K-State SDI Research Spans 20 Years
COLBY, Kan. – This year, 2009, will be remembered for many events, but for Kansas State University scientist Freddie Lamm, it also signaled 20 years of research in subsurface drip irrigation (SDI) for crops grown in western Kansas.
Lamm, a research irrigation engineer with K-State Research and Extension, has worked with K-State colleagues around the state to study the pros and cons of irrigating crops by burying pipe several inches below the surface of the soil and releasing water that goes more directly to roots than alternative irrigation methods allow.
“Since we began in 1989, our SDI research and extension efforts have had three primary purposes,” said Lamm, who is based in semi-arid northwest Kansas, where the average annual rainfall is 17 inches. “Those purposes are to enhance water conservation, protect water quality and develop appropriate technologies for Great Plains conditions.”
“Other K-State scientists currently active in the SDI research and extension efforts are irrigation engineers Dan Rogers, Mahbub Alam, and Abdo Shehata; agricultural economists Dan O’Brien and Troy Dumler; and soil physicist Loyd Stone.
One of the first studies, conducted at Colby and Garden City from 1989 through 1991 examined the water requirement of subsurface drip-irrigated corn.
“Careful management of SDI systems reduced net irrigation needs by nearly 25 percent, and still maintained top yields of about 200 bushels per acre,” Lamm said. “That 25 percent reduction in irrigation needs potentially translated into 35 to 55 percent savings when compared to sprinkler and furrow irrigation systems, which typically operate at 85 and 65 percent application efficiency.”
SDI uses water more efficiently than other methods, primarily because there is less deep drainage during the crop season, less soil water evaporation, and no irrigation runoff as is found in other irrigation techniques. An added benefit, he said, is that drier surface soils allow for greater infiltration of those occasional intense rainfall events that occur in the Great Plains.
What may surprise some people, Lamm said, is that in most years, the results suggest that when using SDI in corn, irrigation frequencies from daily to weekly did not have much effect on corn yields.
Over the years, the scientists have studied the use of different irrigation amounts, frequency of irrigation, dripline spacing and depth and different plant densities. Most of the work has been with corn because it is the primary irrigated crop in the central Great Plains, but alfalfa, soybeans, grain sorghum, sunflowers, melons and vegetables also have been studied. Most of the research has been conducted on deep, well-drained silt loam soils which are common in western Kansas.
“Because properly designed SDI systems have a high degree of uniformity and can apply small, frequent irrigation amounts, there are excellent opportunities to better manage nitrogen fertilizer with these systems,” Rogers said. “Injecting small amounts of nitrogen solution into the irrigation water can spoon-feed the crop, while minimizing the pool of nitrogen in the soil that could be available for leaching into the groundwater.”
The researchers also have studied the application of livestock effluent to agricultural fields using SDI technology and found that the practice can be successful. Irrigators should be mindful, however, of the more complex design considerations when SDI is used for effluent and the fixed location of the system which can introduce the issue of nutrient overloading concerns.
The Nuts and Bolts – SDI Systems Used
Many of the K-State studies have used SDI systems installed in 1989-90. These study areas have dual-chamber drip tubing installed at a depth of approximately 16 to 18 inches with 5-foot spacing between dripline laterals. Corn was planted so each dripline lateral is centered between two corn rows.
Studies also were done with 2.5-, 7.5- and 10-foot spacing. The highest average yield was obtained with the 2.5-foot dripline spacing and the 7.5-foot and 10-foot spacing worked well in higher-rainfall years. When all of the data was plugged into economic models, however, the standard 5-foot dripline spacing was best when averaged over all years for both sites – Garden City and Colby.
“All of the corn has been grown using conventional production practices for each location,” Lamm said.
Cost and Longevity of SDI Systems
The obvious downside to SDI, the researcher said, are the much higher investment costs as compared to other pressurized irrigation systems such as full size center pivot sprinklers. But there are “realistic scenarios where SDI can more directly compete with center pivot sprinklers for corn production in the Central Great Plains – particularly in smaller fields.
“We have developed a spreadsheet template for producers to make their own economic comparisons between SDI and center pivot sprinkler systems. It is available for free on our K-State SDI Web site,” Lamm said.
When a producer makes a substantial upfront investment as is the case when installing a SDI system, there’s the question of “how long will it need to last in order for it to be cost effective,” he said. The K-State studies show that SDI system life must be at least 10 to 15 years to approach economic competitiveness with full-sized center pivot sprinkler systems that typically last 20 to 25 years.
“Using careful and consistent maintenance, a 20-year or longer SDI system life appears obtainable when high quality water from the Ogallala aquifer is used,” Lamm said. “The system performance of the K-State SDI research plots has been monitored annually since 1989 with few signs of significant degradation.”
The benchmark study area has received shock chlorination approximately twice each season, but has not received any other chemical amendments, he said.
More information about SDI research, including detailed reports about various studies conducted by K-State over the last 20 years, is available on the Web: http://www.ksre.ksu.edu/sdi/.
Online Information Available To Compare Economics of Center Pivot to SDI for Corn
K-State Web Site Provides Latest SDI Research, Event Information
COLBY, Kan. – K-State Research and Extension has been engaged in studying subsurface drip irrigation (SDI) technology for use in field crops in western Kansas for the past 20 years.
A comprehensive look at studies surrounding the effort and an online spreadsheet comparing the K-State center pivot sprinkler and SDI are available on the Web site: http://www.ksre.ksu.edu/sdi/.
“We encourage users to ‘experiment’ with the input values on the main worksheet (tab) to observe how small changes in economic assumptions can vary the bottom line economic comparison of the two irrigation systems,” said Dan Rogers, K-State Extension agricultural engineer, based in Manhattan.
Workshop and seminar information of interest to producers, agricultural lenders and others is updated on the site throughout the year.
In addition, K-State Research and Extension has teamed with Texas A&M University on several studies, said Colby-Kan.-based researcher Freddie Lamm. The two universities will team up to hold a series of SDI-related meetings in Texas and Kansas this fall. Information on those meetings will be on the Web site under “Events” as it becomes available.