The increased use of fertilizers and pesticides in the midwest has created growing concerns about water quality. Management Systems Evaluation Areas (MSEA) have been established to evaluate the impact of agricultural management systems on water quality and to develop new or improved agricultural management systems that are profitable while protecting water resources. At the Ohio MSEA, three cropping and tillage systems consisting of a continuous corn (chisel plow), a corn/soybean rotation (chisel following corn and no-till following soybeans), and a rotation of corn/soybean/wheat with a hairy vetch cover crop (ridge-till) are being evaluated. Sampling, monitoring, and modeling activities of the vadose zone has indicated that nitrate-N is more mobile than agricultural herbicides in these soils. Research shows that some leaching and/or denitrification of nitrate has occurred. Analysis of soil core data from 1991, 1992, and 1993 show significantly more residual herbicides in the top 6 in (15 cm) than in the 6 to 12 in (15 to 30 cm) increment, indicating relatively slow movement of herbicides. Even though nitrogen and pesticide inputs differed between the treatments, the three agricultural management systems have produced comparable yields during the first three years. Crop rotations help reduce the amount of pesticides used to control weeds or insects. The corn/soybean/wheat management system utilized applied N more efficiently than the other systems. Fertilizer and herbicide costs showed the most difference between the three agricultural management systems. The use of crop rotations resulted in lower total production costs for corn compared to a continuous corn system. Information gathered from an associated regional socioeconomic study concluded that most respondents believed that if nitrogen application rates were reduced, net farm income would also be reduced.Introduction
Agriculture is one of several industries that has an impact on ground water and is a particular concern in the North Central Region of the United States. More than 80 percent of the U.S. production of soybeans and corn occurs in this 12-state region. To maximize production in a limited rotation crop system, North Central producers have historically applied more than 70 percent of the total amount of pesticides and 85 percent of the fertilizer used in the United States. Agricultural chemical usage has increased as an increasing population continues to place higher demands on agricultural production to supply food and fiber.
The impact of corn and soybean farming systems on water resources in the region is a national concern. In order to gain answers to the water quality concerns, the President's Water Quality Initiative established comprehensive research projects called Management Systems Evaluation Areas (MSEA) in Iowa, Minnesota, Missouri, Nebraska, and Ohio (Ward et al., 1994). The goal of the program was to develop research and educational programs that will lead to voluntary adoption of alternative agricultural systems and technologies that will reduce adverse impacts of agriculture on water resources. The focus was on corn and soybean cropping systems using various combinations of tillage, nitrogen management, and pre-plant atrazine, alachlor, metribuzine, and metolachlor. The program has been conducted under the direction of the USDA Working Group on Water Quality and by the joint cooperative efforts of the several federal and state agencies and land grant universities.
The purpose of the Ohio MSEA project, in association with other agricultural and water-resource research in the region, is to evaluate the impact of agricultural management systems on ground-water quality and to develop new or improved agricultural management systems that maintain or increase net farm income while reducing the potential for environmental problems. These management systems utilize various agricultural practices involved with the application of nitrogen and pesticides, water management, and tillage and cropping management. Ohio MSEA researchers are evaluating several production methods and their impact on crop yields, soil structure, water and chemical movement, and biological activity. In addition, the economics and sociological attitudes of management system alternatives are being evaluated.
Information and technology generated from the MSEA research is expected to have broad national relevance, with application to other sections of the country. More importantly, information gathered from these areas would provide farmers and landowners the knowledge and technical means to respond independently and voluntarily in addressing on-farm environmental concerns and related State water quality requirements. Therefore, the Ohio MSEA project recognized the importance of communicating research findings and has developed comprehensive educational programs and materials for the agricultural community and general public to aid in the protection and preservation of our water resources. The purpose of this paper is to summarize some of the results from the Ohio MSEA ground-water quality research project.
Site CharacterizationThe Ohio MSEA site is located on a 650 ac (260 ha) farm two miles south of Piketon, in Pike County, Ohio. Huntington (fluventic hapludoll), Rossburg (fluventic hapludoll), and Nolin (fluventic eutrochrept) silt loams are the predominant soil series at the site. These soils overlie sands that grade into gravel at a depth of 6 to 10 ft (2 to 3 m). The water table normally ranges from 10 to 20 ft (3 to 6 m) below the soil surface, except during seasonal high water levels.
The soil layer overlies the Scioto River Buried Valley Aquifer. This aquifer is a shallow, permeable, and unconfined aquifer with high recharge rates. These types of aquifers are vulnerable to contamination from surface applied materials because short flow paths to the water table decrease the potential for adsorption, chemical reactions between contaminants and minerals in the soil, and biodegradation. The Scioto River Buried Valley Aquifer was formed when glacial and fluvial material, consisting chiefly of sand and medium-sized gravel, was deposited to depths of 60 to 80 ft (18.3 to 24.4 m). Ohio shale forms the walls of the river valley upland hills, and the base of the eroded valley that is partially filled with the alluvial and outwash deposits. The valley is more than 1.25 miles (2 km) wide.
The location of the Ohio MSEA site was chosen because it is representative of many other locations in Ohio and in the nation which have similar permeable soils, geological formations, and crop production systems. The sand and gravel deposits of the Scioto River Buried Valley Aquifer form one of the most productive aquifers in the State. Research on buried valley aquifers is important because about 75 percent of the ground water consumed in Ohio is pumped from these types of aquifers. Buried valley aquifers are common throughout the North Central Region. These sand and gravel aquifers supply substantial amounts of drinking water all across the twelve-state region. In addition, the majority of pesticides used in Ohio and in the Midwest are used on corn and soybean cropping systems, which are common throughout the Scioto River Valley and most of Ohio.
MethodologyThe regional MSEA project was primarily interested in evaluating the use of nitrogen, atrazine, alachlor, metribuzine, and metolachlor in agricultural systems. Management systems and rotations were selected by a team of scientists to represent existing and innovative practices for Ohio, within the constraints of the chemicals of interest. Three agricultural management systems are being evaluated at the Ohio MSEA site:
Each agricultural management system has been established on a 25 ac (10 ha) plot. In addition to the large plots, the management systems were established on one ac (0.4 ha) replicate plots with each phase of each rotation being present each year. Farming activities were initiated at the Ohio MSEA in the fall of 1990 and research data collection began in 1991. The project is completing its fourth year of intensive data collection and analysis. The Ohio MSEA agricultural management systems methodology is described in more detail elsewhere (Nokes et al., 1994).
Data CollectionAn extensive ground-water monitoring system was installed during January-March, 1991. Thirty-seven wells were installed across the entire farm; 11 are water table wells, 4 are bedrock wells, and 22 are multi-port wells. Multi-port wells have been located to provide two upgradient and two downgradient wells for each of the three 25-ac (10 ha) fields. Ground-water samples were obtained from the multi-port wells (4 or 6 ports/well) monthly and analyzed for atrazine, alachlor, metribuzine, fonofos, pesticide metabolites, nitrate, nitrite, ammonium, orthophosphate, potassium, and dissolved organic carbon. The wells have sampling ports at 12, 16, 20, and 24 ft (3.7, 4.9, 6.1, and 7.3 m) below the soil surface. The multi-ports allow a total of 108 sampling locations throughout the aquifer underlying the research site. Water table depth, specific conductance, and temperature data have been continuously recorded from the 11 water table and 4 bedrock wells from August 1991 to January 1994.
In 1992, porous cup suction lysimeters were installed in the large plots to monitor pesticide and nutrient movement in soil water of the unsaturated zone above the water table. Banks of lysimeters were placed at 3.3, 6.6, and 9.8 ft (1, 2, and 3 m) depths at three locations in each of the 25-ac (10 ha) fields. Near each lysimeter bank, a neutron probe and frequency domain reflectrometry access tube was installed to measure soil-water content distribution to depths of 10 to 12 ft (3.0 to 3.6 m).
In addition to the large number of water quality samples, routine plant and soil sampling every 2-4 weeks has included above-ground plant biomass, plant N content, and soil sampling to 5 ft (1.5 m) depth to determine soil-water content and pesticide and nutrient concentrations. Other periodic measurements included root length, canopy cover, crop height and population, pest infestation, and weed biomass. Routine soil and plant sampling was conducted on grids of 100 and 25 ft (30.5 and 7.6 m) in the 25-ac (10 ha) fields and 1-ac (0.4 ha) plots, respectively.
Soil cores for chemical analysis were obtained with a 0.9-in (22 mm) dia. soil probe, having a 3 foot (0.9 m) long acetate liner to eliminate cross-contamination between samples. The samples were analyzed for nitrate, atrazine, and alachlor at the USDA National Soil Tilth Laboratory in Ames, Iowa. Near surface soil samples extracted at 0 to 6 in (0.0 to 0.15 m) were collected approximately monthly and analyzed for extractable N (NH4, NO3-N, and dissolved organic N) and microbial biomass N to determine N cycling under the different management systems.
Automated weather stations at the site record local climatic data hourly. The weather stations record air temperature, precipitation, relative humidity, solar radiation, wind speed and direction, and soil temperature. Natural rainfall is sampled for herbicide and nitrate content.
Economics and Sociological AspectsAn economic study investigated the feasibility of various agricultural management systems (Batte et al., 1993). Farm-level models of expected profitability, including crop rotations, input substitutions, and capacity (both labor and equipment) constraints were developed. The economic evaluation of alternative cropping systems aids in capturing private costs and returns which is important for designing policies that will influence the social and environmental impacts of production agriculture. A regional socioeconomic study was conducted to evaluate farmers' perceptions of the impacts of agriculture on water resources, and their attitudes towards adoption of alternative farming systems (Napier and Camboni, 1993).
Results SummaryBefore a proper evaluation of the effects of agricultural practices on ground-water quality is undertaken, a good understanding of the spatial variability and physical and chemical characteristics of the soil profile and underlying water resources is necessary. The Scioto River, which is adjacent to the Ohio MSEA research site, is hydraulically connected to the Scioto River Buried Valley Aquifer. Intensive monitoring of the aquifer has shown differences in ground-water flow direction and flow velocity during stage changes in the Scioto River. Big Beaver Creek, on the eastern edge of the site, periodically recharges the aquifer in pulses during high stream stage. Shallow ground water at the western edge of the site discharges to the Scioto River, except during times of high river stage. At these times, ground-water flow reverses and water moves from the river into the adjacent aquifer. Ground-water flow reversals recorded during high river stage conditions have resulted in movement of water 260 ft (79 m) inland from the river during one 17-day event. This is significant because, to date, pesticides have been detected much more frequently in surface-water supplies than in the ground water. Routine water-level measurements made in the network of monitoring wells at the site indicate that ground-water flow generally is from east-to-west toward the Scioto River but the exact direction of ground-water flow varies seasonally.
Water QualityNitrate, atrazine, and alachlor concentration data obtained from soil cores at the 0 to 6 in (0 to 15 cm) and 6 to 12 in (15 to 30 cm) depth increments during 1991, 1992, and 1993 show some differences for each crop of each system (Figure 1). Chemical distributions for the C/C and C/S/W systems are shown in Figure 1. The behavior of chemicals in the other four phases (C/S, S/C, S/W/C, and W/C/S) are similar. Concentration values detected in the 6 to 12 in (15 to 30 cm) depth for nitrate, atrazine, and alachlor do not show any clear differences between systems because of limited downward movement of these chemicals below the 6 in (15 cm) depth.
The nitrate concentrations in the 0-6 in (0-15 cm) depth increment for 1991 show that the C/C system received excess nitrogen and resulted in more carryover of nitrate to the 1992 cropping year. Nitrate concentrations were approximately 8 ppm (8 µg nitrate-nitrogen g-1) for the C/C system compared to 5 ppm (5 µg nitrate-nitrogen g-1) for the C/S/W system in February of 1992 at the 0 to 6 in depth. In March of 1992, nitrate concentrations were approximately 6 ppm (6 µg nitrate-nitrogen g-1) for the C/C system compared to 2 ppm (2 µg nitrate-nitrogen g-1) for the C/S/W system. Soil cores were taken within the row during 1992 and 1993 to assure that the banded areas were sampled. The 1992 and 1993 nitrate data show that very little nitrate moved over to the row position during these two years. Cores were gathered within and between the rows in 1994 but have not been analyzed.
Assessments of soil nitrogen levels, transformations of nitrogen from organic and inorganic forms through microbial activity and other processes, and the uptake of nitrogen by crops have been conducted. At the start of the project, the majority of the nitrogen application at the Ohio MSEA site was done with anhydrous ammonia injection. Results showed that anhydrous ammonia injection between rows was potentially inefficient in supplying nitrogen to corn roots in chisel-plow and ridge-till systems (Subler et al., 1993). Little movement of nitrogen was detected from place of application to the seedlings. However, from the amount of nitrogen that was applied, it was found that corn in C/S/W system used nitrogen more effectively than the C/C system. This reflects in the C/S/W system in Figure 1 during 1991. The C/S/W system shows a greater decrease in nitrate concentration over time compared to the C/C system.
Nitrate concentrations declined in the C/S/W system during 1992 and 1993 because of the soybean and wheat phases of the rotations. This was a result of no nitrogen being applied to soybeans or wheat and partial supplement of nitrogen from the hairy vetch cover crop. Nitrate concentrations were greater at periods following harvest for soybeans and wheat of the C/S/W system. This is a result of the transformation through microbial processes in the soil system.
Given the permeable nature of the soils at the Ohio MSEA site, herbicides are moving more slowly than anticipated. Analysis of soil core data indicates much more atrazine and alachlor in the top 6 in (15 cm) than in the 6 to 12 in (15 to 30 cm) depth increments (Figure 1). As expected, peak atrazine concentrations in the 0 to 6 in (0 to 15 cm) depth were greater with corn in both systems. Peak atrazine levels were approximately 800, 600, and 150 ppb (800, 600, and 150 µg kg-1) for the C/C operation for 1991, 1992, and 1993, respectively. Peak atrazine levels for corn in the C/S/W system was 250 ppb (250 µg kg-1) in the 0 to 6 in (0 to 15 cm) depth.
A reduced rate of atrazine was applied to the C/S/W treatment compared to the C/C system. Therefore, the initial atrazine concentration peak is less during 1991 for the C/S/W system. Subsequent atrazine levels in the C/S/W system throughout 1992 and 1993 are residual and show the relatively slow dissipation of the slowly reversible portion of atrazine. This portion of atrazine moves into the soil micropores and degrades at a slower rate. The C/S/W rotation data illustrated a greater decline in atrazine concentration over time compared to the C/C system data.
Productivity and ProfitabilityNo significant differences were detected for average corn yields during 1991 and 1993 for each of the three systems (Table 1). Average corn yields for 1991 were 112.9 bu/ac (7.1 Mg ha-1) and 111.6 bu/ac (7.0 Mg ha-1) in 1993. In 1992, the average corn yield was significantly greater (p>F=0.1) in the C/S system [176.6 bu/ac (11.1 Mg ha-1)] than the C/C [167.5 bu/ac (10.5 Mg ha-1)] and the C/S/W system [160.3 bu/ac (10.1 Mg ha-1)]. Corn yields were much higher with all three systems in 1992 than the other two years. This may be a result of greater rainfall amounts.
A significant difference in soybean yields was found in 1991 between the C/S and C/S/W system; however, no differences were found in either 1992 or 1993. The average soybean yield in 1991 for the C/S system [53.3 bu/ac (3.6 Mg ha-1)] was significantly greater than the C/S/W system [36.0 bu/ac (2.4 Mg ha-1)]. Average soybean yields for 1992 were 47.0 bu/ac (3.2 Mg ha-1) and 38.3 bu/ac (2.55 Mg ha-1) in 1993. The wheat yields reported are low, primarily because no additional fertilizer was added to the wheat. The intent was to allow the wheat to use any excess nitrogen in the soil that might leach below the root zone, and not to add nitrogen to the system. Also, the decreased yield in 1992 resulted from the lower planting rate used compared to that for 1991 and 1993.
The reduced pesticide applications at the site have provided adequate weed control among the systems. Herbicide inputs in the C/S/W system were reduced by 2/3 by banding the application. No yield reductions have been observed with reduced chemical inputs in the corn phase. Crop rotations have played an important role in reducing the amount of pesticides needed to control weeds and insects.
Determining the economic feasibility of the different farming strategies is another important objective at the Ohio MSEA. The per bushel cost of production for corn, soybeans, and wheat produced on the various management systems has been determined (Table 2). An important point to note is that the C/S and C/S/W systems in corn have similar total costs; but, are noticeably less expensive than the C/C system. The C/C system generated greater variable costs such as herbicide and fertilizer costs compared to the other systems. When comparing C/S to C/S/W corn, production costs only differed by $ 0.01 per bu ($0.39 per Mg).
Another interesting finding of this project is the cost advantage of soybeans with the C/S/W versus the C/S system. Even though there was no significant differences in yields for 1992 and 1993 between the soybean phase of these systems and soybean yields from the C/S system were statistically greater than from the C/S/W system in 1991, the C/S/W system has a cost advantage of $ 0.60 per bu ($21.98 per Mg). The lower production costs are the result of reduced herbicide costs resulting from banding, and the lower fertilizer costs from using less commercial fertilizer. The production cost for wheat was no surprise. Unlike many farmers in the region, the MSEA researchers did not apply nitrogen to the wheat, which resulted in a lower yield, and subsequently, increased the cost per bushel of production. Overall, the two variable costs indicating the most difference between cropping and tillage systems were for fertilizers and herbicides. Other variable costs such as operating expenses, seeds, interest on operating capital, and an allowance for miscellaneous expenses are similar between all tillage systems for each crop. One aspect this study does not consider is the cost of converting from one production system to another. Changing production systems will generate transitional costs (i.e. purchasing or modifying machinery and utilizing different managerial skills) that must be recovered over time (Batte et al., 1993).
Socio-economic research in Ohio (Napier and Camboni, 1993) indicated that social attitudes and economics will affect the adoption of practices by land owners in the Scioto River Valley. Information was collected from 1,305 land owner/operators in 1991 to assess how they perceived ground-water pollution. A perceived threat to the health of family members was found to be the best indicator of attitudes toward ground-water pollution. Most respondents believed that net farm income would be reduced if nitrogen application rates were reduced.
SummaryMany of the potential impacts of farming systems on ground-water quality are continually being evaluated through research at the Ohio MSEA site. Information about the long-term consequences of agricultural practices on ground water is limited. The Ohio MSEA project needs to be continued for a sufficient amount of time to account for climatic variations, such as drought or excess precipitation. MSEA research is evaluating entire farming systems, whereas most agricultural research projects in water quality have dealt with only one or two components of a farming system.
There is evidence that crop rotations have an influence on atrazine, alachlor, and nitrate concentration levels in the top few feet of the soil system. Soil core data suggest that the majority of the nitrate, atrazine, and alachlor applied to the site did not move below the top 6 in (15 cm) of the soil system. A monoculture system that repeats the same chemical usage year after year reflects more chemical use to control weeds and insects. The continuous corn system ("high chemical input") showed greater agrichemical concentrations than the corn/soybean/wheat system in the 0 to 6 in (15 to 30 cm) depth of soil. Rotating different crops such as soybeans and wheat into the system can break up the cycled chemical application each year thereby reducing chemical concentrations in the soil. Therefore, chemicals may not accumulate in the soil because there is time between applications for the soil system to decompose the chemical.
Even though nitrogen and pesticide inputs differed between the treatments, the three agricultural management systems have produced comparable yields during the first three years. The rotations reduced the amount of pesticides used to control weeds or insects. The ridge-till management system utilized the applied N more efficiently than the other systems.
The continuous corn system using chisel plowing is more expensive than the corn/soybean system (chisel plow and no-till) and the corn/soybean/wheat system (ridge-till). Fertilizer and herbicide inputs showed the most cost difference between the three agricultural management systems. Including rotations resulted in lower total production costs for corn compared to a continuous corn system.
AcknowledgmentsThis research was conducted as part of the Ohio Management Systems Evaluation Area (MSEA) project which is a cooperative research and educational effort of the Ohio Agricultural Research and Development Center and Ohio State University Extension at The Ohio State University, the USDA-Agricultural Research Service, the USDA-Extension Service, the U.S. Geological Survey, the U.S. Environmental Protection Agency, and other state and federal agencies. The Ohio MSEA project is being conducted by several scientists, engineers, educators, technicians, students, and other support personnel. Practical considerations prevent their inclusion as authors or mention by name in the acknowledgments. However, the outstanding efforts of the many people who have contributed to the information presented in this summary document is greatly appreciated. The authors thank the many federal and state agencies that provided the necessary leadership, cooperation, coordination, and resources to conduct the interdisciplinary, inter-agency MSEA Program.
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