By Dan Undersander
Late summer is the most common time around the world to seed forage crops. We do somewhat less seeding at this time in the Midwest due to the possibility of dry weather during August and early September with resulting poor germination and establishment. However, with adequate moisture, late summer seeding is a good option for many Midwestern growers.
This year, late summer seeding may be a good way to recover from some of the thinned and lost stands from this spring and summer.
Late summer seeding works well for alfalfa, clovers, and cool season grasses. It would not be recommended for warm season grasses, such as switchgrass, the bluestems or side-oats gramma.
Before attempting to establish any forage, consider the potential for herbicide residue – was any herbicide applied to the field this year or last year that may prevent adequate forage establishment?
If establishing alfalfa, follow the same practices as for spring seeding, except that a cover crop should not be used. Cover crops slow establishment of the alfalfa seedlings which then may not grow sufficiently to survive the winter. You can tell if alfalfa has established sufficiently to survive the winter by pulling up a plant and checking for a ridge between the top growth and root. This is the crown which, if present, means that the plant has perenniated and can survive the winter. The crown usually develops when alfalfa is 3 to 4 inches tall.
Late summer seeding can be done with no-till, reduced tillage or conventional seeding methods. The recommended seeding date is shown in the figure. Seed can be drilled or broadcast (however, seed must be covered and soil firmed around the seed). The same seeding rate (12 to 15 lbs/acre) is recommended and soil pH and fertility recommendations are the same as for spring seeding.
If a thin alfalfa stand resulted from seeding this spring, it is possible to reseed the field now. Large areas exist with no plants can be seeded as described above, but if the stand is thin, I recommend disking and starting over rather than trying to thicken the stand by interseeding. Generally, seeding into a thin stand fails to result in a good stand because the existing plants provide too much competition for the new seedings which will germinate but not become fully established. So disking to kill the few plants in a thin stand and starting over is best.
A major concern with late summer seeding is weed control. Weeds during the first 60 days after establishment can thin the stand resulting in low yields. Many late summer seedings will not require weed control if the seed was planted into a weed-free field. However, those seedings following a small grain will often have volunteer small grain that must be controlled if more than 1 or 2 small grain plants per square foot germinate and compete with the alfalfa.
Late summer is also an excellent time to seed cool season grasses (tall fescue, orchardgrass, timothy, smooth bromegrass and others). They can be seeded alone or with alfalfa or clovers. The best seeding date is shown in the graph. However, slower establishing grasses, such as smooth bromegrass and reed canarygrass, need to be seeded near the beginning of the seeding window while other grasses can be seeded at any time during the recommended window and up to two weeks later. Studies have shown that the earlier grasses are seeded in the late summer seeding window, the more they will yield the next year. So do not delay seeding grasses after the beginning of the recommended date if the field is available.
Late summer seeding can be an excellent way to establish forage stands. One advantage of late summer seeding is that forages will yield similar to an established stand next year, thereby avoiding the seeding year yield reduction of a spring seeding.