Water Smarter

Soil-Moisture Sensibility with Sensors

AquaSpy soil-moisture sensors with telemetry transmit soil-moisture data wirelessly to laptop or cell phone. (DTN/Progressive Farmer photo by Debra L. Ferguson)

During the corn bull market of the early 2010s, Coahoma County, Mississippi, farmer Pete Hunter pulled out all the stops to make sure his crop got everything it needed. Unfortunately, he consistently overwatered some of his heavy clay fields, causing yield and revenue to fall.

Hunter vowed to do a better job monitoring moisture the next time around. There was only one problem on the 4,800-acre cotton, corn, soybean and wheat operation: "This was too big of a farm for me to be running around by myself with a moisture probe poking the ground all day," Hunter said.

So, he decided to make his farm a little smarter. He purchased AquaSpy soil-moisture sensors with telemetry, which transmit soil-moisture data wirelessly to his laptop or cell phone. Government cost-share programs aimed at improving water conservation in the Delta offset the cost of the sensors and telemetry, Hunter explained.

During the first season with the new technology, Hunter rose at 3:30 a.m. daily to get ahead of the learning curve for the new sensors. It took a couple of hours each day to figure out what the graphs on his laptop were telling him, but eventually, he could synthesize the information in about five minutes.

"There are no magic numbers to look for," Hunter said. "You just start watching the graphs. During the day, there will be a stairstep down of your water availability. It will fall and level off at night when there is no photosynthesis. You have to establish a median line and understand when soil moisture reaches that line, you need to pump water."

The sensors use an electronic capacitance probe to take a reading, which provides the volumetric water content in the soil. The soil-moisture information is carried over a cellular network.

START OUT AHEAD

For Hunter, sensors and telemetry "are about getting ahead, so the crop doesn't stress before I start irrigating," Hunter said. "You can evaluate soil moisture before you leave home for the farm and have your to-do list for the day."

It's also helped Hunter do a better job of watering his heavy clay soils, which he had typically overwatered. "I realized what I had been doing wrong -- irrigating based on how the crop looked -- especially during hot spells."

Hunter added that Mother Nature can always turn good water management on its head. "We can make the smartest call in the world on when to irrigate, and after we're done, the sky starts spewing forth, and we wish we hadn't."

Hunter recently turned over management of the farm to two close friends who farm nearby, John McKee and Bo Crumpton, and retired -- sort of. Hunter continues to manage telemetry on the farm and drives a tractor or sprayer when needed.

For McKee, telemetry is a step toward the ultimate smart farm, where everything on an operation is connected and communicating.

For example, his tractors and sprayers instantly transfer data on planting and spraying directly to the cloud via Ag Leader's AgFiniti mobile app rather than recording the data on a thumb drive. "Not having to consolidate all that data manually saves me a lot of time," McKee explained.

He can also set up learning blocks with the app, for example, by changing plant population in the field. The data can be reviewed postharvest when yield results are in. The app can be used with any mobile device.

CENTER-PIVOT CONNECTIVITY

About 60% of the farm's center pivots are managed by AgSense telemetry, Hunter said. Pivots can be monitored, sped up and shut down remotely. "We have one fully electric pivot that we can start up and shut off with telemetry," he pointed out. Equipping a single center pivot with telemetry costs an average of $1,500.

For McKee, the big payback for center-pivot telemetry is the reduction of legwork. "During the summer, when we have center pivots running, we don't have to drive 20 miles to check on one. We can see instantly if it's stuck or running. It saves a truck, gas and a man's time. Once again, it's machinery replacing human beings. That's the march of progress I guess."

Telemetry also helps McKee immediately assess the effect of rainfall on soil moisture, always a tough call for irrigators. "If your center pivot is running, and you get a half-inch rain, do you shut off the pivot or not? Telemetry will help you quickly make that decision," he said.

Center-pivot telemetry also alerts Hunter to would-be copper crooks. "At one time, we were having a lot of trouble with thieves stealing wiring harnesses off the pivot for the copper," Hunter notes. "The pivot sends you a 'wire theft' text if the wires are cut."

TAILWATER TELEMETRY

About 10 years ago, Hunter, Natural Resources Conservation Service (NRCS), Delta F.A.R.M., U.S. Geological Survey, the Gulf Coast Association and the U.S. Army Corps of Engineers constructed a 22-acre tailwater pond and a separate holding pond on Hunter's farm as a showplace for water conservation. The farm paid a percentage of its cost.

Tailwater recovery ponds are designed to collect excess irrigation water and storm runoff. Hunter's tailwater pond holds more than 160 acre-feet of water and is connected to underground pipes used to irrigate.

Both ponds are completely automated with water-level sensors and telemetry. When water gets low in the holding pond, sensors trigger an automatic shutoff of water to the tailwater pond. When the tailwater pond is full, the pump from the holding pond automatically shuts off.

Through telemetry, Hunter is always aware of the status of the ponds. He can also control both ponds' pumps through his laptop or cell phone.

Hunter knew the perfect place to put the tailwater pond, too. For years, one of his center pivots, which spanned 560 acres, consistently got stuck in the same place every time. The pivot "should take eight hours to make a full circle," Hunter pointed out. "It was taking closer to 12. I wasn't able to put out enough water out to stay ahead."

The sticky spot in that 560-acre field is now the 22-acre tailwater pond, and instead of being a drag on yields and the progress of the pivot, it irrigates 260 acres.

There are costs from the loss of the land for farming, but Hunter figures he's ahead on two counts. He's pumping more surface water to irrigate, which is less expensive to pump than groundwater. He's also reducing pressure on the Mississippi River Valley alluvial aquifer, which supplies most of the irrigation water to Delta producers.

RETURN ON INVESTMENT

Hunter's sensors were installed by Circle S Irrigation, in Clarksdale, Mississippi, for about $1,250 each. Cost of sensors with telemetry typically start around $900 and increase according to the depth of measurement. Hunter has nine 48-inch sensors that measure soil moisture every 4 inches.

Coleman Middleton, manager of Circle S's EnviroSolutions division, said Delta farmers can offset most, if not all, of the cost of the sensors through the Environmental Quality Incentives Program and the Natural Resources Conservation Service's Water Conservation Program. "Most programs through NRCS are going to reimburse around $1,500 to the producer for a soil-moisture sensor with telemetry, regardless of what the producer pays for the sensor," he explained.

"We work with the farmer and the NRCS office, and walk the farmer through the paperwork," said Middleton, who services about 500 sensors in the area. Most producers see an immediate benefit in irrigation efficiency and labor savings. High-end soil-moisture sensors typically last eight to 10 years, he added.

(ES)