Agriculture and the agri-food sector contribute significantly to the Canadian economy and to our quality of life. In 1991, farm cash receipts in Canada totalled $21 billion while generating $131 billion (1990) in economic activity and providing jobs for 1.5 million Canadians. Ontario's primary agriculture industry is the largest in Canada accounting for almost 25% of the country's farm cash receipts. The annual farm-gate value of crop and animal production is more than $5 billion. The total area of land in crops in the Province is about 3.4 million ha with approximately 80% of that land base located in the Great Lakes basin ecosystem. Agriculture and the agri-food sector are clearly central to Ontario's economic development.
Environmental stresses are part of the reality facing all segments of the agri-food sector. Farmers are concerned about soil degradation and the continued ability of the land to produce food for future generations. There is concern about the effects of agricultural pollutants on water, soil, and air as well as the impact of agricultural wastes on the environment. Further, there has been public concern about the reduced capability of the landscape to support a diversity of wildlife populations.
The Great Lakes Action Plan is part of the federal government's Great Lakes Strategy. The overall priority for all federal action on the Great Lakes is to achieve sustainable development, a healthy environment and strong economy. Announced in 1988, the Action Plan is a $125 million, 5 year plan to restore degraded areas, prevent pollution, and conserve ecosystems around the Lakes. As a partner in the Action Plan, Agriculture and Agri-food Canada has invested $5 million to study improved use of toxic substances in agriculture as related to land and air quality, as well as overall ecosystem health.
This agricultural initiative will strive to develop technologies which will help farmers be effective stewards of the land and water resources, as well as to improve water quality in the Great Lakes basin.
While large in size, the Great Lakes are sensitive to the effects of pollutants. Persistent pollutants that enter the lakes are retained in the system for long periods since less than 1% of the water flows out of the lakes annually. The long retention time permits persistent contaminants to accumulate in sediments, be released back into the water, bioaccumulate in the food chain, and be recycled. The large surface area of the lakes also creates the potential for direct dry or wet deposition of atmospheric pollutants on the lakes surface.
New provisions in the 1987 International Great Lakes Water Quality Protocol stressed the need to address agricultural issues of non-point source pollution, especially toxic substances such as pesticides and microbiological contaminants. The basis of public concern has been the potential occurrence of pesticides in public and private drinking water supplies as well as public beach closures resulting from bacterial contamination.
Historically, perceptions about agricultural pesticides originated from problems associated with persistent chlorinated hydrocarbon insecticides such as DDT, mirex, and dieldrin. Although banned for many years in North America, these compounds are still found in trace amounts throughout the environment. More recently, pesticides have evolved toward more innocuous chemicals which are effective at low applications rates, less persistent, less toxic to non-target species, and not bioaccumulated. However, the continued need and use of substantial amounts of these new generation of pesticides for agricultural production has motivated public interest in the fate of these chemicals in the environment.
A 1993 survey of pesticide usage in the Great Lakes basin reports that at least 25 million kg of pesticides are used annually in the United States and Canada. Herbicides, which account for about three-quarters of all agricultural pesticides used in the Great Lakes basin, are generally sprayed once a year to control weeds in field crops. Fungicides and insecticides, which account for the remainder of the agricultural pesticides are applied to fruit and vegetables as many as 8 times a year to control diseases and insects. A 1988 survey of agricultural pesticide use in Ontario showed that pesticide use had declined by about 25% from the previous five years to about 6 million kg. These pesticides were reported to be 80% herbicides, 14% insecticides/nematocides and 6% other pesticides.
Livestock production continues to be an important agricultural industry in Ontario. In 1989, over half of all farms with greater than $2500 in sales reported livestock or poultry as their main source of business. Production from the 5.7 million livestock and 32.1 million poultry was valued at $2.2 billion. The fertilizer replacement value of the manure produced by this livestock population was computed to be about $158 million.
With increased specialization in agriculture, there has been a separation of livestock production from crop production. Today, most of the poultry and swine, and much of the beef production are concentrated on a small land base. As a result of this specialization, more livestock wastes are being applied to less land. At the same time manure handling techniques have been changing from solid to liquid systems. Today it is estimated that about 50% of livestock manure is disposed of as a liquid. These trends have led to the potential for excessive land application of livestock manures.
The disposal of both solid and liquid forms of livestock manure on land creates the potential for water pollution. Solid or liquid manures, when not incorporated into the soil, can run off the soil surface. Liquid manure has been observed to flow through the soil via large cracks and pores to the groundwater or to the "tile drains" (subsurface pipes) where it is transported directly to the receiving waters. Since about 40% of the improved agricultural land in Ontario has some form of tile drainage system, the importance of tile-water contamination can not be overlooked.
The concern for elevated levels of nitrogen and bacteria in water from livestock sources and nitrogen from chemical fertilizer arises out of a threat to human health and wildlife habitat. Human health concerns are related primarily to the effects of certain forms of nitrogen on infants. Wildlife concerns are related to toxic effects of ammonium on fish populations. Bacterial populations in manure are sufficiently high that any inputs of manure to surface or subsurface water supplies can result in bacterial contamination exceeding most water quality standards.
Preliminary measuring techniques indicated that atmospheric transport could be a significant pathway for pesticide movement. The extent of pesticide exchange between the land and atmosphere was relatively unknown. The effects of incorporating the pesticides into the soil on reducing atmospheric exchange was also unknown.
For the purpose of addressing specific requirements of the International Great Lakes Water Quality Agreement Protocol, the Great Lakes Action Plan was developed by participating Federal agencies on the basis of several issues. The Agriculture and Agri-food Canada program addressed the following issues: land based pollution sources, contaminated sediments, and airborne contaminants. The specific objectives that Agriculture and Agri-food Canada addressed in the Great Lakes initiative were as follows:
In rolling agricultural landscapes, surface runoff appears to be the dominant pathway of herbicide transport to tributaries. Plot studies of atrazine and metolachlor loss from both natural and simulated rainfall runoff events indicated that maximum runoff concentrations occurred for storms closely following chemical application. High intensity storm events produced losses of up to 10% of the applied chemical. Concentrations of these chemicals in the surface runoff waters from the small simulation plots exceeded water quality guidelines for up to one month after herbicide application. Further research is required to establish if these results can be extrapolated to the field scale.
On level agricultural landscapes that are characterized by high clay content cracking soils, the large cracks and pores contributed significantly to herbicide transport to the tile drains. Groundwater sampled to about 5 m depths under conventional and conservation corn cropping systems showed no significant levels of pesticide accumulation. Subsurface drainage during winter months was the dominant nitrogen transport pathway.
Pesticide runoff losses closely following the time of application were dominated by movement in the water phase, as opposed to movement on eroded soil sediment. For the conventional and conservation tillage cropping systems studied, between 90 and 95% of the atrazine and 80 to 85% of the metolachlor was transported in the water phase.
Although the methods of herbicide application and manure application are different, the pathways for surface water contamination are quite similar.
Vertical transport of bacteria and herbicides in soil has been found to be a significant process that may lead to the contamination of subsurface water and tile drainage. The risk of herbicide and bacteria transport through macropores is greatest immediately following surface application, especially if a heavy rain occurs, or if the volume of liquid manure applied was sufficient to activate macropore flow. As the bacteria and herbicide become increasingly adsorbed to soil particles or the herbicide breaks down by natural processes, the risk of transport through macropores is considerably reduced.
Since there was relatively little known about the exchange of pesticides between the land surface and the atmosphere, new systems had to be developed for measuring the exchange of agrochemicals at the air-soil surface interface. Pesticide atmospheric emissions peaked following their application or rainfall. Atmospheric measurements of atrazine and metolachlor deposition over land and extrapolated over a 5 month growing season represented about than 0.75% of the original herbicide application.
Formation of bound residues was identified as an important sink for soil-applied herbicides. Pesticide residues bound in soil are less available for biodegradation or bioaccumulation, and are not transported in the surface runoff water. However, bound pesticide residues can be transported on suspended soil particles in runoff, and may be released into solution at a later date.
The level of contamination of water by agrochemicals is determined by the balance between the rate of transport and the rate of degradation in soil. Improved techniques for determining the kinetics of atrazine and metolachlor degradation and soil-bound residue formation in different soils at various temperatures and moistures permitted the use of more accurate breakdown constants in the pesticide transport model LEACHM. Incorporation of this information into the transport model has improved our capability to predict the location and conditions under which pesticides will move in soils.
Much of the pesticide that is transported to the Lakes from agricultural land passes through wetland or marshes. Microorganisms obtained from wetland sediments have been found to degrade atrazine rapidly and completely. The kinetics and conditions for the biodegradation to occur have been established to determine optimal wetland management strategies and potential remedial applications.
Field scale models that predict the fate and transport of agrochemicals and bacteria in soil and water have been tested and calibrated for Ontario conditions. Study results show that these models have great potential for use in detailed farm planning exercises to locate environmentally sensitive landscapes and evaluate alternative remedial solutions. The CREAMS (Chemicals, Runoff and Erosion from Agricultural Management Systems) model is one field scale model that was calibrated with data from this research program. DRAINMOD (DRAINage MODel) is another field scale model used to examine the effects of tile drains on soil water flow. The DRAINMOD and CREAMS models have been combined to examine the effect of agricultural management systems on surface and subsurface water quality.
At the watershed scale, a simulation model (LEACHP) and geostatistical procedures were used within a geographic information system (GIS) to characterize non-point source pollution of groundwater by infiltrating chemicals. A 10 year simulation was run for the Grand River watershed, assuming an initially atrazine-free soil, continuous corn cropping over the entire watershed area, and atrazine applied each year at the recommended rate of 150 mg m-2. The Canadian drinking water guideline for atrazine was never exceeded at the 90 cm depth. However, the USA standard was exceeded on or before the tenth simulation year in about 5% of the watershed area.
A provincial scale analysis of current agricultural practices in the Canadian basin was conducted which established the relationships between the type and location of agricultural systems, and their potential for land and water contamination from pesticides, nitrates and bacteria. Study results identify the location of some significant areas of rural non-point source pollution.
Biomonitoring studies on streams within agricultural regions have revealed that the activity and the relative species mix of the invertebrate (mostly insects) community reflects the surrounding land use. For example, invertebrate communities from streams with predominantly forested land use are very different from communities within agricultural land areas. These faunal differences appear to be the greatest in agricultural areas where organophosphorus insecticide use is also greatest. Study results suggest that all agricultural activities generally reduce biodiversity and change community structure, compared to forested lands, but how these changes relate to water quality has not been established.
Several remedial measures that will contribute to environmentally sustainable agricultural production were investigated. Since there is a wide range of pesticides available for farm use that vary widely in toxicity and persistence, the choice of pesticide for use on sensitive land is critical. Two simple and practical decision making tools have been evaluated that can assist a pesticide applicator in selecting safe products for use on land where wetland, wildlife habitat, or water quality could be adversely affected. Both decision making aids are able to address environmental quality and agricultural production issues in a balanced manner.
Controlled water table management on level clay loam textured soils has been demonstrated to offer potentially huge benefits in terms of water quality and higher crop yields that are less weather-dependent. The integrated management system evaluated incorporates controlled drainage/subirrigation, conservation tillage and intercropping as sustainable production management practices. The system has been found to improve water quality (reduce atrazine loss up to 47% and nitrate loss up to 66%), increase crop yields in dry growing seasons by optimizing moisture availability, and reduce input costs (by reducing herbicide input by 50% through banded application and improving N fertilizer efficiency).
Banded application of herbicide reduced surface water quality impacts. Concentrations of herbicide in runoff where banded application methods were used was found to meet Provincial water quality guidelines. Banded herbicide application methods will result in improved water quality regardless of weather conditions because less chemical is applied. Conservation practices that reduce herbicide runoff losses will be those that keep both soil and water within the field since the predominant amount of herbicide transported near the time of application is in the aqueous phase.
Crops produced with reduced tillage systems did not require more herbicide than when grown under conventional tillage systems. In studies of water and contaminant losses from conventional and reduced tillage cropping systems, several important observations were made. First, there were no significant differences in herbicide losses from the conventional and reduced tillage systems. Even though macropore flow was greater under the reduced tillage system, the total water loss (surface and subsurface) was greater from the conventional tilled system. Nutrient losses as a whole were lower from the reduced tillage systems but exhibited higher nutrient loss in soluble forms than conventional systems.
Liquid manure injection systems that disrupt soil macropore continuity immediately around the point of manure injection have been found to be effective in reducing direct movement of contaminants to tile drains. The rapid movement of contaminants through soil cracks and pores to the tile drains contributed significant bacteria loads but low total nitrogen loadings.
The technology transfer opportunities are listed below but discussed in greater detail in the Findings section of the report:
The concept of sustainable development has been described as activity in which the environment is fully incorporated into the economic decision-making process. The approach offers genuine hope of economic development without environmental decline. Canadians have accepted the merits of sustainable development and the federal government has established the Green Plan to set out how to achieve it in the years to come. Canada's Green Plan offers a framework for change.
In 1990, The federal and provincial ministers of Agriculture adopted a framework for action on environmental sustainability. The federal government used this framework to establish its policy for environmentally sustainable agriculture. The objectives of the federal policy were as follows:
The GLAP program has been instrumental in enhancing the federal vision of increased environmental sustainability for the agricultural sector. New technologies and management systems have been developed that contribute to making production systems more competitive in the global market. These same technologies will be appropriate for addressing agricultural water quality issues in the Remedial Action Plans (RAP) of Clean Up Fund programs. Equipment has been obtained, field monitoring sites instrumented, and technical expertise developed to address the environmental issues facing the agricultural sector. Studies on biodegradation and biomonitoring with indicator organisms initiated in the program will assist in the development of further ecosystem-based studies that remain critical to solving Great Lakes basin issues. The successful development of a multi-disciplinary team to address the highly complex agricultural nonpoint source pollution issue contributed significantly to study findings.
While much has been accomplished much remains to be done. Important insights into the pathways and processes of toxic chemical transport in agricultural soils have been achieved. Further work is required to assess the implications of findings to predict toxic chemical transport at the field, watershed and national scales. Further studies will ultimately lead to the development and implementation of ecosystem-based farm management strategies throughout the Great Lakes basin. An agro-ecosystem approach to managing the agricultural sector is key to conserving or enhancing the natural resources that agriculture uses or shares. This approach will also effectively address the off-farm environmental quality concerns which are so closely linked to management practices, inputs and technology used on the farm.
Bruce T. Bowman, Archivist
Friday, March 06, 2015 04:10:15 PM