Farm Progress

Ag Water Stewardship: Reduced phosphorus and sediment loss are evident, yet nitrate levels are increasing.

Warren Formo

March 22, 2017

3 Min Read
RIVER HEALTH: Changes in tillage practices and adding more conservation practices to the land help keep nutrients and soil in place.

Results from the Minnesota Pollution Control Agency Milestone River Monitoring sites show improving trends in five pollutants, including phosphorus and suspended solids.

This is good news and an indication that on-farm efforts to curb soil erosion are working.

An MPCA analysis, Water Quality Trends for Minnesota Rivers and Streams at Milestone Sites, summarizes pollutant measurements at 80 locations, some of which date back to the 1950s. The monitoring locations include several rivers and streams in primarily agricultural regions, many of which show improvements in phosphorus and suspended solids concentrations. Overall, 85% of the 80 sites showed a decreasing trend for phosphorus, while 63% showed reductions in suspended solids.

These improvements coincide with significant reductions in tillage intensity, refinements in nutrient applications and the retirement of environmentally sensitive lands, all of which were the primary focus of environmental programs led by the USDA Natural Resources Conservation Service and local soil and water conservation districts for most of the last century. The NRCS report Assessment of the Effects of Conservation Practices on Cultivated Cropland in the Upper Mississippi River Basin quantified some of these improvements.

This NRCS report covers much of Minnesota, Iowa, Wisconsin and Illinois, along with small portions of Indiana and Missouri. Model results show that cropped acres in the region have reduced surface water flow from farm fields by 16%, reduced sediment loss from fields by 69% and reduced phosphorus loss from fields by 49%. These improvements align with farmer efforts to address erosion and the emphasis of NRCS programs available to farmers.

The report also notes that “conservation practices have the greatest effect on the more vulnerable acres, such as highly erodible lands and soils prone to leaching. Targeting treatment of these vulnerable acres is the most efficient strategy” for reducing pollution. While this simple observation may seem obvious to many readers, it is too often lost in the analysis of the extent of adoption of conservation practices.

Using no-till, strip-till
For example, some people are concerned about overall adoption of no-till or strip-till, or acres enrolled in the Conservation Reserve Program. Perhaps a better measure would indicate the adoption of these conservation practices on the land where they are most needed. Regardless, the MPCA Milestone report showing positive trends provides another line of evidence that many farmers are indeed applying good conservation strategies in the most sensitive areas at a higher level.

The Milestone report also reveals increasing trends in nitrates as an area of concern. Of the 80 milestone sites, 56% had an increasing trend for nitrate, pointing toward a future area of emphasis for both agricultural and urban stakeholders. Within agriculture, increasing nitrogen use efficiency for both profitability and environmental benefits has become a major focus in recent years.

This new focus is not at the expense of past efforts to reduce soil erosion, but an added commitment. I expect that your efforts to reduce nitrogen losses will follow a similar pattern, turning water quality trends in a positive direction in future Milestone reviews.

Formo is executive director of the Minnesota Agricultural Water Resource Center.


About the Author(s)

Warren Formo

Warren Formo is executive director of the Minnesota Agricultural Water Resource Center.

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