The state’s new groundwater protection rule officially takes effect this week, although it won’t be until next year that farmers will no longer be allowed to apply nitrogen fertilizer in the fall, in areas where soils are porous. Spokesman Larry Gunderson says there’s a zoomable map on the Minnesota Department of Agriculture website (

“So somebody can go in there and put in their address or zoom into their area where their farm is to determine whether or not we’ve determined if it’s a vulnerable groundwater area or not.”

Gunderson says porous soils are most common in southeast Minnesota, in the central sands area along the Highway 10 corridor, and in some parts of southwest Minnesota.   The new fertilizer restrictions will also apply to areas with high levels of nitrates in public water supplies.   Gunderson notes many farmers already do not apply nitrogen fertilizer in the fall.