Field-Moist Soil Testing Makes A Comeback

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A soil-testing technique first perfected decades ago, field-moist soil testing is once again generating a buzz within the precision ag industry due to its reported higher level of reliability when measuring soil nutrients.

Mountain View, CA-based Solum, Inc. is pioneering the technology via an automated, field-moist preparation system. This was the subject of a recent CropLife Media Group Webinar, which was presented by Mike Prenier, Solum’s co-founder and president, and Landon Morris, the company’s vice president of marketing and business development, along with Iowa State University professor Dr. Antonio Mallarino.

Dry Vs. Moist

Soil testing estimates a section of a field’s probable nutrient sufficiency and response to fertilization. Basically, the tests are used to determine how much nutrient is needed to optimize yield response, although soil tests cannot predict actual yield levels due to the myriad of other factors that affect yield.

According to Solum, the time of sampling in the field or during sample handling at the laboratory may partially account for high variability of STK (soil test K) results. Iowa State University research in the 1960s and 1970s demonstrated soil K extracted from field-moist samples was better correlated with crop K uptake than K extracted from air or oven-dried samples.

However, dry soil testing remains the more widely used technique, mostly because the practicality of large-scale field-moist soil preparation initially brought with it more questions than answers, a predicament that Solum’s system pledges to alleviate.

“The dry test has no good predictive capacity along with a lot of variability,” says Mallarino. “So we thought ‘maybe it’s time to bring back the field-moist test.’”

Advantages Of Automation

A hallmark of the Solum system is the level of automation that users enjoy.

Whereas with most conventional dry-testing systems, a grower or retailer must first homogenize the sample by grinding it before allowing it to dry for 12 to 24 hours prior to testing, with the field-moist system, users either simply mail the sample in to the company’s Ames, IA, facility (which will begin accepting samples this fall) or test the sample immediately with one of Solum’s field-deployable No Wait Nitrate Field Labs, which delivers lab-quality soil nitrate results in minutes.

“The key is the level of automation that we’ve been able to scale to handle field-moist samples in a consistent framework for homogenization,” Preiner says. “That also enables soil-N testing in real-time.”

Field-Moist Implications

As creatures of habit, growers and retailers alike may be slow to make the switch to field moist, but the benefits of making such a move are tangible.

According to Solum, those benefits are two-fold: 1) Measuring field moist is a better predictor of a crop’s potassium needs, and 2) Moist measurements are more consistent with time and allow users to better identify long-term trends in a field. 

“When you dry and grind a sample, that increases the potassium level that you measure,” Mallarino says. “But the really important thing to consider is that it does it in a way that makes it more difficult to predict crop response.”

In 2011, Solum launched a comparative analysis of field moist and traditional soil preparation techniques across multiple cropping environments. The company surveyed 20 locations with multiple retailers across multiple regions with varied fertility histories, and found the variability introduced by drying and grinding indeed made the field-moist test the better option. 

“There’s a lot of unpredictability that’s introduced from drying and grinding of soil samples, and it varies tremendously from field-to-field,” Prenier says.

Universal Compatibility

Early feedback on the field-moist system is encouraging, as one facet of the program users are receiving quite well is the data and analytical reporting software that’s included. A cloud-based system with mobile access across all platforms and compatible with all current precision ag systems, users clamor for the ease-of-access to their own data that Solum allows.

“Again, this system is online and very transparent — and can be shared with groups or subgroups,” Prenier says. “We’ve set this up to be very, very easy and sharable at any place, at any time.”

Grassi is the Assistant Editor for the CropLife Media Group, including CropLife and CropLife IRON magazines and the PrecisionAg Special Reports. He joined the staff in February 2012.

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