Can soil health tests determine fertilizer needs?

As farmers increasingly use soil health tests, many wonder if these test results can or should determine fertilizer needs for corn and other Minnesota crops.

These tests, such as the Haney test, help measure soil health indicators such as microbial activity, the amount of carbon in the soil and nutrient availability. While these tests can be useful for contrasting management practices, they shouldn’t be used to determine fertilizer application rates.

Unlike University of Minnesota fertilizer guidelines, soil health tests often don’t follow the standard procedures used to develop recommended rates. This could cause farmers to use too much or too little fertilizer.

Understanding fertilizer guidelines

When determining your crop’s fertilizer needs, it’s recommended to stick with standard soil testing procedures and fertilizer guidelines that have been correlated and calibrated through many years of research in your own state.

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Comparison: Haney test vs. standard soil-testing procedures

To better understand whether soil health tests could help determine fertilizer needs, University of Minnesota researchers conducted comparison trials. They used the Haney test (a non-standard test) and standard soil testing procedures to estimate:

  • Available nitrogen, potassium and phosphorus per acre.

  • Corresponding fertilizer recommendations.

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Lizabeth Stahl, Extension educator; Fabián G. Fernández, Extension nutrient management specialist and Daniel E. Kaiser, Extension nutrient management specialist

Acknowledgments

The 2015 trials conducted at the Southwest Research and Outreach Center in Lamberton in 2015 were supported by the Minnesota Soybean Research and Promotion Council and North Central Region Sustainable Agriculture Research and Education (NCR-SARE).

The 2016 comparisons were conducted with funding from the Minnesota Agricultural Fertilizer Research and Education Council.

Reviewed in 2018

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