarter to one-half inch. Deeper than this and you can kiss the stand goodbye.” Thompson adds that some sandy soils may require deeper placement. In addition to Warren Thompson’s statements, make sure that your newly established seed has good seed-to-soil contact.

Many alfalfa seedings could be greatly enhanced if the seeding is in a firm seedbed with good seed-to-soil contact (the fewer air pockets, the better). If the seedbed is not firm, maybe you should be prepared to pack the soil after you drilled or seeded the new alfalfa field. It could make a difference between seeding success or failure.

What about enhancing thinning alfalfa stands? It’s a sad thing, but alfalfa stands don’t last forever. Ironically, due to autotoxicity, you can’t even add new alfalfa to old alfalfa, and you can’t follow alfalfa with alfalfa. That’s why it’s important to evaluate your current alfalfa stands to determine the best time to over-drill with other crops, or to decide if it's time to let the field rest with a crop rotation. Warren Thompson, in conjunction with Dr. Jim Moutray, offers the following guidelines:

If your alfalfa stand drops below sixty percent, you should consider over-drilling with orchard grass either in the fall or early spring. Use a no-till drill to seed at about four to six pounds of orchard grass per acre, and make sure the orchard grass seed is actually covered by soil. Another option is to over-seed with red clover at about six to eight pounds per acre. Whichever option you choose, Thompson says, “Don’t dilly-dally around. The sooner the seed gets in the ground, the better chances are for a satisfactory stand.” If your alfalfa stand is between thirty to forty percent, you should consider over-drilling with both orchard grass and red clover. “This will help fill the holes in the alfalfa and prevent widespread weed encroachment,” says Thompson. “You might also consider moving this field into a grain rotation system to harvest the accumulated nitrogen.” If your stand is below twenty percent, it’s time to plant an entirely different crop. Consider row crops for a couple of years, then you can start over with a new seeding of alfalfa “from scratch”.

Planting Tips:

  • A very firm seedbed is required. You should be able to dribble a basketball across the acres you plan to seed!
  • Seed-to-soil contact is absolutely necessary.
  • Fifteen to twenty pounds per acre is a good seeding rate.
  • In clay-loam soils, plant ¼” to ½” deep – no more!
  • In sand, plant ½” to ¾” deep.
  • In the seeding year, a good stand will have 15 to 25 plants per square feet.

Alfalfa Stand Analysis

Stand Analysis by Plant Count

This is the conventional way of checking the condition of a stand – Counts must be based on live, HEALTHY plants – do not count plants that have severely damaged roots or develop shoots of different lengths. (Plants per square foot)

Alfalfa Age (yrs) Good Marginal Tear up
1 12+ 8-12 <8 (overseeding may still be an option)
2 8+ 5-6 <5 (autotoxicity limits overseeding success)
3 6+ 4-5 <4
4+ 4+ 3-5 <3

More growers are looking at stem count as a more accurate way of analyzing a stand. Products like TS 4007 have the potential to produce a lot of stems without a high plant count.

Stand Analysis by Stem Count – at 4” – 6” avg. height – count stems over 2” (Stems per square foot)

Alfalfa Age (yrs) Good Marginal Tear up
2 yrs + 55+ 40-55 <40
 

 

Factors Affecting Winter Survival of Alfalfa

Following is some information released by the University of Minnesota and other sources. Six factors (combined with weather) influence alfalfa stand winter survival. These factors can be used to help educate growers assess and lower their risk of winter injury.

  1. Stand age: Because of cumulative stress of plant diseases and physical injury, older stands are more susceptible to winter injury than younger stands.
  2. Variety: Varieties with greater winter-hardiness and disease resistance are less susceptible to winter injury than varieties with less winter-hardiness and disease resistance.
  3. Soil K level: Soil potassium (potash) is very important in enhancing alfalfa tolerance to winter injury. However, plants stressed by low pH (<6.5) or other deficiencies such as P, B, and S will also be more susceptible to winter stress. Soil drainage: Poorly drained soils are more likely to lead to plant diseases and ice sheeting.
  4. Harvest management:
  5. Harvest number: Although growing seasons vary throughout the state, normally, more frequent cutting will cause more plant stress. That’s why two cuts are less risky than four cuts in southern Minnesota.
    Last harvest date: For least risk, make the final cut by 1 September. This allows time for alfalfa to regroup, accumulate carbohydrate reserves, and undergo the normal changes associated with fall dormancy. Fall cutting on 15 September, causes alfalfa to regrow but the regrowth period is inadequate to replenish carbohydrate reserves and for the plant to obtain a high level of dormancy. Cutting on 15 October about the time of the first killing frost lessens the risk of winter injury because there is normally a minimal chance for regrowth.
  6. Stubble: Stubble from unharvested plant residue insulates the soil, catches snow for insulation, and by shading the soil surface from the sunlight can minimize freezing and thawing cycles. Therefore, harvesting in the fall may greatly enhance the risk of winter injury especially during winters with minimal snow cover. This information is a general guideline. Other factors such as soil conservation, production potential and fertility levels may play a part in the decision of whether or not a stand is adequate.