Our wet weather conditions throughout much of 2017 prevented spring establishment of perennial forages for many producers. Additionally, the wet weather has caused stand loss in alfalfa fields due to compaction and crown damage from harvest on wet soils, and from root rot in poorly drained field areas. As a result, replacement of some of those acres is necessary. August provides growers with another window of opportunity to establish a perennial forage stand.
According to the newly revised, 15th edition of the Ohio Agronomy guide, planting of alfalfa and other legumes should be completed by mid-August in Northern Ohio and by the end of August in Southern Ohio. These timelines take into consideration average frost dates and the time needed for forage plants to develop a root system capable of overwintering. For example, at about 8 to 10 weeks after emergence alfalfa plants pull the growing point below the soil surface, a process termed ‘contractile growth’. The alfalfa plant needs to reach this growth stage to overwinter. Clover plants also need to have a crown formed, and grasses should be at least in the tillering stage of development before the onset of winter.
If the fall is warm and extended, similar to what we have experienced the past few years, it might be possible for successful establishment with later planting dates. It is a question of risk management. How lucky do you feel? The best policy is usually to plant most perennial forages as soon in August as possible, when soils conditions allow and when soil moisture is present.
Sclerotinia crown and stem rot is a concern with no-till seedings of alfalfa in late summer and especially where clover has been present in the past. This pathogen causes white mold on alfalfa seedlings. They become infected during cooler rainy spells in late October and November, the disease develops during the winter, and seedlings literally "melt away" in winter and early spring. It can be devastating where the pathogen is present. No-till is especially risky where clover has been present because the sclerotia germinate from a shallow depth. Early August plantings dramatically improve the alfalfa's ability to resist the infection. Late August seedings are very susceptible, with mid-August plantings being intermediate.
In a no-till situation, minimize competition from existing weeds by applying a burndown application of glyphosate before planting. Using no-till when herbicide-resistant weeds are present creates a very difficult situation with no effective control options, so tillage is probably a better choice in those situations. Post-emergence herbicide options exist for alfalfa. After the alfalfa is up and growing, control late summer and fall emerging winter annual broadleaf weeds.
For conventional tillage seeding prepare a firm seedbed to ensure good seed-to-soil contact. Be aware that too much tillage depletes soil moisture and increases the risk of soil crusting. Follow the "footprint guide" that soil should be firm enough for a footprint to sink no deeper than one-half inch. Tilled seedbeds do not need a pre-plant herbicide. The recommended seeding depth for forages is one-quarter to one-half inch deep. It is better to err on the side of planting shallow rather than too deep.
For more information about late-summer perennial forage seeding, contact the Wayne County Extension office at 330-264-8722.