Liquid manure can burn leaves due to salt injury, and dry manure can smother plants if it is applied too heavily or in large chunks.
Manure can spread weed seeds, and the nitrogen in manure can stimulate grasses or weeds already in the alfalfa to become more competitive. Also, manure application equipment can damage alfalfa crowns and compact soil.
Obviously, to avoid any of these problems, spread the manure on other land if it is available. But if you have no other choice but to spread manure on alfalfa, follow these suggestions:
- Apply to older stands. Any damage will have less long-term consequences than damage to young stands.
- Apply less than 3,000 gallons of liquid manure or 10 tons of solid manure per acre to minimize salt burn or smothering. If manure is dry, adjust the spreader to break up large chunks that can smother growth. If manure has a high salt content, such as manure from swine-finishing houses, apply a reduced rate per acre.
- Spread manure immediately after removing a cutting to minimize direct contact with foliage.
- Only spread manure when fields are dry and firm to limit soil compaction and avoid wheel traffic damaging plant crowns.
- Spread manure uniformly, dry and liquid.
- If you wish to stimulate grass yield, apply manure to fields with lots of grass. Likewise, select fields with little grass if you want to minimize grassy competition.
Manure is a great source of nutrients and can enhance biological activity and soil physical properties. But be careful when applying it to alfalfa so you don't do more harm than good. FG
Bruce Anderson, Ph.D., is an agronomy and forage specialist for the University of Nebraska – Lincoln.