“Manure management is becoming more of a challenge,” said Peter Wright. “The issues of sustainability are becoming more real. The societal impacts of manure constrain some farms, and there is an economic component.”
An ag engineer at Cornell University, Wright said the big picture for manure storage should involve cost control, which means having equipment that matches farm needs. Custom application can help manage costs, and gaining additional value from manure via treatment processes is another cost-cutting option.
“Winters are wetter, and it seems like springs and falls are wetter,” said Wright. “This presents issues with manure application. There’s a lot of variability.”
More intense storms can impact manure management because precipitation fills storage faster and can move manure off the field if it’s applied immediately prior to a major weather event.
Wright believes there will be continued environmental pressure with an emphasis on water quality. There may be an increase in demand for biofuel as a renewable energy source, which could be positive for farms. However, as more people move to rural areas, they may or may not tolerate agriculture.
“We like to think we have the right to farm,” said Wright. “In reality, we have a license to farm, and if we abuse that privilege, it may be taken away from us. The days of thinking we can do whatever we want are over – we need to look at how we can work with the public.”
These components add up to an increased need for manure storage.
In many states, manure application is limited in winter. Even the non-farm public can see that manure on fields in winter followed by precipitation doesn’t make sense.
Wright expressed concern that the wide window for autumn manure application may also be reduced. “If we’re spreading manure as part of a nutrient management plan to meet the nutrient needs of a crop, are we really doing that when we spread it in the fall, or should we wait and spread in spring?” he said. “I think we’re going to head into more and more storage.”
Unfortunately, storage issues often arise when manure is stored until spring for land application. It’s likely more rain has fallen on stored manure through winter and manure waiting for spring application becomes too saturated.
One way around the issue is covered storage. If storage is covered, solid separation may be necessary because it’s more difficult to get solids out of storage. Winter-spread manure can run off fields and may continue into ponds, lakes, streams and rivers.
“I have seen changes in the watershed area of storages,” said Wright. “You have to work really hard to keep clean water out of storages. But when ice and snow fill up those diversions, stormwater might diverted into storage, which is not what it’s designed for and can cause problems.”
Targeting low-risk fields for application involves identifying and setting aside flatter fields, possibly with cover crops established. These areas should be reserved for emergencies to prevent manure storage from overflowing.
In the past, farmers put in storage structures to avoid having to haul manure daily. Wright said there’s value in utilizing nutrients, particularly in spring and summer when plants are growing.
“There are reasons to stay off the fields when they’re wet because of compaction,” said Wright. “People put in storage to avoid that issue. Now there’s more environmental and regulatory pressure for storage, as well as community pressure.”
Ideally, manure storage is sized correctly based on a comprehensive manure management plan and emptied according to the plan. Nutrients going to the field would be maximized to meet crop demand, and solids are controlled – not built up in the storage structure. Drainage is managed to keep clean water out of the storage.
Farmers usually don’t allow for enough space when designing a manure storage structure. Considerations include the normal volume of manure, normal precipitation and runoff. “Add the 25-year storm, and the 100-year storm, and subtract the volume of accumulated solids,” Wright said. “Come up with a designed storage amount and hope life will meet your needs.”
Because storage inadvertently creates a labor peak, problems may arise when it’s time to empty it. Instead of spreading daily, there’s spring manure application to coincide with hay harvest and corn planting, summer application to juggle with hay harvest and a possible grain rotation, autumn application to balance with cover crop establishment and winter application that presents runoff risk.
“I’ve seen farms base the size of storage based on what they could afford,” said Wright. “That leaves them constrained – if they don’t empty in fall and have a wet spring, they’re in trouble. They want to carry more throughout the year, but the storage won’t hold it.”
Storage may not be emptied according to plan because equipment isn’t ready, labor isn’t available or weather isn’t suitable – all of which result in wasted nutrients.
While winter manure application comes with challenges, in some areas, frost tillage is an option: “Low snow cover and two or three inches of frozen soil,” said Wright. “Underneath, when soil freezes, capillary action brings the moisture up into the frozen layer. The layer underneath is quite dry, and it’s possible to spread manure by breaking through the frozen layer. The equipment rids on top of the frozen layer so there’s no compaction. You break through it and inject into the dry soil underneath.”
The problem with frost tillage is that it can’t be counted on because it’s a somewhat specific weather condition.
Public relations are key to successful manure storage and application, and this aspect will become more important in the future. One issue is that no one wants to look at manure storage, so it’s important to construct where the storage is out of sight. Odor is also a major factor in siting storage facilities.
Fortunately, those who plan manure storage structures are trained to consider all the factors to create the best plan that will serve the farm well into the future.
