Why matching manure applications to crop needs is so elusive.

Producers wage a constant battle in their search for value. Most are well aware that the term goes beyond a dollar amount; it’s usually part of a more complex assessment that includes a person’s goals or principles.

When contemplating the use of livestock nutrients (manure) -the considerations surrounding sources, availability, transportation and the volumes necessary to fully benefit crop nutrition and performance are magnified. It’s not a question of whether a producer would prefer to apply manure to their fields; as sources for nutrients, manure is viewed as mostly superior compared to synthetics. The balance of several nutrients, their slow release and the overall benefit of improved soil health are favourable traits.

Unfortunately, the challenges of applying manure usually result in most non-livestock producers relying on synthetic fertilizers for much of their nutrient sources. In the past 50 years, Ontario agriculture has seen a regionalization of various types of farming, particularly with livestock and dairy production. Those have become more concentrated, particularly into Midwestern and Eastern Ontario, creating a separation between producers who actively use manure for crop nutrients and cash croppers who would like to have that access. That and the source, availability, transportation and volume issues make up one group of barriers, but the other is the evolution of practices among non-livestock farmers.

“They’ve developed their operational flows without dependency or utilization of manure,” says Aaron Breimer, a certified crop advisor (CCA) and principal with Moose-Ag. “Incorporating manure is going to take a substantial rethink on operational workflow, which could include investments in equipment and staff as well as time. Many non-livestock operations can plant 200 to 400 acres a day, which is an impossible rate to stay ahead of with manure applications, so synthetics have an ease factor.”

What also affects the default to synthetics is the availability of sufficient volumes of manure. For cash crop growers, the amounts available to them are usually insufficient to meet specific crop demands, which not only means supplementing with added applications of synthetics, they require added applications. The one exception to this rule is nitrogen: its slow release and the complexity of the nitrogen cycle can cause losses at various points. That reduces the full credit of the nitrogen content of the manure and lowers its value, as well.

The time frame in which nitrogen becomes available from sources such as manure can take years before it’s available to plants. That can be confounded by temperature and moisture conditions which can affect pH levels and potentially cause more rapid volatilization of nitrogen. There’s also a concern that testing for the carbon-to-nitrogen ratio (C:N) will indicate the ratio is too high, meaning nitrogen won’t be converted to an available form quickly enough, including a corn crop during its rapid growth phase.

“World fertilizer prices are influenced by world crop prices …”

The same lowering of value with manure is true when a field tests for high fertility levels with a specific nutrient. If a field has relatively high levels of phosphorus but low potassium, the value is diminished since manure has relatively equal levels of the two nutrients.

Global impacts
Asked if geopolitical conditions, such as Russia’s invasion of Ukraine in 2022 or Chinese restrictions on exports from certain countries, can have corresponding effects on the demand for manure, Breimer calls them “minimal”. It’s not that one country’s aggression, whether in trade or militarily, impacts the value of manure, it’s the secondary effect they can have on commodity prices.

“World fertilizer prices are influenced by world crop prices, so when crop prices are low, fertilizer prices are also depressed,” he says, adding the reverse is also true with higher commodity prices. “That said, a common question I have from non-livestock farmers who are considering manure is, ‘What is the value of that manure?’, so global prices do influence how much a manure source is valued.”

Photo 2: Nutrient management a constant search -soil pit -DSC_0015
Caption: Breimer contends that availability is the most prevalent factor affecting manure’s usage. It isn’t the prospect of testing the nutrient value of the material -which is relatively inexpensive -but the fact that most livestock producers use the manure produced on their farms, with little left to offer others. Spreading synthetic fertilizers has become a default and a simpler decision to make for non-livestock growers. The flexibility in applying synthetic fertilizers in terms of timing during key parts of the growing season and access to products doesn’t always translate with manure.

An unspoken issue
One discussion point seldom addressed where manure’s use is concerned is the role of CCAs. Testing manure -or other organic amendments -or developing fertility plans using manure -are all services a CCA might be hired to provide. The issue is that most are employed by agricultural retailers, notes Breimer. This isn’t to say all advisors are governed more by an outlet’s sales figures, but it could influence their willingness to work in nutrient management or with the management of biosolids and other amendments.

“There are questions that don’t get answers when it comes to biomaterials …”

It’s much the same story with adopting the use of municipal sewage sludge, once heralded as an option for non-livestock producers in the late 2000s and early 2010s. For municipalities, it would create customers for biosolids and establish a dollar value for them. For the grower, it was a relatively new source of nutrients for their crops, with at least part of the sourcing issue resolved. But according to Breimer, there have been too many questions surrounding the use of biosolids.

“There are a lot of questions that don’t get consistent answers when it comes to sewage sludge or biomaterials, specifically around consumer perception on crops grown on ground that’s been treated with these products,” he adds. “There are some IP soybean contracts that stipulate no application (of biomaterials) within two years, and on some processing vegetables there cannot ever have been an application.”

According to sources with provincial extension, farmers in Ontario have made progress in adapting to the use of biosolids and organic amendments registered by the Canadian Food Inspection Agency (CFIA). It is an increasing opportunity to obtain organic amendments from municipalities, including anaerobic digestate, biosolids, compost and pellets. The increased focus on soil health in the past five to seven years has helped create awareness of these non-traditional biomaterials.

But there’s a definite learning curve with biosolids and organic amendments that Breimer alludes to, on top of the CCA-retail challenge.

“Including manure or non-synthetic sources of plant nutrients is often viewed as ‘more natural’ than our traditional sources of synthetic nutrients,” says Breimer. “At the same time, including these products also increases the complexity of the recommendations and thus can increase the needed knowledge and time required to make suitable recommendations.”