Soil sensors improve irrigation efficiency
By Doug Rich
Irrigation is at the heart of the Hunnicutt family’s diversified crop portfolio and using water efficiently is at the heart of their irrigation management plan.
When you ask Brandon Hunnicutt what he and his father, Daryl, and brother, Zach, grow on their Nebraska farm he does not say corn he says corn products. In addition to commercial corn they grow popcorn for Preferred Popcorn in Chapman, Neb., and seed corn for Syngenta. Commercial corn can be grown without irrigation but it is a requirement for popcorn and seed corn.
“We have changed a lot in the last 10 years,” Hunnicutt said. “We had a lot more gravity flow irrigation at one time before we switched to center pivot irrigation.”
Hunnicutt said the change to center pivot irrigation was for increased efficiencies in labor and irrigation.
“We had seed corn on some of those fields and it was a hassle to move irrigation pipe three to four times for the different things we have to do for seed corn,” Hunnicutt said.
Their move to improve irrigation efficiency continued eight years ago when they installed soil moisture monitors. Hunnicutt said they have three different monitors or sensors that provide them with information on how much moisture their corn crop is using and how much irrigation water is needed.
By the first week in June, Hunnicutt was just about finished installing Water Mark systems in his fields. These sensors are installed in PVC pipes at 1-, 2-, and 3-foot depths and Hunnicutt checks them with a handheld reader.
The second system is an AquaView system installed by one of the seed corn companies that grows corn on their farm. This is a single sensor installed to a depth of 36 inches. This is tied to a main server and they can check it on their laptop computer. This unit sends out a reading every couple of hours.
“It makes it really nice, we can see what is going on without driving out to the field to hand check it,” Hunnicutt said. “When we think there might be a problem we can see it pretty quickly”
This is a little more sophisticated system with all of the sensors in one tube where the Water Mark sensor requires a tube for each sensor.
“Water Mark systems are cheaper but work just as well as the others that are a lot more expensive,” Hunnicutt said.
There is also an evapotranspiration gauge. Hunnicutt checks this once a week and reports back to the University of Nebraska researchers for their water network. Other producers in the state can go online and view the reports.
“We have discovered over time as we have gone to minimum tillage and no-till, there is enough residue on the soil that what was once a high ET rate is not quite as high any more in those fields,” Hunnicutt said. “Besides when the plants canopy, there is a greenhouse effect so there is a lot of moisture staying in that plant.”
The first year they had soil sensors, Hunnicutt said it was a trial and they really did not know what to do with them. The second year Hunnicutt put the sensors on a field of seed corn.
“When I scouted fields before I only went 2 feet down because we thought seed corn roots did not go deeper than 2 feet,” Hunnicutt said. “But with the sensors we found the plants were using water 3 feet down late in the season. So we learned something important and it saved us two to three waterings.”
Typically, Hunnicutt said they try to put on one inch of water with each pass of the center pivot. Most years they put on 4 to 5 inches during the growing season but last year they had to put on 12 inches to keep up with the demands of crop during hot, dry weather conditions.
“If that had been 1988 it would have been much different, I guess we would have put on closer to 20 inches,” Hunnicutt said. “Between being able to sense the soil, better seed technology, and better conservation tillage practices we used less water.”
The Hunnicutts’ family farm pulls water from the Ogallala Aquifer and they have seen positive changes due to better irrigation efficiencies. The extreme drought conditions last year did lower the water table but it had been up the previous two years.
“There was a really big drawdown for a while, but as we became more efficient we have been able to manage the aquifer better,” Hunnicutt said. “We are right at pre-development levels now. If there is a big rise or drop year to year we are not as concerned now.”
What is the next step in irrigation efficiency? Hunnicutt thinks the next big development will be to tie the soil sensors to the center pivots. Link them together for variable rate irrigations.
“The soil will tell the pivot when to turn on and how much water to apply,” Hunnicutt said.
Add in soil mapping and the pivot could detect when it is moving over poor soil types or historically poor yielding portions of a field and control specific sections of the pivot to adjust water application accordingly.
It would improve water use efficiency and that is the name of the game for Hunnicutt and his family and the variety of corn products they grow.
Doug Rich can be reached by phone at 785-749-5304, or by email at email@example.com.