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Corn+Soybean Digest

New Watering Method Shows Promise

A n innovative twist on subsurface drip irrigation may safeguard your crops from drought and boost yields.

Norris Powell, a soil physicist at Virginia Tech, has designed a user-friendly irrigation system that fits almost any field, regardless of its shape.

Compared with the shallow subsurface irrigation used in the arid West, the Virginia Tech system runs much deeper. A tractor pulling a subsoil shank places 1/2" tubing 14" deep to avoid freezing and allow for cultivation. You still need pumps and a water source. Filters on the pumping system clean the water to keep the tubing's micropores open.

In Virginia Tech test plots from 1986 through '97, corn watered and fertilized through the system yielded an average of about 200 bu/acre. The plots received irrigation totaling 8-12" of water at a cost of $1.50 per acre for each inch. Non-irrigated control plots yielded, on average, about 114 bu/acre.

"We could see yield as high as 225 bu/acre," says Powell.

The system isn't quite perfect, he concedes. It doesn't water within the root zone of seedlings, so it won't help get your crop out of the ground. Start-up costs run about $800 an acre for materials and installation. The tubing lasts about 10 years, he says.

Spread expenses over 10 years at 9% interest, and growers need to make an additional $113 per acre from higher yields to pay for it, he calculates.

The government might cost-share some expenses, Powell adds. Its environmental benefits may fit the Farm Bill's Environmental Quality Incentive Program. Local soil and water conservation districts would determine which farm improvements qualify.

"It uses less water than conventional overhead irrigation. Timers set to irrigate each day, or twice daily, give the crop nutrients as it uses them. Also, you avoid runoff."

If designed properly, the system works on fields with as much as 3-4% slope.

"Work with an irrigation specialist," Powell stresses.

While it's simple to install, it's not a do-it-yourself project.

The system had its first major real-life workout last summer. Working with Powell was grower Phil Wyne. He tried it on 12 acres on his Suffolk, VA, farm. Netafim Corp. supplied irrigation materials for the 800'-long demonstration.

Joe Davidson, of Berry Hill Irrigation near Clarksville, VA, installed the system.

That demonstration featured four acres of soybeans that yielded 60-65 bu/acre. Dry weather reduced non-irrigated bean yields to 20-25 bu/acre.

"We have seen drip irrigation used in high-value crops for a long time," says Davidson. "This brings the technology to major field crops like cotton, corn and soybeans. The system delivers water and nutrients to the root zone where they're needed. It's got all the logistics in place: You get what needs to be delivered going where it needs to go, when it is needed."

This system will even work in the Midwest, believes Powell. He anticipates that, over the next 10 years, Virginia growers may have as many as 200,000 acres of row crops growing under subsurface drip irrigation.

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