Idaho farmers expand productivity through variable-rate lime - See more at: http://www.capitalpress.

Published online: Oct 09, 2013
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ASHTON, Idaho-Thousands of farm acres near here are more productive thanks to a waste pile at a shuttered sugar factory and federal funding aimed at keeping nitrates out of groundwater.

The Natural Resources Conservation Service and the Yellowstone Soil Conservation District are winding up a joint project promoting variable-rate lime application to raise the PH of the region's basic soils, depleted of acidity by years of heavy snowmelt.

Success led the program to expand to 54 growers, covering 19,293 acres. John Taberna Jr., with Blackfoot-based Western Laboratories, samples soil PH within 2-acre grids, providing lime prescriptions according to specific areas rather than generalized throughout a field. The maps enable Valley Agronomics to spread the lime at rates ranging from 0 to 9,000 pounds per acre. Plants can't effectively absorb nitrogen in soils with low PH, contributing to fertilizer leaching.

The lime-a byproduct of sugarbeet processing sourced from a defunct Idaho Falls plant-is cheap, but transportation costs are significant. The $923,386 grant covers about two-thirds of what growers pay to develop a prescription map and spread variable-rate lime. Applications were taken from 2010-2012, and work continues.

Valley Agronomics crop adviser Brian Miller said variable-rate lime application costs roughly $60 per acre, about $20 higher than uniform spreading, but prescription maps can be reused.

"In the Ashton area and the thousands of acres that are grown here, there are only two growers I know of that haven't had us put lime on," Miller said.

When high nitrate levels began surfacing in the region's wells around 2000, Ken Beckmann, Fremont County's NRCS district conservationist, explained officials touted soil tests to hone nitrogen use. When that approach failed, they looked at PH, recruiting 10 growers from 2008-2010 for the initial variable-rate lime trial.

They expanded participation for the ongoing trial, which started in 2010. Beckmann said detectable reductions in water nitrate levels may still be a few years off.

About 12 years ago, long before the federal program, Ashton area growers Tom Howell and Bill Bowersox commenced with uniform lime treatments to address declining yields.

"I think the lime program is just as important as the fertilizer itself. Where we've done it properly, we've probably kicked our yields up a good 20 bushels per acre," Howell said, adding more neutral PH levels also control weeds.

Bowersox said barley is especially sensitive to PH and has shown the greatest yield improvement in the region, where most crops are grown on dry land. He intends to stick with variable-rate lime and expects other growers will do the same.

Miller said Valley Agronomics has fielded inquiries from other growing areas interested in the Ashton method, which he believes holds promise for basic soils in Northern Idaho and near Portland, Ore., and Seattle.

"I've heard of another project similar to this in Virginia, but I haven't heard of any on our side of the country like this," Miller said.

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