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February 18, 2020
If you’re trying to persuade a partner or landowner to install tile, you’ll likely lead with your most convincing argument. Usually, this would mean showing them a yield map where yield fell off in wet areas of a field.
Eileen Kladivko, Purdue University agronomist, says there are plenty of other reasons why installing tile in wet soils pays besides just better corn yield. She bases her conclusions partly on an experiment spanning four decades at the Southeast Purdue Agricultural Center near Butlerville, Ind., comparing tiled plots to essentially an undrained control plot.
Here are two benefits of tile that may not seem as obvious as others.
You will get more cover crop growth in the spring on tiled soils versus untiled, wet soils, Kladivko says. Results over the past five years are clear.
“It really stood out in 2016, when cereal rye grew longer into the spring,” she says. In fact, Kladivko and her crew harvested an average of 3,100 pounds of dry biomass per acre off tiled plots versus about 700 pounds per acre off the control plot. Spacings within the tiled plots vary from 16 to 33 to 66 feet. The plot with the closest tile spacing produced 3,500 pounds of dry biomass as cereal rye that year.
In 2014, 2015 and 2017, total dry biomass harvested was much lower, topping out between 500 and 1,000 pounds per acre for the tiled plots. In each year, however, biomass produced in the control plot was lower than for any of the tiled plots.
Pounds of nitrogen captured in the biomass produced followed a similar trend, Kladivko notes. In 2016, when allowed to grow longer into the spring, the cover crop scavenged roughly 30 pounds per acre of N on tiled plots versus fewer than 10 pounds of N on the wet plot.
In other years, when harvested earlier, cover crop N production was about half that amount, but always higher on tiled plots versus the control plot.
“Good drainage enables other conservation practices to work better and improve the soil,” Kladivko says. “That’s obvious in our studies.”
In a separate nine-year study at the Southeast Purdue Ag Center, Kladivko compared various cover crops and other practices on tiled versus untiled soil in continuous corn. One plot included spring-applied manure, and another involved a crop rotation with a legume. In each case, corn yields were higher for the nine-year average on tiled versus control plots. The average yield increase varied from 12% to 21% between practices.
“Cover crops, rotation and manure had equal or greater corn yields than control in tiled subfields, but equal or lower than control in untiled subfields,” Kladivko says. “The bottom line is that a good drainage system is a necessary first step to improving crop yields and soil health. Agronomic practices alone are not likely to make up for an inadequate drainage system.”
Here’s what that means. Cover crops, manure application, conservation tillage and rotation with hay crops can improve the soil’s physical properties and crop yields on low organic matter, poorly structured soils when adequate drainage is present, Kladivko explains.
“As we talk with the public about soil improvement, we may need to remind them that a good drainage system is a necessary first step to improving soil health and crop production,” she says.
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