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College of Food, Agricultural, and Environmental Sciences


Want to Save on Fertilizer? Run a Soil Test

January 30, 2008

ADA, Ohio -- With fertilizer prices continuing their upward trend, a soil test is the best tool available to farmers that can help them manage their crops while leaving more money in their pockets.

According to a U.S. Department of Agriculture Economic Research Service report, less than 40 percent of corn acreage in the United States was soil tested in 2000 (most recent data available) to make fertilizer management decisions. Robert Mullen, an Ohio State University Extension soil fertility specialist, speculates that number has increased, but those growers not utilizing soil testing are missing out on a huge money-saving opportunity.

"In the past when fertilizers were cheap, there wasn't much of an economic penalty in over-application, so some producers were supplying more than necessary," said Mullen, who also holds an Ohio Agricultural Research and Development Center appointment. "But today, when commercial fertilizer prices are reaching unprecedented costs, that is no longer the mentality to take. Those growers who do use soil tests recognize their value."

That value is the ability to measure the level of nutrients in the soil, such as soil pH, nitrogen, potassium and phosphorus, and from those numbers, make a more informed decision in fertilizer application that's good for the crops, as well as a farmer's budget.

Mullen will be on-hand at the Conservation Tillage and Technology Conference Feb. 22 to walk participants through the soil testing process, how to evaluate the results, and follow recommendations based on specific crop production systems. Mullen will then share Ohio State University research data that supports OSU Extension recommendations.

"You start by putting yourself in their shoes. I'm a producer. I get the soil analysis and I have this piece a paper. What matters on that sheet of paper and how do I use that information to make a decision?" said Mullen. "There is no cookie cutter recipe for fertility management because everyone has different soils and different cropping systems. The idea is more of a case study approach. It's to get them to think about the information in a different way and what they should go through when they start making decisions."

Mullen said that soil tests are an effective resource tool for fertility management because the analysis lets farmers know which nutrients they need to invest in and which ones they can do without for a certain period of time.

"Why sink more money into your crop production system when you don't have to?" said Mullen.

Take phosphorus and potassium as an example, said Mullen. With both nutrients skyrocketing in price, a soil test would reveal how much potassium and phosphorus are currently available in the soil. Unlike nitrogen, phosphorus and potassium are not directly related to yield, so once they are present at adequate concentrations adding more would not result in additional productivity.

"Once you reach a certain concentration of potassium or phosphorus in the field, you don't need to add any more fertilizer, and a soil test would be able to tell you that," said Mullen. "Without it, you may be paying for something you do not need."

Other things growers can determine from a soil test include soil pH, which reveals whether or not lime is needed; buffer pH, which indicates how much lime should be applied; and the amount of fertilizer necessary based on specific cropping systems.

In addition to giving a presentation on soil testing, Mullen will also provide information on the new Ohio State University nitrogen rate calculator, as well as show farmers how they can introduce manure into fertility management recommendations.

The Conservation Tillage and Technology Conference will be held Feb. 21-22 at the McIntosh Center of Ohio Northern University in Ada, Ohio. The conference is being sponsored by Ohio State University Extension, the Ohio Agricultural Research and Development Center, Northwest Ohio Soil and Water Conservation Districts, USDA Natural Resources Conservation Service, USDA Farm Service Agency, the Ohio No-Till Council, and Wingfield Crop Insurance Services.

Registration, received by Feb. 15, is $30 for one day or $50 to attend both days. Registration thereafter is $40 for one day or $60 to attend both days. The fee includes breakfast and lunch.

To learn more about the conference or to register, log on to, or contact Randall Reeder at (614) 292-6648 or

Candace Pollock
Robert Mullen