New Fertilizer Recommendation Coming
Efficient and profitable farming depends on accurate soil testing, but fertilizer recommendations for the same batch of soil differ across the nation. A coordinated effort from researchers across the United States seeks to solve that problem.

The U.S. Department of Agriculture’s Natural Resources Conservation Service is giving more than $1.6 million in grant support to the ongoing development of the Fertilizer Recommendation Support Tool, or “FRST,” as an interface website. It is part of a $40 million investment in 31 new projects through USDA’s Conservation Innovation Grants, or CIG, program.

 “The tool will help save money and resources for producers and identify data gaps for crop consultants and scientists,” said Nathan Slaton, associate vice president for agriculture and assistant director of the Arkansas Agricultural Experiment Station for the University of Arkansas.

 Slaton, principal investigator on the national project, said the online tool will provide greater consistency in phosphorus and potassium fertilizer recommendations across state lines. Those two minerals are the primary nutrients from routine soil testing that are used to predict the need for crop fertilization, Slaton explained.

 The idea for the decision support tool came from discussion among the Southern Extension and Research Activities Information Exchange Group, known as the “SERA 6.” They conducted a survey in 2018 to investigate why fertilizer recommendations change across state lines even when using the same soil test.

 “The way it is now, someone can collect a soil sample, put it in two containers, and ship one to the Division of Agriculture’s soil testing laboratory in Marianna and the other to Waypoint Labs in Memphis, and when they get the reports back, even if the soil test numbers are similar, the fertilizer recommendations are different,” Slaton said. “The end user is going ‘Why?’ When that happens, it erodes the end user’s confidence in our science.”

 This is an issue because farmers and crop consultants sometimes send their soil samples to labs outside of their home state. Some producers have farms that cross a state line, or they may farm in two different states. Soil testing has the common goal of determining which nutrients and how much fertilizer to apply. But soil-testing laboratories in the United States use different analytical methods, interpretations and philosophical approaches to fertilizer recommendations, Slaton explained.

 The FRST website will allow a farmer or crop consultant to select their soil type, crop type, geographic region and soil test extractant to provide tailored soil test recommendations. A model for the FRST website is Australia’s Better Fertilization Decision for Cropping, Slaton said.

 USDA noted in its Conservation Innovation Grants award that improving soil-test-based recommendations and their interpretation “has the potential to significantly reduce nutrient

 applications by accurately identifying the critical soil test value.” The soil test value identifies the point at which soil will no longer respond to fertilizer.

 Deanna Osmond, professor and extension specialist for soil fertility and watershed management at North Carolina State University, said most science-based soil fertility recommendation systems in the United States often derive phosphorus and potassium fertilizer guidance from decades-old soil-test relationships.

 “There are states that have not looked at their soil test recommendations for 50 or 60 years, and I think this will give them a more structured environment in which to make their decisions,” said Deanna Osmond, who is also co-principal investigator of the national project.

 Osmond was instrumental in securing the USDA-NRCS funding and creating cohesiveness for the project, Slaton said.

 There have been many changes to varieties, tillage and cropping systems, which need to be captured relative to nutrient needs, Osmond said. In addition to agronomic benefits to make farming more profitable, the tool should also help provide environmental benefits by keeping excess phosphorus out of waterways, she said.

 USDA Agricultural Research Service funding originally jumpstarted the decision support tool project in 2018 following the SERA 6 survey. The new USDA funding provides support to expand the database and continue to build and test the decision tool.

 So far, research scholar Sarah Lyons at North Carolina State University has collected almost 1,500 data sets to put in the legacy database. However, they are “barely scratching the surface” of the needed data, Osmond said.

 While Arkansas dedicates funds for soil fertility research through fertilizer tonnage fees, Osmond said most states do not allocate tonnage fee resources to soil testing research.

 Arkansas has a fertilizer tonnage fee that supports the state’s soil testing program, and soil testing research to update fertilizer recommendations. The FRST will complement decision support software developed for Arkansas by the Division of Agriculture, Slaton said.

 Slaton said that the team continues to look for additional data, team members and funding to support the next phase of state-led soil fertility correlation and calibration trials.

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