Paired Watershed Studies for Nutrient Reductions in the Minnesota River Basin
(David J. Mulla, Mary Renwick and James Anderson)

Paired Watershed Study - University of Minnesota

Paired Watershed Study Article in The Land, April 9,2004 (pdf 555k)

Project Overview

The Paired Watershed Project, which began in 2002, is a farmer-initiated, farmer-led effort to improve water quality in the Minnesota River Basin through the voluntary adoption of Best Management Practices (BMPs) for crop nutrients

Two watersheds, Seven Mile Creek and Huelskamp Creek, were selected for the study. As part of the project, both watersheds are being monitored at the mouth of each minor watershed (four sites, total) for water flow, sediment, total and dissolved phosphate, and nitrates.

The objectives of the project are to:

  1. Accelerate the voluntary adoption of BMPs in the Minnesota River Basin to achieve measurable improvements in water quality;
  2. Evaluate the effectiveness of farmer-selected BMPs to improve water quality; and
  3. Develop and disseminate farmer-led and farmer-sanctioned water quality initiatives in the Minnesota River Basin. (Initial results of the study are expected to be available in 2005.) The study will continue through 2006.

The water quality data and farm survey data will be used for economic and water quality modeling to determine the costs and benefits of various management practices as a function of farm size and soil type, as well as the advantages of targeted adoption of BMPs, and the level of BMP adoption needed to attain various levels of improvement in water quality. Results from the project will be used to develop educational materials for farmers, fertilizer coops, agency personnel, researchers and extension agents, policy makers, and the general public.

Preliminary Findings
The main findings from the initial year of farmer and field surveys were:

  • Half of farmers used moldboard plowing on corn residue
  • 78% of cultivated land had less than 30% residue cover after planting
  • Of the fields having phosphorus soil test results, 75% were in the very high category (>21 ppm Bray-P)
  • Manure is applied to 20% of the cropland, and 30% of the manure is surface applied
  • Total rates of N from both fertilizer and manure ranged from 50-383 lb N/ac, while Extension recommendations are about 120 lb N/ac
  • Total rates of P2O5 from both fertilizer and manure ranged from 20-405 lb P205/ac, while Extension recommendations are about 25 lb P2O5/ac

During the summer of 2002 and 2003, meetings were held with farmers to discuss results of water quality monitoring and farm practice surveys. Based on these meetings, farmers in the western watershed (treated) decided that they wanted to begin making changes in their farm management practices to improve water quality. Farmers indicated a preference for the following changes in management:

  • Tillage practices that left more crop residue
  • Soil and manure nutrient testing and crediting
  • Buffer strips along ditches
  • Replacement of surface tile intakes with buried rock inlets

During fall of 2002 and 2003, contracts to implement these changes were signed with farmers managing over 80% of the cultivated land in the treated watershed. Simultaneously, contracts were signed with nearly all the farmers in the control watershed to make no changes in their farm management practices. Water quality monitoring will continue for the next two years to determine how changes in farm management in the treated watershed influence water quality. Farm surveys will be administered again for the next year to track changes in the treated and control (if any) watersheds.

Project Team

The farmer-assembled project team consists of University of Minnesota soil scientists, economists, and Extension educators; local government water planners, water quality monitoring specialists, and policy makers; and state agricultural training and education personnel.

  • David Mulla, Mary Renwick, Jim Anderson, and Prasanna Gowda, University of Minnesota
  • Gary Hachfeld, Educator, University of Minnesota Extension Service
  • Kevin Kuehner, Water Quality Monitoring Specialist, BNC Water Quality Board
  • Tina Rosenstein, Nicollet County Environmental Services
  • Pam Rivers, Water Planner, Nicollet County
  • Derek Fisher, Board of Water and Soil Resources
  • Mark Dittrich and Wayne Monsen, Minnesota Department of Agriculture

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