Farmer Spraying Pesticides

    Published: March 2, 2015

    Nitrates in the Water? Don’t Blame Fertilizers

    When nitrates enter public water sources, the blame is usually laid on farmers, or perhaps more accurately, on nitrate fertilizers. In Iowa, nitrate pollution has actually lead to a lawsuit against local farmers by the Des Moines Water Works. The lawsuit demands farmers stop releasing so many nitrates into the city’s water source.

    Counterintuitively perhaps, nitrate fertilizers aren’t actually to blame for the bulk of nitrates in Des Moines’ water supply. The problem isn’t what farmers are using to fertilize crops—it has to do with when the fields are empty.

    Iowan farmers grow fast-growing summer crops such as corn and soy. While the crops are growing, they absorb the nutrients they need, including nitrates. In fact, they suck up so much nitrate that very little escapes a field to enter the water supply.

    But summer crops only take five months or so from planting to harvest. For the rest of the year, the field lies empty and that’s when the problem starts. Plant roots and microbes release nitrate during this period, which builds up in the soil because no plants are there to absorb it. Rain and melting snow carries this nitrate down to rivers and streams, where it contaminates water supplies. Nitrates from empty Iowa fields cause problems for water supplies, wildlife, and fisheries all the way to the Gulf of Mexico.

    The solution, it turns out, is not less fertilizer. It’s more plants farmers need to plant “cover crops,” hardy plants such as rye that grow in the fall, go dormant during the winter, and then mature in the spring. Simply by planting cover crops, a farmer can reduce soil nitrate by a third, with the added advantage that the cover crop protects fields from erosion.

    Cutting nitrates by a third still means a significant amount of the chemical would wind up in public water, along with chlorine, bacteria, and other contaminants. If this concerns you, a whole house water filtration system offers a solution, protecting your home and family from the increasingly wide range of chemicals and contaminants found in our drinking water.