Late summer can provide a window of opportunity to seed perennial forage legumes and grasses, whether you want to establish a new forage crop, or need to fill in bare and thin spots in an existing forage stand.
To help improve the chances for a successful late-summer seeding of forages, consider the following steps provided by Brian Lang, Iowa State University Extension field agronomist at Decorah.
“Planting in the first half of August is the usual target here in northeast Iowa to start a new alfalfa or alfalfa-grass or perennial grass stand for forage for next year,” Lang says. “However, it also helps to have an encouraging forecast for rain after you get the forage stand seeded.”
Field preparation prior to seeding
Here’s what to do before your seed your field:
• Take soil samples and fertilize based on fertility needs of the field. Sampling and testing the soil is the only way to really know the fertility levels and needs in a field.
• Have problematic weeds under control.
• Check the labels of herbicides that you have used previously in the field. Many herbicides can have residual soil activity that could prevent establishment of new forage seedings if the crop rotation restriction intervals are not observed. A good resource to check herbicide labels is cdms.net/label-database.
Timing of seeding and environmental conditions
Ideally, you want six to eight weeks of growth after emergence, and before a killing frost occurs in the fall. Thus, the recommended window for late-summer forage seedings ranges from early August to early September, but it varies slightly depending on location in the state:
• northern Iowa, early to mid-August
• central Iowa, mid-August to late August
• southern Iowa, late August to early September
One of the biggest challenges with late-summer seedings is having adequate moisture available for germination and seedling establishment. This is especially a concern for western Iowa this year. If conditions are dry, a late-summer seeding isn’t recommended.
Seedbed preparation important
Loose seedbeds dry out very quickly. Deep tillage should be completed several weeks ahead of seeding, so rains can settle the soil before final seedbed preparation. A cultipacker or roller is an excellent last-pass tillage tool. The soil should be firm enough for your footprint to sink no deeper than 3/8 of an inch to a half-inch into the soil.
If moisture is a concern, interseeding and no-till forage seeding can help conserve moisture, provided weeds are controlled prior to planting.
Seeding depth is important since most forage species are small-seeded. Final seed placement should be no deeper than a half-inch for heavier soils and three-quarters of inch for lighter soils. If seeding with a drill, it is recommended to set the drill at the quarter-inch depth. You should see approximately 10% of the seed visible on the soil surface. If you are seeing a smaller amount of seed on the soil surface, that means the seed is being placed too deep, and you need to adjust your seeding depth.
Thickening up existing alfalfa stands with more alfalfa is only recommended within 12 to 15 months of the original planting date due to autotoxicity.
If seeding a legume, make sure the legume seed has fresh inoculum of the proper rhizobium.
Do not harvest late-summer perennial forage seedings this fall. It is best to let them establish and develop winterhardiness.
“Late summer can be an excellent opportunity to thicken-up existing forage stands that have become thin due to winter injury or whatever, or to start new forage seedings,” Lang says. “However, follow the suggestions we’ve listed in this article to help ensure success. For more information on late-summer forage seeding or to get specific questions answered, reach out to your local Iowa State University Extension field agronomist.”