March 14, 2005
University Project Demonstrates Irrigation Strategies to Save Water
LINCOLN, Neb. — An ongoing University of Nebraska irrigation management project in the Republican River Basin is showing farmers how to make the most of less water.
The Republican River Basin Irrigation Management Project is exploring practical ways that southwest Nebraska farmers can use limited water more efficiently, said Steve Melvin, Cooperative Extension educator in Frontier County, who conducts the project along with IANR colleagues and the Bureau of Reclamation. The Republican River Basin is one of the areas hardest hit by water shortages.
Using water more efficiently saves farmers money, or allows farmers to produce more bushels of grain with the same amount of water. It recognizes the reality that less irrigation water will be available in the future even when the drought ends, Melvin said.
In addition to the several years drought, the Republican River Basin water restrictions stem from the 2002 settlement involving Kansas, Nebraska and Colorado over the 1943 Republican River Compact. This settlement found groundwater pumping was covered by the compact, which will limit future groundwater irrigation development in the basin.
"In the past, water has been plentiful and relatively inexpensive in most of Nebraska, thus many fields have been managed with the strategy that we will just put on a little extra water to make sure we have enough," he said. "With water supplies stretched very thin and pumping costs going up due to rising fuel costs, these water conserving strategies are needed."
The Republican River Basin Irrigation Management Project began in southwest Nebraska farmers' fields in 1996. It combines field research on how best to reduce water use with demonstration plots that show how these strategies work. Each year educational presentations and tours highlight these water-saving practices.
Melvin and IANR colleagues have found that sometimes farmers over water or irrigate at times when crops respond little to extra water.
"On fully-watered fields, the last few inches of water put on really only adds two or three bushels per acre for each extra inch of water," Melvin said. "At that point, we are at the top-end of diminishing returns."
Irrigation timing is critical to making the most of water. They found that if farmers can irrigate when plants can best use water, such as during pollination and grain fill, they'll get the best yield response.
"Timing irrigation applications closely around pollination and early grain fill – particularly when you go to a restricted amount of water – will give you the best and most efficient use of that water," Melvin said.
The extension project includes three irrigation strategies: traditional, fully-watered irrigation management, which keeps soil water high enough to prevent moisture stress from limiting yields all season; water miser best management, which focuses on saving water during less sensitive vegetative growth stage and fully watering during reproductive growth stages; and deficit irrigation management, which relies on correctly timing application of a limited amount of water during the growing season and over several years.
The project compares the fully watered fields to the water miser- and deficit- irrigated fields that conserve water by limiting water applied during certain growth stages and relying on precipitation and stored soil moisture, Melvin said.
"The water miser strategy is trying to get full yields while saving water at the less critical growth periods, while the deficit irrigation strategy is a way to get the most bang for each inch water in limited irrigation situations," Melvin said.
Using the water miser strategy in southwest Nebraska, farmers typically can save an average of 1 to 2 inches of water annually, which is a 10 percent to 15 percent reduction compared with typical irrigation use in the area, Melvin said.
An example of the water miser strategy was the 2003 plot near Holbrook. The fully-watered field with 14.7 inches of irrigation yielded 202 bushes per acre while the water miser field yielded 201 bushels per acre with 12.5 inches of applied water.
A six-year average of the deficit management strategy on six sites in southwest Nebraska showed encouraging results, Melvin said. The fully-watered fields used an average 10.7 inches of water and yielded 193 bushels per acre. While the deficit irrigated fields yielded 171 bushels per acre with an average of 6.2 inches of applied water.
"When we are restricted, we have to be more water miserly with our water, and the (compact settlement) makes it not just a one-time deal," said Ron Hoyt, a farmer near Culberston who participated in the project and tested both the water miser and the deficit irrigation approaches.
Hoyt said he believes this project will help farmers irrigate more efficiently and give him insight into what he can do in a limited water situation.
"We can still get 180 to 200 bushels per acre if we apply this water correctly," he said. "In addition, a lot of wells use diesel (to power them) and with diesel costs going up we're going to have to be more frugal."
Closely monitoring soil moisture also is critical to the success of limited irrigation.
"Producers need accurate soil moisture estimates," Melvin said. "Water miser and deficit schemes do require more precise water measurements and maybe even a little extra management time. But with this extra effort will come more efficient water use."
Other practices that can conserve water in corn include: good weed control and no-till or other tillage practices that minimize soil drying and leave residue on the surface. No-till under a center pivot can save up to 2.5 to 3.5 inches of irrigation water as compared to a clean-tilled field, he said.
The Republican River Basin Irrigation Management Project will continue this year to educate more farmers in limited water use. For more information about the project, contact Melvin at (308) 367-4424.
3/14/05-SAK Steve Melvin
Cooperative Extension -- Frontier County Extension Educator (308) 367-4424
 
Sandi Alswager Karstens IANR News Service (402) 472-3030
Department:
Cooperative Extension
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