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November 23, 2015

Paul Hollis
Auburn University College of Agriculture

Auburn University’s new Soil Quality Index (SQI), developed by agronomy professor Charles Mitchell and other researchers, could help the state’s farmers increase production and conserve natural resources.

“What’s your SQI?” Researchers at Auburn University are hoping this soon will become a common question among the state’s farmers.

Charles Mitchell, a professor in the College of Agriculture Crop, Soil and Environmental Sciences Department and an Alabama Extension agronomist, explained that the Alabama Soil Quality Index, or SQI—the first of its kind in the South—is a new measurement of soil health that should help Alabama farmers improve production and conserve natural resources.

“For 60 or 70 years now, we’ve been throwing fertilizer and lime on the soil, trying to help farmers get by on some pretty darn poor soils,” Mitchell said. “We thought we needed to do something to change that, so we came up with the Alabama Soil Quality Index.”

A previous survey of central Alabama cotton fields revealed that organic matter in the state’s soils was almost nonexistent.

“In other parts of the world, our soils wouldn’t even be considered soils; they’d be considered simply ‘dirt,’” Mitchell said. “By definition, soil must have organic matter.”
The survey—conducted in 2001—indicated that 55 percent of fields had soil organic matter of less than 0.4 percent, and 67 percent of the fields surveyed had a hardpan within a few inches of the surface, even though farmers were doing in-row subsoiling. At the time, 85 percent of the producers were not using a cover crop, which exposed the bare soil to erosion for six months during the year. On the other hand, most growers were soil testing and then liming and fertilizing based on the results of those tests.

“The ‘Old Rotation’ (circa 1896) experimental field on the Auburn University campus has shown that soils with less than 2 percent of organic matter don’t have a high yield potential,” Mitchell said. And while the Old Rotation has been the impetus behind the development of the SQI, soil samples were taken from 300 other locations throughout the state to help form a basis for the index.

“We feel confident the index reflects the quality and the health of the soil being tested,” Mitchell said. “This also would be useful for soils in Georgia and Mississippi, but not in the Midwest. All of the information we’re getting now about soil quality is coming out of the Midwest, and that’s a different world from what we have in Alabama.

“Some states have already done this, including Cornell University, but our index is unique to the South, and it’s less expensive to run than others.”

The SQI was developed with the following objectives: 1) make producers aware of soil quality/soil health; 2) suggest ways of improving soil quality/soil health; 3) use existing, low-cost, soil test methodologies; 4) use existing, routine, composite soil samples from producers; and 5) provide information in a simple, easy-to-understand manner. Also, best management practices will be recommended to help producers improve their SQI value.

The SQI tests for soil group, soil pH, phosphorus and potassium rating, base saturation, soil organic matter, nitrogen mineralized, soil respiration, aggregate stability and metals.

“We wanted to have specific recommendations for users of the index, so we linked the SQI to Natural Resources Conservation Service best management practices,” Mitchell said. “If you have low organic matter, we’ll recommend a practice like no-till or cover crops to help build organic matter.”

The SQI score is based on a scale of 0 to 100, and each category is color-coded. A total SQI of 80-plus is green and indicates a high soil quality, with a recommendation to maintain current practices. Fifty to 80 is yellow and indicates moderate soil quality. Growers who fall in this range are advised to continue current practices but to consider implementing more best management practices. Less than 50 is red, indicating poor soil quality, with a recommendation to implement one or more of the best management practices.

“We want our soils to be healthy enough to grow row crops, fruits and vegetables and forages,” Mitchell said. “This index can be reviewed every few years to ensure that your soils are improving.”

Taking a sample for a SQI is no different from taking a routine soil sample for nutrient management, Mitchell said.

“Considering the cost of the sample, you can’t afford to take it from every 10 acres of land,” he said. “Select a field you want to evaluate, and take a sample from that field—from any small part of the field or from the entire field. Be sure to take a composite sample. When submitting it, ask specifically for the SQI test. It will take a little longer to complete than routine soil samples. While fall is the best time of the year to take a sample, you can take it anytime.”

The cost of the index is $50. For more information, contact Mitchell at 334-844-5489 or, or go to the Auburn University Soil Testing Laboratory website at

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