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Research Highlights

Research Highlights
Exploring Soybean Performance Interaction With and Without Tile Drainage

An aerial view of the Tile Drainage site and the split research blocks within, located near Wells, Minnesota, in Faribault County.

By Carol Brown

Tile drainage is a way to manage poorly drained soils for better crop management. Engineers and soil scientists across the Corn Belt have been researching tile drainage for many years. Tile patterns, sizes, depth, and materials continue to be studied across the Midwest to improve drainage economics and performance.

Agronomists, including Seth Naeve, also study tile drainage but their focus is on crop production.

“Historically, there has been a lot of drainage research and for different purposes. Two major areas of study are engineering of tile drainage and water quality effects,” says Naeve. “We are looking at the effects of drainage on the crop itself. We want to know how key treatments perform on poorly drained soils versus well-drained soils, and how farmers should manage these soil conditions differently.”

Naeve, a University of Minnesota associate professor and Extension agronomist, is conducting a complex research project at the University’s drainage research site near Wells, Minn. The tiles were installed at the site in 2012 and studies have been conducted continually since then. The project has been supported by the Minnesota Soybean Research and Promotion Council. Naeve is testing several management practices for corn-soybean rotations with and without drainage in split-replicated plots.

“We have eight blocks that are over an acre each and each block has a drainage structure so that each block is controlled independently,” he explains. “The drainage structures can be turned on or off depending on whether the plot in the study is to be drained or undrained, but have been left open or closed since 2012. We have just over a half-acre of corn and a half-acre of soybeans on each side that are rotated each year.”

Naeve has split the plots for concentrated studies that include seed treatments, foliar fungicides, nitrogen management, and more recently for a study on no-till, strip-till and conventional tillage. In addition, he’s added another split that compares residue management and a rye cover crop.

“We have the opportunity to look at 45 corn plots and 45 soybean treatments, and within each one of those are either drained or undrained (plots). These plots allow us to explore all these different split studies,” he says.

Producers these days are farming much broader areas of land and are dealing with different soil types, characteristics and drainage levels, Naeve says. They could farm their own land that is well drained, and also farm on rented ground that isn’t tiled. Each field will have different management methods, and he says this project sets up the Extension agronomists for answers that farmers may have under these situations.

One of the studies with colleague Fabian Fernandez and graduate student Carlos Sanchez focused on soybean and corn production with conventional tillage, strip-till and no-till under drained and undrained soil. The research was conducted in 2021, under continued drought conditions in the state.

Their results showed that soybean yields were actually higher in undrained soils than in drained soils across the three tillage treatments, but Naeve says yields in the strip-till plots were comparable to the conventional tillage yields, indicating that strip-till is a good system across both drainage conditions. Results from this droughty year highlights the importance of conducting this type of research across many years.

Another study focuses on nitrogen. Naeve is working with a crop nutrient specialist Fabian Fernandez to study the relationship of soy to corn, and how nitrogen carryover affects soybeans. They’ve determined the economic optimum nitrogen rate is higher in poorly drained soil than well-drained soils. Farmers are adding more nitrogen to maximize yield, but that maximum yield is lower, he says.

“They’re putting on significantly more nitrogen per unit of grain than they are taking off, because we have more loss from the poorly drained system. We know there’s more nitrogen coming off the soil as nitrogen oxide,” Naeve explains, “and we know it’s happening more on the poorly drained soils. We think this is a big player and an important finding.”

The next step is to see how this affects the carryover to the subsequent soybean crop and they are looking at how nitrogen fixation plays a role in poorly drained soils.

“There’s clearly different cycling going on between the well-drained soils and the poorly drained soils, and we’re digging into this more,” he says.

These are just a few of the studies being conducted in drainage test plots and because of the numerous split plots, Naeve is able to explore different aspects within each study.

“We can look at all those things directly, but then we look at all other interactions with drainage,” Naeve says. “For example, in our residue management study — which will start this upcoming season — we can look at several things independently: how to manage cornstalk residue in soybeans in both no-till and strip-till, and then also with cover crops. But then we can apply all the interactions as well as the poorly drained soils vs. well-drained conditions.”

And, when seasonal environmental conditions are considered within each study, it becomes difficult to draw solid conclusions from short-term data analyzation.

“This is a long-term research site. At this single location, we can conduct crop research over several years and consider the impacts of the environmental conditions as well,” says Naeve. “But also, because we have the structure in place, it allows us a place to jump off and research specific topics that arise.”

This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.