Nitrate Runoff, Explained

Midwest farmers need fertilizer to help their crops grow. The problem is, nitrogen spread on farm fields in addition to existing ground nitrogen can turn into nitrates that leach off fields and into local waterways. Here’s why you should care:

1. It’s gathering in the Gulf of Mexico, creating a “dead zone”

Nitrates in the Midwestern water system run down the Mississippi River and into the Gulf of Mexico. The nitrates in the Gulf feed the growth of large algae blooms. The algae uses up lots of oxygen, creating an effect called hypoxia and endangering the existing ecosystem. According to the USGS, the dead zone is about the size of Connecticut

2. Cleaning nitrates out of water can get expensive

Iowa’s Des Moines Water Works, a utility company, is suing three nearby counties for the high levels of nitrates in the rivers. Because the EPA regulates how much nitrate can be in drinking water, utility companies have to clean it out. This can get expensive — in 2013 Des Moines Water Works says it spent $900,000 on cleaning out nitrates and the company expects the 2015 cost to be even higher.

3. It’s not the only kind of agricultural runoff

Although nitrate runoff makes the news a lot, other nutrients like phosphorus and potassium also get into the water system as an effect of agriculture. Sediments, pathogens and pesticides can also become runoff, according the the EPA.

For more in-depth information on what nitrate runoff is and how it works, watch our explainer video.