Nutrients, Pesticides Still Leaching into Upper Mississippi Waterways

Nutrients, Pesticides Still Leaching into Upper Mississippi Waterways

WASHINGTON, DC, June 17, 2010 (ENS) – Conservation practices employed on cropland in the Upper Mississippi River Basin are reducing sediment, nutrient and pesticide losses from farm fields, but producers need to better manage nutrients to keep them out of waterways, finds the first in a series of regional reports by the U.S. Department of Agriculture.

“This important new report confirms that farmers and ranchers are stepping up and implementing conservation practices that can and do have a significant impact on the health of America’s soil and water,” said Agriculture Secretary Tom Vilsack, releasing the report on Wednesday.

But the study also found that consistent use of nutrient management – the proper rate, form, timing and method of application of fertilizers such as nitrogen and phosphorus – is generally lacking throughout the region.

The study found that the most critical conservation concern in the region is the loss of nitrogen from farm fields through leaching, including nitrogen loss through tile drainage systems.

“Improved nutrient management would reduce the risk of nutrient movement from fields to rivers and streams,” the study states. “Treatment with nutrient management practices in addition to soil erosion control practices is required to effectively control the loss of soluble nitrogen and phosphorus from farm fields in the Upper Mississippi River Basin.”

“The information gathered for this study will make it possible to quantify the effectiveness of conservation practices for the first time and enable USDA to design and implement conservation programs that will not only better meet the needs of farmers and ranchers, but also help ensure that taxpayers’ conservation dollars are used as effectively as possible,” Vilsack said.

The Upper Mississippi River Basin covers about 190,000 square miles, or 121.5 million acres, between northcentral Minnesota and the confluence of the Mississippi and Ohio rivers.

The basin includes large portions of Illinois, Iowa, Minnesota, Missouri, Wisconsin and small portions of Indiana, Michigan and South Dakota. Nearly half the basin is planted in corn and soybeans.

Contoured farmland in Polk County, Iowa (Photo by Carl Wycoff)

Commercial fertilizers and pesticides are widely used throughout the region. In 2007, the latest year for which figures are available, 47 million acres of cropland were fertilized, 47 million acres of cropland and pasture were treated with chemicals for weed control, and 20 million acres of cropland were treated for insect control. About 5.3 million acres had manure applied in 2007.

Conservation practices include installing structures such as riparian buffers, grass filter strips, terraces, grassed waterways, and contour farming to reduce erosion, sedimentation, and nutrients leaving the field;

Farmers may adopt conservation systems and practices such as conservation tillage, comprehensive nutrient management, integrated pest management, and irrigation water management to maintain the long-term productivity of crop and pasture land.

They may retire land too fragile for continued agricultural production by planting and maintaining grasses, trees, or wetland vegetation.

Researchers found that conservation practices have the greatest effect on the most vulnerable acres, such as highly erodible land and soils prone to leaching.

Uses of soil erosion control practices are widespread in the basin. Most acres receive some sort of conservation treatment, resulting in a 69 percent reduction in sediment loss.

However, about 15 percent of the cultivated cropland acres still have excessive sediment losses and require additional treatment, the study found.

The study found that suites of conservation practices work better than single practices and that targeting critical acres improves effectiveness. A suite of practices that includes both soil erosion and consistent nutrient management is required to simultaneously address soil erosion and nitrogen leaching loss.

Even when fully treated, however, some of the most vulnerable acres will have unacceptable losses, especially during years with extreme weather events, the study states. “For these acres, a change in the cropping system, land use change, or establishment of long-term conserving cover may be necessary to meet watershed protection goals.”

USDA conservation programs are voluntary. Many provide financial assistance to producers to help encourage adoption of conservation practices. Others provide technical assistance to design and install conservation practices suitable to the goals of the agricultural operation and the soil, climatic, and hydrologic setting.

Key partners in this study were USDA’s Agricultural Research Service and Texas AgriLife Research, part of the Texas A&M University system.

This research is part of a larger multi-agency effort, the Conservation Effects Assessment Project led by USDA’s Natural Resources Conservation Service, to assess the effects of conservation practices on cropland, grazing lands, wetlands, wildlife and watersheds across the country.

More regional cropland studies on the effects of conservation practices will be released over the next several months.

Click here to read the report, “Effects of Conservation Practices on Cultivated Cropland in the Upper Mississippi River Basin.”

Copyright Environment News Service (ENS) 2010. All rights reserved.

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