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While composting dairy manure is not for everybody, it’s a “great tool in the toolbox” for those who try it, says Andy Skwor, a professional licensed across the Midwest who helps farmers work out the details of composting and other on-farm systems.

As well as working for MSA Professional Services on engineering projects for farms, he became “personally engrossed” in composting a few years ago on his own land, which helped shape his belief in the value of this system.

He believes that a compost pile can create a lot of “value-added” on the farm. As a finished product, compost is especially helpful in increasing nutrient availability when it is spread between cuttings of alfalfa.

Skwor said he sees composting as a reasonable alternative for farmers who are already doing headland stacking of raw manure. With a little tweaking, headland stacking can become composting. Rather than hauling manure to a pile, then later reloading it and hauling it onto a field, he suggests composting it and hauling it out as finished compost. Since the process creates about a two-thirds reduction in volume, the material hauled out will require fewer trips and its nutrients will be much more soil-available.

Even on larger farms he believes there’s a place for composting, especially with bedding pack manure. Wetter liquid manure can be used to add moisture that the process requires.

The compost process involves creating a windrow of the right mix of carbon-heavy and nitrogen-filled components. Keeping air in this windrow “manages the bugs,” he said. It optimizes bacteria, fungi and bug populations and they must be kept at the right temperature to keep breaking down manure, straw and fodder into their organic constituents. Those “bugs” need a certain amount of water to keep “working” too.

He recommended anyone who is interested in getting started get a long-tined thermometer that can reach down into the windrow or pile to monitor the temperature of the material. If it is too hot it will kill the “bugs” doing the composting work. If it gets too hot the pile could “spontaneously combust,” he said. If it’s too cool it won’t achieve the goal of killing pathogens and weed seeds.

A temperature of about 145 degrees means that the bugs have the right environment to work in. At 175 degrees, it’s too hot. A pile that reads 80 degrees is too cool, Skwor explained, and it may indicate that the pile was too big to start with or maybe the feed stocks (the material that went into it) were not mixed well enough.

Variety of materials

Farmers he has worked with on compost projects have used a variety of materials – everything from refused feed from the dairy freestall barn to steer bedding that included shredded drywall.

In order to break down in the compost process, materials need to have the right blend. Corn fodder is high in carbon and dairy manure has the nitrogen, so on many farms the mix coming out of dairy barns is “right in the sweet spot,” for composting, he said.

One of the advantages of composting he stressed is that when manure and bedding are piled, windrowed and composted, they will break down to about one-third in volume. That means fewer trips to the field to spread it. Three hundred tons of manure will break down into 100 tons of compost, he said, and the plant nutrients in the compost will be more available to crops than they would be in raw manure.

Finished compost’s ratio of nitrogen, phosphorus and potassium (N, P, K) measures 1:1:1 and “doesn’t compare to commercial fertilizer at all,” Skwor said. “But the process converts the feedstock into organic matter so it’s immediately available to plants.” An added advantage is that it helps increase the organic matter value in the soil and helps it retain moisture.

That’s important because as rain events seem to be getting larger, the presence of compost allows that soil to hold onto that water and release it slowly to the plants, helping reduce erosion and increase infiltration. That characteristic also helps plants survive and thrive in drought conditions.

Several of the farms he consults with begin using compost after it has been worked for 10 weeks and they use it for livestock bedding. At that point it’s not fully broken down into humus for field application, but the pathogens are gone and it is “clean” to use as bedding.

Farmers who take compost further into the process and use it as a soil amendment have found advantages to applying it on growing alfalfa fields. They find that it’s more beneficial than spreading liquid manure on those fields because there’s less burn on the plants.

The advantages of using compost, Skwor said, are that if done properly, composting kills weed seeds and pathogens; it can be used for bedding at the appropriate point in the process and once spread on the fields it raises the organic matter level of that soil profile, bringing all the benefits that come with that.

Disadvantages are few

Asked about the disadvantages of composting Skwor is hard-pressed to find one. The only one he could think of is that farmers “are not getting any more hours in the day” and working the material takes a bit of effort. “Compost needs to be managed in order to be successful,” he notes.

The first important criteria, he said, is site selection for the compost windrows. He prefers a clay base rather than concrete or asphalt because clay has the ability to “hold onto nutrients” and also because it is easier on equipment than the harder surfaces.

Windrows should be no more than six feet tall and no more than 17 feet wide and they need to be mixed in order to keep the “bugs” happy. Skwor said he’s seen farmers successfully compost manure using the equipment they already had – skid steers or loaders. The piles generally need to be composted for a minimum of 12 weeks and ideally 16 weeks.

Some farmers work with a custom operator to keep tabs on the temperature of the compost and turn it with a tractor-driven implement specifically designed for turning compost.

Alternative to winter spreading?

He advised against starting a compost pile in the depths of winter, but said that if the compost process gets started by the fall, it will continue to “work” during the winter months.

Skwor worked on a comprehensive composting project with three dairy farmers under the USDA’s Farmer Rancher Grant Program and he believes that composting manure in winter versus winter spreading has great potential.

His project report from that grant cites the dollar value of finished compost in the range of $24-$37 per ton from an agronomic perspective. That’s just based on known (tested) nutrient values without accounting for its other values, he said -- fewer trips to the field resulting in less soil compaction, more bio-available nutrients and fewer tons per acre applied.

Once compost is “finished” it is a stable product, he said, and can be stockpiled for use when weather conditions are most beneficial. “That gives you a lot of flexibility on when you spread it. You don’t have to go on your fields when you really don’t want to.”

Once it is on the fields Skwor said compost improves soil structure and soil biology which ultimately helps improve crop yields.

For farmers who care about what their urban neighbors think, Skwor notes that composting is viewed socially as a better management practice than direct field-spreading and most people consider it to be an environmentally friendly practice.

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