Up to 40% better haylage yields have sold Jerrell and John Young on the benefits of subsurface drip irrigation in their Halfway, TX, operation.
The father and son switched some of their acres from center pivots to drip three years ago. And even with the $1,300/acre cost, more intense management and sometimes trouble from gnaw-happy rodents, they're eager to add more drip acres.
“There are pros and cons of installing and using drip for irrigating alfalfa,” says Jerrell, who markets forage to a local dairy. “Seedlings can be tricky to get up in dry weather. We had to install wire cages around zone control areas to keep coyotes from chewing on valves trying to find water. And we've had mice dig down to reach water at drip lines.
“But those things can be handled with a little more management. From what we're seeing with higher yields, it's time well spent.”
With drip irrigation, the Youngs are harvesting nearly 2 tons of haylage dry matter/acre in each of five cuttings, which are 28 days apart. That approximately 10 tons/acre compares to 6-7 tons from center pivot-irrigated fields.
High yields from drip irrigation are common in West Texas, mostly in cotton production. In all, there are more than 250,000 acres of drip in the area.
In a drip system, (see diagram) a main line (PVC pipe up to 12" in diameter) leads to a pump station from a well. Water flows past a backflow-prevention device, through filters, then through sub-mains, usually 6" PVC. Sub-mains are adjacent to the field and buried about 3' deep. They feed various zones.
Connectors and a 2" PVC pipe carry water from a sub-main to ½-⅝" drip line or “tape.” Tape is buried 12-18" deep. Tiny holes called emitters are positioned every 12-24", depending on engineer recommendations. Water flows from emitters at about 0.2 gallon/hour.
For row crops, tape is usually run in 60" spacings. For alfalfa, 40" spacings provide the best production, according to research at Kansas State University.
The Youngs, who have separate farming operations, have 6” mains fed by wells that range in capacity from 200 to 400 gallons/minute. Water flows through a disk-type filtration system.
“Even the tiniest particles of sand or soil can clog emitters,” says John Young. “Disk filters work for our cleaner groundwater. More-sandy wells usually require a more-elaborate filtration system.”
The Youngs have two roughly 50-acre fields of drip-irrigated alfalfa. Each field has 12 zones, with 4.1 acres/zone. Three-quarter-inch connectors lead from sub-mains in 40" spacings. Each tape runs ¼ mile and is buried 14-16" deep, depending on field slope.
Installing a new drip system costs a lot. The Youngs spent about $1,300/acre, but got help from USDA's Environmental Quality Incentives Program (EQIP). That's at least twice the cost of a quarter-mile center pivot. However, Jerrell says the size of his field made drip more feasible in that he would have paid a full pivot price to water just the 50 acres.
“We couldn't get full use from the pivot, so drip looked more attractive,” he says. “And from the yields we've seen, it was a good decision.”
John adds that, with the 30-40% added production, the system will pay for itself in less than five years.
University of California research has shown that drip irrigation can conserve water while maintaining or improving alfalfa yields. At Brawley, CA, a 16"-deep drip system had 20% higher yields than furrow-irrigated plots, with 6% less water used. However, surface soil wetting was observed in drip-irrigated plots, so the lines were buried up to 28” deep. That solved the problem, and during the following four years, 19-35% higher yields were achieved under drip.
The Youngs often stop watering a few days before cutting to prevent soft field situations. They blame their rodent problem on dry weather, which caused mice to dig down to tape in search of water. Mice can also gnaw on electrical wires leading from a computerized control panel to the various drip components. So rodent control is a must.
Leon New, Texas A&M University ag engineer, says some growers refrain from using drip in alfalfa because of rodent problems.
“If you have had gophers in the past, you really have to make sure you treat a field for gophers before you install a drip system,” he says. “A granular toxicant or other poison can be used. And remember, these treatments can be dangerous and tricky if not applied correctly.”