Some farmers have a routine of chemical fertilizers and manure on these fields. But, the land poses a far greater environmental problem to freshwater lakes than previously, potentially polluting the water for hundreds of years, according to new research. Phosphorus in those substances has built up in the soil and can slowly end up in many lakes, where the nutrients lead to plant and algae growth. The environmental problem, known as eutrophication, can turn pristine lakes into smelly, weed-filled swamps with lots of dead fish.
The National Academy of Science from University of Wisconsin Stephen Carpenter said “the buildup largely on industrial agriculture’s use of fertilizer and manure since the 1940s. The concentration could cause the eutrophication of lakes for centuries as the treated soil slowly washes into lakes and streams. The problem leads to fish kills and the growth of toxic algae that can make lakes unsuitable for swimming. A very small percentage of the phosphorus moves into the lake each year and that small amount is sufficient to cause a great deal of water pollution,” Carpenter said. The study concluded saying that we need major changes in soil management to preserve what is left. We need the government to act with an urgency to stop the phosphorus before it gets into the lakes and streams. Stephen Carpenter did a study in Lake Mendota (Urban Lake in Madison, WI), where he found that the lake water quality has declined over the years. This is a popular spot for fishing. The main reason for farmers to use chemical fertilizer over natural fertilizer and manure is cost. They simply can’t afford it, so many use the cheaper option.
The light green water color in Southern California’s Salton Sea (lower right) is an algae bloom caused by farm fertilizer runoff.