By Wendy Powers

Today’s constantly increasing fertilizer prices make minimizing manure nutrient loss more important than ever. The fewer nutrients lost to the air during storage, the more nutrients you have to apply on your field later. During manure storage, nitrogen can volatilize into the air. (Carbon and sulfur may volatilize, too, but to a much lesser extent.) Depending on how manure is handled — as dry manure, a slurry or a dilute liquid — and then stored, nitrogen losses are estimated to be as much as 70 percent from the time that manure is excreted by the animal to the time that manure is land applied as a source of crop nutrients.

Manure storage covers are perhaps the best way to keep nutrients in the manure. Here’s a look at some options.

Biocovers are made of organic material such as straw or cornstalks. Pros: low up-front costs. Cons: such covers are permeable — some gases do escape; covers must be replaced (usually annually) because the cover material eventually sinks (sinking makes removal a challenge, too). Biocovers reduce odor by 40 to 50 percent and reduce nitrogen loss by up to 50 percent.

Geotextile covers are nonbiodegradable. Pros: long life; no issues with rain and snow load. Cons: more expensive than biocovers. Reduce nitrogen loss by 80 percent or more.

Impermeable covers are typically composed of plastics or petroleum-based products. Pros: no gases can pass through from manure to air. Cons: rain and snow must be removed from the cover to avoid sinking or breaks in the cover; in some cases, high winds have blown covers off or caused significant tearing — enough to make the covers ineffective. Impermeable covers reduce both odor and nitrogen loss by 80 percent or more.

Impermeable covers may cost $2 per square foot installed. Retaining half of the nitrogen in your manure storage by installing a cover, however, may be a bargain compared with current costs for nitrogen fertilizers (80 cents to $1.03 per pound).

Click here to read the full issue of the November Scoop.