Influence of Cropping Systems on Contamination of a Shallow Aquifer in the Northern Great Plains

Project Overview

ANC91-004
Project Type: Research and Education
Funds awarded in 1991: $0.00
Projected End Date: 12/31/1994
Matching Non-Federal Funds: $63,000.00
ACE Funds: $63,000.00
Region: North Central
State: North Dakota
Project Coordinator:
David Klinkebiel
North Dakota State University

Annual Reports

Commodities

  • Agronomic: corn, cotton, potatoes, soybeans, wheat

Practices

  • Animal Production: manure management, watering systems
  • Farm Business Management: whole farm planning, agricultural finance
  • Soil Management: soil quality/health

    Abstract:

    [Note to online version: The report for this project includes tables and figures that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact North Central SARE at (402) 472-7081 or ncrsare@unl.edu.]

    In 1992, a project was initiated at the Carrington Research Extension Center-North Dakota State University near Carrington, ND, to study the influence three different cropping systems (Conventional, Integrated, and Biological) would have on production, economic cost and benefits, soil, and environmental integrity (pesticide and nitrate contamination) of a northern Great Plains shallow confined aquifer. A spring wheat, Triticum aestivum L. (1992) – sunflower, Helianthus annuus L. (1993) – fallow (1994) crop sequence was applied to each cropping system.

    Ground-water recharge and solute movement were controlled primarily by climate and field microtopography, and not by management practices. Short-term differences between effects of conventional and biological farming practices on ground water quality appear to be minimal. During the first two years average annual nitrate-N concentrations in the vadose zone (2.1 m), in the saturated glacial till (4.0 m), and in a confined sand and gravel aquifer (6.0 m) did not differ significantly (p=0.05) between biological, conventional, and integrated farming methods. However, there were differences in nitrate-N concentrations between years in the saturated till and in the Carrington aquifer. In the saturated till nitrate-N concentrations for all treatments in 1993 (a year with precipitation more than 50% over annual average) were almost double (4.26 to 8.49 mg/L) the concentrations (1.9 to 3.03 mg/L) measured in the previous year, which was a dry year. In 1993 average nitrate-N concentration in the Carrington aquifer was approximately 2 mg/L, compared with a fraction of a mg/L in 1992 and in previous experiments at Carrington, however, the larger 1993 mean was caused by a few non- or sparsely-replicated large concentrations. Most measurements were still less than 1 mg/L throughout the experiment. In all cases, elevated nitrate-N concentrations were highly variable, sparsely replicated, and sporadic, indicating that nitrate movement was occurring primarily as localized preferential flow at all sites. In six pesticide sets (spring, mid summer and fall of 1992 and 1993) there were no plausible detection’s of pesticides under any of the treatments.

    In 1993, cropping system treatment did have an affect on certain (available potassium, phosphorus, partially humified organic matter that is nitrogen, soil bulk density, soil organic matter content, and nitrate-N content) soil properties. Spring wheat yield and yield components were similar across the different cropping systems except for seed protein which was higher under the Conventional and Integrated cropping systems. Sunflower yields were similar under the Conventional and Integrated cropping systems. The Biological system resulted in a significantly lower yield than the other two systems. This was probably the result of low available nitrogen resulting from slow decomposition and mineralization of existing organic matter, since no additional nitrogen sources were added to the Biological system in 1993. Since cropping system treatments have only been applied for two years it is difficult to draw any final conclusion from the present results. Biological cropping systems usually take many years to reach a state of equilibrium, especially in the north where growing seasons are short.

    Total costs of inputs applied to the soil plus cost of the field operations vary between the production systems for spring wheat and sunflower. The conventional spring wheat has the lowest cost per acre followed by the biological. With the sunflower the biological practices had the lowest total cost, followed by the conventional practices. The integrated practice system had the greatest total cost per acre for both spring wheat and oil sunflower.

    Conventional production resulted in the greatest return to land, labor, and management for both spring wheat and oil sunflower production. The difference between returns from conventional and the other farm practices provides an indication of the differential created by the different management styles. Since these different management practices do not include costs or impacts on the environment or on the health of the laborers, there is an opportunity for determining a trade off between the returns and to the environmental and human impacts.

    This study will be continued for the length of time necessary to determine the long-term effects of the Conventional, Integrated and Biological cropping systems.

    Introduction:

    In 1992 a project was initiated at the Carrington Research Extension Center-North Dakota State University near Carrington, ND, to study the influence of three different cropping systems on production, economic cost and benefits, soil, and environmental integrity (pesticide and nitrate contamination) of a northern Great Plains shallow aquifer. One of the cropping systems studied can be defined as a "Conventional" farming practice common to the central Northern Great Plains. The other two cropping systems are two different examples of "sustainable agricultural" systems. In the Northern Great Plains, two general philosophies seem to have developed concerning practices perceived as sustainable.

    One philosophy, which will be defined as an "Integrated Input" approach, perceives that sustainability can be achieved if purchased inputs are more selective and are used more timely, efficiently, and economically. Coupling these practices with methods to reduce soil erosion and decrease environmental degradation results in a combined approach that is broadly described as "sustainable". These ideas are promoted by movements such as operation S.A.V.E. (Sustainable Agriculture that's Voluntary and Economical) or HITSA (High-Technology Sustainable Agriculture). The other philosophy, described as a "Biological" cropping system, perceives that long term economic and environmental sustainability can be achieved with greater use of non-purchased inputs. Virtually all inputs, except fuel and the raw products it takes to power and build the needed machinery, are supplied Biologically. By properly selecting crops and rotations, soil fertility renewal and pests are Biologically managed, thereby reducing or eliminating the need to buy purchased inputs. This idea is being promoted by organizations like the Northern Plains Sustainable Agriculture Society.

    Project objectives:

    1. To examine the influence a "Conventional", "Integrated Input", and "Biological" cropping system would have on pesticide and nitrate contamination of a shallow confined aquifer. Current assessment of environmental risk is based on general groundwater surveys, or on risk assessment models and indices that rely on simplified environmental and climatic assumptions such as steady water flow, or "annual average" infiltration rate. While such indices provide reasonable overviews of comparative risk, they would tend to misrepresent contamination processes in environments characterized by infrequent large precipitation events or by complex recycling of soil water. Because of concern over safe water supplies, more site specific information is needed to determine the effects of cropping system, landscape, climate, and management practices on the contamination of ground water.

    2. Evaluate the potential of each cropping system to maintain effective long term sustainable crop production. Since the beginning of the sustainable agricultural movement, industry, universities, professional and farm organizations, and producers have attempted to define the role of sustainable agriculture and the course that sustainability should take. This objective will evaluate the agronomic components of sustainable cropping systems, and compare it with a Conventional practice.

    3. Determine and compare long term economic stability of each of the cropping systems, based on costs and returns of production and environmental integrity. Enterprise budgets will be developed that will specifically compare the variable costs and resulting returns to management for each cropping system.

    4. Involve producers in the decision process on cropping system practices. A panel of farmers was assembled to aid in the decision processes of this study. This allowed producers to get involved with the project and reduced the bias that might be entered by the principal investigators.

    5. Establish a experimental location in the state that combines basic ground-water studies and agricultural management experiments. The Carrington Research Extension Center is a natural location for this project because of its hydrologic setting (overlying a shallow confined aquifer, Figures 1 and 2) and its history of applied agriculture research and the ability to provide practical and useful information to farmers in the Northern Great Plains.

    6. Continue this project long enough to evaluate the impacts of these cropping systems on farm profitability and soil and water conservation.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.