How much less nitrate flows into ditches and streams?
Studies have found reductions in annual nitrate load in drain flow ranging from about 15 percent to 75 percent, depending on location, climate, soil type, and cropping percentage as drain flow is reduced, since most studies have found that drainage water management does not change the nitrate concentration in the drain flow. In regions where much of the drainage takes place during the winter (such as Illinois, Indiana, and Ohio), the reduction is likely to be greater than where most of the drainage takes place in April or later, such as in parts of Iowa and Minnesota.
