What is in this article?:
- Center pivots contain crop costs
- Center pivot efficiency
- Center pivot technology allows Doug Dunlap, Willcox, Ariz., to farm more effectively. He estimates his water efficiency at about 90 percent.
- Center pivot use boils down to efficiency — lowering costs.
- Dunlap’s crop yields are 15 percent to 20 percent higher with pivot irrigation.
- Pivots allow for utilization of minimum tillage.
If I had to go back to row water (furrow irrigation), I wouldn’t be farming today,” says Doug Dunlap, who credits center pivots with helping to keep him in business in arid Arizona.
Dunlap, a fourth-generation crops farmer, owns Dunlap Farms in the Sulphur Springs Valley at Willcox in southeastern Arizona, an area bordering New Mexico and Mexico.
Dunlap and his brother, Darren, who operate separate farms, grow 4,500 acres of alfalfa, pinto beans, chile, corn, and milo in the high desert at 4,400 feet above sea level in Cochise County.
The farm fields are shadowed to the north by the picturesque Pinaleño Mountains and the Winchester range to the west.
Dunlap farms in 160-acre crop circles (one-quarter section), which allows crop production on 120-125 acres in the circle. The mountainous terrain can drop 20 feet from one end of a circle to the other.
Wells and rain are the main water sources. Most well water is pumped from a depth of 300 to 400 feet. The area averages 7 to 10 inches of rain annually.
Soil types vary across Dunlap’s fields, from a Tubac sandy loam and Tubac clay loam on the north side of the farm near Bonita to a sandy Pima loam closer to Willcox. Center pivots allow him to adjust the irrigation based on rainfall and the various soil types.
The Dunlap family is among an entourage of farmers who brought their center pivot experience from West Texas in the late 1960s to this mostly row water (furrow and other types) irrigated Arizona community.
One of the first changes the Dunlaps made was to switch from row water to center pivots.
“Today, it would require about 20 irrigators and 20 pickup trucks to irrigate this farm with row water, including turning the water on and off,” he says. “The labor savings with center pivots are huge.
“Pivots irrigate the ground more evenly; row water irrigated unevenly, especially near the lower levels in the field.”
The bottom line: center pivot technology allows Dunlap to farm more efficiently and effectively. He estimates his water efficiency at about 90 percent.
Original pivot systems were designed for hilly ground that could not be row watered, he says. The systems had high impact nozzles, with 50 to 60 pounds of pressure per square inch (PSI), which increased soil compaction. Modern pivot systems can deliver 15 to 30 PSI.
Another change in pivot use in the Willcox area was placing the irrigation drop hoses closer to the ground. Today, drops are often 30 to 60 inches apart and hang two to three feet from the ground.
In corn, Dunlap places the drops 20 inches from the ground, which provides improved water delivery to the plants with less evaporation.
He uses Nelson and Senniger nozzles. Smooth spray pad nozzles break up the water into a fine mist for soils to better absorb water. A corrugated pad with large droplets is used on heavier soils.
Dunlap, who is proficient in center pivot technology, operates High Desert Irrigation, a Valley Irrigation dealership.
“We figured out years ago that, with center pivots, we make just as much money farming 120 acres as we would 160 acres, due to fewer expenses and reduced water use,” he says.
Pivot irrigation works better than row water on all of his crops. Depending on rainfall, his average for a pivot-fed corn crop is 24-30 inches of water annually, 36-38 inches for alfalfa hay, 20-22 inches for milo, 24 inches for chile, and 18-20 inches for pinto beans.