The average irrigated cotton yield in Steve Bodine's county is about 700 lbs/acre. But by farming "one drip at a time," his yields are consistently 1,500 lbs or more - a good three bales.
Bodine is in his fifth year of using subsurface drip irrigation on his West Texas farm near Ackerly.
"We are on the very end of the Ogallala Aquifer," says Bodine. "Our wells are small. They produce only 50 gallons/minute (gpm). We feel drip is our only course for irrigating."
He's installing his fourth drip system that will be online for 2000 production. Initial costs are high, about $710/acre installed. His equipment includes Netafim tape with emitters spaced every 24". Tape is laid in 72" spacings, 12" deep. His older drip systems are laid in 40" spacings to facilitate terraced contour of the fields, which require more precise watering patterns.
The system includes a 6" main line tied to irrigation wells. Water flows through sand separators that remove 85% or more of the sandy loam soil that can clog emitters. Water then flows through chemical check valves, filters and air ventilators, then to the subsurface lines, to which drip tape is connected.
Fields are irrigated at a rate of 3.3-3.5 gpm/acre. About 0.18" of water is applied over a 24-hour period.
With annual input from Netafim regional consultants, Bodine has learned new production-boosting tricks every year of drip production. Along with preplant fertilization, he applies additional nitrogen through the drip lines. He plants Stoneville 474 and 132, two picker-type varieties, as opposed to stripper varieties normally planted in the region. PIX is applied to control growth. He also applies growth regulators to terminate growth in early fall.
"We don't let the cotton grow above waist high," he says. "We're able to begin harvest in late September, before we normally see fall rains and cold weather that can hamper harvest and hurt quality."
The result has been high production every year. The 1996 yield was 2.2 bales/acre. "By obtaining a greater understanding of using the drip systems, our yields have increased by up to 3/4 bale every year," says Bodine. "We averaged 3.7 bales in 1999. And the cotton was extremely high in quality, generating good premiums (2-3 cents/lb)."
The return on his drip-system investment is high, even with depressed cotton prices. "My input costs are about $300/acre," he says. "In 1999, we grossed $1,184/acre, a net of $880, based on a price of 64 cents/lb (including his LDP). We paid for the drip system in one year."
Producers often measure the value of drip systems against low-energy precision application (LEPA). Both are efficient. But as water availability decreases, Jim Bordovsky leans toward drip for overall efficiency. The Texas A&M University ag engineer has five years of data showing that drip-irrigated cotton often outyields LEPA cotton by about 100 lbs/acre.
In drip vs. LEPA research at the Halfway Texas Ag Experiment Station near Plainview, lint yields were higher for drip-irrigated cotton over a four-year period. At irrigation rates of 0.1, 0.2 and 0.3" per day, drip resulted in a four-year average yield of 1,109 lbs, 1,190 lbs and 1,215 lbs, respectively. That compared to LEPA yields of 978 lbs, 1,091 lbs and 1,156 lbs.
"The increase in yield is attributed to less soil-surface evap- oration in the drip program," says Bordovsky. "This resulted in higher water use efficiency for drip over the four-year period."
He points out that drip systems normally require more maintenance. Also, conversion to LEPA from low-pressure center-pivot systems can be done for much less cost. In addition, LEPA can enable producers to apply greater amounts of foliar materials.
But if water availability continues to decrease, more growers likely will convert to drip irrigation to make the best use of this valuable resource.