By Van Wert H2Ohio Technician Kate Myers
With input from Kip Studer, Peter McDonough, and Clark Hutson
“By helping farmers implement these practices [H2Ohio Best Management Practices] today, H2Ohio will ultimately save them money, increase their profits, and reduce their phosphorus runoff in the future. Although a decrease in Lake Erie algal blooms will take time, we must invest now if we want clean water for future generations.”-Governor Mike DeWine
I think this quote from Governor DeWine effectively sums up what I believe are the main goal, plan, and important impacts of the Phosphorus Reduction component of the H2Ohio program.
Based off the desired goals and impacts of H2Ohio, the nutrient recommendation framework chosen was the Tri-State Fertilizer Recommendations. The Tri-State Fertilizer Recommendation framework calculates nutrient recommendations that maximize economic return for the producer while also minimizing environmental impact and is strongly encouraged in practice beyond the H2Ohio program.
2020 Tri State Recommendations
This year the Tri-State Recommendations have been updated. Many of the components have remained the same or only slightly changed, but there are some differences that may impact your nutrient management plan. This article will have figures from both the 1995 and 2020 Recommendations but will discuss the 1995 figures as we transition into the new recommendations. For now, both the 1995 and the 2020 recommendations can be used for the H2Ohio program. The VNMP template that we have available for producers to use currently uses the 1995 recommendations. To learn more about both the 1995 and 2020 Tri-State Recommendations, the research and data that are being used to modify recommendations, and the differences between the 1995 and the 2020 recommendations, check out this video from OSU Fertility Lab.
Cover page of the Tri-State Fertilizer Recommendations Guide.
Phosphorus and Potassium
The H2Ohio program is using the Tri-State Fertilizer Recommendations for the basis of application of phosphorus, potassium, and nitrogen. All producers enrolled in the H2Ohio program must have a Voluntary Nutrient Management Plan (VNMP) or Comprehensive Nutrient Management Plan (CNMP) which both serve as the foundation for all other practices. Producers’ nutrient management plans will use and include soil tests taken at least every 4 years, yield goals, and crop rotations to generate nutrient recommendations using Tri-State Recommendations. According the Tri-State Fertilizer Recommendation guide, recommendation rates for phosphorus and potassium are determined by the “Critical level,” which is the soil test level that will provide adequate nutrients with a 95% probability of maximum economic return. This is illustrated in Figure 1 of the Tri-State Fertilizer Recommendation Guide to the right:
(See page 10 of the Tri-State Fertilizer Guide for this graph and more explanation).
When soil test values are above the “Critical level” but have not reached the “Maintenance limit” the soil can provide the necessary nutrients for the several years of crops, and recommendations are made by applying what the crop removes through grain, forage, or stalks. Applying nutrients based on removal rate takes place when soil tests are in the “Maintenance range” of Figure 1.
When soil test levels exceed the “Maintenance limit” of Figure 1, there is a low likelihood that a yield response will be seen from applying fertilizer and recommendations should be less than removal rate down to potentially 0 to utilize existing nutrients. This may be extremely different than what many producers are currently used to, but the Tri-State approach asserts that there is no agronomic reason to apply fertilizer above the “Maintenance limit.” Recommendations using the Tri-State framework assume regular (every 3-4 years) soil testing, so if soil tests are being taken regularly and you are monitoring your nutrient levels you should not experience any nutrient deficiencies or economic loss from not applying nutrients while test values are above the “Maintenance limit.” Ohio State University Soil Fertility Associate Professor Dr. Steve Culman explains this framework and the new Tri-State framework here in this video starting at 10:12.
Since nitrogen levels are difficult to test and availability can be varied due to a variety of factors, nitrogen applications are determined at maximum return to nitrogen investment. When planning nitrogen needs, make sure to account for crop rotation planned, timing, application method, nutrient source, soil texture, and number of planned applications. For more information you can compare results based on economic inputs. http://cnrc.agron.iastate.edu
The top graph is the 1995 framework. The bottom graph is the 2020 framework.
Using the Tri-State Recommendation guidelines for determining fertilizer need can help producers maximize economic return and reduce environmental impact by utilizing the nutrients available and minimizing the loss of these nutrients. Please check out the Tri-State Recommendation Guide, Video from OSU Soil Fertility, and the H2Ohio webpage (links below) for more information and reach out to Kate Myers with any questions. You can also email Kate (email@example.com) to get the VNMP template.
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