Can't safely spread manure? Then compost it

Pat Murphy
Yahara Pride Farms

Manure composting is a practice that can be used to safely store manure during periods when field crops do not allow immediate spreading, or there is a high risk for runoff of land applied manure.

composting was the subject of a Yahara Pride Farms pilot study.

Last summer Yahara Pride Farms carried out a three month trial composting bed pack manure to document the management practices for in-field manure composting. All sites used bed pack manure.

Initial findings

Reduced nitrogen: Composting manure reduces the available nitrogen. This may be negative if you typically rely on your manure nitrogen as your primary nutrient source. The finished compost retained one to three pounds of nitrogen per ton of compost. When manure is surface applied and not incorporated within 3 days, a similar loss of nitrogen can occur.

Reduced risk of nitrogen leaching: Temporary in-field stacking of manure can leave behind areas of high nitrogen concentration in the soil under the stacks. Nitrogen in the manure is converted to nitrate in a manure stack and is easily leached from the stack. The turning (aerating) of a manure composting pile releases the nitrogen as a harmless gas protecting groundwater.

Drier manure: Composted manure has less moisture than raw manure.

Composted manure is lighter to haul and compost stacks are less likely to weep manure liquids.

Loose and spreadable: Composted manure is more uniform in texture and doesn’t pack into a clump when loaded into a spreader. The turning and decomposition of the manure removes the natural stickiness that causes the clumps you typically see in field spread manure.

Natural heating in compost reduces pathogens and weed seed.

Concentration of phosphorus and potassium: P and K levels in composted manure typically double (2 x increase) in composted manure. This makes composted manure a more efficient fertilizer source. The drier and looser nature of composted manure described above makes it easier to haul longer distances and apply more uniformly to cropland.

Odor reduction: After three turns of a pile with a composting machine the smell of manure is significantly decreased. The compost begins to smell mustier, like humus or soil. If there are non-farm neighbors near fields where manure will be applied, this is a significant benefit.

Pathogen reduction: During the first three turns of a manure pile during composting temperatures routinely exceed 140 degrees F. This natural heating significantly reduces the presence of pathogens and weed seeds in composted manure.

The sterilization of the manure by heating will allow dairy farmers to spread composted manure over growing forage crops without risking the spread of livestock diseases.

In addition, hay fields that received a topdressing of composted manure immediately after hay cutting showed an immediate growth response to the added nutrients.

Pat Murphy

YPF is now experimenting with late winter composting of manure. The effect of cold temperatures and thawing soil are challenges that will need to be addressed.

Murphy is a conservation planner for Yahara Pride Farms. This article originally appeared in Yahara Pride Farms Forward Farmer newsletter.