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25 years studying drainage

By Staff | Sep 5, 2015


GILMORE CITY – Farmers who think they know what is flowing from their tile lines and when should give attention to the lessons being learned at the Drainage Research and Demonstration Project site near Gilmore City, because they may well be wrong.

Besides celebrating the site’s 25 years of ongoing and evolving drainage research, more than 50 farmers and other researchers were updated on Aug. 27 on rates of nitrate escapes from corn and soybean fields under different management practices, and the results are similar, regardless of the row crop on top.

But they were also assured there are ways to implement field management practices that reduce nutrient loads in tile water, while not sacrificing yields.

The DRDP is celebrating its 25th year, and those who manage and direct its research invited farmers to help celebrate and learn its history, as well as its lessons about which practices are most efficient in ridding tile water of nitrates.

agriculture, addresses an audience of about 50 people on Aug. 27 at the Drainage Research and Demonstration Project site near Gilmore City.

“We owe a big debt of gratitude for the folks who set this up,” said Bill Northey, Iowa’s secretary of agriculture. “There are absolutely things we’ve learned about nutrients, certainly nitrogen, only because of the way this thing was set up.

“There’s no way we’d have been ready to put together a nutrient reduction strategy, to be able to say we’ve got to move into more mainstream nitrogen management without the data gathered on sites like this in parts of Iowa.”

Directors in other states, Northey said, have nothing like this site.

“And they can’t rely on us because their soil is different, the timing of water is different and even their cropping systems are different,” Northey said. “And whatever they do, they’re not going to have 25 years worth of history to benefit from in putting some of their strategies together.”

He said there is no possibility by field activity alone that Iowa can meet the Iowa Nutrient Reduction Strategy without some type of edge-of-field practice.

“And now we have 72 nitrogen-reducing wetlands around the state,” he said, “some connected to new drainage projects and is a great model in how we can increase productivity, while having better water quality coming out of the drainage districts.

“Without this site, we wouldn’t be where we are right now.”

But there is more work to be done.

He said he thinks Iowa is scaling up to see more farmers planting cover crops to make a big reduction in tile water nitrates.

“Meanwhile, we have to find better ways to do it,” Northey said. “Some of the things we’re going to use 10 or 15 or 20 years from now, are things that will be discovered here, to optimize cover crops and other practices.”

Current studies

Matt Helmers, an ISU ag engineer, who now directs the study site, listed seven results researchers are learning from current studies. These are:

  • Data showed conclusively there is a direct correlation between nitrogen application rate and the amount of nitrates leaving the field via drainage. This has been replicated at other sites.
  • From 1990-1993 they studied a system with no nitrogen application and found 7 to 8 parts per million of nitrate coming out of the tile line, well higher than the 3 or 4 ppm they expected from a perennial system.
  • Reduced nitrogen application sees less nitrate escapes. After seeing there is nitrate loss even with no fertilizer program, it led to looking at wetlands for capturing runoff water in wetlands.
  • When implementing cereal rye as a cover crop, 2006-2014 data shows another reduction in nitrates, averaging 20 to 25 percent.

These numbers will fluctuate at times, Helmers said, based in when the water is flowing and how established the cover crop was at the time of drainage events..

  • In 2013, high rates of nitrate was found in tile, because of the 2012 drought, that killed plants early, left vast amounts of unused N in the profile.
  • Current treatment including fall fertilization versus spring-applied has been studied for 15 years.

“At this site, with the weather conditions we have, we see very little difference” Helmers said. “We expected to see a different impact, but when we put it on in the fall, it gets cold, little winter drainage.

“So that is actually an important finding.”

From 2011 to 2013, they found little nitrate reduction using a nitrogen stabilizer.

  • When comparing nitrate escapes from plots with corn on the ground and during a soybean year, “We thought we should see more loss from corn,” Helmers said.

However, with common fertilization rates, he said samples show the same concentration of nitrates in the tile lines during the corn and soybean years.

“In 2015, some of the highest concentration losses were from the soybean plots, probably due to residual nitrogen in the profile that was lost during April and May drainage,” Helmers said. “Many farmers think there is no N loss during a soybean year, but its not true.

“This also highlights the challenges we have within our system, because what do we have growing out there in April and May? Not much.”

Helmers said cover crops are shown to reduce nitrates loads by as much as 25 to 30 percent.

In the future, he said he wants to try over-seeding cover crops to get a thicker stand earlier.

Managing cover crops

Carl Pederson, the site manager, explained to those attending how the site manages cover crops and the challenges it faces.

He said they started experimenting with cover crops in 2003.

“I guess that was before cover crops weren’t cool,” Pederson said.

Currently they have 16 plots under cover crops, eight fields under chisel plow, or conventional tillage, and eight in no-till, all in corn/soybean rotations.

“It’s a challenge to get the (planting) timing just right,” Pederson said.

He said he drills cereal rye at 90 pounds per acre, getting in as soon after harvest as possible.

They drill 7.5-inch row spacing on either side of where corn and soybeans will be planted to avoid idiopathic affect of the rye with the crop.

Termination of the cover crops is two weeks ahead of planting using herbicide.

“The challenge is we’re always anxious to get the corn crop in,” Pederson said, noting that seeding doesn’t happen until October.”So we may not get that growth we’d like to see to help take up that nitrogen, but again, that’s kind of a timing issue we have there.

“Now we’re talking about how to over-seed this rye in the future. I’d like to see it go a little bit earlier, because the further north we are, it’s harder to get it established.

“There were some years it (fall) was so dry, the seed sat on the surface.”

He said he’d like to see earlier-season cover crop planting, even at V6 in corn.

Future study

Helmers said an effort called delivery-scale monitoring is being partnered between the research site with Iowa State University, IDALS, Iowa Corn Promotion Board and Natural Resources and Conservation Service.

“We’ve been working in six drainage districts in Pocahontas, Palo Alto and Clay counties, to collect crop yield information and better relate that to what we see coming out of the system and delivered to the stream,” Helmers said. “This can also be a learning experience for farmers – how much fertilizer can be reduced and still not lose yield.”

He said he also hopes to eventually get long-term, large drainage district-sized areas with cover crops or other practices and see the impact on nutrient reduction on a grander scale.

Ben Gleason, sustainable program manager for the Iowa Corn Growers Association, said the group has been trying to get edge-of-field practices moved off research farms and implemented on ICGA leadership’s farms.

He said Iowa Corn is asking growers in the six targeted drainage districts to submit their nutrient application data during the season, then their yield data post-harvest.

This data will be used to improve drainage, which improves yield, while also improving water quality, Gleason said.

As for volunteering nutrient management data, and yield information from growers in the six drainage districts, Helmers said getting a vast majority of the information will be good “and we’ve gotten a lot of positive response from people interested in what we’re doing.

“We feel it’s important that farmers are engaged in this process and we’re collecting it for our better understanding, so we can articulate how that affects the land and how that relates to the water.”

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