West Lafayette, IN -- A study of the cost of proposed changes in nitrogen management needed to eliminate the hypoxic zone, or dead zone, in the Gulf of Mexico has found that the American farm system can afford these changes -- barely.
Scientists estimate that to eliminate the hypoxic zone in the gulf, the United States should reduce the amount of excess nitrogen flowing down the Mississippi River by 20 percent or more, and much of the burden of that reduction would be placed on farmers.
Otto Doering, a professor of agricultural economics at Purdue University, has found that farmers can use a variety of methods to cut the flow of excess nitrogen by 20 percent to 25 percent without hurting food prices or farm exports. "Beyond that, however, American agriculture begins to fall out of bed," Doering says.
The Gulf of Mexico hypoxic zone is a 7,000-square-mile area in the northern gulf that has too little oxygen to support most marine animals (hypoxic means oxygen deprived). The zone begins at the mouth of the Mississippi River and extends west toward the Texas coastline, occurring in the middle of the most important commercial and recreational fishing zone in the lower 48 states.
The zone exists because of the flood of excess nitrogen that comes down the Mississippi River each summer. Nitrogen is an important plant nutrient, and with so much of it in the gulf, small plants such as algae grow so much that they use up the available oxygen in the sea water.
The dead zone doesn't actually kill any fish, because they are able to swim away from the area. Other types of sea life, such as starfish and sea anemones, may not be able to escape and may die.
Although other hypoxic zones exist in the Black Sea, Baltic Sea, Chesapeake Bay and New York Bight, the Gulf of Mexico is unique. Because the Gulf of Mexico is open to ocean currents, unlike other enclosed seas, scientists think that the problem can be corrected
Only a small portion of the nitrogen coming down the Mississippi is from sewage treatment plants and factories. The bulk of it is non-point nitrogen. That means it is not from a specific pipe or source, but is nitrogen that comes off the land or through the soil. A large portion - but not all - of the nitrogen that comes through the land and soil comes from fertilizer applied by farmers.
Farmers aren't completely to blame. Huge amounts of nitrogen are found naturally in the air, in the soil and in living organisms, and all of these contribute to the nitrogen moving down the Mississippi. "If farmers stopped putting nitrogen on the fields today, we would still get nitrogen leaking out of the system," Doering says.
But he quickly adds that agriculture doesn't get off the hook. "Agriculture still has to be concerned about all of this," he says. "Municipalities and industries release a total of 270,000 metric tons of nitrogen per year into streams and rivers, and the excess nitrogen delivered just to the gulf is 1.5 million tons per year. So agriculture, which uses 6.5 million metric tons of nitrogen a year, is clearly the major player."
To address the problem, the White House Office of Technology embarked on a scientific assessment of the causes and consequences of hypoxia in the Gulf of Mexico. Doering is one of six team leaders, and he is responsible for determining the economic consequences of proposed changes. He and the other team leaders presented their findings Jan. 23 at the annual meeting of the American Association for the Advancement of Science in Anaheim, Calif.
Doering looked at the effects of reduced nitrogen use on consumer prices, exports and land use. "We found that you can adjust farm practices and reduce nitrogen losses by about 20 percent without causing serious dislocation in agriculture," Doering says. "Beyond that, there is serious disruption in terms of high food prices, an increasing drop in exports, and a loss of farmland."
Doering says that farmers can reduce nitrogen loss by 20 percent by improving farm management practices. "Fertilizer management will be the key thing," he says. "No more fall fertilization. More precise application in terms of place and time for spring planting. Buffer zones along streams. Fewer inputs -- about a 20 percent reduction of the amount of nitrogen used."
If a farmer just reduces the amount of fertilizer without improving management practices, the farmer would have to cut the nitrogen application by as much as 45 percent to achieve the same results, Doering says.
Agriculture also can reduce nitrogen loss by reconstructing more wetlands. "It's a way of dealing with the nitrogen that's already in the system," Doering says. "The wetlands allow you to hold the water for periods of time, and the nitrogen tends to go into the atmosphere."
Doering says that wetlands have their own economic benefits for those living near them. "There is increased wildlife habitat, more hunting opportunities, water quality improvements, things that are very direct in the basin where the wetlands are," he says. "With wetlands the benefits accrue, if not to the farmer, at least to his immediate neighbors. That makes a certain amount of wetland reconstruction an attractive component of reducing nitrogen loss."
Materials provided by Purdue University. Note: Content may be edited for style and length.
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