Mark Peterson could talk all day long about the scientific aspects of monitoring the nutrients leaving the farm through his tile lines, but he takes another approach as he explains the importance of his focus on water quality. During a field day at his Stanton, Iowa, farm last fall, held in partnership with Practical Farmers of Iowa and the Iowa Soybean Association (ISA), he showed pictures of his granddaughter and grandson. “We have to do this for future generations,” he insisted. “The legacy
I want to leave for their generation is clean water.”

Technology to measure and monitor yield is commonplace in today’s agriculture, but only recently has there been a surge of interest in applying technology to quantify a farm’s impact on the environment. Researchers, farmers, and industry partners are gathering information to complete the picture of nutrient movement in corn-soybean rotations—and how to better protect water quality for future generations.

Tale of the tile. Peterson has partnered with ISA over the past half-dozen years to collect samples of water leaving his tile lines. The association began its tile water monitoring program in 1999, working with Agriculture’s Clean Water Alliance. ISA staffers in its environmental program, a division of the association’s research arm, collected more than 4,000 samples in 2018 from drainage tiles as well as streams and edge-of-field practice locations. While the data from individual farms is confidential, the research team aggregates the data to evaluate effects of management practices and to help spot trends.

The tile water monitoring program does not sample from a controlled experimental design, so results are considered “observations.” But these observations do highlight interesting trends. “When you zoom out from the individual level, you see how things such as how nutrient loss varies between the different landform regions of the state,” says Theo Gunther, an ISA resource management specialist.

For example, an analysis of the three largest landform regions of the state, based on 2018 samples, found that the Des Moines Lobe had the highest nitrate loss. The Iowan Surface landform and the Southern Iowa Drift Plain had lower levels of nitrate-N loss, and did not different statistically from each other.

Savannah Burnett is studying the impact of 4R practices on water quality at the University of Missouri’s Greenley Research Center.

At Peterson’s field day, Gunther pointed out that ISA studies show that sites with cover crops average 4.7 mg/L lower in nitrate concentration than sites with no winter cover. And the good news at Peterson’s Bent Gate family farm was that, for the majority of the year, tile lines were running below 10 mg/L—the federal standard for drinking water. The drone picture (above) shows a heavily instrumented field where another research effort is underway. During a 2018 field day at the University of Missouri’s Greenley Research Center, graduate research assistant Savannah Burnett introduced visitors to a field where scientists hope to quantify the impact of “4R” nutrient stewardship practices. Eight locations in corn-growing areas across the U.S. and Canada are part of the massive effort, known as the Coordinated Site Network for Studying the Impacts of 4R Nutrient Management on Crop Production and Nutrient Loss—or, by its more compact name, Nutri-Net.

“No research in Missouri has evaluated nutrient losses from tile drainage in a corn/soy rotation,” Burnett says. “We hope to close that research gap.”

This massive project, which received partnering support from the North American fertilizer industry’s 4R Research Fund, looks to quantify the impact of 4R practices on crop yield, soil health, nutrient use efficiency, nutrient loss due to leaching, and gaseous nitrogen loss. Nutri-Net sites will focus on nitrogen management, but all sites will look at P and K nutrient balances as well; all eight sites are set up to capture nutrient leaching losses from tile outlets.

The study is a three-year effort. Data generated is destined for a central database, where future studies on nitrogen management can help build a knowledge base. Scientists involved with the study—which also includes Iowa State University, University of Illinois, Purdue University, University of Minnesota, National Laboratory for Agriculture and the Environment-Agricultural Research Service, Agriculture and Agri-Food Canada, and the Environmental Defense Fund—say they hope results will help answer key questions about water quality in the Mississippi River basin.

For Iowa farmer Peterson, the benefits of water quality are clear. When a news crew recently followed him around the farm to discuss the issue, Peterson stopped to fill a glass with cool, clear water from his tile outlet—and proceeded to drink it.

“Getting a refreshing drink from a tile line was a common practice back when Iowa farmers used horse-drawn equipment,” Peterson says. “It is important that we get back to the point where only pure water leaves our fields.” 

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