Some caution is needed to prevent damage to established alfalfa fields from summer manure applications.
Summer manure spreading on hay fields – some factors to consider
By Kevin Shelley, Nutrient and Pest Management Program
Some caution is needed to prevent damage to established alfalfa fields from summer manure applications. The potential to damage alfalfa crowns, injure plant tissue due to salt toxicity, overapply nutrients, or even transmit disease should be considered. On the positive side, topdressing manure can build soil fertility with on-farm resources and help expand acres for spreading. There is also some research and farmer experience showing manure applications can increase yields if detrimental side effects are avoided.
Consider these agronomic guidelines for applications to established hay:
· Make applications as soon as possible after harvest to avoid salt burn injury and wheel track damage to regrowing alfalfa.
· Limit rates to 3000 to 5000 gallons/acre of liquid manure or 10 to 12 tons/acre of solid dairy manure.
· Use equipment that applies uniformly and without clumps.
· Apply to fit soils. Avoid compacting wet soils.
· Apply to older, poorer stands. Grasses benefit from manure nitrogen and are less prone to damage.
· Apply where nutrients are most needed.
Also consider the potential for forage contamination with the Johne’s organism. Although most herds are not infected, prevention is very important because Johne’s disease is not treatable. The bacterium is not absorbed by plants, but resides on manure and soil particles for a limited time. To reduce the risk of forage contamination:
· Allow more time between manure applications and forage harvest.
· When harvesting, minimize forage contact with soil and manure particles.
· Use the forage as silage because fermentation kills the organism.
· Avoid feeding the forage to calves, the most susceptible age group for infection.
· Spread manure from herds with low infection levels.
· Apply lower manure rates.
Check these UW sources for more information:
Applying Manure to Alfalfa, Pros, cons, and recommendations for three application strategies. Keith Kelling and Michael Schmitt, North Central Regional Report 346 on the Soils Extension website (
http://www.soils.wisc.edu/extension)
Johne’s Information Center of the UW School of Veterinary Medicine on the web at
http://johnes.org