Take the Risk Out of Manure Fertilizer

February 11, 2012 07:30 AM
Take the Risk Out of Manure Fertilizer

Manage the unknowns to provide your crops with the necessary nutrients

Manure fertilizer can be a gamble, but with the right risk management strategy, it can pay off for your farm.

John Lory and Ray Massey of the University of Missouri Extension’s Commercial Agriculture Program acknowledge that threats exist when dealing with this type of fertilizer. Commercial fertilizers normally have a higher concentration of nutrients, are uniform, offer a guaranteed analysis and are more predicable in nitrogen availability, Lory says. Manure fertilizers might not possess all these qualities.

"When something is less predictable, it is less valuable," Lory says.

Despite the variations, if manure is priced right and readily available, it can serve as a reliable source of fertilizer or a supplement to your fertilizer program. A key to mastering the unknowns of manure fertilizer is to analyze what you are applying and use the proper application strategy.
"Manure may not have the same nutrient quality throughout," Massey says.

"If you’re buying manure, make sure the seller provides you with an analysis so you have some idea of what you’re getting," Lory adds.

A deep-pit slurry system with dragline injection is one of the least risky sources of manure for fertilizer. This system usually offers a stable and uniform source of fertilizer. The dragline system also reduces application time.

A medium-risk manure source is surface-applied chicken litter. "Applying chicken litter won’t take as long due to its high nutrient content," Lory says. This type of manure has good uniformity, and producers can determine an accurate nutrient estimate by testing the stockpile.

Another average-risk source of fertilizer is unagitated lagoon effluent applied with a dragline injection. To get an accurate nutrient estimate, test the fertilizer source the week before application. If the dragline intake is close to the surface, unagitated lagoon effluent can be quite uniform.

Surface-applied agitated lagoon effluent is one of the most risky manure fertilizer sources. "There’s a tremendous amount of fertilizer potential, but it is very risky," Massey says. Fully agitating most lagoons is difficult, so nutrients greatly vary.

Use these risk management practices for manure fertilizer:

  • Meet your potassium (K) and phosphorus (P) needs first. "You can use manure for your P and K, then make up any nitrogen [N] differences with commercial fertilizer," Lory says.
  • Plan for the perfect application time. Manure has the unfavorable characteristic of being available only when livestock producers have it, Massey says. From a purely agronomic perspective, you should try to apply it as close as you can to the time of need for the crop. Yet, in the fall, you’ll have a larger application window. Lory says you should plan ahead and see which application time is the most feasible for the crop you’re growing and your source of manure.
  • Test your N in the spring. If the manure is applied in the fall, you’ll see how much made it through the winter. "You never want to calculate your N amounts by the total N available in manure," Lory says. "Some of the N will never become available." You might still have time to apply commercial fertilizer to meet N needs.
  • Do a stalk nitrate test after harvest to tell you if the fertilizer met your crops’ needs. "Over the course of a few years, you can really learn how you’re doing on nutrient management," Lory says. Use this information to make future nutrient decisions.


Read more on nutrient management.

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