Late summer forage crop seeding

by Anthony Anastasi
NRCS Summer Intern

When crop rotations allow for it, late summer seeding is a viable alternative for the establishment of forage crops. According to Stephen K. Barnhart, Professor of Agronomy at Iowa State University and Extension Forage Agronomist, soil temperatures are higher in late summer than in early spring, so plants will germinate and grow faster and will be less susceptible to disease. Barnhart states that as long as proper late summer seeding practices are followed this practice can result in highly productive stands and can also be used to patch up spring established stands that have thin or bare spots.

Barnhart says the first step is to make sure that the site is appropriate for late summer seeding and test soils so that corrective fertilizer can be incorporated during forage seedbed preparation. He adds that producers should make sure that perennial weeds are under control and check the labels of any herbicides applied to the previous crop to make sure that they will not impact the new seedlings. “Some (herbicides) may have residual soil activity and will harm new forage seedings if proper waiting periods are not observed.” He also warns against late summer seedings of alfalfa into a field with older established alfalfa, because established alfalfa releases autotoxic compounds that will prevent good establishment of new alfalfa.

For seedlings to grow enough to be able to survive the winter, they should be planted by August 10th. “Slow establishing species like birdsfoot trefoil or reed canarygrass should be planted in early August, while most forage grasses such as smooth bromegrass, orchardgrass, tall fescue and timothy can actually be seeded 15 days or more later than August 10th.” He says. “Planting later than the dates mentioned above is sometimes successful depending on fall and winter weather patterns, but there is increased risk of failure and reduced yield potential for the stand as planting is delayed.”

Adequate moisture must be present in order for late summer seeding to work. Barnhart cautions that loose seedbeds will lose their moisture rapidly, so it is best to prepare a firm seedbed. He recommends a cultipacker or roller as a last pass tillage tool to help firm up the soil. “The soil should be firm enough for a footprint to sink no deeper than 3/8 to 0.5 inch.”

As far as seeding equipment to use, Barnhart says that drills with press wheels tend to work best for late summer seeding. “Broadcasting seed on the surface without good soil coverage and without firm packing is usually a recipe for failure in the summer.” One final suggestion from him is to make sure to use high quality seed and to ensure that any legume seed has fresh inoculum of the correct rhizobium for that variety. “Cheap seed often results in big disappointments and shorter stand life.”