||Parts of Minnesota, Wisconsin, North Dakota and South Dakota have coarse textured soils overlying sand and gravel aquifers. The aquifers are shallow. The high hydraulic conductivities of overlying soils make them vulnerable to contamination.
The Minnesota MSEA site is in the Anoka Sand Plain near Princeton, MN. The Anoka Sand Plain is characterized by high hydraulic conductivity, shallow depth to water table, flat topography, and low runoff. The underlying 1,700 square mile aquifer is one of the largest in the state.
The Wisconsin River Sand Plain site has deep permeable sandy soils (Sparta sand) that are farmed intensively. The soils are excessively drained. Ground- water occurs at 6 to 10 feet below the soil surface. Irrigation is necessary for profitable crop production.
The Oakes Irrigation Research site aquifer in North Dakota consists of medium sand to gravel. The depth to the water table is approximately 10 feet. Annual precipitation averages 18 inches.
The Big Sioux Aquifer site in South Dakota focuses on multiple aquifer studies, including those by USGS and EPA. The aquifer underlies some 1,200 square miles in eastern South Dakota, and is the water supply for Sioux Falls, Brookings, and many smaller communities. (The water table is within 15 feet at some locations).
Preliminary ground water samples from the Anoka Sand Plain in 1990 showed nitrate nitrogen levels at 15 to 18 ppm. Sampling established the presence of atrazine and/or its metabolites in shallow ground water at all locations, except North Dakota.
STUDY OBJECTIVES AND RESULTS:
- Measure the impact of prevailing and modified farming systems on the content of nutrients and pesticides in ground and surface water.
- Atrazine, alachlor, and metribuzin, used in the corn-soybean farming system, have not affected ground water quality during the first five cropping seasons, except for South Dakota and Wisconsin where some atrazine reached the surface of ground water.
- Nitrate-nitrogen concentrations at the water table seldom exceeded 20 ppm and decreased with time and depth as better fertilizer nitrogen management practices were implemented.
- Ridge tillage reduced the leaching of atrazine and nitrate, and subsequent contamination of ground water at the WI site when compared to moldboard plowing. This was due to the herbicide placement on the less hydrologically active ridges.
- At the MN site, corn is shallow rooted as a result of high soil strength (penetration resistance) and high bulk density. The resulting dense root mat near the soil surface enhances nitrogen use efficiency and protects ground water quality.
- Atrazine movement through the silty clay loam soil at the SD site was reduced by physically separating placement of fertilizer and herbicide.
- Identify and increase understanding of factors and processes that control fate and transport of agricultural chemicals.
- In the Big Sioux Aquifer, denitrification is occurring during the spring.
- Atrazine is ten times more tightly adsorbed onto soil particles under field conditions than is being currently modeled.
- The RZWQM model predicted nitrate and atrazine fate and transport fairly accurately in the early growing season, but discrepancies were found in late season predictions.
- Assess the projected benefits to water quality of implementing modified farming systems.
- Improved soil sampling strategies increase the accuracy of the fertilizer recommendation.
- In fields where N is band applied, sampling a zone approximately halfway between the band and the crop, can reduce soil sampling requirements by 50%.
- Better timing and placement of herbicides in relation to fertilizer placement reduces the potential for herbicides to move into the lower root zone.
- Better predictions of herbicide movement, based on new characterizations of soil-herbicide binding at realistic soil-water contents, will improve the design of farming systems for protecting water quality.
- The ridge tillage farming system reduces atrazine use without great capital investment on the farmer's part. Atrazine concentrations never exceeded 3 ppb, and were usually less than 1 ppb.
- Improved techniques to determine plant-nitrogen requirements will reduce nitrogen inputs to ground water.
- Assess the impact of agricultural chemicals and practices on ecosystems associated with agriculture.
- Nitrate-nitrogen is denitrified in the aquifer. Concentrations decrease to less than 0.2 ppm at 8 to 24 feet below the water table.
- Nitrate concentrations are less than 0.2 ppm in adjacent wetlands which are sustained by shallow ground water.
- Evaluate the social and economic impacts of using alternative management systems.
The site is located within the Anoka Sand Plains (ASP) Demonstration Project, where five recent focus group discussions revealed:
ASP Demonstration Project cooperators have:
Transfer appropriate technology for land use.
A total of 165 agribusiness dealers, area farmers, and conservation agency staff attended a day-long Diagnostic Training Clinic held at the site. Some 150 small plots illustrated "real-world" examples for workshop participants on insect, weed, disease, fertilizer, and cultural production problems common to corn and soybeans.
A total of 24 certified crop advisors earned the 6.5 hours of continuing education credits (CEUs) offered to workshop participants.
Multiple field days were held at all locations to discuss research findings and progress with users.
Several customized fact sheets have been developed for specific audiences.
ARS - Robert Dowdy, 612-625-7058
CSREES/UM - James Anderson, 612-625-8290
USGS - Geoffrey Delin, 612-783-3231
EPA - William Fenville, 218-720-5550
ES - Frederick Bergsrud, 612-625-9733
NRCS - Jeff St. Ores, 612-298-3670
Wisconsin - Birl Lowery, 608-262-1229
North Dakota - Ray Knighton, 701-237-8777
South Dakota - David Clay, 605-688-5081