It All Ends Up in the Water

Power to the Peeples is an exclusive Earth911 series written by Bob Peeples, our resident chemical engineer and Program Manager of Earth911’s sister site Beaches911. Bob combines his extensive knowledge of the environment and how things work with an off-the-cuff sense of humor.

I get lots of inquiries in regards to what happens when chemicals are introduced to our water sources. One interesting question I got recently is what effect do fertilizers have on water and the environment? One would think that, since fertilizers are sort of like vitamins for plants, they were a naturally occurring material, but let’s dive further into the issue.

There are three basic types of environmental impact for any process: chemical, biological and physical. In farming, chemical impacts are usually from nutrient runoff when too much chemical fertilizer has been applied, or too soon before a rainfall that washes it off of the cropland. Biological impacts are usually from the application of manure that washes away. Typical physical effects are things like soil erosion from wind or rain. Soil that ends up in the water can block the sun from the water below and kill everything off by stopping any chance of photosynthesis.

Chemical impacts are rarely toxicity issues with fertilizers unless it is a catastrophic spill. Toxic impacts are related more to pesticide and herbicide runoff contamination. These are sometimes combined with fertilizers, though, to reduce application costs. Pesticides and herbicides are very general in their action. They are not very species-specific. That can be bad for the things that you didn’t intend to kill.

The most common chemical impacts are from what would be called “nutrient loading.” This is because fertilizers are pretty general, too, and will encourage the wrong sort of growth along with the good kind. Algal blooms can have the same physical impacts as soil runoff by blocking light from the top of the water column, as well as the dissolved oxygen depletion that comes with huge algal blooms, and algae can out-compete everything else (lesson: don’t mess with the balance of nature—or, if it’s not broken, don’t fix it).

Biological impacts are usually through the introduction of pathogenic organisms to the environment, caused by using enteric materials (poop) as crop fertilizers, such as untreated animal manure. You have probably already heard of people getting very sick or even dying from exposure to an Escherichia coli (E. coli) genotype known as O157:H7.

E. coli is most commonly associated with poorly cooked hamburger that has been contaminated with cattle manure during slaughter, but lately it has also been associated with use as a fertilizer in crops like lettuce, where it can be difficult to clean well between leaves. I can also tell you from personal experience that it can also get into the water and infect swimmers.

There are other sources of more detailed information on fertilizer impacts. The best jumping off point, in my opinion, would be USDA Extension Agents because they know the local realities better than anyone. This contact will obviously vary based on the state you live in, but performing a search for “land grant” in your state will narrow it down. The deal was that farmers would grant land to build the state universities and the universities would return the favor by providing research and education to the community. There are also hundreds of free USDA bulletins available through the Extension offices that you can use as resources. A trip there will prove well worth your time if you are interested in learning more about fertilizers’ effect on water.