Use soil health test as a guide

No-till farmers who are pioneering the way with cover crops and soil health sometimes scratch their heads when getting results from an official soil health test. The report may indicate that they could do better — much better — in certain areas, particularly soil biology.

Use soil health test as a guide

No-till farmers who are pioneering the way with cover crops and soil health sometimes scratch their heads when getting results from an official soil health test. The report may indicate that they could do better — much better — in certain areas, particularly soil biology.

How could they do better when they’re already light years ahead of those who have yet to try no-till or cover crops in terms of replenishing soil quality?

Eileen Kladivko, a Purdue University Extension soil quality specialist, looks at soil health and soil health testing as part of the Conservation Cropping Systems Initiative grant. She and co-workers have several plots in various locations dedicated to soil health. Knowing practices like no-till and cover crops help the soil is one thing, she says. Proving it is another.

Kladivko performs simple, visual tests to show how water moves better in soils with both no-till and cover crops, even compared to no-till soil alone. She can set up a demonstration in a classroom to show it. Often called “the earthworm lady,” she can also talk about how long-term no-till tends to increase numbers of earthworms, sometimes drastically.

Key Points

Soil health tests look for more than just nutrient values in soil.

Treat soil health tests as another tool, not the absolute answer to soil testing.

Test values can vary depending on how the lab calibrates tests.

Dig further

What is more difficult to do, Kladivko says, is pull samples and analyze them for “soil health,” and receive results that make sense. One issue is that soil health testing is new. “There are only about three labs in the country that do it,” she says.

Another issue is that the labs tend to compare soils from other areas to soils in their database. Variations from one area to another can greatly affect the kind of microbes found in the soil, she notes.

A trip to a lab that does actual soil health testing helps answer some questions. Brookside Labs in New Bremen, Ohio, is one of the labs currently doing soil health sampling. Brookside has a long history in the soil testing business.

“The soil health test we do here is just another tool to help manage your soils better,” says Luke Baker, an agronomist and lab specialist who oversees analysis of soil health tests at Brookside. “It’s not meant to be a replacement for regular soil testing. Instead, it’s another step you can take to further understand those results.”

Two practical reasons illustrate why the soil health test isn’t a replacement for the traditional soil test, he says.

No. 1, the soil health test gives information about available nutrients, but not pH and buffer pH. At some point that might change, but for now, pH is not part of the soil health report.

Secondly, a soil health test is more expensive because of the lab time and procedures involved. A traditional soil test might cost $12, while one soil health test could cost five times that amount, Baker notes.

So if you send 100 soil tests representing 250 acres for analyses, your bill would be $1,200. If you sent 100 soil health tests, it would be more like $6,000, or more.

The good part is you don’t need to send a hundred soil tests to get information that can help you manage better, Baker says.

If you have a 100-acre field where you no-till and use cover crops, one soil health test could give you information that adds to what you already know from your regular soil tests, he says. The real value comes after you have soil health samples over a five- to 10-year period from the same field. That can help you get a handle on whether changes in management that you make to improve soil health are paying off.

Reasonable expectations

If you send a sample to a lab three states away, or even one state away, the results may not be meaningful until you sit down with a crops consultant who understands the tests and can explain them to you, Baker says.

The tests are typically calibrated on soils most often sent to the lab. An East Coast lab will have different soils with a much different soil profile of microbes than a Midwest lab. That’s why results for your sample run by a lab outside your area may indicate microbes aren’t as high or active as you would think. It may not be measuring the same type of microbial activity.

“Use it as a tool to follow changes over time,” Baker suggests. “You receive information that you can’t get from a regular soil test that speaks to the microbial activity going on in your soil. But it’s a guide, another piece of information. It’s not the ‘be-all, end-all’ test for everyone.”

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Lab tester: Luke Baker oversees soil health testing at Brookside Labs.

A closer look at soil health tests

If you begin researching soil health testing, you’re going to learn about the Solvita test. You will also meet Rick Haney, a USDA researcher based in Texas, who developed the test now being used by the Natural Resources Conservation Service. He pioneered the test that NRCS uses to measure soil health.

Luke Baker says the test for soil health he runs at Brookside Labs is the same test pioneered by Haney. Anyone who runs soil health tests is trying to obtain the same information: How active are microbes in the soil, and how does that affect nutrient availability? The methodology used to get those answers can vary from lab to lab.

The Brookside soil health test delivers a number that only has meaning when compared to other tests. One well-known no-till and cover crop farmer who has concentrated on soil health for decades sends samples that score in the 25 to 30 range. Yet as long as the score is 7 or higher, the soil is likely doing a good job of releasing nutrients that roots can get, Baker says. He has seen samples from long-term no-till fields that haven’t been disturbed for more than 30 years, but that only score in the mid-8 range. However, digging further, he found a test taken from an undisturbed area nearby that scored a 9, suggesting the potential of this soil is not as high as in other soils, and never will be.

The soil health tool helps get a handle on the carbon-to-nitrogen ratio, and helps quantify how much nitrogen could be available from the soil for corn. It can be used as a tool to help fine-tune N rates if you know the history of yields, N rates, soil tests and soil health tests on your farm over time, he says.

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Improve soil: Cover crops help improve soil health, Eileen Kladivko says. This happens over time, and soil health is relative to other soils in the area, making interpretation of test results critical.

This article published in the December, 2014 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2014.

Soil Analysis

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