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Home > Protecting Our Lands & Waters > Clean Water Fund > Groundwater & Drinking Water Protection > Byron Township Timber to Row Crop > Key Study Components

Key Study Components

A combination of monitoring methods are used to measure nitrate-nitrogen in soil water and groundwater.

Soil Water Monitoring

Suction Tube Lysimeters

People kneel in a bare field to install pvc pipe and lysimeters in a narrow trench.

During growing seasons, soil water is collected weekly from 15 suction tube lysimeters, and samples are analyzed for nitrate-nitrogen. The lysimeters were installed at a 4-foot depth to collect soil water that has moved past crop rooting depth and could potentially move down to groundwater. The tips of the lysimeters are made of a porous ceramic material that water flows through when suction is placed on the tubes. 

Soil Pore Water Nitrate-Nitrogen Concentrations
Byron #1 Site 2014-2016

Graph illustrating the soil pore water nitrate-nitrogen concentrations observed four feet beneath the study site. The dates along the x-axis begin June 18, 2014 and end October 10, 2016. The average nitrate-nitrogen concentration (PPM) is along the y-axis and ranges from 0-70. Concentrations of 30-70 PPM are common under similar cropping conditions.








The graph shows the average soil pore water nitrate-nitrogen concentrations observed four feet beneath Byron #1 in 2014 under soybeans, 2015 under corn and 2016 under soybeans. Other fields in central MN managed with best management practices have shown nitrate-nitrogen concentrations that  range from 30-70 ppm throughout a corn/russet/bean rotation. This preliminary data shows nitrate-nitrogen concentrations from Byron #1 measuring in a range comparable to or less than other locations.  

Samples are analyzed for nitrate-nitrogen concentration using an ultraviolet spectrophotometer. Results are averaged to gain more representative information. For quality assurance, 10% of the samples are sent to a certified lab for analysis.

Drain Gauges

Installed below the crop rooting zone, at a 4-foot depth, drain gauges measure the volume of water that moves through the soil profile.  This information combined with nitrate-nitrogen concentration data from lysimeters can provide an estimate of groundwater loading in terms of pounds of nitrate-nitrogen per acre.

Groundwater Monitoring Wells

As part of this field study, seven shallow monitoring wells were installed around the field perimeter in early November 2014. Over time, these wells will help provide a better understanding of the movement of shallow groundwater below this field and provide a way to measure the nitrate-nitrogen concentration of this water throughout the year.