Under the Great Lakes Water Quality Agreement, the governments of Canada
and the United States are committed to addressing water quality issues in
the Great Lakes basin.
Through a federal initiative called the Great Lakes Action Plan, Agriculture
and Agri-Food Canada funded research to:
increase our understanding of how agricultural chemicals interact
with the environment, and the Great Lakes in particular,
improve water quality in the Great Lakes basin,
develop and fine-tune farm practices that help farmers conserve soil,
water, and air quality in the short and long term for all Ontarians.
The 5-year, $5-million project is now complete, although multi-disciplinary
research continues in these important issues.
Here is a summary of results, which sheds light on the subject of pesticide,
nitrogen, and bacteria movement in the environment, and provides food for
thought to help us all advance farm management practices. If you would like
more information, please refer to the list of Program Studies and Scientists
on the flipside of this brochure.
THE GREAT LAKES AND ONTARIO AGRICULTURE
The Great Lakes are sensitive to pollution for two main reasons:
the long retention time (less than 1% of the water flows out annually)
allows some persistent contaminants to accumulate in sediments - in
some cases, these may be released back into water.
the large surface area leaves them vulnerable to direct deposits
of wet and dry atmospheric contaminants.
Agriculture and the agri-food sector contribute significantly
to the Ontario economy. The annual farmgate value of crop and
animal production is more than $5-billion. Its economic worth
can also be counted in employment: about 150,000 Ontarians have
production and processing jobs in the agri-food sector.
The Great Lakes basin is home to 80% of Ontario's cropland.
Now more than ever, farmers face significant challenges in their
efforts to produce low cost, high quality food products in an
environmentally sustainable way.
The annual farmgate value of crop and animal production
in Ontario exceeds $ 5 billion. PHOTO:
Contaminants in the Great Lakes originate from all kinds of human activities.
The chemicals and bacteria discussed here are those that are derived from
agricultural sources. The most commonly used crop-protection chemicals (atrazine
and metolachlor), manure and fertilizer nitrogen, and manure bacteria are
the focus of the study.
Today's crop-protection chemicals are less persistent and less toxic
to non-target species than their predecessors. Application rates are declining
and crop-protection products are being used more efficiently. They are not
accumulated in the food chain, and are effective at low application rates.
Nonetheless, because of their important role in food production, significant
amounts of pesticides are applied each year in the Great Lakes basin. The
combined Canada/USA use is about 25-million kilograms. Ontario farmers apply
about 6-million kilograms.
Usage looks like this:
- account for 75% of pesticide use
- generally applied once a year to control weeds and optimize
yield in field crops
fungicides and insecticides:
- account for 25% of pesticide use
- applied up to 8 times a year to control diseases and
insects on fruits and vegetables.
are usually sprayed once annually with herbicides.
When crop-protection chemicals are applied according to
is there a potential for contamination of surface and
how much of applied pesticide is lost into the air?
what are the effects of agricultural pesticides on stream
and wetland ecology?
RESEARCHERS HAVE FOUND
How Herbicides Can Move From Fields
Level Landscapes with Cracking
Soils (e.g. Essex County)
surface runoff is the main pathway:
runoff losses are maximized when rain storms closely follow application
- field plot studies revealed high intensity storms caused up to 10%
loss of atrazine and metolachlor
losses measured at edge of fields and from entire watersheds amount
to less than 5% and 1% respectively
in small test plots in farm fields, chemicals in runoff waters exceeded
water quality guidelines for up to 1 month after application.
large cracks and pores are the main pathways for herbicide transport
to tile drains
groundwater sampled at 5-metre depth met water quality guidelines
for herbicides under conventional and conservation corn cropping systems.
while surface runoff is a dominant pathway for herbicide losses,
some chemical is also lost in tile drains .
in the runoff water collected in the field shortly after application,
the majority of atrazine and metolachlor is dissolved in the water and
not attached to the sediment - this was true for conventional and conservation
tillage cropping systems.
flow through large soil cracks and pores is an important transportation
route that can lead to water contamination .
risk of transport through large pores is greatest shortly after application
especially in cases of heavy rains:
when herbicides adsorb to soil particles, or herbicides break down
naturally, the risk of transport through soil cracks and pores is largely
How Herbicides Move Between The Land And Atmosphere
crop-protection chemical lost to the atmosphere is a small percentage
of applied material
three new measurement systems have been developed to more accurately
quantify the exchange of agrichemicals between soil and air.
What Happens To Herbicides in the Soil
Some Herbicide Residues Bind with Soil and Organic Material
herbicides that bind with soil particles are held in the field where
they are active - they are also retained in place for biological breakdown
bound herbicides in soil increase with time after application
if soil is eroding, bound herbicides can move with suspended soil
particles in runoff.
Herbicide Breakdown And Movement in Soil
Wetland Micro-organisms Can Help
|Much of the agricultural crop-protection
chemicals that reaches the Great Lakes passes through wetlands or
MANURE AND NITROGEN
Some poultry, swine, dairy, and beef feedlot production is concentrated
on farms with insufficient land for proper waste disposal. Furthermore,
many farmers are changing their manure handling systems from solid to
liquid - about 50% of manure is disposed of in liquid form. Both of
these facts increase the potential for water pollution.
Manure, when not incorporated into the soil, can run off the soil
surface. Liquid manure can flow rapidly through soil via large cracks
or pores to subsurface water, or to tile drains. Since roughly 40% of
Ontario's improved agricultural land has some form of tile drainage,
there is a high potential for contamination of tile water by nitrogen
Nitrogen from manure and chemical fertilizers is required for crop
production. Since nitrates are soluble in water, they can move rapidly
in surface runoff or groundwater. The issue becomes:
|WHAT RESEARCHERS HAVE FOUND
How Bacteria and Nitrogen Travel in Water
Tile Drains and
risk of bacteria being carried through large soil pores
is greatest immediately after surface application, especially
when followed by heavy rains.
nitrogen losses often occur primarily during the non-growing
nitrogen losses are predominantly through the soil to
the tile drains or subsurface water.
|Liquid manure injection systems that
disrupt large cracks and pores in the soil can reduce tile drain
HOW FINDINGS CAN HELP ONTARIO FARMERS
CHOOSING SAFE AND EFFECTIVE PESTICIDES
MANAGING THE WATER TABLE
controlling water table levels and using conservation practices will
help lead to:
higher crop yields and improved nitrogen use, especially in dry
conditions, by optimizing moisture availability
improved water quality by reducing atrazine loss up to 47% and
nitrate losses by about 50% - nitrate concentrations are reduced
to within acceptable limits
lower farm production costs by improving N fertilizer efficiency.
REFINING PESTICIDE APPLICATION
USING CONSERVATION PRACTICES
since agricultural runoff may contain crop-protection products
and nutrients, conservation practices (e.g. contour and strip cropping,
terracing, and buffer strips) that keep soil and water in the field
will improve surface water quality
farm wetlands have important value in improving water quality
- wetland organisms recycle nutrients and act as a sink for bacteria
if you're considering adopting (or already have) a reduced tillage
system, here are some observations regarding reduced and conventional
tillage cropping systems:
crops grown with reduced tillage do not require more herbicide
those grown with conventional tillage
there are no net differences in herbicide losses
flow through large cracks and pores is greater under reduced
tillage, but total water loss (surface & subsurface) was greater
with conventional tillage
total nitrogen loss is lower from reduced tillage systems, but
reduced tillage also shows higher nutrient loss in soluble forms
than conventional systems.
INJECTING LIQUID MANURE
THE EXTENT OF AGRICULTURAL NON-POINT
(* not from one location)
Field-scale models can evaluate the effect of farm management systems
on surface and ground water quality. These can be used for detailed
farm planning exercises to:
Streams that are in farming areas have very different insect populations
from forested areas. These differences are greatest in localized areas
where insecticide use on crops is greatest. Agricultural activities
generally change insect populations, but how these changes relate to
water quality has yet to be established.
Researchers were able to predict potential non-point source pollution
of groundwater by atrazine. The downward movement of annually applied
atrazine over 10 years was simulated on a computer. Based on computations:
A provincial-scale study has developed methods to locate agricultural
areas with high potential for non-point source pollution. These were
based upon relationships among:
the type and location of farming systems
their potential for land and water contamination from herbicides,
nitrates, and bacteria.
This study identified areas where the results of field studies can
Crops produced with reduced tillage systems
do not require more herbicide than when grown under conventional
The rapid movement of contaminants through soil
cracks and pores to the tile drains contributes significant
bacteria loads, but low total nitrogen loadings.
INTO THE FUTURE
Implementation of study findings will increase the environmental
sustainability and maintain the competitiveness of the agricultural
sector. Further work is required to:
implement findings at the farm level
apply technologies for solving agricultural water quality problems
in areas where Great Lakes Remedial Action Plans are being implemented
develop and test ecosystem-based management systems that protect
the environmental quality of rural areas
use the findings on chemical transport at the watershed and provincial
level to locate environmentally sensitive areas.
The assistance of the
Ontario Soil and Crop Improvement
Association (OSCIA) in the production and distribution of the brochure
(from which the information herein was obtained) is gratefully acknowledged.
Thursday, May 05, 2011 01:06:39 PM