Late-summer seedings of alfalfa

Now is the ideal time to put your plans in place for a new alfalfa seeding that may have been postponed this spring.

If the muddy, wet April and May kept you from seeding alfalfa this spring, now is the time to begin putting the finishing touches on your plans that may not have gotten underway earlier in the year. Summer is a good time to consider planting alfalfa since insect and weed pressure is less than in the spring of the year.

Following some key principles will help producers have a successful late-summer seeding.

  • Have a current soil test before planting
  • Control perennial weeds
  • Select a good variety for your site
  • Plant on time

Get a current soil test

Having a current soil test for a new seeding is important, whether it’s for a spring or late-summer seeding. MSU recommends taking a soil test prior to seeding your alfalfa field. Knowing current fertility levels allows producers the opportunity to add fertilizers based on MSU recommendations. Without proper fertility, nutrient uptake may suffer, causing alfalfa to be weak and unable to compete against weeds. MSU recommendations are for soil pH to be 6.8 to 7.0 for new alfalfa seedings. Make lime applications to raise soil pH at least six months prior to planting. If you have not applied lime six months prior to planting, you should apply lime before planting and work it into the top layer rather than waiting to apply after planting. Maximum lime application is around 4 tons per acre, anything greater will require split applications spaced a couple of months apart.

Research shows a significant reduction in first cutting alfalfa yield when pH falls below 6.7. Phosphorus (P) and potassium (K) recommendations take into consideration the soil test level and the crop yield. When inadequate amounts are present in the soil, the new crop will respond to P and K additions. However, there is no yield benefit to applying P and K when the available soil level is greater than adequate. The adequate soil level for P is 25 ppm for mineral soils and 30 ppm for organic soils. The recommendations for K take into account the cation exchange capacity of the soil. The maximum annual K recommendation for any crop or soil test level is 300 pounds of K2O/acre.

Control perennial weeds

Successful new alfalfa seedings will need to have weeds controlled prior to planting. In some cases, you may have to work a field a full season ahead. Brush and weeds, such as quackgrass, should be dealt with using a treatment of herbicide or tillage before sowing. If necessary, a herbicide, such as glyphosate, can be used according to the label to control these weeds. Field preparations should be done as early as possible so that the field is free of weeds and has a firm seedbed for good soil-to-seed contact.

Select a good variety for your site

A good variety of alfalfa is one that is well suited to the environmental conditions where it will be grown. Even the best varieties of alfalfa can fail if they are not well-managed. Alfalfa is a crop that prefers to be on adequately drained soils. Producers should consider stand life of the crop. Most dairy producers prefer a three- to five-year stand life of alfalfa versus a longer stand of over five years, where winter-hardiness becomes of primary importance. Producers should also consider disease resistance such as bacterial wilt, Phytophthora root rot and insect resistance to potato leaf hoppers. Seeding rates for alfalfa should be 14 to 16 pounds per acre and planted 0.25 to 0.5 inches deep.

If you plan to reseed into a thin-established alfalfa stand, resist the temptation. Alfalfa toxicity will prevent the new seedlings from establishing. Those fields rotating to another crop is the best recommendation.

For a complete listing of the MSU alfalfa variety trials, read MSU’s Forage Varieties for Michigan in 2011.

Plant on time

Successful late-summer seedings depends on soil moisture during the establishment period and having enough plant growth prior to a killing frost. Six to eight weeks of growth are needed before a killing frost. I have personally seen lush, thick, new alfalfa seedings look terrific in the fall following an early September seeding date. But because the alfalfa had less than 6 inches of growth before a killing frost, the stand was a disaster in the spring due to winterkill. Summer seedings should be planted between June 15 and August 1 in the northern regions and Upper Peninsula of Michigan and before August 15 for the southern regions. If very dry weather persists late in the summer, consider waiting until next spring.

In summary, having a plan, paying attention to detail prior to going out to the field, and following basic steps for planting will pay big dividends for your new stands of alfalfa.

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