Fertilize, Optimize, Analyze, Repeat

Unless you live in a cave – and no one is judging here – interaction is hard to avoid. Human relationships are powerful and complex, and the same is true for the interplay of cropping practices. To minimize costs and maximize output for growers, it is vital to understand farming dynamics: What are the effects of Nitrogen (N) inhibitors and N rates on the soil microbiome and soil health in spring wheat systems (The plant soil microbiome is the dynamic community of microorganisms associated with plants and soil, including bacteria and fungi that can have both beneficial and harmful effects on plant growth and crop yield)? How can different soil conditions impact the soil microbiome’s response to agricultural practices such as fertilizer management, fungicide application and crop rotation?

Fortunately, science is all about seeking answers with projects like "Understanding the interactions of N fertilizer technologies, fungicides, and the soil microbiome to optimize sustainable agriculture".

“Nitrogen fertilizers are critical for crop production,” said Dr. Monika Gorzelak, research scientist with Agriculture and Agri-Food Canada (AAFC) at the Lethbridge Research and Development Centre in Lethbridge, AB. “Agriculture relies heavily on synthetic nitrogen inputs, primarily urea.”

Sorting out the inputs

As the costliest input for growers, optimizing nitrogen inputs for crops is essential to achieve 4R nutrient stewardship (the right source, rate, time and place for fertilizer application). The proper source of nitrogen fertilizers to ensure optimal nitrogen use efficiency (NUE), while minimizing losses to the atmosphere and surrounding waterways, is key for crop production and environmental stewardship.

“Enhanced Efficiency Fertilizers (EEFs) are a potential solution to improve the bottom line for growers,” said Gorzelak. “EEFs work by altering nitrogen transformation and synchronizing release with crop uptake to improve NUE.”

Some studies have demonstrated mixed results for the efficacy of EEFs in wheat, with management practices and environmental factors impacting the results. For instance, tillage has been shown to impact the outcome, yet there is little or no information on how fungicides and previous crops can interact with EEFs. Scientists have also identified a need to better understand EEF efficiency in the context of its impact on the soil and microbial communities.

“With this project, we will determine how EEFs used in Canadian Western Red Spring wheat affect the soil microbiome, and how different agricultural practices interact with EEFs. We also want to examine ureases and the genes coding for them to see if the soil is responding to their application.”

Ureases are naturally occurring enzymes in the soil, typically produced by soil bacteria, that convert urea to ammonia and carbon dioxide.

Specifically, scientists have a number of objectives. They plan to monitor changes in the soil microbiome and soil health with five different N inhibitors applied at four separate rates. An N inhibitor is a substance used to inhibit the biological oxidation of ammonium nitrogen to nitrate nitrogen in soil. It also helps manage the conversion of urea to ammonia and carbon dioxide until adequate rain or irrigation can occur.

Made to measure

Secondly, the team will measure and quantify N inhibitors in the soil to assess the fate of these compounds and understand their potential impacts on soil health. As well, they aim to determine the effects of fungicides and N inhibitors on crop performance, soil health, and beneficial soil microbial communities.

“Part of our motivation is to support growers in making the best possible decisions for nitrogen management, but to do so, we must understand when and why EEFs are most effective. For example, the ability of nitrapyrin, an EEF, to reduce N losses can be diminished by practices such as long-term incorporation of crop residues.”

Consequently, it is likely that different crop residues also play a role in the efficacy of EEFs. As well, pesticides shift microbial communities, yet their impact on the community structure, and how they interact with other agricultural practices, is under studied. Knowledge of best management practices for fertilizer impacts on crop NUE and the relationship with the soil microbiome community is limited, particularly in the Prairies.

“To allow growers to make informed decisions with respect to the optimal fertilizer type under different management scenarios, we must study how the soil microbial community will respond to these inputs in conjunction with other management practices.”

Meeting her match

Given her interests and expertise, this project was a natural fit for Gorzlak.

“My background is in the crop microbiome and plant and soil health, looking at how microbes deal with different agricultural inputs. It became apparent that, by necessity, EEFs inhibit natural biological processes. From a soil microbiology perspective, I’m intrigued by what is happening below ground and how effectively the crop microbiome is functioning.”

Of course, scientific progress is closely linked to collaboration, and researchers are quick to give credit where it’s due.

“This project leverages a robust and on-going agronomic field experiment studying EEFs to further our understanding of the impact that EEFs, pesticides, and crop rotations may have on the soil microbiome and overall soil health. That experiment, which is currently in its final year, is being conducted by Dr. Brian Beres, a fellow research scientists at the Lethbridge Research and Development Centre.”

The leveraged Beres project will allow the study of EEF interaction with soil microbiomes in a full-scale field experiment, and the results will inform complementary greenhouse experiments designed to further identify potential impacts.

“Globally, as the demand for wheat continues to grow, the need for more sustainable nitrogen (N) fertilizers to reduce greenhouse gas emissions and losses to the environment is apparent. Additionally, profitability is being threatened with increasing fertilizer costs. Information obtained in this work will ultimately help to inform growers regarding optimal practices for N management and protecting and maintaining soil microbial communities and soil health.”

Though it’s only year one of this project, researchers have their eyes firmly on the prize for growers.

“We have been gathering a lot of soil samples from the field, and currently we are busy collecting the final post-harvest soil samples. Once we process all of them, we can use the data to home in on one or two EEF products that will benefit producers. In the end, more efficient use of N means cost savings for growers and less wear and tear on the environment. As long as costs don’t outweigh profits, this feels like a real win-win to me.”

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