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Corn+Soybean Digest

Pay Dirt From pH

Corn and soybean farmers will soon have access to a new data-collection tool that promises to save them money and boost crop yields. Thanks in part to a USDA Small Business Innovator Research grant, Veris Technologies, Salina, KS, has developed a unique instrument called the Soil pH Manager. It records soil pH every 10-12 seconds while moving rapidly through a field.

“We know soil pH varies much more than what a 2.5-acre grid can accurately measure,” says Eric Lund, Veris Technologies president. “That's why we've devised a better way to get lime recommendations.”

The Veris pH sensor is designed to work efficiently with global positioning systems and variable-rate machinery, says Lund. In 2003 company field tests, the Soil pH Manager improved lime application accuracy by 37%, compared to fields either applied at a standard blanket rate or at a rate based on recommendations from 2.5-acre grids.

“We've really improved the accuracy of lime predictions,” Lund adds. “The increased accuracy represents about a one-third ton per acre savings in lime.”

The new soil sensor, which should be available for use at a number of ag fertilizer dealerships this spring, is also quick and thorough. At a maximum field speed of 10 mph, the Soil pH Manager can record between 5 and 10 pH samples per acre, providing 12-25 more data points than fields sampled in a typical 2.5-acre grid. Results from the on-the-go sensor are recorded instantaneously, notes Lund, whereas results from grid soil sampling might take days or weeks.

Depending on the services offered, Lund expects the cost will be about $6-10/acre.

Scott Staggenborg, northeast area extension agronomist at Kansas State University, agrees that this new tool offers advantages over grid soil sampling. “The biggest thing I see with this equipment is getting real-time data,” he says. “Within a matter of hours of using it, you could go back in the field and apply variable-rate lime.”

The extensive data that the new sensor generates should also help farmers make better decisions and avoid mistakes. “With an on-the-go sensor, you cover the entire field, and you get a much clearer picture of what's happening,” says Staggenborg. “The beauty of this technology is that if you have an unrepresentative data point (from grid soil sampling), this will find it. You'll get an inexpensive, dense and rapidly collected data set that can improve your understanding of yield variability.”

Although acidic soils predominate over the entire eastern half of the U.S., low-pH soils are becoming more prevalent further west. “Any farm east of Saline County, KS, probably needs lime somewhere,” says Staggenborg. “I've actually found areas of fields in northeastern Kansas with a pH of 4.”

South Dakota soils are generally high in pH, but pH readings in the low 5s can still be found in many fields. “In reality, there are parts of a field that are low in pH, when the field itself may average high,” says Jim Gerwing, South Dakota State University extension soil scientist. “So, variable-rate lime applications could be of value here as well.”

Problems can arise from fields that are over-applied with lime as well as under-applied, says Staggenborg. He cites herbicide carryover concerns from high-pH soils as an example. He also says just about every farm east of Manhattan, KS, has some soil pH issues that need correction.

The Soil pH Manager is just one more tool being added to the Mobile Sensor Platform that Veris Technologies originally developed to detect different soil types and textures by examining soil electrical conductivity (EC). Lund says that original tool, the Veris EC Surveyor, has proved itself useful in finding underlying clay pans and a range of soil types and textures that impact yield.

The Veris pH sensor, when combined with the electrical conductivity instrument, should be useful to almost any farm operation, says Lund. Staggenborg concurs. “These tools will generate another data layer that will add to all the other data layers we already have,” he says. “They should help us discover trouble spots we might not have discovered with grid soil sampling alone.”

Bob Narem, a Twin Brooks, SD, crop consultant, has been using the Veris electrical conductivity instrument to measure soil properties since 2001. In conjunction with yield maps, grid soil sampling and a farmer's knowledge of the ground, this instrument has helped Narem's farmer-clients create management zones with varying yield goals, plant populations and fertilizer and herbicide recommendations.

All three factors that lead to high soil electrical conductivity — fine-textured soils, high water content, and elevated salt levels — are the same factors that would indicate a need for tiling. “This technology gives us wonderful maps to use for tiling,” says Narem.

Staggenborg also envisions using the new soil sensor to vary soybean inoculant levels in areas where low pH soils slow or hamper natural inoculation. He adds that fertility could also be varied based on yield goals.

Will the new on-the-go soil sensor replace the need to grid soil samples altogether? Neither Narem nor Staggenborg think so. “This will just enhance what we are already doing,” says Narem.

Soil tests done in a lab will likely still be necessary to confirm readings in the field from new, on-the-go sensors, predicts Staggenborg. “With this new technology, we may only need to soil sample certain spots of fields where we have concerns,” he says. “Or we may only need to soil sample fields every five to seven years. But soil sampling will probably be needed to make sure lime and fertility rates are on track.”

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