Updated Tri-State Crop Fertilizer Recommendations

The Tri-State field crop fertilizer recommendations for Indiana, Michigan, and Ohio were originally published in 1995. After research and on-farm trials the recommendations have recently been revised and updated. Documentation for the revised recommendations can be found in the following link,  Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa. Ohio State University has provided a Quick Reference Guide to the Tri-State fertilizer recommendation changes. 

Significant changes were made to both the phosphorus and potassium recommendations and the soil pH and lime recommendations. Updated calculators and nutrient scripts were added to Field360 Studio to reflect the recommendation changes. The original Tri-State calculators and nutrient recommendation scripts still remain in Field360 Studio as an option for use. In the Advanced Nutrient Recommendations extension one will see six scripts for Tri-State recommendations. 

1 . Tri-State Calculator (Harvest)              4.  2020 Updated Tri-State Calculator (Harvest)

2 . Tri-State Calculator (Yield Target)        5.  2020 Updated Tri-State Calculator (Yield Target)

3.  Tri-State Calculator Lime Calculator    6.  2020 Updated Tri-State Calculator Lime Calculator

The updated calculators and Scripts in Field360 Studio attempt to replicate the University recommendation as close as possible. Below is a list of major changes reflected in the updated calculators 

• Recommendation based Mehlich 3 ICP as opposed to Bray P1
• Bray P1 samples are converted to Mehlich 3 with a factor of 1.35 as opposed to Encirca equation. (How do I convert phosphorus extraction results?)
• Mehlich-Col and Olsen samples are converted to Bray P1 using Encirca equations, then converted to Mehlich 3 ICP with a factor of 1.35.
• P and K calculator has an additional variable to select for Michigan or not. 
• Critical levels updated for K with consideration for sandy soils
• Critical levels for phosphorus  reflect Mehlich. (20 ppm-40 ppm)
• Crop removal rates updated for both P and K
• No drawdown for P and K
• Lime calculator has an additional variable to select for Ohio or not. 
• Lime calculator has an additional Target pH variable. However the equation is based by rounding the target pH up to the next pH target Tri-State has a recommendation for.(6, 6.5, 6.8, and 5.3 for organic soils) The equation is still limited by the target pH. For example, If the target pH is set to 6.7 the equation will be the 6.8 target pH equation, but the equation is not executed 6.7 and up. 
• The current Encirca Tri-State lime calculator has a 0.3 pH limit. Where the calculator does not initiate if pH is above 6.2. The updated Tri-State calculator does not have the 0.3 limit.

Additional Resources

• Ohio Data that Shaped the Tri-State Fertilizer Recommendations
• Nutrient Recommendations for Field Crops in Michigan
• Ohioline Soil Acidity and Liming for Agronomic Production
• Converting between Mehlich-3, Bray P, and Ammonium Acetate Soil Test Values
• Nutrients Removed with Harvested Corn, Soybean, and Wheat Grain in Ohio
• Extension Bulletin E-2567 (New), July 1995