Simply Science: The transformation of manure for gardening

COLD SPRINGS,Minn.- Cold Spring's-based Mississippi Topsoils is a company that takes partially decomposed manure from a dairy farm in Morris and transforms it.

In the world of gardening, manure is a key ingredient for a lot of plant fertilizers, but it doesn't go straight from the cow pasture to the garden. It's actually a time consuming process.

First, it spends a little over a week in what owner Brad Matuska calls the active phase. The pile is simply left alone while fungi break down cell walls. Bacteria consume and decompose the manure.

Just like our bodies give off heat and energy, when we eat as an aerobic process, so do the bacteria.

"If you'd stick your hand inside there, it's at about 140 degrees Fahrenheit," said Matuska. "So, it's pretty toasty."

The manure remains in the active pile for at least a week above 130 degrees Fahrenheit. This is hot enough to kill harmful animal and plant pathogens, but not hot enough to kill the bacteria, Matuska says.

Perforated PVC pipes with a fan attached run deep inside the active pile to keep air flowing, which prevents temperatures from rising high enough to sterilize the manure.

"If it were sterile, there wouldn't be any biological activity in it," Matuska said. "And that is one of the biggest benefits of the use of compost is the fact that you're adding beneficial organisms to a growing environment."

In addition to controlling the temperature, the PVC piping brings much needed oxygen.
After about a week in the active stage, the pile is moved to the curing phase.

"(It's kind of) like a good wine or a good beer, it needs to stabilize and cure," Matuska said.

The same decomposition process is occurring in the curing phase as in the active, but at a much slower pace, since the bacteria begin to run out of food.

After aboutthree months, the compost cured. It is bagged and ready to be used by nurseries, fruit and vegetable growers and even personal gardeners.


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