This spring, a muddy lake on the Mississippi River sparked a flurry of controversy about agricultural drainage. Lake Pepin, on the Minnesota-Wisconsin border, is filling up with silt. Most of the sediment is carried into the lake by the Minnesota River, a turbid prairie river that meanders through some of the most productive – and heavily tiled – cropland in the world.

Who is to blame for the sediment clogging Lake Pepin and other waterways that flow through farm country? It seems that lots of fingers point at farmers and their drainage practices.

Midwest soils are fertile but often have poor natural drainage. The Corn Belt’s network of surface-drainage ditches and subsurface tile helps farmers meet the world’s growing demand for food.

Artificial drainage also reduces soil erosion, promotes timely field operations, reduces soil compaction and allows farmers to use less tillage, says Minnesota farmer Bill Gordon, vice-president of the Minnesota Soybean Growers Association.

But artificial drainage also carries nutrients, sediment and other pollutants along with drainage water into streams and rivers, contributingto poor water quality.

“People have very high expectations for water quality, and they are paying more attention to this issue,” says Warren Formo, director of the Minnesota Agricultural Water Resources Coalition, which works on behalf of farmers. “Questions about the effects of drainage on water quality have really burst onto the scene in the last few years.”

Conservation practices have slashed the amount of soil moving from farm fields into rivers and streams, but “every farm can find one or two things to do better. I talk to farmers about their responsibilities to manage and maintain their drainage systems. To non-farmers, I talk about the conservation benefits of good drainage management,” Formo says.

The Corn & Soybean Digest asked Midwest experts to answer some common questions about farm-field erosion, clarify some misconceptions about drainage and suggest some practical remedies that can immediately cut sediment losses and improve drainage water quality.