This is less than the amount of pesticide carried in surface runoff with eroding soil. Researchers tracking run off from poorly drained fields often find 1 or 2 percent of pesticide applications in surface water during the first or second storm after application. According to Kladivko, field drainage tiles keep pesticides out of surface water in two ways. First, less water runs off tiled fields, which means less pesticide gets carried away in water. Second, when water percolates down through soil before it runs into tiles, many of the chemical molecules stick to soil particles.
Less pesticide is left in the water to get carried away to ditches and streams.
Kladivko's research leads her to counsel farmers to tile poorly drained fields and to use conservation tillage, buffer strips and other erosion-control techniques along the edges of fields to slow erosion.