Manure Manager

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Keeping up with the 4Rs

The 4R approach is not a silver bullet to sustainability, but remains a key piece

March 31, 2022  by James Careless

Manure is applied on an Ontario field in the summertime. Photo courtesy of Christine Brown.

The practice of 4R nutrient stewardship is based on the ‘4Rs’ of fertilizer (including manure) application, “which refers to using the right source of nutrients at the right rate and right time in the right place,” says Andrew Allman, director of business operations at the Ohio AgriBusiness Association and executive director of the Nutrient Stewardship Council. “This approach provides a science-based framework for plant nutrition management and sustained crop production, while considering specific individual farms’ needs.”

At the same time, “As much as we would like to think that the 4Rs are a silver bullet, we know this is not the case,” says Erica Rogers, environmental extension educator with Michigan State University. “It is one part of a bigger equation to help promote sustainable farming.”

A 4R primer
“The principles of 4R Nutrient Stewardship were developed in order to apply nutrients in a way that considers growers’ economic, social, and environmental goals,” says Brittany Thibaudeau, communications specialist with Fertilizer Canada. “4R Best Management Practices and recommendations from an agronomist will ultimately vary depending on numerous factors, including a farm’s location, crop rotation, climate, soil type, nutrient sources available and equipment.”

Rogers adds, “Right source means proper fertilizer nutrients [commercial or manure] being utilized for immediate or delayed crop uptake. Right rate means match the amount of applied fertilizer to the crop nutrient uptake, making sure to do a manure and soil analysis to appropriately match [the] actual amount of fertilizer needed for crops based on individual field fertility. The right time means applying the manure as close to the plant uptake of nutrients as possible, with consideration given to weather, seasonal conditions, and the mitigation of potential odours. Finally, the right place means fertilizer placed as close to the root zone as possible for best plant uptake, taking into account potentially sensitive areas like surface waters.”


Manure poses 4R challenges
Compared to commercial fertilizers, manure can be more challenging to manage in line with 4R principles.

The core challenge: “Due to the volume of manure applied to get the same fertilizer value compared to commercial fertilizer, achieving the right time and right place and right rate is more difficult,” says Christine Brown, sustainability specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs’ field crops unit. “Manure composition doesn’t respond to a customized fertilizer blend so application rates can easily over or under apply nitrogen or phosphorus. As well, the Right place for fertilizer focuses on placement, but with manure the need to apply to the ‘right’ field is just as important as the ‘right’ placement.”

A further challenge: “In Ontario, I think the biggest emphasis of manure 4Rs management has been ‘right time,’ and the importance of not applying manure during the wrong time, such as on frozen and snow-covered fields,” says Brown. Although surveys show a high level of 4Rs awareness and acceptance among young farmers and those who run larger farms, “weather is the biggest barrier to implementing 4Rs in livestock farms,” she notes. 

The realities of manure disposal on livestock farms can also complicate adherence to 4Rs principles. “Most farms still need to apply manure in the late fall or spring to manage limited winter storage,” says Brown. “A wet spring or fall will result in manure being applied with longer intervals to incorporation, or may increase some winter manure application. Higher rainfall can also limit usual storage capacity and lead to application timing that doesn’t meet 4Rs standards.”

Changes to farming practices required for 4R
Implementing the 4Rs to achieve more sustainable agriculture doesn’t start and stop with applications to fields. “Ultimately, there is some cost associated with implementing more advanced practices such as enhanced efficiency fertilizers, variable rate technology or purchasing equipment upgrades to allow for banding placement,” says Thibaudeau. “These investments contribute back by reducing nutrient losses to the environment while maintaining or improving yields.”

“I think there are just as many economic advantages as barriers when manure nutrients and organic matter is utilized to its maximum benefit,” says Brown. Still, there is a cost associated with acquiring and implementing the new technology required to fully implement 4R principles. When it comes to using applying, this purchases can include technology to apply/inject manure into standing crops, tires and inflation systems, storage technology t and the cost of labor. “Government grants to subsidize new technology helps,” she says.

This said, there is no one-size-fits-all solution to 4Rs implementations. As no two farms are alike, so too are the 4Rs approaches that can make them sustainable – and not all require a big outlay of cash.

“Even the smallest change can make the biggest difference: It does not always have to involve big, expensive equipment or technologies,” says Rogers. “Farmers can just start where they are at now, using whatever resources are available at their fingertips. This doesn’t mean that they can’t invest in some of these more expensive options at a later point. But if they don’t start somewhere, that isn’t very effective either.”

No silver bullet
For all their benefits, the 4Rs are not a “magic solution” that can fix all issues in agriculture.

“No, the 4Rs are not silver bullets that will clean up water quality issues in the Western Lake Erie Basin or other water bodies and achieve overall sustainability, which has different meanings to different people,” says Allman. “The 4Rs are a piece of the puzzle and exist to provide proven, science-based best management practices and education at the retailer, independent crop consultant and farmer levels.”

Brown cuts to the heart of this issue when she observes that “sustainability is more than just the 4Rs. Sustainability includes environmental, social and economic considerations, and goes beyond just balancing nutrients. Environmental sustainability includes water, air and soil.” At the same time, she says, when manure management practices align with 4Rs principles, the result is improved crop nutrient utilization and reduced environmental impacts. •


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