Drainage project yields less-than-stellar results
WORTHINGTON -- A two-year study conducted in northern Nobles County that tested a drainage water management (DWM), or controlled drainage, system showed little impact on yield, while nitrogen losses were considerably less than on land with conventional tile drainage.
Jeff Strock, University of Minnesota soil scientist, presented the results of the study Thursday afternoon to a crowd of nearly 40 people at the USDA Service Center in Worthington.
Funded by a $974,000 Conservation Innovation grant from the U.S. Department of Agriculture and the Natural Resources Conservation Service, the drainage research project involved Minnesota, Iowa, Illinois, Indiana and Ohio. Four systems were tested in Minnesota, with one located on land east of Wilmont and owned by Son-D-Farms of Adrian. Monitoring was done by the Heron Lake Watershed District, with Loosbrock Farm Drainage Systems also partnering on the demonstration site.
"The whole objective we had was to look at this demonstration site and the win-win situation that we're trying to set ourselves up for," said Strock. "We looked at the yields, in terms of improving and increasing yield, and at water quality -- nitrogen was the main one."
The demonstration site has been in a corn-corn rotation for the past several years, said Strock. With that type of rotation, he said a farmer can expect to lose somewhere between 20 and 30 pounds of nitrogen per acre, per year. That compares with an approximately 20 pound loss per acre per year in a corn-soybean rotation.
"In 2008, we lost considerably less nitrogen (on the drainage water management system)," said Strock. As for yield, those acres located within the DWM area yielded 168 bushels per acre, while those acres in the conventional tile drainage area yielded 173 bushels per acre. Water flow off the land was about the same in both zones, he said.
In 2009, more than twice as much water flowed off the land through conventional tile than through the DWM. At the same time, the amount of nitrogen that left the field was considerably less -- 8.4 pounds per acre per year on the conventionally drained land vs. 2 pounds per acre per year on the DWM land.
"What that tells us is ... because of the fact that we're reducing the flow of the water from the system, we're reflectively reducing the loss of all that nitrogen from the system," Strock said.
Still, yields did not see an improvement on the DWM as expected. In 2009, the producer averaged 173 bushels per acre on the DWM land, while the conventionally drained land yielded an average of 175 bushels per acre.
The loss in bushels in the Wilmont study does not reflect results found in other areas of the state.
"In other sites, some (DWMs) have outperformed by as much as 7 to 10 bushels per acre yield increase," said Strock.
In his conclusions, Strock said a controlled drainage system is valuable for mitigation of annual nitrogen loss, while they have shown to be inconsistent in terms of yield benefit. Still, he said he was optimistic about the use of controlled drainage structures.
"The last three summers we've had some fairly dramatic drought conditions," he said. "I believe some of those yields would have improved with controlled drainage."
With up to 60 percent of the land in southwest Minnesota requiring drainage, Strock said the advantages of a controlled drainage system are that water can be held back and benefit the crop during dry periods in the summer.
"Wouldn't it be nice to be able to store another 7 to 14 days worth of moisture in the soil?" he asked.
The test site in Nobles County consisted of two different soils -- very poorly drained and poorly drained -- both with a high clay content.
"(It was) a good candidate for having a drainage system put in," Strock said, adding that clay and clay loam soils have a high water holding capacity.
Leonard Binstock executive director of the Agricultural Drainage Management Coalition, spoke briefly about the costs of a controlled drainage system.
Giving the example of a 160-acre field with roughly 140 of those acres benefitting from controlled drainage, he said the landowner would need one control structure for every 20 acres, for a total of seven structures, and a total cost of $15,620.
While the yield advantages may not be enough to pay for the system in the short term, Binstock said there are some programs available to producers interested in controlled drainage structures. The NRCS has funds available through both the EQIP (Environmental Quality Incentives Program, and CSP (Conservation Stewardship Program). It is possible to obtain funds from both programs for a project, he added.
In the CSP, the average producer payment is $38 per acre, while cost-share on drainage water management structures is about $500.
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