In order to establish alfalfa fields with six to eight inches growth before a killing frost occurs, University of Illinois extension educator Jim Morrison encourages you to start planning now for late-summer seeding of perennial legumes.
"Producers in the northern quarter of the state should seed alfalfa August 10 to 15," Morrison said. "For the central half of Illinois, the suggested dates are August 30 to September 4, and for the southern quarter, September 5 to 10. Cool-season perennial grasses can be seeded one to two weeks later, but warm-season grasses should not be seeded until spring."
Planning ahead is critical for successful alfalfa and grass seedings.
"Be sure there is no herbicide carryover from a previous application," he said. "Perennial weeds should have been controlled, soil tests taken, and any corrective limestone already applied."
Fertilizer can be applied during seedbed preparation. However, if there is not adequate soil moisture to establish the stand, seed should not be planted as it is very risky to plant seeds into dry soil, Morrison said. To achieve a good seeding, a firm seedbed is necessary to ensure good seed-to-soil contact.
"Follow the 'footprint guide' — soil should be firm enough for a footprint to sink no deeper than one-half inch," he said. "Don't plant seeds deeper than five times their diameter. For most forage crops, the seeding depth should not exceed one-half inch on medium- and heavy-textured soils, and one-inch on sandy soils."
Tilling the seedbed may not be necessary as no-till forage seedings can be successful. However, don't seed alfalfa following an older established stand. Autotoxic compounds released by the older alfalfa inhibit the growth, development, and production of new alfalfa seedlings.
If the alfalfa is more than one year of age, it is best to rotate to another crop before going back to alfalfa. If less than a year, alfalfa can be replanted, Morrison said.
He encourages producers to look for the blue seed tag indicating certified seed of adapted, tested varieties. He also recommends using fresh inoculum of the proper Rhizobium bacteria on the legume seed.
"Late-summer seeding rates are the same as spring seeding, but a companion crop is not recommended," he said. "Since weeds are slow to germinate in the late summer, a pre-plant herbicide is typically not required. However, a post-emergence herbicide can be used if weed problems develop and become competitive."
Finally, harvesting of late-summer seeded alfalfa and cool-season grass fields should not occur in the fall of the establishment year.
Source: University of Illinois