While many crop farmers are aware of the agronomic and soil health benefits associated with livestock manure, hurdles still remain to increasing its usage on cropland.
Recently, researchers from the University of Nebraska-Lincoln, Iowa State University and the University of Minnesota surveyed 957 farmers and advisers from across the U.S. and Canada to understand perceptions of benefits and challenges associated with manure use in cropping systems — and address the need for manure on cropland to improve soil health and, as a result, improve water quality.
"Where animal operations import a lot of nutrients as animal feeds, we only capture a portion of those nutrients in the animals we feed," says Rick Koelsch, professor in UNL's Biological Systems Engineering and Animal Science departments and one of the survey's authors. "We've got to recycle that remaining manure, and we've got to get some nutrients back to those crop farms that are selling the corn and soybean meal to animal producers. That's the next step for protecting water quality in animal production systems."
Cost, odor issues
The survey identified several challenges that can become barriers to adoption. Koelsch says the No. 1 challenge identified was cost, including the costs of transporting and applying manure.
"As I work with farmers, I think we have a somewhat dated understanding of what that cost really is," he says. "Over the last 10 years, a lot of individuals and small businesses have started providing services for sourcing and transporting manure. As we've used bigger and more efficient equipment, our costs for transporting manure have become lower than what they were historically."
The No. 2 challenge is a little more "on the nose" — the odor associated with manure handling and maintaining good neighbor relations, and applying manure in a way that reduces odor.
MANAGEMENT DECISIONS: Survey participants' responses to what they personally believe is most true in their management decisions (or recommendations) with respect to use of manure and fertilizer in cropping programs. Source: Perceptions of Barriers and Benefits of Manure Use in Cropping Systems, 2020 American Society of Agricultural and Biological Engineers (ASABE) Annual International Meeting.
For producers applying manure, this might mean using weather forecasts to apply at the ideal time — avoiding the wind shifting and causing odor issues, and also avoiding temperature inversions.
"I tell people to think about when they see smoke from fire on the horizon that stays at the ground level, versus smoke that rises up and disperses," Koelsch says. "It's always in the evening when we notice that, when the air outside is still and the air is cooling. It's possible to look at a weather forecast over the next three to five days and say, 'This is an ideal day to spread because we won't have those inversions.' You can then time your manure application to avoid those high-risk situations."
Manure's true value
While farmers are usually aware of the agronomic benefits of manure, the survey found many growers have mixed perceptions on manure's impact on water quality.
"I think we have a historical frame of reference that manure is a negative from a water-quality perspective," Koelsch says. "I think that stems from a period when we were applying manure far beyond agronomic rates. I would suggest if you apply at an agronomic rate, the rate the crop will use, then you retain and recycle those key soil nutrients — nitrogen, phosphorus and potassium — then, manure actually has potential to benefit water quality."
Applying at an agronomic rate improves physical properties of many soils, resulting in less runoff and erosion, which, in turn, reduces the impact on water quality. In addition, many nutrients associated with manure are available in organic forms, which are less mobile than traditional inorganic sources. These nutrients are less vulnerable to leaching and runoff, and become available at a time when corn requires those nutrients.
PERCEPTIONS OF BENEFITS: Perceptions of factors and benefits from manure to crops or soils. Source: Perceptions of Barriers and Benefits of Manure Use in Cropping Systems, 2020 American Society of Agricultural and Biological Engineers (ASABE) Annual International Meeting.
Because these organic nutrients often become available later in the season, most survey respondents — about 70% — agreed manure should be managed in a way that complements commercial fertilizer.
"For example, feedlot manure and poultry litter are high in organic nitrogen," Koelsch says. "That provides an outstanding nitrogen source in June, July, August, as soils are warming and the crop needs nitrogen. But organic nitrogen typically isn't available to the crop earlier in spring. If we were to just replace fertilizer with beef manure, we may be short on N early in the growing season."
Working with growers
Survey respondents also indicated another challenge — working with crop farmers to demonstrate a manure product is agronomically comparable to commercial fertilizer.
"We need to think about the product we're going to deliver to that crop farmer and manage in a manner that would normally be expected for commercial fertilizer," Koelsch says. "That means uniformity of application, avoiding compaction, getting it applied in a timely manner. All of those are top concerns or challenges that became barriers in different circumstances."
Moving forward, Koelsch encourages advisers to work with growers to recognize the benefits that can accompany manure use, and to find solutions for these challenges.
"We're also hoping these survey results will guide decisions as to where service providers place their priorities, what services they provide," he says. "We're hoping this will help the service industry grow and expand transfer of manure from our animal feeding operations to more crop farms."