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Sampling soil this fall can save on fertilizer next spring

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A farmer conducts a soil sample out in his field in Kansas.

To help with high fertilizer prices, a Midwest soil scientist recommends farmers test their soil. They may have higher than expected nutrient levels, which means they may be able to cut fertilizer rates without penalizing yields next year.

The best time to sample soil is immediately after fall harvest and before the soil freezes.

“You may find out that you may not need as much fertilizer, which is good news,” said Dorivar Ruiz Diaz, professor of soil fertility and nutrient management at Kansas State University. “You have to know what you have in the soil.”

K-State recommends sampling every two years for phosphorus and potassium.

With high fertilizer prices, Ruiz Diaz said soil sampling is “a farmer’s best friend for a strong investment.”

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Soil nutrients are analyzed at the K-State University soil testing lab.

Fertilizer prices for the next growing season are expected to be comparable to last spring, although it could change. Those in the industry don’t anticipate problems with availability.

“It’s just that fertilizer could be expensive ahead, so we recommend farmers let us know how much they think they’d need,” said Bruce Ball, owner of Rural Gas Inc., in Belleville, Kansas.

The conflict with Russia and Ukraine is behind some of the spike in fertilizer prices. Some of the natural gas, one of the key ingredients used to make fertilizer, was coming out of Russia. There’s less being produced because of the war, resulting in high prices. There are other fertilizer plants in Europe, but a lot of them use expensive natural gas as an ingredient, Ball said.

Last year, a dip in supplies of fertilizer products was blamed on the fierce cold snap in Texas in January 2021. There was lack of natural gas, fertilizer plants were shut down, and pipes froze.

Earlier this fall, U.S. Department of Agriculture Secretary Tom Vilsack introduced a $500 million program to increase the production of fertilizer made in America. While some fertilizer is now coming into the U.S. on barges, river levels are too low to move them because of drought conditions.

Farmers are hoping for pleasant fall weather to be able to apply anhydrous ammonia and take some of the pressure off using the other forms of fertilizer, dry or liquid, Ball said.

By saving on fertilizer and taking advantage of the current good grain prices, there are good opportunities for farmers who maintained a soil test above optimum, Ruiz Diaz said. A test that comes back showing a problem with low pH, for example, can benefit from adding lime. It will make nutrients more available to plants and help with uptake, Ruiz Diaz explained.

As he put it, “The last thing we want to do – is waste fertilizer.”

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A close-up view of the K-State soil testing lab.

What to know about soil testing

Farmers collect the sample themselves with a soil probe or a consultant will provide the service.

When to do the test

Every two years is recommended (instead of the previous suggestion for three to four years).

How to do the test

Sample the soil at a 6-inch depth for immobile nutrients. This gives an accurate sample for phosphorus, potassium, pH, Ruiz Diaz said.

Sample the soil at 24 inches for mobile nutrients such as nitrates, sulfur and chloride.

With drought conditions, it’s not easy to get down to 24 inches, Ruiz Diaz said. In that case, sampling at 18 or 12 inches can provide some information.

“That is better than nothing,” he said.

Farmers from anywhere across the country can send samples to K-State, or can use another lab, many of which are run by universities. Soil samples can be submitted to local extension offices in Kansas, which then forward the samples for lab analysis on the K-State campus in Manhattan.

Reporter Amy Hadachek is a two-time Emmy Award winning meteorologist and a storm chaser who earned her NWA and AMS Broadcast Meteorology Seals of Approval. She and her husband live on a diversified farm in Kansas. Reach her at

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Reporter Amy Hadachek is a two-time Emmy Award winning meteorologist and a storm chaser. She and her husband live on a diversified farm in Kansas. Reach her at

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