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Research Highlights

Research Highlights
Confirming Best Fertility Guidelines for Ohio Soybeans

By Barb Baylor Anderson

Are Ohio soybean farmers following the best recommendations for nutrient management? That is the question Steve Culman, Ohio State University soil fertility specialist, set out to answer with funding from the Ohio Soybean Council. Culman was the study’s principal investigator.

“Soybean fertility advice in Ohio widely follows ‘Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa.’ While this publication has served as a cornerstone for field crop soil fertility for more than 20 years, another look was warranted,” he says.

Ohio soybean farmers must manage fertilizer inputs as efficiently as possible, applying sufficient fertilizer to meet crop demand while avoiding major losses to the environment. Culman says the ability to find the optimal balance is highly reliant on tools and information available to farmers.

The research project conducted on-farm field trials from 2014-2018, and specifically set out to update recommendations for phosphorous (P) and potassium (K) use in soybeans and determine best practices based on soil test and leaf tissue levels. Trials conducted included 48 for P, 48 for K and 15 sulfur (S) trials. Researchers also compiled 144 soybean studies for yield response to micronutrient fertilization to develop additional best management practices.

“I think our work convincingly found that the P and K recommended critical levels for soybeans are still relevant today,” he says. “This information gives us greater confidence in P and K use in Ohio soybeans and best management practices for nutrient management and water quality.”

Culman previously had conducted a multi-faceted approach to examine soil fertility rates with pest and disease interactions by working with pre-existing research sites and conducting on-farm strip-trials across the state. The goal of that effort was to provide practical and unbiased information on economically optimal fertilizer application rates for soybean farmers in Ohio, but also identify the role soil fertility plays in managing soybean pests and disease.

And while Culman’s work is specific to Ohio, he does believe the conclusions drawn may be applicable in other states with some caution and adjustment. For example, field trials in neighboring states Michigan and Indiana have yielded similar results.

As for the future, Culman says, “We need a better understanding of which soils are more or less prone to building and drawing down soil test potassium. Some growers have reported difficulty in maintaining soil test K values, while others have not. We need to understand which factors contribute to this and how to better manage it. This is hopefully our next area to explore.”

Photo: United Soybean Board

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.