Linda Benedict, Bogren, Richard C. | 4/5/2005 1:15:02 AM
Researchers at the LSU AgCenter’s Macon Ridge Research Station at Winnsboro have found a way to irrigate their fields during the summer without resorting to pumping water from wells. They’ve created a 16-acre pond they fill with surface water during the winter and use for irrigation in the summer.
The pond came about because of necessity. The irrigation water from wells on the station had become relatively high in salt content. Cotton is tolerant of this salinity, said Bob Hutchinson, LSU AgCenter Northeast Region director, but other crops, such as corn, soybeans and rice, are not.
“We’re blessed to have a lot of water and not too deep,” Hutchinson said of the irrigation wells at the station.
Although groundwater is available, some wells produce salty water because of salt domes. For farmers in the area, “the choices are don’t farm or develop other sources of water,” Hutchinson says.
An alternate source of water is a pond.
The pond at the Macon Ridge station was constructed in conjunction with a wetland that couldn’t be farmed. A permit from the U.S. Army Corps of Engineers allowed the wetland to be included inside the levee. Researchers dug a trough around the wetland and used the soil to build a levee. A nearby canal drains several thousand acres and flows heavy with water following periods of intense rain during the winter and early spring. Using lift pumps, the research station captures a portion of this water and fills the pond.
“Research has shown the benefits of supplemental irrigation to crop production on the Macon Ridge,” Hutchinson said. That’s despite an average annual rainfall of around 53 inches. “We get periods of excess rain and periods of inadequate rain.”
The Macon Ridge, for which the station was named after, is a geological formation that runs through northeast Louisiana and into Arkansas. Soils along the ridge are droughty soils over a fragipan – a natural ground layer that’s low in organic matter and extremely hard when dry. It’s root-restricting, too. Hutchinson said farming in these conditions is difficult.
Irrigation replaces rain during the hot, dry summer months. Farmers generally apply 6 to 7 inches of water for cotton during the course of a growing season. “It’s not a tremendous amount, but it’s water that’s critical,” Hutchinson said.
Hutchinson said early research showed the value of irrigation on the Macon Ridge. “You usually get a statistically significant increase in yield with irrigation,” he said.
Hutchinson said that when land values and production costs were lower, a farmer could sustain a bad year now and then. But not any more. “We have to even out production and eliminate the low-yield years,” he said.
Northeast Louisiana farmers typically use furrow irrigation, where water is piped across one end of a field and allowed to flow between rows. As it moves down the furrows, some water is absorbed by the soil, and the remaining water drains out the other end of the field.
“Our local silt loam soils have an infiltration rate that’s not too fast and not too slow,” Hutchinson says. “And the soils don’t waterlog.”
Although the quantity of irrigation water is rather low, farmers could capture the runoff from the fields and pump it back into the pond for later use. This could be most advantageous for rice farmers, who use larger quantities of water for flooding.
“This allows us to be more efficient with what Mother Nature gives us,” Hutchinson said.
To get water from the pond to fields, researchers at Macon Ridge use two techniques – pumps and gravity, said Wink Alison, an agronomist at the station.
One side of the pond features a pump that lifts water out of the pond and sends it into a pipe alongside a field. A field on another side of the pond is fitted for gravity flow from the pond. Risers in both fields distribute water for furrow irrigation. Allison said it’s imperative for the water level inside the levee to be high enough to allow adequate flow in the gravity-flow system throughout the irrigation season.
Using ponds for storing irrigation water can have both crop production and environmental benefits, Allison said. And it can provide leisure benefits for operators as well as the potential for a recreational business enterprise.
(This article appeared in the spring 2004 issue of Louisiana Agriculture.)