What's good for Minnesota's corn and soybeans can be deadly to crabs and shrimp in Louisiana. A national task force meeting in St. Paul last week heard that fertilizer from farm fields washing down the Mississippi River continues to help create a seasonal "dead zone" that this year extends across 5,800 square miles of the Gulf Coast. "It's too much of a good thing," task force chairman Benjamin Grumbles said, referring to the nitrogen and phosphorus from urban lawns, cropland and sewage treatment plants that enter waterways. The fertilizers cause tremendous algal growth in near-shore areas of the Gulf of Mexico, said Grumbles, who is also acting assistant administrator for water at the Environmental Protection Agency. The algae bloom, sink and decay, consuming virtually all the oxygen in the bottom waters and killing most aquatic life. The 2004 Gulf dead zone, measured in late July, is about the size of Connecticut and Rhode Island combined, and slightly larger than the average size that has been recorded each summer for the past 20 years. The seven-year-old task force set a goal three years ago of reducing the dead zone by about 30 percent by 2015, but so far little progress has been made. The task force mission is to identify ways to reduce the nutrient runoff, and Grumbles said its recommendations and strategies, especially for farmers, must be voluntary, practical and cost-effective. Previous reports have estimated that 6 to 8 percent of the agricultural nitrogen that reaches the Gulf comes from the Minnesota River, which drains much of the state's farmland. Steve Morse, senior fellow at the University of Minnesota's College of Agricultural, Food and Environmental Sciences, said part of the problem is that millions of acres of cropland in the Upper Midwest have virtually no cover for several weeks in spring, when the rains are greatest and corn, soybeans and other crops have barely emerged. As a result, he said, much of the rain runs off the fields, and the water is often laden with fertilizers. "We've spent a disproportionate amount of research money on how to grow corn and beans and that's been extraordinarily successful, but they also have some inherent problems as we've been finding out on the environmental side," said Morse, who was formerly deputy commissioner at the Minnesota Department of Natural Resources. Among the practical ways to reduce nutrient runoff are establishing green buffer zones along ditches and streams to intercept runoff, restoring wetlands to hold the water, educating farmers not to over-fertilize, and rotating a greater diversity of crops so that more of the landscape has "continuous living cover" during the spring and fall, he said. Morse said the university is organizing a multistate consortium in the Upper Midwest to develop a new generation of agricultural systems and techniques that will reduce nutrient runoff and at the same time benefit farmers, water quality and wildlife. The groups will include land-grant institutions, agricultural and nonprofit organizations and government agencies, he said. The task force, which includes 20 members from states, Indian tribes and federal agencies, will reassess its earlier predictions about nutrients and hypoxia by the end of 2005. A recent EPA draft report suggested that phosphorus may play a larger role in the Gulf than previously estimated, and that reducing the amount of nitrogen runoff from farm fields may not shrink the dead zone as much as computer models predicted. American Farm Bureau Federation officials said that if earlier assessments were flawed, then public and private money has been misdirected and is being spent to solve the wrong problem. Grumbles said the federation misinterpreted the report, which is a draft that was not peer-reviewed for accuracy. If anything, said Grumbles, the report suggests that runoff from both nitrogen and phosphorus into waterways is causing problems, and both need to be addressed. Tom Meersman is at meersman@startribune.com. The Mississippi and the 'dead zone' Nitrogen does the same thing in the ocean that it does on land: It boosts plant growth. In the Gulf of Mexico, just beyond the mouth of the Mississippi River, it causes immense algal blooms. When the algae die and sink, oxygen is depleted from the water, choking off the marine ecosystem in a phenomenon called hypoxia. Shrimp and fish can flee the suffocated area, but less-mobile animals such as snails, crabs and clams cannot. The bloom starts each spring in April or May and lasts until October. Minnesota River It's blamed for about 6 percent of the nitrates in the 'dead zone,' a significant amount considering the size of the Mississippi basin, which includes 31 states. What happens 1. A government report says nitrogen and fertilizer runoff from farmland in the Mississippi River basin flows downstream to the Gulf of Mexico. 2. Algae feed on the nitrogen, grow and die off. Zooplankton and bacteria feed on the algae, using up dissolved oxygen. 3. Eventually, this process robs teh water of oxygen. The result? A nearly lifeless swath of ocean as big as Connecticut and Rhode Island. Source: National Oceanic and Atmospheric Administration, July, 1998Star Tribune
