Tile installation “must be paired with careful nutrient-management practices for rate, form, timing and application method,” says the NRCS’s Don Baloun.

According to the NRCS CEAP report, two-thirds of Upper-Mississippi cropland requires better nutrient-management practices to reduce N or P loss.

Tiling greatly reduces surface runoff and soil erosion from fields, Sands says.

“A large percentage of Midwest soils have poor natural drainage; they’re more prone to surface runoff. Subsurface drainage allows a greater portion of water to infiltrate the soil.” Tiling also increases crop yields, allows timely field operations, and makes it more practical to reduce tillage, retaining more protective residue on the soil, he says.

But, tiling also increases the risk of N leaching, which the NRCS calls “the most critical conservation concern.” Dried-out soils are more susceptible to wind erosion than wet soils, too, says Baloun. And many wet soils being tiled to improve yields don’t have water-erosion problems, he adds.

It’s easy to demonize tile drainage, Sands says. “We’ve traded some environmental issues for others.”