Those are some of the questions being raised in a water usage/cost study funded by Louisiana rice producers through check-off funds provided to the Louisiana Rice Research Board.
Knowing the amount of water used in rice production is necessary for several reasons, says Johnny Saichuk, Extension rice specialist with the Louisiana State University AgCenter, who is conducting the study with irrigation specialist Bill Branch.
“For years, we have used data from past studies that says it takes 30 to 36 acre-inches. However, we don’t know when those studies were done,” Saichuk notes. “We do know they were conducted with older varieties that required much more water to control weeds.”
The semi-dwarf varieties used today require less water, Saichuk says, and growers use less water because of more precision-leveled ground, which allows them to control the amount of water that is used.
“We also feel that herbicide-resistant technology, such as the Clearfield Production System for rice, will save more water because it enables us to control red rice in a dry-seeded system in areas which now use water-seeded practices to control red rice,” he added.
The interest in water usage also has been prompted by several other factors, including the droughts of 1999 and 2000. Additionally, several studies have targeted the state’s rice industry as being a heavy user of water, particularly from the Chicot Aquifer, which is a major aquifer in southwest Louisiana.
“The recent droughts emphasized the need to answer this question,” Saichuk said. “Louisiana was the last place we thought we’d ever have to worry about water. But we’re taking a pro-active stance by identifying first how much water we really use, and secondly determining what measures we can take to conserve even more water.”
The first step to this is to find out how much water it really takes to grow a modern rice crop.
The Louisiana study involves eight sites in seven parishes with different wells, soil types and management practices, including drilled and water-planted rice. Each site represents about a $1,500 investment in equipment, including an automatic rain gauge, a manual rain gauge, a flow meter, PVC pipe and a hydrant.
The eight sites mainly pump water from wells, although several use surface water. One site was dry planted to Clearfield rice, and the others were planted to conventional rice varieties. Additionally, two of the fields planted to conventional rice – one in Avoyelles Parish and one in Concordia Parish – were drill seeded.
In southwest Louisiana, where 80 percent of the state’s rice crop is grown, water-seeded practices dominate.
“It would take a herbicide-resistant technology like the Clearfield system for growers to switch to a drill-seeded system, “Saichuk said. “The herbicide-resistant technology has a distinct advantage to us because it can help us control red rice. Once we control red rice, we will have a lot more options.”
In fields infested with red rice, many growers have no option except water seeding if they plant rice.
“You have to water plant and pinpoint flood, or red rice will eat you alive,” says Saichuk.
Michael Hundley, who along with his brother Jim, owns and runs Hundley Bros. Farm in Branch, La., said dry planting one field to Clearfield rice this year has resulted in a 50 percent water use reduction.
“Three years ago, that same field was 80 percent red rice. If we cut 27 barrels, 20 were probably red rice,” he said.
“Last year, CL121 was our highest yielder at 47 barrels and 17 barrels (first and second harvest). Our grade was better, too,” adds Jim Hundley.
In previous years, Troy Fruge from Basile, La., has controlled red rice by rotating some land into crawfish ponds or planting soybeans. In some years, when he couldn’t get soybeans planted, he just plowed all season long to control the weed.
This is Fruge’s second year for trying the Clearfield Production System for rice. The system is made up of herbicide-tolerant rice varieties, Newpath herbicide to manage red rice and other problem weeds and a stewardship agreement with growers to preserve the technology.
“Clearfield rice gives me the opportunity to switch completely to drill-seeded rice,” said Fruge. “Clearfield allows me to plant two years in a row, when necessary, and still control red rice. I would never have attempted planting continuous rice without Clearfield because of our heavy red rice infestation.”
Fruge said he sees soil conservation as a major benefit of dry planting.
“You lose soil with water runoff by muddying up and water seeding,” he said. “With drill-seeded rice, I see less silt in ditches.”
This season, Saichuk and his colleagues have primarily been recording water use data from the eight sites, but Saichuk said preliminary findings on the amount of water pumped on two test fields on the same farm – one a Clearfield-drilled field that previously had been pinpoint flooded for seven years and the other a conventional water-planted field – show potential water savings in a drill-seeded system.
Darryl Rester, an Extension agricultural engineer with the LSU AgCenter, mapped the planted acreage in each test field using a Global Positioning System. By the first week of July, 29.43 acre-inches of water had been pumped on the water-planted field, and 20.25 acre-inches on the drilled field.
“Rainfall is not included, but the differences should be relative because of the proximity of the fields and the relatively low rainfall during most of the growing season,” Saichuk said. “Most of the rain that we have received recently has contributed little toward irrigation.
“Water cost is more difficult to capture, but we can come pretty close.”
For example, if a grower has a new well and power unit, he can amortize the cost of the well over 20 years, and spread the cost of the power unit over 10 years. That will give him an annual cost for each item. Then add maintenance cost for a given year. Divide the total cost for that unit for that year by the number of acres that it was used on, and the grower can get a pretty close per-acre cost on water.
“In most cases, we think it averages $50 per acre,” he said.
Farmers who use surface water supplies, such as re-lifting from bayous, spend less money than those who use a well. Re-lifting is more efficient in the amount of water pumped per gallon of fuel used, too, Saichuk said.
Overall, Saichuk said he is pleased with the amount of data that is being gathered in this first year of the water use/cost study. With further refinements, the study holds the promise to help Louisiana rice growers make their production programs even more economic.
“To be accurate, the study should run about at least three to five years because of changing weather conditions,” Saichuk said. “For example, you use much less water in heavy rainfall years than you use in a low rainfall year.”
Switching from water-planted rice to drill-seeded rice also could help the state’s efforts to meet the Environmental Protection Agency’s Total Maximum Daily Load limits of pollutants and soil runoff in Louisiana waterways, says Saichuk.
“Drilled fields generally have less soil particles moving out of the field into the streams,” he said.
Fred Sanders, associate professor at Louisiana State University, said the amount of runoff reductions varies for each body of water, but a 50 percent reduction in runoff for streams in southwest Louisiana is not uncommon.
Sanders provided the following examples to illustrate how the Maximum Daily Load limits vary according to water body. They show percent reductions for several streams in southwest Louisiana rice country. For example:
- Bayou Plaquemine Brule: 50 percent reduction in man-made non-point source loading (both summer and winter)
- Bayou Des Cannes: 50 percent to 75 percent reduction in man-made non-point source loading
- Bayou Nezpique: 90 percent reduction of man-made non-point source loading in winter, 85 percent reduction of man-made non-point source loading in summer