U.S. farmers are spreading too much fertilizer on their fields, causing air pollution in the eastern part of the country, as well as boosting emissions of planet-warming greenhouse gases, according to a new study by scientists at NASA and several universities.
To combat this boom in nitrogen-based fertilizers, federal officials are pushing new software and sensor technologies to help farmers be more precise about when and where they use fertilizers.
"American agriculture wants to be part of the solution and not part of the problem," said Secretary of Agriculture Tom Vilsack in an interview with Discovery News. "We are learning more about the individual character of each acre of farmland. "With new technologies we can better understand the precise condition of each acre, so we can be more precise about each application."
The new study, published this week in Geophysical Research Letters, found that emissions from farms are greater than all other industrial sources of particulate air pollution in the United States, Europe, Russia and China. The culprit is nitrogen fertilizers and animal waste that combines with industrial pollution to form solid particles. These particles are a big source of various respiratory diseases and death.
"What we found surprising is simply the large amount that is attributed to farming that leads to near-surface air pollution," said Susanne Bauer, an atmospheric scientist at Columbia University and NASA's Goddard Institute for Space Studies.
Bauer said that while farming occurs throughout the United States, the biggest impact on air pollution is in the Northeast where nitrogen emissions from fertilizer and ammonia from animal waste combine with sulfates and nitrogen oxides from industries and automobiles.
These particles combine and form aerosols which are about 1/30th the width of a human hair, the study said. Aerosols get into your lungs, causing heart or lung disease and an estimated 3.3 million deaths worldwide annually.
The more polluted eastern United States has some areas where annual aerosol and particulate matter concentrations exceed health standards from the World Health Organization and U.S. Environmental Protection Agency. Agriculture is responsible for about half of the total human-caused pollution in both the eastern and western United States, the new report found.
Vilsack said his agency is helping farmers move in the right direction by becoming smarter about how they use fertilizers through a new software program that allows them to calculate the best time, place and amount of fertilizer to use. The USDA is also working on new technologies and practices to cut the amount of food Americans throw away, currently about 30 percent.
Less wasted food means less fertilizer and less air pollution.
"To the extent we can cut food waste in half, that should also better reduce the amount of fertilizer that is being applied," Vilsack said. "When food is wasted, it also goes into landfills where it is single largest producer of methane."
Methane, along with carbon dioxide, is one of the most potent greenhouse gases responsible for climate change. The agency has completed the first year of a new program to cut farmers' carbon footprint by reducing soil erosion, using "no-till" crops that cover the soil, installing methane biodigesters than turn cow and pig waste into methane gas and then into electricity, and using more efficient crop irrigation to cut the use of electricity, and therefore burn less fossil fuels.
"We want to equip our farmers, ranchers and producers with tools and technology to allow them to adapt and mitigate (climate change)," Vilsack said. We also want to give them to contribute to (greenhouse) reduction goals, and still remain productive."
Vilsack said these new efforts will reduce net emissions and enhance carbon sequestration by over 120 million metric tons of CO2 equivalent by 2025 -- about 2 percent of U.S. economy's overall emissions.