MU Research Shows Subsurface Drip Irrigation Increases Crop Yields

Russ Quinn
By  Russ Quinn , DTN Staff Reporter
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MU Extension agronomist Rusty Lee shows a modified conservation ripper used to bury drip tape for irrigating corn and soybean fields. (DTN/The Progressive Farmer photo by Linda Geist)

Over the years, irrigation of crops has continued to evolve. Flood irrigation, also called surface or furrow irrigation, was likely the first form of irrigation used by humans as they began growing crops.

While this irrigation method is still in use today, many farmers have shifted to center pivot irrigation systems to provide water to their crops.

Center pivots have certainly become the most popular method of irrigation, especially in the High Plains region. There is less labor with pivots compared to setting irrigation pipes and opening gates in flood irrigation, and pivots are also much more efficient at applying water.

While still somewhat early in development in U.S row crops, the next advancement in irrigation could be subsurface drip irrigation (SDI). Water is applied to the crop root zone drip by drip using buried, polyethylene tubing.

The main advantage of SDI over other methods of irrigation is that it has the potential to be the most efficient irrigation system. Since drip lines are buried about 13 to 18 inches below the surface, the soil surface stays dry, which means very little irrigation water is lost to the environment.

New research from the University of Missouri (MU) finds that SDI boosts yields in both corn and soybean production as part of integrated drainage water management systems on poorly drained flat soils.

MU Extension agronomist Rusty Lee showed the results of the research as part of a recent field day at his Truxton, Missouri, farm. Lee's work is part of an SDI study conducted by MU agronomist Kelly Nelson, graduate researcher Rafid Al Ubori and nutrient management specialist John Lory.

For the study, Lee trenched a 5/8-inch-diameter plastic line at 12 inches, 14 inches and 16 inches deep. Water exits the drip line from emitters spaced every 2 feet along its length.

Corn in the plot produced 41 more bushels per acre over last year's yields, Lee reported. With corn prices at $3.50 per bushel, this would represent $158 more per acre in profits.

Soybean yields were also increased in this study. Lee said bean yields at the plot were up to 14 bushels per acre higher compared to the previous year's yields.

Other positives with SDI in corn included increases in kernel size and increased test weight. The roots of the plants also reached deeper in the soil.

Lee estimated there would also be the one-time installation expense of about $700 per acre. Energy costs were about $30.75 per acre for this year's pumping. The cost is similar to pivot irrigation systems, but SDI gives farmers with small and irregularly shaped fields, including corners of all fields, more flexibility to be irrigated.

Other advantages with SDI: This method prevents wetting of leaves and thus results in fewer foliar diseases; it doesn't require large pumps and irrigation wells, and it uses less energy than pivot irrigation. In addition, farmers end up using less water with usage being reduced by 25%, he said.

No irrigation system is perfect, and SDI does have some drawbacks, said Lee.

The system has to last 10 years to recoup the initial installation cost. Lee has found most systems will make it that long. Rodents can chew through the lines, but finding the source of the leak is a quick five-minute fix, he said.

Another disadvantage to SDI is water filtration systems need to be monitored quite often, Lee said. Particulates and bacterial growth require periodic system flushing to prevent clogging.

The Missouri Soybean Merchandizing Council financially supported the project. The Higher Committee for Education Development in Iraq provided the funds for a graduate student to assist in the project.

To read the entire MU press release, go to….

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