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.