Research helps develop remote sensing as tool to assess conservation implementation

October 6, 2022

Map of Iowa shows estimated crop residue cover from 2011-2021, based on remote sensing data compiled by Dr. Brian Gelder, Forrest Williams and other researchers at Iowa State University. Black lines within the map delineate Major Land Resource Areas. Illustration courtesy of Forrest Williams.   

AMES, Iowa — Being able to measure residue cover from satellite imagery is a long-term challenge that’s still a work in progress, but researchers are making headway.

Improving remote sensing protocols for conservation tracking and planning has been a long-time focus for Brian Gelder and a team of scientists he’s working with at Iowa State University and the USDA Agricultural Research Service. Gelder, manager of research in Iowa State’s Department of Agricultural and Biosystems Engineering, will report on that work at the upcoming water quality research seminar Wednesday, Oct. 12, sponsored by the Iowa Nutrient Research Center (INRC).

An accurate inventory of in-field and edge-of-field conservation practices is important to document implementation of conservation programs, including progress toward water quality goals in the Iowa Nutrient Reduction Strategy.

In a study supported by INRC, Gelder and his team worked on developing remote sensing protocols to accurately identify the level of residue cover resulting from conservation tillage, a conservation practices important to reduce soil erosion and improve water quality.  

“Some practices, such as crop rotations and structural practices like terraces or stream buffers, show up pretty well in available or aerial satellite imagery allowing their presence or absence to be estimated relatively easily,” Gelder said. “For many other conservation practices, like residue cover or flow control structures or bioreactors, it’s much harder to match estimates based on imagery with what’s happening on the ground.”

Residue cover levels show up as differences in reflectance between soil and the residue, according to Gelder. “However, to use that information to accurately account for the dynamic vegetation changes that happen over a growing season requires developing reference values across many different soil types, colors and moisture contents. To improve residue cover estimates will likely require increased satellite observation data and/or refined models that better account for how soil type and moisture vary over time and space.”

The availability of new Lidar elevation imagery datasets, technologies like Google Earth Engine and other remote sensing resources, as well as modeling programs to use the data, are improving the ability to identify what’s happening on the land.

“These related technologies are allowing us to do things at scales we couldn’t have dreamed of just a few years ago,” Gelder said.

Conservation planners are optimistic about the practical potential of these resources to monitor progress toward goals like improved water quality and increased soil carbon -- and pinpoint lagging areas that need the most attention.  

“Understanding the level of in-field conservation practice implementation is a critical component of the Iowa Nutrient Reduction Strategy and other conservation efforts,” said Matt Helmers, director of the Iowa Nutrient Research Center. “Development of these techniques can help quantify areas where practices are quite extensive or where there are opportunities for greater implementation. All of this can help with future efforts to increase adoption and understand the overall impacts of our conservation work.” 

As part of the project, Gelder and his partners developed statewide maps of residue cover for Iowa from 2011 through 2021. They are currently analyzing updated imagery data to develop estimates over a longer time range.

Learn more about Gelder’s research Wednesday, Oct. 12, from 3:10-4 p.m. He will be one of two presenters for the upcoming INRC seminar in the series, “Highlights from a decade of research and impacts.” October’s other presenter will be Chris Jones, research engineer at the University of Iowa IIHR-Hydroscience and Engineering and the Iowa Flood Center, who will focus on water monitoring.

The monthly hybrid seminar sessions, which are free and open to the public, are held on the Iowa State campus in Elings Hall and online. Events are recorded for later viewing with the permission of presenters. Get more information or register to participate online at


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