Sunday, June 18, 2000
Furrow dikes are used extensively across the South Plains
to help growers trap rainfall and reduce soil erosion. And that,
in turn, reduces pumping from the Ogallala Aquifer.
By WAYNE BOARD
Whether they're producing crops dryland or on irrigated acreage, an ever-growing list of South Plains growers are using furrow dikes to conserve moisture.
Dikes, which have been a mainstay in the area for many years in one form or another, are small mounds of soil mechanically installed in the furrow, sometimes during listing and more often in conjunction with rod weeding just prior to getting seed in the ground. Simply, the paddles on a row damming rig, create a small reservoir.
In many instances, soil infiltration rates across the South Plains are adequate to absorb small amounts of rainfall with little runoff. When rainfall occurs in amounts exceeding soil infiltration rates, which is sometimes the case early in the season on the South Plains, the furrow dikes hold the water in place until it can soak into the soil.
"I think a lot of dryland guys dike every acre, especially on straight rows," says Benny Claunch, a grower near Bula in Bailey County. "I'm contour, but I still use them Ð they're just no telling how much water they save. And, they really stop washing."
Some growers in the area put the dikes in when they list, Claunch says, although he installs his when a rod weeder is pulled across the fields just prior to planting because he doesn't always have enough dirt at listing.
Like many, Claunch leaves his dams in place throughout the growing season, taking them out when it's time to gather the crops because the strippers and combines run smoother.
Although Wesley Butchee, who farms near Seagraves and Loop, hasn't started using furrow dikes, it's a practice he knows is coming in his operation. Because of the sandy loams, Butchee sees the need for row dams to hold his fields in place following a dashing rain.
"Water is the most limiting factor in crop production in this area," says Scott Orr, acting water use/conservation division director of the High Plains Underground Water Conservation District in Lubbock. "It must either be obtained from precipitation or by pumping ground water from the Ogallala Aquifer.
"Maximizing precipitation benefits reduces the amount of water pumped from the aquifer, reduces agricultural production costs associated with meeting crop water needs and has the potential to significantly increase crop yields."
A three-year study at the Texas A&M University Research and Extension Center at Lubbock indicated an average annual runoff of 2.73 inches from land with varying degrees of slope.
Keeping rainfall on the field rather than allowing it to flow into roadside ditches and/or playa basins provides additional water for crop use.
For every inch of water available above the basic water needs for plant development, cotton will yield 50 to 100 pounds of lint per acre, grain sorghum will yield 300 to 400 pounds of grain per acre and wheat will yield two to three bushels per acre.
The potential crop yield increase resulting from two to three inches of additional water on cotton could increase production by 100 to 300 pounds of lint per acre, and grain sorghum production could be boosted from 600 to 1,200 pounds per acre. Other crops grown in the area should have similar yield increases when furrow dikes are used to retain similar amounts of additional water.
When scientists with the USDA's Agricultural Research Service at Bushland began looking at water runoff from Low Energy Precision Application (LEPA) irrigation systems in 1996, they measured both diked and undiked furrows, said Arland Schneider, one of two agricultural engineers involved with the endeavor.
"Fully-irrigated plots received an inch of water per application," Schneider says. "Then our attention is focused on plots where we employ deficit irrigation, using only 80 percent, 60 percent and 40 percent of that applied to the fully-irrigated plots on the same day.
" A zero percent or non-irrigated treatment is also maintained for comparison purposes. We plant grain sorghum, although the study results are certainly applicable to corn or other row crops."
The experimental area has 30-inch beds, divided into equal sections, half with dikes and the other sans the man-made dams. They used a commercial trip and roll-type diker, and the spacing varies from 5 to 8 feet.
Runoff from the 30-feet wide (12 rows) by 66-feet long spaces is collected at the lower corner of the plots and pumped with small sump pumps into steel tanks for volumetric measurement.
"The field slope is 0.23 percent along the furrows and 0.18 percent across the furrows," said Schneider, who works on the project with Terry Howell. "The LEPA irrigation system uses double-ended socks which have been spaced 60-inches apart on a three-span lateral move irrigation system."
With ample rainfall during the late summer of 1996, they had only three irrigations where runoff could be measured from the irrigations.
The scientists said that, with open furrows and full irrigation using LEPA, at least 40 to 50 percent of the applied water could run off the plots. When the furrow dikes became partially eroded, as much as 20 percent of water applied with LEPA ran off the plots.
With a normal-sized field, all the runoff water may not actually leave the field, Schneider says, although it would move down the field gradient to the lowest point. And that, in turn, results in uneven infiltration, he adds.
Furrow diking resulted in two inches more soil water storage in the upper three feet with LEPA irrigation and one inch more with spray irrigation after seven seasonal applications.
With the unusually large amounts of summer rainfall in 1996, however, grain sorghum yields were approximately 7,000 pounds per acre for all irrigation treatments, expect the 40 percent deficit ones, which had yielded about 6,000 pounds per acre.
"Furrow dikes should be an essential part of a water use efficiency program on any farm. This is a low-cost, high-return practice that can increase profitability for High Plains producers," Orr says.
Wayne Board can be contacted at 766-8729 or email@example.com
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