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Technical Thematic Report No. 16. - Soil erosion on cropland – introduction and trends for Canada

Ecozones+ Results

Atlantic Maritime Ecozone+

Although Cropland Footnote8 only occupies 4% of the Atlantic Maritime Ecozone+ (Figure 3), it is a locally important land use in many areas such as Prince Edward Island, St. John River Valley, and Annapolis Valley. The Atlantic Maritime Ecozone+ has some of the highest erosion rates in Canada. Tillage is generally intensive and the climate creates a constant threat of water erosion on unprotected soils. Even with conservation practices, potato production on erodible landscapes has high rates of tillage and water erosion. Potato is an important crop in several areas and is often grown on highly erodible landscapes. Fully 36% of the Cropland has unsustainable erosion risk. This is down from 41% in 1981 (Figure 4). In 2006, 18% of the land had moderate to very high erosion risk compared to 20% in 1981.

Figure 3. Cropland in the Atlantic Maritime Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 3

This map in the Atlantic Maritime ecozone+ by soil erosion risk class in 2006. Cropland only occupies 4% of the ecozone+, and is generally a mix of very low to moderate classes, with the exception of a region in the mid-Appalachans, which is largely in the moderate risk class and the southern portion of the ecozone+ in the high risk class. Small regions of very high risk class are shown on the east coast of Nova Scotia and in the southern portion of the ecozone+

All Soil Landscapes of Canada (SLC) polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 4. Soil erosion risk on Cropland in the Atlantic Maritime Ecozone+, 1981-2006.

graph

Long Description for Figure 4

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198158.521.610.63.16.3
198661.121.19.934.9
199160.421.51035
199662.519.810.42.94.4
200161.11910.73.75.6
200664.2189.93.24.7

Source: data from the National Soil Database and the Census of Agriculture

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Boreal Plains Ecozone+

Much of the southern and western portions of the Boreal Plains have been developed for agriculture (Figure 5). Fully 11% of the ecozone+ is Cropland.Footnote9 In the Boreal Plains, tillage erosion on Cropland located on hummocky landscapes represents the greatest erosion risk. On these same landscapes, both wind and water erosion also contribute to erosion risk. Water erosion on the longer slopes and wind erosion on the sandiest soils represent additional landscapes with important erosion risk. This ecozone+ has had important reduction in erosion risk due to reduction in tillage and summerfallow. The conversion from annual crops to perennial forages and tame pasture on some of the more erodible soil landscapes also helped reduce erosion risk. From 1981 to 2006, the area with very low erosion increased from 83 to 91% of Cropland (Figure 6). At the same time, the amount of land with moderate to very high erosion risk decreased from 7 to 3%.

Figure 5. Cropland in the Boreal Plains Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 5

This map shows Cropland in the Boreal Plains ecozone+ by soil erosion risk class in 2006. Cropland is fully 11% of the ecozone, located along much of the southern and western portions of this ecozone+. Agricultural land is predominantly in the very low risk category, with some patches of low risk throughout.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 6. Soil erosion risk on Cropland in the Boreal Plains Ecozone+, 1981-2006.

graph

Long Description for Figure 6

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198182.610.45.80.50.7
198681.210.57.10.40.8
199182.39.96.80.40.6
199685.59.14.70.40.4
200188.17.13.80.60.4
200691.15.42.60.50.3

Source: data from the National Soil Database and the Census of Agriculture

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Boreal Shield Ecozone+

CroplandFootnote10 is a minor land use in the Boreal Shield Ecozone+ amounting to only 0.3% of the land area (Figure 7). The risk of erosion has not changed greatly with time. In 2006, 85% of the Cropland had very low erosion risk and 10% had moderate to very high erosion risk (Figure 8). Tillage erosion on hummocky landscapes represents the major contributor to risk.

Figure 7. Cropland in the Boreal Shield Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 7

This map shows Cropland in the Boreal Shield ecozone+ by soil erosion risk class in 2006. Cropland is a minor land use, amounting to only 0.3% largely along the south of the ecozone+. Risk class is predominantly very low, with a few areas in Ontario showing low and moderate risk classes. The southern St. Lawrence region shows areas of very high soil erosion risk class.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 8. Soil erosion risk on Cropland in the Boreal Shield Ecozone+, 1981-2006.

graph

Long Description for Figure 8

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198184.74.16.91.42.9
198685.73.96.61.22.6
199185.83.57.01.02.7
199685.74.06.81.12.4
200184.34.47.71.32.3
200685.15.06.61.22.1

Source: data from the National Soil Database and the Census of Agriculture

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Mixedwood Plains Ecozone+

CroplandFootnote11 is a major land use in the Mixedwood Plains accounting for 40% of land area. The 2006 distribution of soil erosion risk classes is shown on Figure 9. Overall this region has the greatest erosion risk in Canada (see Figure 1). Large intense rainstorms occur every year so water erosion is always a concern. Tillage is generally intense. Within the Mixedwood Plains, the St. Lawrence Valley and adjacent lowlands have relatively shallow slopes so that part of the ecozone+ has relatively low erosion risk. However, the western part of the ecozone+ has large areas of Cropland on hummocky landforms with maximum slopes of 10% or more. On these landforms, the risk of both tillage and water erosion is great. Row crops of corn and soybean produced with intensive tillage have relatively high erosion risk and the proportion of these crops has been increasing. Nevertheless, the adoption of reduced tillage practices for conservation purposes has provided significant reductions in erosion risk. The proportion of land in very low risk class increased from 42 to 53% from 1981 to 2006 (Figure 10). That with moderate to very high erosion risk decreased from 44 to 34%.

Figure 9. Cropland in the MIxedwood Plains Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 9

This map shows Cropland in the Mixedwood Plains ecozone+ by soil erosion risk class in 2006. Cropland is a major land use in this ecozone, accounting for 40% of the area. The northern portion of the ecozone+ is in the very low risk class. The southern portion, around the Great Lakes region, is a mix of low to very high risk classes.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 10. Soil erosion risk on Cropland in the Mixedwood Plains Ecozone+, 1981-2006.

graph

Long Description for Figure 10

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198141.514.216.17.121.0
198643.214.116.07.019.8
199143.814.715.26.819.5
199647.614.414.56.816.7
200149.114.113.97.015.9
200652.813.613.16.414.0

Source: data from the National Soil Database and the Census of Agriculture

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Montane Cordillera Ecozone+

CroplandFootnote12 is a minor land use (0.4% of total land area) and located in lower elevation intermountain areas in the Montane Cordillera Ecozone+ (Figure 11). From 1981 to 2006, the amount of Cropland with very low erosion risk increased from 85 to 93%, while that with moderate to high erosion risk decreased from 7 to 3% (Figure 12). The greatest erosion risks are on that portion of Cropland on the most steeply sloping landscapes. Tillage is quite intensive so tillage erosion dominates. These erosion reductions reflect a shift from annual crops to perennial crops. Perennial crops generally require less tillage and provide better protection of landscape from water erosion.

Figure 11. Cropland in the Montane Cordillera Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 11

This map shows Cropland in the Montane Cordillera ecozone+ by soil erosion risk class in 2006. Cropland is a minor use (0.4% of total land area) and located in the lower elevation intermountain areas. Most of the Cropland is in the very low risk class, with the exception of a portion of low to moderate risk in the south of the ecozone+.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 12. Soil erosion risk on Cropland in the Montane Cordillera Ecozone+, 1981-2006.

graph

Long Description for Figure 12

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198184.68.84.91.20.6
198685.48.84.01.00.7
199185.58.44.41.10.6
199690.05.83.10.60.4
200191.25.52.70.40.2
200692.74.72.20.20.1

Source: data from the National Soil Database and the Census of Agriculture

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Newfoundland Boreal Ecozone+

There are just over 7,000 ha of CroplandFootnote13 Newfoundland Boreal Ecozone+, representing less than 0.1% of the ecozone+. In 2006, erosion risk varied across the landscape (Figure 13). The erosion risk on Cropland has not changed much over time (Figure 14). Most (79%) of land had very low erosion risk while 12% had moderate to very high erosion risk. Tillage intensity has also not changed greatly explaining why erosion risk is almost unchanged.

Figure 13. Cropland in the Newfoundland Boreal Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 13

This map shows Cropland in the Newfoundland Boreal ecozone+ by soil erosion risk class in 2006. Cropland represents less than 0.1% of the ecozone+ along the west and north coasts and risk class varied across the landscape. Areas of very low, moderate, and very high classes are spread throughout the landscape.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 14. Soil erosion risk on Cropland in the Newfoundland Boreal Ecozone+, 1981-2006.

graph

Long Description for Figure 14

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198179.69.45.00.65.3
198683.19.05.10.22.7
199180.011.65.90.22.3
199683.68.74.90.22.6
200180.610.25.50.33.4
200678.49.86.40.64.8

Source: data from the National Soil Database and the Census of Agriculture

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Pacific Maritime Ecozone+

Only 0.3% of the Pacific Maritime Ecozone+ is Cropland.Footnote14 The largest area of Cropland is the lower Fraser Valley with the remainder in small pockets in the coastal lowlands of the southern mainland, southern Vancouver Island, and on the Gulf Islands (Figure 15). Although only covering a small proportion of the ecozone+, the Cropland is adjacent to and within the largest metropolitan areas so its relative impact on the human environment is much greater than its relative area. Although much precipitation can occur during precipitation events, it falls at low intensity so the risk of water erosion is low. Tillage is quite intensive so tillage erosion dominates. The greatest erosion risks are on that portion of Cropland on the most steeply sloping landscapes. From 1981 to 2006, the amount of Cropland with very low erosion risk increased from 87 to 89%, while that with moderate to high erosion risk decreased from 9 to 7% (Figure 16).

Figure 15. Cropland in the Pacific Maritime Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 15

This map shows Cropland in the Pacific Maritime ecozone+ by soil erosion risk class in 2006. Only 0.3% of the Pacific Maritime ecozone+ is Cropland. The largest area of Cropland is the lower Fraser Valley with the remainder in small pockets in the coastal lowlands of the southern mainland, southern Vancouver Island, and on the Gulf Islands. The majority of Cropland is in the very low soil erosion risk class.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 16. Soil erosion risk on Cropland in the Pacific Maritime Ecozone+, 1981-2006.

graph

Long Description for Figure 16

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198186.74.66.90.71.0
198688.84.45.50.60.6
199189.83.65.30.50.8
199689.04.55.70.50.3
200189.13.76.40.50.2
200688.93.96.70.30.2

Source: data from the National Soil Database and the Census of Agriculture

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Prairies Ecozone+

CroplandFootnote15 is the dominant land use in the Prairies Ecozone+ (54% of area) and it accounts for two-thirds (67%) of all Cropland in Canada (see Figure 1). The 2006 distribution of soil erosion risk classes is shown in Figure 17. Because of the dry climate and large fields exposed to wind, wind erosion is a continual concern in the Prairies Ecozone+ if conservation measures such as maintaining windbreaks and/or adequate soil cover with plants or crop residue are not used. Sandier soils are most prone to wind erosion but erosion will occur on all soils without conservation measures. Excessive tillage can pulverize soils and leave any soil vulnerable to severe wind erosion. Tillage erosion is the largest source of erosion on hummocky landscapes. Due to climate, the risk of water erosion is relatively low except on the landscapes with long steep slopes such as cropped soil along the Manitoba Escarpment. Water erosion in the form of gully erosion is not considered in this analysis but can also be important in this ecozone+ on sloping landforms without use of conservation practices such as grassed waterways.

Figure 17. Cropland in the Prairies Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 17

This map shows Cropland in the Prairies ecozone+ by soil erosion risk class in 2006. Cropland is the dominant land use in the ecozone+, largely in the very low erosion class, with scattered areas of low and a few areas of moderate risk throughout the ecozone+.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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The Prairies Ecozone+ accounts for the greatest reductions in erosion risk in Canada. The proportion of Cropland with very low risk increased from 64% in 1981 to 84% in 2006 (Figure 18). During the same time period, the amount of land with moderate to very high erosion risk decreased from 18 to 7%. The reasons for these reductions in erosion risk have been the combination of widespread adoption of conservation tillage, especially no-till, and the marked reduction in summerfallow. Further, some of the more erodible land has been converted from annual crops to perennial forages and tame pasture with associated dramatic reductions.

Figure 18. Soil erosion risk Cropland in the Prairies Ecozone+, 1981-2006.

graph

Long Description for Figure 18

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198164.118.313.22.22.1
198664.718.712.62.12.0
199167.317.211.91.91.7
199671.715.59.91.61.3
200177.212.57.81.41.1
200684.48.75.11.00.7

Source: data from the National Soil Database and the Census of Agriculture

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Because of the risk of wind erosion, coarse-textured soils (sandy loams, loamy sands, and sands) generally have the greatest erosion risk in the Prairies Ecozone+. For these soils, complete no-till or conversion from annual crops to perennial cover is recommended. In addition to coarse-textured soils, the soils under irrigation in the extreme southwestern Prairies are especially prone to wind erosion, regardless of texture. Vulnerability to wind erosion in these areas results from climatic conditions which include high winds and often little snow cover due to Chinooks allowing erosion to occur throughout the winter. In addition, tillage is generally intensive on irrigated Cropland. The erosion risk on irrigated land is particularly severe after potato and sugar beet crops. After these crops, planting a cover crop of spring or winter cereals will help control wind erosion. Applying solid manure will also help control erosion.

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Western Interior Basin Ecozone+

CroplandFootnote16 is a minor land use in the Western Interior Basin Ecozone+ (1% of the land) and is located in valleys such as the Okanagan and Thompson River. The 2006 distribution of soil erosion risk classes in the Western Interior Basin Ecozone+ is shown in Figure 19. Like many other ecozones+, the Cropland is generally in close proximity to where the majority of people live so its potential impact on air and water quality around human settlements is greater than suggested by its low fraction of total zonal area. Due to dry climate in the valleys, the risk of water erosion is low. Generally, erosion risk is low except on tilled complex slopes where tillage erosion is important. From 1981 to 2006, the amount of Cropland with very low erosion risk increased from 91 to 95%, while that with moderate to high erosion risk decreased from 4 to 2% (Figure 20). Production of more perennial crops such as grapes largely explains the reduction in erosion risk.

Figure 19. Cropland in the Western Interior Basin Ecozone+ by soil erosion risk class, 2006.

map

Long Description for Figure 19

This map shows Cropland in the Western Interior Basin ecozone+ by soil erosion risk class in 2006. The majority of cropland is in the very low risk class throughout the ecozone+. Some areas of low and an area of moderate risk are found in the eastern regions of the ecozone+.

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Figure 20. Soil erosion risk on Cropland in the Western Interior Basin Ecozone+, 1981-2006.

graph

Long Description for Figure 20

This bar graph shows the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198191.44.71.70.61.6
198691.74.91.40.71.3
199193.13.81.50.51.1
199694.53.41.20.30.6
200191.44.42.50.61.1
200694.53.41.10.20.8

Source: data from the National Soil Database and the Census of Agriculture

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Footnotes

Footnote 8

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference8

Footnote 9

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference9

Footnote 10

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference10

Footnote 11

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference11

Footnote 12

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference12

Footnote 13

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference13

Footnote 14

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference14

Footnote 15

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference15

Footnote 16

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

Return to reference16