Home / Crops / Another look at 20 years of fertilizer recommendations
Steve Culman, Ohio Agricultural Research and Development Center, is working on revising the Tri-State Fertilizer Recommendations.

Another look at 20 years of fertilizer recommendations

There are likely as many varied opinions on the validity and the accuracy of the Tri-State Fertilizer Recommendations as there are farms and soil types. No matter what that opinion may be from field to field, it is hard to deny that the document has had an incredible impact on crop production in Ohio.

“The Tri-State Fertilizer Recommendations for corn, soybeans, wheat, and alfalfa were first published in 1995,” said Steve Culman, assistant professor of soil fertility at the Ohio Agricultural Research and Development Center and state Extension specialist in soil fertility. “It was the culmination of 40 years of calibrated field studies. They calibrated fertilizer rates with agronomic response. The idea is that it is a self-contained document that looks at the three macronutrients in our agronomic crops. For phosphorus and potassium it looks at soil test levels and the probability of seeing a yield response. This is a precursor to the 4 Rs in many ways. There is also some discussion of some secondary macronutrients and micronutrients as well.”

The information from the recommendations has undoubtedly saved millions of dollars in on-farm fertilizer expenditures, helped contribute to increased yields, and had tremendous environmental benefits, but Culman knows there is still plenty of room for improvement for the 20-year-old document.

“Since then, many things have changed in agriculture. We grow crops very differently than we did 20 years ago. We grow soybeans differently and genetics are different,” he said. “This was before glyphosate resistance and there is a lot more no-till now which changes how nutrients are cycled in soils. With the backdrop of water quality issues in the state today there is a lot of justification in re-looking at this and a lot of interest in revising things a little. Certain soil types are going to require more or less fertility  — not two or three times more or less — but we are looking at this with an open mind. We are entertaining the possibility that these recommendations may have been too high or too low.”

With funding from the Ohio Soybean Council and soybean checkoff, the massive undertaking really got started in 2014.

“Checkoff funding is really important for these kinds of projects because federal dollars are not used for regional research like this,” Culman said. “Last year we started our first field season looking at phosphorus and potassium in soybeans and that is continuing this year. We are looking at nitrogen, phosphorus and potassium in corn and wheat too.”

The research will result in a new updated document and recommendations within a few years.

“We need good information and our process needs to be transparent. Several years from now we will have 50 and 100 site years per crop and nutrient to look at. That is the goal,” he said. “We are trying to collect as much data as we can in the next few years and see what it means and extract as much information from that as possible. My timeline for an official revision would be in three to five years. It may be broken down by state and even region, so it may not be tri-state any more. I am in contact with the state specialists at Michigan State and Purdue to see what we are going to do moving forward.”
The success of the project is largely dependent on the cooperation from farmers and private agribusinesses.

“The original was done primarily on OSU research farms over 30 or 40 years. We do not have that luxury now. The success of this project is incredibly reliant on farmers buying into this and wanting to be part of the solution for better nutrient management,” Culman said. “We are branching out to work with not only Extension researchers, but also people in the industry like crop consultants, ag retailers, co-op agronomists, and CCAs. The devil is in all the details of coordinating that. There are a lot of moving parts to this.”

This year the field trial numbers will be increasing as the research continues.

“We have more than 20 growers putting trials out. Last year we had 10. The majority of the folks we are working with will be putting in trials this fall when the majority of fertilizer is applied, though there are a few sites going in this summer,” Culman said. “We have around 30 different OSU sites going in this year as well. We are working with a dozen or so private consultants and if others are interested in working with us, we are more than happy to add more. We are getting the wrinkles ironed out, but we have money in the budget to put out a lot of different sites. We are trying to scale up and make farmers aware that we are running fertilizer trials. We are appreciative of the growers who are working with us now and hope to get more. We are very flexible about the size of the plots.”

To get relevant results, Culman is looking for adequate representation of the soil types in the state.

“We are working at getting a good representation of the variability that is out there in the state. There are sites on research farms and small plot work on private land. It is a mix of small and large plots but it is all replicated to get sound data,” Culman said. “We are especially interested in low testing soils. If you are just renting new ground where the fertility has been neglected — those sites are hard to come by. The research is really looking at low testing N, P and K fields. There are a lot of well-managed, productive fields already. We are looking for as diverse of a sample as we can get.

“For a field plot, we look at a pre-season soil sample, then mid-season tissue test, yield, and nutrient content in the grain for an elemental analysis. You scale the test strips to the size of your equipment. The farmer can pick the nutrients they want to look at. So for soybeans and phosphorus, for example, where they use a spinner spreader, they would have a strip of phosphorus and an unfertilized strip. That will be replicated three times. Then we do a mid-season tissue sample at flowering and then look at yields and get some of the grain for analysis. A lot of the farmers want to do it themselves and we can work with them to do it as well.”

The participants get to see all of the results for their plots and receive an honorarium for their participation and cooperation.

“It is a commitment of time, but we are flexible and it is not a large time commitment. All the data is anonymous and all the data from the individual’s farm will be given to them. We are just trying to see what is out there,” he said. “It does cost a little bit of time but we hopefully pay for that. And really, the only way you are going to know what is happening with your fertility is if you conduct a trial.  In terms of smart economics, this can really help with one of the main things you are spending money on. You don’t want too much fertilizer out there but we don’t want too little either.”

The individual results will be combined for the eventual recommendations.

“We envision the next generation of recommendations to include digital media like apps or software to generate fertility recommendations based on your soil test values. We see this as a more fluid document that can be revised as we learn more. An electronic resource is more conducive to those kinds of changes,” Culman said. “The data will be published and available so farmers can have it to make their own decisions. Keeping this process open and transparent will help dispel some myths about nutrient management.”

With the incredible focus on nutrient management and water quality issues in Ohio in recent years, the reassessment of fertility recommendations takes on even broader implications than 20 years ago, particularly for phosphorus.

“We can either be proactive about this or sit on our hands and let this be regulated. Most people I have talked to are reserving judgment about whether the current phosphorus recommendations are too high or too low,” Culman said. “We know there are problem areas out there and that there are all kinds of approaches. This is primarily a document focused on rate, but maybe rate is not the most important part of improving water quality. We don’t know that yet.”

In the end, no fertility recommendation is going to be perfect for every field every year, but Culman thinks that significant improvements can be made that will lead to improved nutrient management on farms in the future.

“There are some people who say the Tri-State is too high, some say it is too low and some that think it is right on. We want to get growers the best possible information to manage their farms and give them the confidence that our information is reliable. That is what we want to do,” he said. “We want to keep folks that are selling fertilizer honest in terms of their recommendations. You need current information to make the best decisions and we are just hoping to make this a transparent process and provide the best possible recommendations. And, better nutrient management is ultimately going to reduce runoff and provide more nutrient use efficiency and better profitability.  There will never be 100% certainty, but we are hoping to get a lot better information to help growers make decisions.”

For more information, contact Culman at culman.2@osu.edu or (330) 263-3787. For much more on the soybean checkoff, visit the Soybean Rewards web page at http://www.soyohio.org/council/for-ohio-farmers/soybean-rewards/. Also, see the related video at ocj.com by searching for keywords “Culman fertility.”

Check Also

Drought conditions expand but there is some relief

By Aaron Wilson, Ohio State University Extension As of the Thursday July 30, 2020 release …

Leave a Reply

Your email address will not be published. Required fields are marked *