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Nitrogen-fixing biological products: New report summarizes research from across the Corn Belt

Cover of report issued by NDSU Extension

By: Dan Kaiser, Extension nutrient management specialist

I have been fielding a lot of questions about biological soil fertility products the last few years. With the sheer number of products that are available to farmers, it is not feasible to conduct research on all of them. So, what resources are available? There is a new regional publication put together by Dave Franzen from North Dakota State University summarizing the NCERA 103 committee’s recent research on biological products. While this will not cover every product on the market, the new report contains independent research on several of the most common products being marketed to farmers in the Midwest.

Read the full publication (PDF)

What are biologicals?

While there are many classes of what we call “biostimulants,” most of the more heavily marketed products fall under the category of beneficial bacteria. The bacteria are commonly free-living N fixers that are already found in most of our soils. What is being attempted is to get these organisms to provide additional inorganic nitrogen to the plant. 

Do these products work?

Well, it depends on who you ask. Most independent research does not show much, if any, benefit from these products. One reason for the lack of a response is that our soil is already very biologically active, so whatever these organisms do may pale in comparison to what is happening natively in our soils.

Does this mean that these products will never work?

There is always a chance, but it is hard to predict what an organism will do in the soil. Fertilizer is more predictable in what forms will be available and when and if the nutrients can be taken up by plants.
If you are looking to add a biological soil fertility product, I would suggest that you set up tests in your field to see if the product works. One important component of testing is to make sure you have a direct comparison where all factors are controlled equally. Avoid making comparisons using just a standard rate versus a reduced rate with the biological product. There is a substantial amount of data I see presented that claims product efficacy if a reduced rate with the product yields the same as a farmer’s normal practice. An important comparison that is missed in this situation is the reduced rate without the product, as that would provide a direct comparison.

Another resource for information on non-traditional fertilizer products is the Compendium of Research Reports on Use of Non-Traditional Materials for Crop Production. For those who have used the compendium in the past, please note that the website address has changed to Knowing what is in a product is important. This tool allows you to search for active ingredients and see what research has been conducted on them.

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