Schlichting Farms Nitrate Monitoring Using Suction Lysimeters

Schlichting Farms Nitrate Monitoring Using Suction Lysimeters Rice MN, Benton County, FAll 2021

The Schlichting Farms partnered with the Minnesota Department of Agriculture (MDA) and the Benton Soil and Water Conservation District (SWCD) in 2011 for the installation of 12 Suction Lysimeters which holds water for nitrate analysis. Nitrates move through the soil profile and could potentially leach into groundwater.

The city of Rice has higher nitrate levels, near 8ppm, in the public drinking water supply. The Schlichting Farm site is located within Rice's public drinking water supply management area (DWSMA). This makes it an ideal study location to gleam what may be occurring in the ground on the agricultural land. What makes this nitrate analysis unique is that the farming techniques and nitrogen applications are performed in real time for their crop management.

Schlichting Farms Nitrate Lysimeter Demonstration Site is located within the City of Rice's Drinking Water Supply Management Area.

Initial installation was in 2011 with 12 lysimeters in two dug trenches with 3 feet depths.

Fall 2021 expansion with updates and install of new to total 16 functioning lysimeters in two additional dug trenches with 3 feet depths shown.

Lysimeters are placed with the tops at 3 feet below the field surface and collecting water in the ceramic porous tip at 5 feet below ground. This depth is to protect the lines from farm field tillage. (Photo credit: Jessica Hoheisel and Tiffany Muellner)

The 2021 Installation Crew included the Schlichting Farms, Benton SWCD, and MDA.

Suction lysimeters consist of a porous ceramic tip which holds water when vacuum pressure is placed on the lines. Silica and Bentonite are used to seal the lysimeter from drying out or having air pockets.

The sample and vent tubing lines are placed in a series of PVC pipe to rodent proof and weather protect it. The PVC pipe is then recovered with soil with the end cap sticking out to allow for water sample collection.

There are 6 Runs of suction lysimeters with Runs A, B, & W on the West and Runs C, D, & E on the East side. The majority of the Runs are held within the perspective part of the irrigated crop fields while Runs C and E are in a dryland corner.

The 2021 crop consisted of Corn and Burbank Potatoes. The dryland corner was planted to Cereal Rye. The Schlichting Farms rotate among Corn, Burbank Potatoes, Edible Beans (Kidney), with Cereal Rye cover crops.

Water samples are collected bi-weekly and analyzed for nitrate levels by the Benton SWCD staff. Water samples are collected during the growing season which can vary in length from year to year. Typically it begins in May and ends around freeze up in early November. This demonstration site shows how nitrate levels may leach through the soil profile in real farm applications.

There is a declining trend between 2012 and the present. In 2015 and 2016 there was an increase in crop yield and may have contributed to more efficient nitrogen usage. The Schlichting Farms has been utilizing cover crops in their rotation since the 1970's. Cover crops are not utilized on the corn stubble. In 2021, this site experienced a D3 stage drought. In drier years nitrate levels tend to be higher due to less water moving through the soil profile and increasing the nitrate concentrations in the water. This could contribute to the increase in the previous years growing seasons. Data collection will continue into the future.

Land management is compared between the irrigated crop field and the dryland corner. Nitrate levels are visibly lower in the dryland than the irrigated crop field. Dryland corners with a rye crop receives some fertilizer but not to the extent that the cash crop requires during it's critical growth stages.

Soil pore water nitrate-nitrogen concentration in water samples collected from suction lysimeters will continue at the Schlichting Farms site as a partnership with Schlichting Farms and the Benton SWCD. One goal is to enhance the study by adding additional drain gauges to the site to better analyze the amount of nitrates moving through the soil profile.

Thank you to the Schlichting Farms Family, Minnesota Department of Agriculture, and the Benton Soil and Water Conservation District, along with the University of Minnesota, for continuing a great research partnership. Photos credit: Jessica Hoheisel with the Benton SWCD

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Jessica Hoheisel

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Photo Credit: Jessica Hoheisel