Synthetic Fertilizer Leads Nitrate Pollution in Central Iowa Rivers

A Polk County water assessment cited by Axios finds synthetic fertilizer is the largest nitrate source in the Raccoon and Des Moines rivers at about 40%. Manure, nitrogen released from soybeans and atmospheric deposition from fertilizer and manure make up most of the remaining load.

The Bigger Picture

The source breakdown shifts the debate from farm ownership toward production systems and nutrient management: agricultural sources dominate while urban sources are minor. Because agricultural runoff is largely outside Clean Water Act permitting, fertilizer use remains difficult for the public to track.