In the small town of Edgerton, Minn., where a shallow aquifer readily absorbs leaching farm chemicals, residents pay extra every month for muncipal treatment that makes their water safe to drink. The nitrate-removal system -- now woven into the infrastructure of this heavily Dutch settlement - reflects a dilemma that is spreading across Minnesota farm country: Corn and soybean fields pump money into local economies, while pumping unwanted chemicals into the groundwater.