This post originally appeared via Soybean Research & Information Network. 

By Carol Brown

Photo: United Soybean Board

When conducting research in the agriculture industry, there are many moving parts including crop selection, nutrient inputs, weeds, pests, and weather. And these components are rarely evaluated all together, which makes it challenging to reach solid assessments and results.

Soils expert Andrew Margenot and his team are conducting a research project in Illinois to better understand how management practices interact for improved soil health and sustainability. The University of Illinois Associate Professor of Soil Science is embarking on a multiple-year benchmarking project across the state, measuring indicators for a comprehensive profile of nutrients and carbon in the soil. The project is funded by the Illinois Soybean Association.

“This project is looking at multiple outcomes all at once, centered on yields and profitability of soybean production, while also looking at soil health, water quality and climate impacts,” Margenot explains. “A lot of studies have explored one or two of these aspects, but rarely all of them together. These are systems and, depending on a producer’s management choices, there are trade-offs within the system that may not be clearly understood.”

Margenot says the benchmarking part of the project is to collect fundamental data that hasn’t been focused on in the past.

“The term benchmarking means answering questions such as, what does good soil health value look like under no-till versus chisel tillage, cover crops or no cover crops? And what does the water quality impact look like under these outcomes?” he says.

To answer these questions and others, Margenot has established plots at three university properties in northwest, central and southern Illinois. At each location, the plots contain combinations of a cereal rye cover crop, no cover crop, tillage (defined by region ranging from full chisel tillage, strip-tillage, and light vertical tillage), no-tillage, and crop rotations of corn–soybean and a double cropped wheat/soybeans with corn. Both phases of the crop rotations are present every year at each site, totaling 200 plots across the state.

Data Collection

The project includes testing for nitrate and phosphate leaching through subsurface water, soil health and fertility, and climate footprints measured by carbon stocks and greenhouse gas assessments, in addition to crop yields.

“For soil health, we’re running a battery of tests that the USDA recommends,” comments Margenot. “Our lab works closely with the USDA-NRCS on soil health tests, allowing us to test novel soil health indicators in addition to established ones. But what takes the most effort are the greenhouse gas measurements, as we take these at all 200 plots every week.”

Research technician Natacha de Gracia prepares to measure greenhouse gas emissions on one of the research plots in northwestern Illinois. Greenhouse gas emissions can be quantified by measuring small but detectable changes in gas build-up when the soil is covered. The green PVC sampling chamber is covered for a set amount of time, and the change in gas concentration is assessed. The team can then estimate the amount of greenhouse gases emitted over a larger area and time period to derive total greenhouse gas emissions per acre under a given practice. Photo: Andrew Margenot

The greenhouse gas tests, as Margenot explains, measure the “burps,” or the gas emittance from the soil as a result of biological activity. The team is measuring three major gases: carbon dioxide (CO2), methane, and nitrous oxide (N2O). These are important for soybean growers and for those who use cover crops.

“We know that nitrogen fertilizer isn’t usually applied with soybeans. But we sometimes miss the fact that soybeans can contribute a good amount of the corn–soybean rotation’s total N2O budget,” he explains. “I’ve seen estimates suggesting approximately one-third of the N2O from a two-year corn–soybean rotation comes from the soybean phase, despite no nitrogen application. In other words, N2O losses are not simply a matter of more N fertilization, and how we manage soybeans can help decrease this climate-forcing gas.”

This is where cover crops can enter the conversation. Cover cropping helps soybeans reduce their greenhouse gas footprint, Margenot says, as they use or tie up the excess nitrate that has built up in the soil. He believes this data is good to have, especially for international grain markets where buyers want to have a lower greenhouse gas footprint for their grain.

Next Steps and Outcomes

Margenot is preparing for the upcoming crop year and will be planting crops at the southern sites soon. He and his research team have a full year’s worth of data already collected, but crop year 2023 wasn’t ideal with drought conditions across the state, which were historically dry for the first half of the summer. He’s hoping that after three crop seasons, there will be enough data collected to make solid assessments.

“There are several outcomes we’ll have that will be helpful for farmers,” he says. “We should be able to give farmers a data-based assessment of a realistic carbon credit. Right now, carbon credits are the Wild West, and farmers may not be getting the proper information when looking at a carbon credit contract associated with their management practices.”

The second major outcome focuses on soil health. After running different soil health tests, the team can help to answer farmers’ questions on which tests are worth investing in or which tests are the most sensitive to match their agriculture practices.

“Currently, soil health tests are not at a place where they can support yield-based outcomes, but they are useful to understand long-term conservation goals. Through the project data, for example, we’ll have a better sense of how long before farmers see a change in their soil health after using cover crops or adopting no-tillage, and which soil health tests best pick up on these practices,” Margenot says.

The third outcome is water quality impact. The water quality tests he is conducting indicate how much nitrate and phosphorus are leaching from the soil into nearby waterbodies. Results from these measurements can contribute to the state’s nutrient loss reduction strategy, mandated by the federal Gulf of Mexico Hypoxia Action Plan for nitrogen and phosphorus reductions. Twelve states in the Mississippi River watershed have reduction plans in place, including Illinois.

The research project that Margenot is leading is robust, and outcomes from the project will have long-term impacts for Illinois farmers as well as others within similar soil regions and climates.

Other Resources:

ILSoyAdvisor webinar: What are Climate Smart Agricultural Commodities and How Do Soybeans Fit In? – Andrew Margenot, presenter

Project Highlight fact sheet – Illinois Soybean Association PDF file

Published: Apr 8, 2024