Liquid manure — particularly liquid hog manure, which is more readily available than solid or semi-solid manures — has always been viewed as a valuable nutrient source for field crop production. But it’s expensive to transport, so access is localized near hog operations.
“I talk to a lot of growers growing oilseeds and cereals, and they would take liquid hog manure any day if they had access to it,” says Mario Tenuta, Canada research chair in applied soil ecology and professor at the University of Manitoba. “To move it costs a lot of money, so unless you have a hog producer next to you, or you have pigs yourself, it’s too expensive to move or transport.”
Tenuta has just wrapped up a five-year research project looking at options for separating solids and liquids in hog manure, composting separated solids to concentrate phosphorus (P) at smaller volumes, while also stabilizing nitrogen (N) losses.
“We’ve found that it composts very well. We need to add bulking agents to it, like straw. It can compost very readily and produces a decent compost final product, and when we add that to soil, it’s a very good source of P and can also provide some N,” he says.
Once the liquid is separated into N and P “streams” using a commercial centrifuge, explains Tenuta, the researchers take the P from the liquid manure and concentrate it. “This increases its value and gives it potential to be shipped farther,” he says. “One of our approaches was to compost the material, produce a fertilizer that’s beneficial for soil and has other benefits.”
The University of Manitoba, along with the Manitoba Livestock Manure Management Initiative (MLMMI) and Manitoba pork industry representatives, has investigated several technologies for mechanical manure separation.
“I think it’s important to recognize that most soils in the province are deficient in nitrogen and phosphorus — we need nutrients,” says John Carney, executive director of MLMMI. “Manitoba is in a P deficit but there are a few areas that have a surplus because of livestock density. We have a P distribution problem. MLMMI is looking at various alternatives for relocating that phosphorus from a surplus region to a deficit region.”
Carney says Manitoba producers are showing more and more interest in optimizing manures. “They are motivated to try to get the most value from the nutrients in liquid manure. They want to get the nutrients into their crops and are motivated to do that both environmentally and economically.” he says.
Most producers hire professional applicators to get the job done, due to the high cost of customized application equipment and the difficulty of transporting manure.
According to Don Flaten, a soil science professor at the University of Manitoba, custom applicators must meet a rigorous set of standards. They must be licensed, and they must justify the cost of highly specialized and sophisticated equipment.
A large-scale intensive focus on manure management has improved the accuracy and efficacy of liquid manure application, says Flaten. “For larger livestock operations, it’s more effective to rent the services of manure management planners and custom applicators.”
Industry has sprung up around manure management; custom applicators sometimes work with nutrient management consulting companies. Scott Dick is part-owner of one such company, the Landmark-based Agra-Gold Consulting.
“We write nutrient management plans for submission to Manitoba Conservation, we work with producers in coming up with agronomic solutions using manure as a nutrient source, and we coordinate and schedule application for producers,” explains Dick.
Any livestock facility in the province with more than 300 animal units must file a manure management plan with Manitoba Conservation each year by July 10.
Agra-Gold’s consultants file plans indicating the amount of manure to be spread in the coming year, then does a series of soil tests and collects yield goals on a field-by-field basis. The company submits this information to Manitoba Conservation.
“Once the application is done we create an application map using GPS data, and the manure applicator takes samples that we send to the lab to get an accurate number on the amount of nutrients in that manure,” Dick explains. “Post-addition, we take the data and create a map, take the samples and soil tests and put together an agronomic report and economic summary of what happened on each field. We’ll then visit the producers and give them reports.”
With precision and specialized equipment farmers are getting much more out of liquid manure. “If you viewed it as a nutrient source rather than a waste product, by applying the science and following through with analysis and implementation, every step increases the value of that product,” he says.