Water and agriculture: heartland issues

Key Concepts

• Modern intensive row-crop production of corn and soybeans in the Midwest—increasingly supplemented by irrigation systems in the great plains and elsewhere—generates a massive supply of affordable grain for food, animal feed, and biofuels.
• But these methods also contribute to soil erosion and a wash of nutrients into streams and groundwater.
• The accumulation of nutrients in fresh water—whether from soil erosion, fertilizer runoff, animal waste runoff, or other sources—contributes to health-threatening levels of nitrate in some downstream drinking-water sources.
• Nutrient accumulations (primarily nitrogen and phosphorus) in the Mississippi watershed contribute to harmful algal blooms and oxygen-depleted “dead zones” in the Gulf of Mexico, which can kill fish and other marine life.

A Few Facts to Know

• In 1940 about one-third of Iowa farmland was used to grown corn and soybeans (with soybeans a very small fraction at that time). Much of the remaining agricultural land was used for small grains, pasture, and hay production. Today about two-thirds of Iowa’s acres are used for corn and soybean production.
• U.S. domestic corn use has more than doubled since 1980, largely due to corn’s use in the production of ethanol fuels.
• Nutrient pollution mitigation strategies can reduce downstream impacts, but they add costs and adoption has been slow. For example, planting winter cover crops and eliminating the plowing under of corn stalks in the fall can minimize erosion and runoff, and diversion of water into wetlands and bioreactors allows resident bacteria to break down pollutants.

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