Transcript WEEK 10.ppt

A community of living organisms,
together with the physical resources
that sustain them, that are managed
for the purposes of producing food,
fibre and other agricultural products
• Agriculture now covers more of Earth’s
surface than forests.
38% of planet’s land surface = agriculture
26% pasture/rangeland
12% cropland
• Intensive monocultures completely displace
natural ecosystems and have a heavy
impact on the land.
Source: Statistics Canada
Animal Units per km² of Farmland
on Very Large Livestock Operations
LEGEND
5-15
16-25
26-35
36-50
50-100
>100
No large operations
Non-agricultural/no data
•Requires large capital investment
•Mechanized
•Chemical inputs (fertilizers, pesticides
and herbicides)
•Monocultural
•Huge farms
•Irrigation and/or drainage (some areas)
•Little summerfallow
Area of Land Irrigated (hectares)
LEGEND
0
1-100
101-1000
1001-5000
5001-20000
20000-115000
No data
Satellite Image of
Lethbridge and
Surrounding Area
False colour &
True colour
Grains, oilseeds and meats
http://www1.agric.gov.ab.ca
1.8 million people employed
in agri-food industry
Total export value:
$6.0 billion in 2001
$5.2 billion in 2002
$4.2 billion in 2003
http://www.physicalgeography.net
Type of Mineral
Particle
Size Range
Sand
2.0 - 0.06 mm
Silt
0.06 - 0.002 mm
Clay
less than 0.002 mm
Maximum water content before gravity
drainage begins
Water content below which water is held
so tightly to the soil that plants cannot
take it up
Ranges of
porosities, field
capacities, and
permanent wilting
points for soils of
various textures.
(from Dunne and
Leopold, 1978)
1. ORGANIC MATTER
• 15-30% reduction from original level
• Generally stable today (improved tillage,
crop residues, manure and fertilizers)
2. SOIL EROSION
• Most severe soil degradation problem
(due to wind and water in absence of
natural vegetation, and appropriate tillage)
• Topsoil contains most nutrients and
organic matter
• Wind erosion problematic everywhere,
but especially on Prairies
• Water erosion most severe in Maritimes,
British Columbia and Ontario
• Water erosion affects water quality
Oldeman, Hakkeling & Sombroek (1990)
PLOWING STYLE
Contour Farming
Terracing
TIMING
Field tilled in spring
Especially important
on steeply-sloping terrain,
and in wet areas
EROSION CONTROL
MOISTURE CONSERVATION
REDUCED LABOUR
LESS FUEL USED
EQUIPMENT SAVINGS
CROP IN COMPETITION WITH WEEDS
MORE HERBICIDES USED
FROST DAMAGE?
STRIP FARMING
Plant another crop between rows
Covers ground with vegetation
Prevents erosion
Water infiltrates instead of running off
POLYVARIETAL CULTIVATION
Entire field is not exposed at once
ADDING ORGANIC MATTER
Manure
Plowing crop residues
Green manure
3. SOIL STRUCTURE
• Vulnerability to structural degradation
(i) low organic matter
(ii) wet environment
(iii) fine texture
• Soil Compaction
Often due to heavy machinery
Affects rooting
Not a big problem on the Prairies
Visible salinity in 12 sets air photos (Alberta)
http://www1.agric.gov.ab.ca
1. HEAVY METAL CONTAMINATION
(eg. cadmium, lead and zinc)
FROM WHERE?
a) Atmospheric deposition (industry+natural)
b) Fertilizers, manure and sewage sludge
2. ACID PRECIPITATION
•Leads to nutrient deficiency
3. GROUNDWATER CONTAMINATION
High nitrate levels (due to fertilizers)
Fecal coliform bacteria (manure & septic tanks)
Phosphorus levels can increase (eutrophication)
Pesticides are often found in water, but are
generally found in concentrations considered
acceptable (Canadian Water Quality
Guidelines)
Benefit
Very profitable – competitive on global scale
Downside
Health, environmental and nuisance effects
North of Lethbridge
500,000 cattle
200,000 hogs
600,000 poultry
An infectious degenerative brain disease occurring in cattle
One of many transmissible spongiform
encephalopathies (or TSEs)
•First recognized in Britain in 1986
•Caused by a prion, a protein normally
believed to be involved in neuronal
plasticity (serves memory function)
• In a case of BSE, an insoluble form of a
prion accumulates in the brain
•BSE is fatal
CJD is a brain-wasting disease causing
anxiety, disorientation, memory loss,
numbness and death within a year
•Affects 1 person in 1 million
Its cause is uncertain
1. Random genetic mutation?
2. Meat consumption? (controversial)
Tends to affect people over 55
•vCJD is the new variant form of CJD,
which is believed to be caused by eating
infected beef
•145 deaths in the UK so far
40000
35000
30000
(# of Canadian cases = 2)
25000
20000
15000
10000
(# of Canadian deaths = 0)
5000
2004
2002
2000
1998
1996
1994
1992
1990
1988
0
(World Organization for Animal Health)
•No meat and bone meal (MBM) imported from the
UK or other BSE countries since 1978
•Ban on ruminant MBM to ruminants since 1997
•Compulsory notification and investigation of
all ‘downers’ for past 7 years.
•An education and awareness program in place
for years
•A few animals likely could have become
infected before the feed ban (vast majority
culled, slaughtered or died long ago)
•A limited number of live cattle imported from the
UK in the 1980s. Did any have BSE?
•One to a few of these animals may have entered
the animal feed chain (further spread impossible
after 1997 and infectivity was low then)
•BSE incubation time is 6 years (important for
analyzing the Canadian case
•Surface waters affected by runoff
•Groundwater contamination
•Manure & commercial fertilizers are key
to economic viability/soil nutrient maintenance
•Most N, P and K assimilated by plants or
absorbed by soil: remainder affects surface
runoff or groundwater
•Pesticide contamination also problematic –
Alberta levels generally within CWQG
•Pesticides now specialized & less persistent
•Feedlots required to meet domestic +
offshore demand
•Major market for Canadian grains
•‘Canadian Bacon’ well-known: economical
and high quality
Problem: volume of manure produced
•Excellent slow-release fertilizer
•Source of organic matter
•Potential biogas source
2003 Manure Conference (Lethbridge)
•Causes groundwater contamination
•Leaching of nitrates
•Bacteria and parasites
•Air quality: nuisance effect for some
•Health effects may include headaches
and nausea (psychosomatic?)
Biogas reservoir bag for electric power generation
at facility in Valle del Cauca, Colombia (near Cali)
http://www.ias.unu.edu/proceedings/icibs/ic-mfa/chara/paper.htm
•Feedlot runoff collected in slurries or ‘lagoons’
•Manure stored in impervious facilities and
allowed to decompose (6 months +)
•Applied to land when crop nutrient intake
rapid and runoff least likely
•Manure is trucked away and deposited on
area fields to prevent local contamination
•Increases range of crops that can be grown
•Dramatically increases yield
•Highly consumptive use of water
•Evapotranspiration
•Causes salinization in prone areas (ET&WT)
•Reservoir construction required
•Alters fish and wildlife habitat
•Floods cultural/historical sites
•Provides recreation opportunities
of Burdett, Alberta
Source: Zimmatic
Source: Zimmatic
• Replacement of indigenous plants with
crops on a massive scale
• < 1% of tallgrass prairie remains
• 18% of shortgrass prairie
• 24% of mixedgrass prairie
• 25% of aspen parkland
•Drying of biodiverse wetlands
•Use of insecticides and herbicides
Most of North America’s wetlands have
been drained, filled, and converted for
agricultural use.
Some ecosystems used for grazing
•Tallgrass prairie
•Mixedgrass prairie
•Fescue prairie and foothills fescue
•Forested rangelands
•Wetlands
•Coulee complexes
Rangelands
Done badly, it can ruin soils, and cause
erosion and desertification.
Done responsibly, it can sustain
grasslands, and allow wildlife use.
Before European Settlement
•Hundreds of plant species
•Grazing animals
•Bison, elk, deer, antelope plentiful
•Predator and scavenger populations high
•Grizzly bear, prairie wolf, coyote,
swift fox, eagles as well as magpies
and crows (latter two are still plentiful)