Soil moisture sensors tell you when, how much to water

01/20/2012 01:13:00 PM
By Tom Burfield

The system can help save labor, save water, increase yields, improve the quality of the product and reduce environmental risks, he says.

Miller has been conducting his research in small plots at a research station for five years and now is beginning to conduct tests at larger locations in satellite research sites with varying soil types.

In one such test, he compared his results irrigating with sensors in a test plot in grower Billy Jenkins’ field in Jefferson, S.C., with Jenkins’ traditional method of irrigating once a day.

“We were able to get 15 percent to 20 percent over his yield and used 20 percent less water,” Miller says.

During the test, Jenkins noted that the system started irrigating whenever the water level dropped, no matter the time of day, whereas on the control portion, he would irrigate at certain times each day, whether it was needed or not.

The system would be “worth its weight in gold,” especially on farms of about 40 acres or more, he says.

The number of sensors can vary, depending on the number of soil types in a field. Usually one or two sensors are sufficient for up to 75 acres.

They are fairly durable. Miller has used 12 sensors for five years with few problems, but they are electronic components, he emphasizes, and need to be installed properly.

The Enviro Scan sensors he uses are made by Sentek Pty Ltd. of Kent Town, South Australia. They’re available in the United States from Earthtec Solutions LLC of Vineland, N.J.

A simple manual monitoring system with two sensors and a weather station can cost less than $3,000, says David Lankford, general manager for Earthtec.

A more elaborate setup with automatic irrigation and controller valves can range from less than $5,000 to $30,000, depending on the irrigation system the grower already has.

Sensing improvement

Coosaw Farms in Jefferson has been using sensors for about eight years, says Brad O’Neal, operations director.

“They’ve definitely worked,” he says. “We’re very pleased with them.”

Coosaw Farms uses six sensors to monitor 30 acres of blueberries and 70 acres of cabbage on various soil types. During the spring, they’re used on 65 acres of watermelons along with blueberries.

O’Neal hopes to incorporate more sensors into the farm’s 500 acres over time.

He says quality is improved, and yields can increase by 10 percent, depending on conditions.

He found the system to be most effective in drought years, when low humidity and high temperatures “are really sucking the water out.”

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