Find more fertilizer pollution solutions

By The Gazette Editorial Board

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The primary source of nutrient pollution in Iowa's streams is nitrogen and phosphorous fertilizers from our state's corn and soybean fields, the Iowa Policy Project reported in late September.

A week later, Iowa Secretary of Agriculture Bill Northey announced a new initiative aimed at reducing by 45 percent the amount of phosphorous and nitrogen finding its way into waterways.

Coincidental timing? Probably.

But we're encouraged to see more constructive attention being paid to this problem.

To be sure, Iowa's highly productive farmers have made substantial strides in reducing the amount of runoff from their row crop fields. They've done that in large part by increasing use of minimum- or no-tillage practices that leave more residue on top of the ground and don't disturb the soil as much. The amount of land with 30 percent or more of the crop residue left intact for the next planting increased from about 6 million acres in 1989 to more than

13 million acres by 2005, according to the Iowa State University Agronomy Department.

But there's still more progress to be made. Iowa Policy Project researchers, citing U.S. Department of Agriculture data, said that 22 percent of Iowa's cornfields are still intensively tilled. They suggest that farmers also could reduce the amount of fertilizer used by doing more soil testing and improving the timing of applications. More than half of Iowa's crop acreage is fertilized in the fall, when land is more vulnerable to runoff and fertilizer leaching.

Northey also pointed to more use of cover crops that hold nitrogen in the soil during winter months and building more wetlands that hold runoff and filter water. However, the initiative he launched with Iowa State University first will determine, by mid-2011, the most effective land practices and their costs.

Efforts to curb fertilizer runoff are important not only to Iowa's water quality but to downstream neighbors. Iowa is among 12 states working with federal agencies to reduce the size, severity and duration of the Gulf of Mexico's “dead zone” - an area the size of Massachusetts that is low on oxygen and can't sustain marine life because of algae growth produced by excess nutrients washed down the Mississippi River. Iowa and Illinois area among the major contributors. The U.S. Geological Survey says agricultural sources account for more than 70 percent of the nitrogen and phosphorous found in the Gulf.

Reducing ag-land runoff also is a key to our state government's formal goal of better managing our watersheds to improve water quality and reduce flood damage that has plagued Iowa in recent years. Devising public policy built on sound research, while engaging farmers as partners with shared responsibility, is an immense challenge but one Iowa is obliged to tackle.