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Conservation Practices Reduce Runoff and Erosion in Lake Erie Basin

March 29, 2016


The Great Lakes. Photo credit: NASA.

The Great Lakes. Photo credit: NASA.

Each year, the U.S. Department of Agriculture (USDA) invests billions of dollars to help farmers, ranchers, and foresters conserve natural resources and wildlife habitat on and around their land. With thousands of producers across the country planning to implement conservation practices, understanding if and how conservation efforts are working is critical.

According to the Conservation Effects Assessment Project (CEAP), the multi-agency effort led by the USDA’s Natural Resources Conservation Service (NRCS) and charged with assessing federal conservation investments, conservation activities are paying off in the Western Lake Erie Basin (WLEB). On Monday, March 28, USDA released a new CEAP report detailing the successes of conservation efforts thus far in WLEB: Effects of Conservation Practice Adoption on Cultivated Cropland Acres in Western Lake Erie Basin, 2003-06 and 2012.

The WLEB supplies water to farmers and communities in multiple states (Ohio, Michigan and Indiana). In the past Lake Erie has been plagued by toxic algae blooms, caused by a combination of climate change and agricultural runoff, which made the water unsafe for drinking or for use on the farm. Thanks to aggressive conservation efforts in the region, NRCS estimates that between 2009 and 2014, farmers kept “7 million pounds of nitrogen, 1.2 million pounds of phosphorous, and 488,000 tons of sediment” on the farm and out of the water supply. The latest update, which builds off a 2011 report focused on the broader Great Lakes region, estimates that even greater annual reductions in nutrient runoff can be expected over the next three years.

Agriculture Secretary Tom Vilsack announced this week that USDA will invest $41 million over three years to clean up the Western Lake Erie Basin. According to the WLEB report, producers will limit phosphorous runoff and sediment loss by an additional 640,000 pounds and 260,000 tons, respectively, over this period.

The WLEB report analyzes the quantitative impact of implementing a variety of voluntary conservation practices available through USDA conservation programs including: riparian buffers, grass filter strips, conservation tillage, integrated pest management, and land retirement. The report uses the cropland farmer survey from 2012 and modeling simulations to compare the impacts of conservation practices adopted between 2003-06 and 2012. The entire Great Lakes region will be sampled again in 2015-2016, with new results to follow.

Key Findings

  • Cropland acres managed with one or more structural practice controlling erosion increased from 34 to 54 percent of acres.
  • Edge-of-field trapping practices that reduce runoff losses, such as riparian buffers and grass filter strips, increased from use on 18 percent of acres to use on 31 percent.
  • Average sediment lost at the edge of fields decreased from 1.1 to 0.5 tons per acre, per year, largely due to the increased adoption of edge-of-field trapping practices.
  • Average phosphorus application rates declined, with average annual application rates decreasing by nearly 2.7 lb/A (from 21.5 to 18.7 lb/A per year).
  • Average nitrogen losses to surface flows decreased from 7.1 to 4.6 lb/A per year, although nitrogen inputs and subsurface losses did not change significantly, nor did nitrogen removed by crops at harvest.
  • Fewer than 6 percent of acres were managed using cover crops in 2012.

Using simulated modeling, the study identified the following conservation treatment needs and solutions:

  • Soluble phosphorus loss is the greatest treatment need in WLEB. 42 percent of WLEB acres exceeded an average annual loss threshold of 1 lb/A per year.
  • Average annual total phosphorus loss is simulated at 1.9 lb/A. The majority of it, 1.3 pounds, is lost via subsurface pathways, leaving 0.5 pounds of phosphorus on the field as legacy phosphorus.
    • Simulations including cover crop adoption demonstrate the need for close monitoring of soil phosphorus, because crop yields decline once excess phosphorus is mined from soil.
  • Subsurface nitrogen loss is the second greatest treatment need, with 29 percent of acres exceeding the 25 lb/A 
average annual threshold.
  • With regard to sediment losses, increased conventional tillage tends to increase sediment losses and reallocate phosphorus from soluble losses to sediment-attached losses.

The report also included simulated modeling, which compared the effects of WLEB conservation practices used in 2012 to a scenario in which no conservation practices were in place. According to the results of the simulated model, the WLEB conservation practices reduced annual sediment losses by 81 percent (9.1 million tons per year), total nitrogen losses by 36 percent (40.6 million pounds per year), and total phosphorus losses by 75 percent (11.4 million pounds per year).

Conclusions

The report concludes, “voluntary conservation is making significant headway in reducing nutrient and sediment losses from farm fields”. However, it also emphasizes that continued progress would depend on both comprehensive conservation planning, as well as precision conservation technologies:

“Acres needing treatment very rarely exist in isolation within single fields. The findings support the need for individualized, comprehensive conservation planning that addresses the variability within fields.”

The National Sustainable Agriculture Coalition (NSAC) has long encouraged NRCS to integrate comprehensive conservation planning into each of its conservation programs. This would help producers to consider a range of options for addressing multiple resource concerns over time.

The WLEB report is the second in a series of Great Lakes Region reports on conservation practices on cropland that will be issued as part of CEAP. Additional information is available on the NRCS CEAP webpage. Read NSAC’s coverage on past CEAP projects on the Lower Mississippi Basin and the Chesapeake Bay region here and here.


Categories: Conservation, Energy & Environment


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