About 400 earthen manure storage structures are in the state. Over the past decade, almost 50 permitted livestock manure lagoons have been closed, and many more requests for ceasing lagoon operations are expected in the coming years. That's why research conducted at the old swine manure storage lagoon at University of Nebraska’s Haskell Agricultural Laboratory near Concord is so valuable.

The swine research unit dedicated at HAL in 1969 brought about a new age of swine studies. Much of the research centered on the unique modified open-front design. A waste lagoon built as part of the system meant that manure management and agronomic studies were also a part of that research. The lagoon used to be much larger. When it was built, it was nearly twice the size it was before closure began. In the late 1980s and early 1990s, the lagoon was renovated and the south berm was moved essentially to the middle, creating the most recent lagoon size of about 0.7 of an acre at its greatest depth, with a base measuring 150 feet by 80 feet. The working volume depth was between 7 and 12 feet.

With the departure of former Nebraska Extension swine specialist Mike Brumm, the swine research unit was eventually shut down in 2009. However, the unit is still contributing to research as studies are being conducted on the closing of the livestock lagoon that was part of the finishing system. While the lagoon closing at HAL was not a typical farm closure, the process provided data and perspective on the workings of the system overall.

"We started by mapping the sludge layer in the lagoon, using sonar mapping, to learn more about this mapping method," says Leslie Johnson, Extension animal manure management coordinator. "Because we were testing this equipment, we needed high-quality baseline information about the sludge layer." Floating Circul-O2-Rater aeration units from eXpertCompany were installed on the lagoon to study the results over nine months before sludge was removed, she says.

"We mapped the lagoon again to find any differences in the sludge layer," she explains. "By knowing how much sludge was in the pond, it allowed us to calculate how much liquid was above the sludge. Based on this calculation and the nutrient analysis from the samples we collected, we could figure out how much water we could apply through our pivot before running out of water in the lagoon."

Sludge layer studied
The goal was to remove as much water as possible so researchers could actually see the sludge layer to compare the mapping and show what the sludge looked like during a demonstration day last fall. "We sampled the remaining sludge to do a nutrient analysis so we could calculate the amount of sludge needed to meet crop nutrient needs on our fields," Johnson explains. "During the demonstration day, we had a long-reach excavator and a slurry manure spreader on hand. We began hauling the sludge to the field and calibrated the manure spreader to match our needed application rate, which was about 8 tons per acre." White plastic was set in place in the field during the demonstration, to allow producers to observe the sludge spread pattern in the field. "We also dug a soil pit in the bottom of the lagoon below the sludge so producers could look at the soil below, which was quite interesting," she says.

Since last fall, the work has continued, Johnson says. "We have continued hauling and stockpiling the sludge," she says. "We are not yet done with that part of the process." The next steps include calling Nebraska Department of Environmental Quality for an inspection that would give researchers approval to cover the lagoon. Then the berms would be pushed in from around the lagoon to bury the bentonite clay liner. All access points in the barns have been plugged, so no manure can leave those barns, because there is no longer a lagoon to collect it. A cover crop will be planted to hold the soil until planting time. Eventually, the land where the lagoon once was can be farmed as usual.

Normally, producers would use some sort of agitation equipment and drag hose machinery to apply the liquid and sludge at the same time, Johnson says. "Pumping the water off and dealing with the sludge at a later time is much more labor-intensive — that probably is not economical," she adds. "It is imperative that proper procedures be followed to decommission an earthen manure storage structure to ensure minimal risk to the environment and, in some cases, to meet permit requirements," says Johnson. "Interestingly enough, even non-permitted structures and concrete pits under barns also need a DEQ inspection for closure. The best advice is to make sure you're working with DEQ before pushing in any manure storage."

You can learn more by contacting Nebraska DEQ at deq.state.ne.us or Johnson at [email protected].