‘Go with the flow’—
Newell-If it weren’t for the steady hum of a 4,000-watt standby generator, it might not be apparent how Tom Olsen has achieved 200-plus bushel corn yields on his Buena Vista County farm north of Newell.
His corn production is even more impressive knowing that parts of his field contain Salida soil, a gravelly, sandy loam with a corn suitability ratinf of 7, and Estherville soil with a CSR of 14.
Olsen’s high yields are made possible by a controlled drainage system that was installed in May 2008.
“The results have exceeded our expectations,” said Olsen, an Iowa State University Extension farm management field specialist, who recently hosted a controlled drainage field day at his farm, which has been in continuous corn for nearly five years.
“I’ve been very surprised by this system,” he added.
The controlled drainage site, which contains 1,000 feet of tile, has a control box located about 145 feet from a county drainage ditch.
This allows the field to be drained when there is a high water table. During the winter, the water table can be raised to increase the water-holding capacity of the soil and improve the water quality of the system.
During the summer, water is pumped back into the tile line, which is located at a depth of about 3.5 feet, to provide water to the crop during periods of dry weather.
This sub-irrigation occurs when the water travels back up the lines to reach the crop.
“I’ve read about controlled drainage and am interested in learning more about it,” said Dale Drey, a Sac County farmer who attended the field day. “It would be interesting to see if it would work on a larger scale.”
Bringing water to the crop
Olsen, who is working closely with his ISU colleagues on the research project, installed the controlled drainage system because he wanted to determine if sub-surface irrigation can make economic sense in Iowa, particularly on sandy knolls and other spots within a field where poor soil leaves crops vulnerable to dry conditions.
“Since I’m close to a water supply, I thought it was an interesting proposition to see what would happen if we pumped water back into the system, when the crop started to show stress,” said Olsen, who noted that the 5-inch tile cost approximately $1,200.
In addition to the tile, the drainage control structure cost about $500, while the well pump totaled $250.
When the weather turned dry in 2008, Olsen pumped water back into the tile lines during mid August and again in early September. He used the same tactic this year on the demonstration area, which covers 1.8 acres. Olsen relies on a generator, which can run for 15 hours when filled with five gallons of gasoline.
The system, which also includes a one-half horsepower submersible well pump, can deliver 20,000 gallons of water, or approximately 1,300 gallons per hour.
He calculated that the system costs about 50 cents per 1,000 gallons of water delivered, using his gas-powered generator. If electricity were run to the site, Olsen figures that the cost would drop to 11 cents per 1,000 gallons of water delivered, based on a price of 10 cents per kilowatt hour.
If more than 25,000 gallons of water per day are pumped from a drainage ditch, a permit from the Iowa Department of Natural Resources is required, noted Kris Kohl, an ISU Extension ag engineer, who has been researching controlled drainage at a number of locations in northwest Iowa with various soil types.
During each “watering session” at the Olsen farm, the crop received the equivalent of 1.3 to 1.5 inches of rain.
“The water wicks out of the tile and moves into the soil, where the crop can reach it,” said Olsen, who figured that the controlled drainage would provide moisture for 40 feet on either side of the tile line. “It’s very obvious to see where the tile is, because you can visually tell a difference in the height, green color and leafiness of the corn.”
Counting the cost
Matt Helmers, an ISU Extension ag engineer, who specializes in drainage issues, estimates that a controlled drainage system similar to the one on the Olsen farm might work for 5 to 10 percent of the fields in Iowa.
He added that the system can be used with a variety of soils, and it works well on flatter fields.
“Interest in controlled drainage continues to grow, and I think it’s important to be proactive about nitrate loss and local water quality issues,” said Helmers, who noted that a number of Midwest industry professionals and universities are involved in the Agricultural Drainage Management Coalition, which is looking at options like controlled drainage to help improve water quality and increase yields.
“I’ve been surprised by the yield response we’ve gotten with systems like the one on the Olsen farm.”
Olsen has not only determined that it’s possible to deliver water economically through a controlled drainage system, but he knows the water does a lot of good when it reaches the crop.
Last fall, the corn right by the tile line yielded 224 bushels per acre, while the corn 40 feet from the tile yielded 192 bushels. Even the corn 70 feet from the tile managed to produce 124 bushels per acre.
“Even though the pumping system could be much more efficient, and the capital cost is high for this small, experimental area, it looks like the system will pay for itself in three to four years,” Olsen said. “Since I’ve made the investment, I plan to keep pumping water back into the tile every summer.”
Contact Darcy Dougherty Maulsby by e-mail at firstname.lastname@example.org.
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