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Study: Agronomists support reducing nitrous oxide emissions

A recent publication shows Manitoba agronomists support agricultural practices that reduce soil nitrous oxide emissions.

The publication is based on survey data collected during the 2015 Manitoba Agronomist Conference. A total of 135 conference attendees participated in the survey, which was led by researchers at the University of Manitoba, including soil science professor Brian Amiro.

Amiro says the survey resulted from a five-year Agriculture and Agri-Food Canada science project on the topic. The project funding covered studies but also a communication component, including interactions with agronomists who understand current practices.

“We wanted to get an idea of how we could reduce greenhouse gas (GHG) emissions from agricultural production. The question is always, ‘What are the limitations to implementing the science?’ There has to be policy, but the grassroots is always where the change happens,” Amiro explains. “We wanted to get a sense of how farmers would like to move forward. Agronomists are in the business of helping producers farm.”

Prior to the survey, the researchers offered an introduction to GHG emissions in agricultural contexts. In agriculture, emissions are mostly caused by nitrogen fertilizer application; about one to four per cent of applied N is lost as gas to the atmosphere. Beneficial management practices (BMPs) that reduce these emissions do exist for agriculture, Amiro says. One such BMP is attention to the “4Rs” (right place, right rate, right source and right time for fertilizer application).

Survey questions

Survey questions were built around the 4Rs of agriculture.

Three questions tackled fertilizer source use. Participants were asked whether they were willing to use or recommend the use of slow-release nitrogen or products incorporating the use of urease or nitrification inhibitors. While only 13 per cent of respondents used these products, 63 per cent were “willing or very willing” to use or recommend them; an additional 35 per cent of respondents would be willing were the cost of such products subsidized.

When it came to fertilizer rates, 63 per cent of respondents said they based their recommendations for N application rates on soil testing for a yield goal.

Fertilizer timing is generally decided on the basis of fall or spring application, note the study’s authors in the publication. Fall-applied N tends to result in low N₂O emissions over winter due to cold temperatures. In the survey, two-thirds of the agronomists noted they choose fall applications due to workload or other considerations.

In terms of fertilizer placement, banding of N fertilizer is generally recommended to reduce potential emissions and other losses. Roughly half of the survey respondents said they band or recommend banding fertilizer; one third commented that they would do so if equipment were available.

Cost is a limiting factor

Amiro says the survey was designed to help researchers understand what factors are inhibiting the adoption of BMPs that have potential to reduce nitrous oxide emissions in agriculture.

“Usually the limiting factor is the extra cost that people would pay. If there’s an agronomic advantage, they’d adopt the practice much more readily,” Amiro says. “Fertilizer banding, for example – there might be some producers who just don’t have the equipment.”

Amiro believes most agronomists are in tune with producers’ needs and economic realities, and their responses to the survey questions accurately reflect how producers view the issues.

“On the producers’ part, I think they’re going to adopt practices that give them an agronomic advantage. They are responsible environmental stewards but there has to be an economic advantage,” he says.

In response to one question on the survey – “Is the N fertilizer rate you recommend or apply primarily based on obtaining the highest possible yields rather than the most economical return?” – 57 per cent either disagreed or strongly disagreed, meaning most surveyed agronomists would make decisions based on obtaining the best possible economic return rather than the highest yields.

“We often think about the balance between economic return and yield. Achieving high yield could come at a cost,” Amiro says.

When researchers do experiments to show how effective products or practices are in reducing GHG emissions and benefiting the producer’s bottom line, the results often depend on the year, the place, moisture levels and soil types, among many other factors, meaning producers might need to make decisions based on their unique conditions, he explains. “That means you can’t make big global statements about practices everyone needs to adopt.”

But Amiro points to the first question on the survey to highlight prevailing attitudes: “Providing that it is cost effective, do you believe that the reduction of N₂O emissions should be a high priority?” Ninety-four per cent of survey respondents either agreed or strongly agreed that it should.

“It’s overwhelming that people want to do things that are better for the environment as long as they are cost-effective. That’s a pretty powerful message,” Amiro says.