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A Worm’s-Eye View

Getting “precision agriculture” off the ground may require a better way to look beneath it.
September 26, 2001

A new imaging device that can reveal the composition and contours of underground soil may help to lay the missing foundation of “precision agriculture,” an anticipated revolution in farming that has been slow to materialize.

The bullet-shaped metal probe has a super-hard, sapphire porthole in the side, through which a tiny camera peers, says Dan Rooney, a WI-based soil scientist and entrepreneur. The “soil-imaging penetrometer” acts like a surgeon’s endoscope. As the probe enters the soil, a computer screen above ground shows images from the camera.

“Dirty videos,” Rooney jokingly calls the footage.

Software interprets the images in real time, quantifying qualities such as color, porosity and organic content in soil strata that the probe descends through. The system also records the camera’s depth with an attached gauge and its geographic coordinates by global positioning system (GPS) satellite. The aggregated information allows a scientist to map a landscape three-dimensionally underground and to diagnose the needs of any patch of earth. Rooney described field tests of the device at last month’s meeting of the American Society of Agricultural Engineers in Sacramento, CA.

Hidden Truths

“You drive past miles of corn field and everybody says it’s all the same,” says Illinois farmer John Reifsteck. “But as a farmer I know one area yielded 250 bushels an acre and a hundred feet away another yielded nothing.” Those yields could even be reversed the following year if there was a big difference in rainfall or infestation.

Reifsteck says many farmers already own machines for precision agriculture. This lets them adjust their seeding, fertilizing, spraying and depth of furrows row by row-even inch by inch-with computer automation. But because farmers remain largely ignorant of how the composition of their soil varies beneath their fields, they are flying blind, he says. This could explain why precision farming has yet to deliver predictable crop yields or reduce by much the use of costly chemicals that endanger the environment.

Illinois state soil scientist Bob McLeese says surveying soils is slow and expensive. His agency has nowhere near the resources to do it in the detail that farmers like Reifsteck would like. For example, the state-wide soil survey finished just a few years ago dissects Illinois into patches no smaller than about 100 meters square. But the information for zones 16 times that size may reflect just two soil samples, McLeese says, if the areas looked homogeneous from the sky.

The standard survey tools include a pick, shovel and hand auger, plus a spiral-bound stack of color chips, through which surveyors flip for a match against whatever soils they expose, McLeese says. To estimate proportions of sand, silt and clay, surveyors typically rub some dirt between a thumb and two fingers, then use their judgment. Even with hydraulic machines to extract cores from seven feet down, soil surveys are still limited by the availability of specialists and the speed with which they move their fingers.

On the Soil Horizon

A device like Rooney’s could transform the landscape, McLeese says. Rooney envisions squadrons of technicians on all-terrain vehicles fitted with push-button hydraulics; he’s testing a prototype. Penetrometer imagery and data would travel wirelessly to a soil scientist at “mission control” by cell or satellite connection. With smaller cameras and smaller probes, Rooney says, users could carry the whole system on foot into the thick of swamps and rainforests.

“The potential applications are endless,” says McLeese.

He points, for example, to “carbon credits,” a cornerstone of plans to counter global warming. The United States probably will implement carbon credits in an upcoming five-year plan for agriculture, McLeese predicts. “But they’re going to need some way to measure what a farmer is or isn’t storing,” he says. That’s where the penetrometer might come in.

Under one such scheme, farmers could earn credits for storing carbon in the soil, which reduces the buildup of carbon dioxide in the atmosphere. The decomposed stems, leaves and roots of harvested and buried crops represent carbon that the plants once took from the air as carbon dioxide. But the carbon would have to be measured.

Rooney says his small company, Earth Information Technologies, is looking for a larger partner to do the hardware manufacturing while it focuses on the software. Agricultural engineer Glen Riethmuller, who runs a research farm in western Australia, intends to buy one of Rooney’s devices as soon as he can. “We’ve got one guy spending his whole life digging holes,” he says, “and it’s bloody hard!”

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