||The Goodwater Creek MSEA watershed is near Centralia in the north-central part of the state. The project is associated with claypan soils, which occur throughout much of the southern Corn Belt. Claypan soils have a high clay horizon located 6 to 9 inches below the soil surface that limits infiltration and crop root growth. The goal is to evaluate the effect of prevailing farming systems on the quality of surface and groundwater, and to develop alternative farming systems and practices that maintain and improve the quality of water.
Research sites consist of instrumented watersheds, fields, and plots.
- Watersheds: Goodwater Creek is gaged at the watershed outlet and at two upstream subwatersheds. Surface water quality is evaluated from weekly grab samples of base flow and from surface runoff samples collected with automatic samplers. Groundwater quality is being evaluated from quarterly sampling of 25 groundwater wells.
Fields: Research is conducted to evaluate and model the influence of alternative management systems on surface and groundwater quality and on chemical movement within the root zone. Each of three fields is farmed with a different rotational cropping system. Each field is instrumented with a streamflow recorder and pumping sampler at the drainage outlet to measure surface water quality. Production costs and returns are measured to determine the profitability of each farming system. Grain yields are mapped using grain flow monitors with Global Positioning System (GPS) receivers mounted on the combines.
- Plots: There are two sets of plot sites. One set of thirty 0.8 acre plots, evaluates the influence of five alternative farming systems on the quantity and quality of water moving through the root zone. In addition, some plots have been instrumented to measure the quantity and quality of surface runoff. The second set of forty 0.1 acre plots, is being used to evaluate crop production systems designed to reduce surface runoff and associated chemical losses.
STUDY OBJECTIVES AND RESULTS:
Measure the effects of conventional and alternative farming systems on surface and groundwater quality.
- Mean annual streamflow discharge from the 28-square mile Goodwater Creek watershed is 11.4 inches, 30 percent of the mean annual precipitation. Most (85 percent) of this flow is surface runoff from farm fields within the watershed.
- On field-sized watersheds, herbicide concentrations in surface runoff were evaluated for a 6- to 8-week period following chemical application. The highest concentrations occurred from a no-till farming system where the herbicides were applied without incorporation. Incorporation with a field cultivator reduced herbicide concentrations. Reduced herbicide application rates also decreased concentrations in surface runoff.
- Concentrations in the groundwater are very low. Atrazine and alachlor concentrations have not exceeded 0.12 and 0.14 ppb. respectively. Of the more than 1,000 well water samples collected between May 1991 and March 1996, atrazine was detected in 8 percent of the samples. Alachlor was detected in only 0.4 percent.
- Approximately 25 percent of the groundwater wells have nitrate concentrations greater than the current drinking water standard of 10 ppm. The average concentration of all the groundwater wells is 7 ppm. Trends are beginning to show that current management systems are influencing nitrate concentrations.
Determine mechanisms responsible for the fate and transport of agrichemicals in soil and water.
- Cracks in the soil profile begin to appear in early July, peaking in mid-September, with 6 percent of the profile volume occupied by cracks. Even though the cracks visibly close, the rate and amount of water moving in these fracture zones is much higher than that moving through the pore system of the soil.
- In such soils, atrazine and nitrate can leach to a depth of 36 inches within 24 hours of a rainfall event.
- Water flow and chemical transport were highly variable due to differing landscape and soil features.
Determine how information from plots and fields can be scaled to watershed and/or regional levels.
Atrazine, cyanazine, and metolachlor are often detected in Northern Missouri streams and rivers. At 1994 post-plant, herbicide prevalence was 100 percent for atrazine, 94 percent for cyanazine, and 77 percent for metolachlor. Cyanazine exceeded 1 ppb in 71 percent of the post-plant samples. In 1995, herbicide prevalence was similar to 1994, except that cyanazine concentrations exceeded 1 ppb in 47 percent of the post-plant samples. Under flooding conditions at post-plant 1996, 15 rivers with drainage areas ranging from 233 to 6,880 square miles had atrazine concentrations of 6 to 30 ppb. Dissolved nitrogen concentrations in 1996 were generally less than 5 ppm.
Refine and develop models of the physio-chemical, economic, and social processes affecting the movement of chemicals.
- Predictions of atrazine and alachlor concentrations in surface runoff from the Root Zone Water Quality Model (RZWQM) agreed closely to those measured for events occurring 2 days and 2 weeks after chemical application. Atrazine concentrations in surface runoff 2 days after application were 273 ppb (predicted) and 300 ppb (measured). Alachlor concentrations were 187 ppb and 235 ppb.
- A soil cracking component is being added to the RZWQM to better predict water and chemical movement in claypan soils.
Develop and evaluate alternative cropping systems and technologies designed to protect water quality through the use of site-specific management.
- A system to measure the depth of topsoil above the claypan was developed using an electromagnetic induction meter.
- Four combines have been equipped with Global Positioning System receivers and continuous yield monitors to map crop yields over 1,000 acres.
- Intensive soil grid sampling has shown that most soil nutrients and pH show strong spatial trends coupled with large differences in nutrient status across a field.
Establish the relative profitability of, and farmers attitudes toward, adoption of alternative farming systems and practices.
- Alternative farming systems are less profitable but pose a lower risk to nitrate contamination of surface and groundwater.
- Economic and water quality objectives appear to be competitive.
- Barring regulation, farmer adoption of alternative farming systems is likely to require subsidies.
Develop education programs to increase farmer's awareness and adoption of alternative farming systems practices that are profitable and protect water quality.
- A newsletter containing water quality information is published quarterly and mailed to about 1,800 farmers, county extension agents, non-farmers, scientists, and others.
- An annual field day is held to showcase recent findings and their implications to area farmers.
ARS: Eugene Alberts, 573-882-1114
CSREES/UMO: Tony Prato, 573-882-0147
USGS: Don Wilkerson, 816-254-8172
ES: Jerry Carpenter, 573-882-9417
NRCS: Odie Swanagan, 573-876-0900