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, top-dressing 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 3,000 to 5,000 gallons per acre of liquid manure or 10 to 12 tons per 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. FG
—Excerpts from University of Wisconsin Extension Agricultural Newsletter, Vol. 13, No. 3
Kevin Shelley, Nutrient and Pest Management Program, University of Wisconsin