Iowa Fine-Tuning Nitrogen Management Research Project

  • The Corn Nitrogen Rate Calculator, developed by Iowa State University, is an easy to use on-line tool for famers to calculate the maximum return to nitrogen (MRTN) application rate.
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  • Iowa Soybean Association and other interested partners are soliciting farmer cooperators statewide to compare their standard N rate side-by-side to the MRTN rate in their own on-farm comparison study.
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  • A goal of the study is to compare the profitability of the MRTN recommended N rate versus the famer preferred N rate.
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The Corn Nitrogen Rate Calculator (CNRC) for Iowa and other Midwestern states has been available to farmers for about 10 years. The CNRC is an easy to use online tool developed by Iowa State University. The tool calculates a nitrogen (N) application rate based on the cost of N, expected selling price of corn ($/bu), crop rotation (corn after soybean or corn after corn), and geographic location. The online tool provides a recommended N rate expressed as the maximum return to N (MRTN), which is the N rate where the economic net return to N application is maximized. The N recommendations are based on previous N rate research trials coordinated by Iowa State University. For example, if a farmer chooses a recommended N rate for corn after soybeans for the main part of Iowa (which excludes poorly drained soils in SE Iowa) the MRTN rate is influenced by the results of 219 previous N rate trials in Iowa.

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Cooperators Needed for Fine-Tuning Nitrogen Management On-farm Research Project

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The Iowa Nutrient Reduction Strategy is a science and technology-based framework to assess and reduce nutrient load by 45% to Iowa waters and the Gulf of Mexico. Additional adoption of MRTN rates could contribute to this goal. Non-economical high rates of N on a single farm within a sensitive watershed may undo the sustainability efforts of several neighboring farms. Thus, it is becoming increasingly imperative to increase the scale of MRTN and adaptive N management.

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Iowa Soybean Association and other interested partners are soliciting farmers to apply their standard N rate side-by-side to the MRTN rate in their own on-farm comparison study. The goal is to sign up 10,000 cooperators. Project goals include the following:

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  • Compare the profitability of the MRTN recommended N rate versus the famer preferred N rate.
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  • Increase the understanding of the most profitable N rates in Iowa.
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  • Demonstrate Iowa farmers cooperation to improve water quality to consumers and policy-makers.  
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To Participate:

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  • Go to the Corn Nitrogen Rate Calculator (CNRC) website to find the suggested range of N rates for your farm: cnrc.agron.iastate.edu.
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  • Go to the Iowa Soybean Association website to sign up for the Nitrogen Fine-Tuning Project.                     www.iasoybeans.com/programs/isa-research/get-involved/sign-up/.
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  • Apply the MRTN rate suggested by the CNRC according to the plot layout in Figure 1. Note there are two options: self-assessment - one replication per field or research assessment - three replications per field.
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  • At harvest, capture yield data from the plot by making a separate load on your yield monitor.
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  • After harvest, go to iasoybeans.com to anonymously report your results. Due to respect for data privacy, the survey will not ask for cooperator names. County location will be asked, but is not required to complete.   
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Figure 1. Self-assessment plot layout with one replication (left) and research assessment plot layout with three replications (right).
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For more information about the MRTN or the on-farm research study, contact the Iowa Soybean Association at research@iasoybeans.com

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