If the muddy, wet April and May kept you from seeding alfalfa this spring, now is the time to put the finishing touches on your preparation for late-summer seeding, says Phil Kaatz, Michigan State University Extension forage educator.

Summer is a good time to consider planting alfalfa since insect and weed pressure is less than in spring, says Kaatz. He lists these key principles for successful late-summer stand establishment:

  • Get a current soil test. Knowing current fertility levels allows you to add fertilizers based on recommendations. Without proper fertility, nutrient uptake may suffer, causing alfalfa to be weak and unable to compete against weeds. Soil pH should be 6.8-7.0 for new alfalfa seedings. Research shows a significant reduction in first-cutting yield when pH falls below 6.7, says Kaatz.

“Make lime applications to raise soil pH at least six months prior to planting,” he advises. “If you have not applied lime six months prior to planting, you should apply it 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.”

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 maximum annual K recommendation for any crop or soil-test level is 300 lbs of potassium oxide per 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, says Kaatz. 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. 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 alfalfa variety is one that is well-suited to the environmental conditions where it will be grown. Even the best varieties can fail if they are not well-managed. Alfalfa prefers to be on adequately drained soils.

Consider the crop’s stand life. Most dairy producers prefer a three- to five-year alfalfa stand life vs. a longer stand of over five years, where winterhardiness becomes of primary importance. Also consider disease resistance such as bacterial wilt, Phytophthora root rot and insect resistance to potato leafhoppers. Kaatz recommends a seeding rate of 14-16 lbs/acre and says the seed should be placed 0.25-0.5” deep.

  • Plant on time. Successful late-summer seedings depend 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. Kaatz says summer seedings should be planted between June 15 and Aug. 1 in the northern regions and Upper Peninsula of Michigan and before Aug. 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,” says Kaatz.