Soils and Agricultural Capability
Agriculture can be defined as the systematic and controlled use of living organisms and the environment to improve the human condition. According to the Agriculture Land Commission Act (the “ALC Act“) agricultural land means land designated as agricultural land under the Act and includes agricultural land under a former Act. In general ‘agricultural land’ is the land resource upon which agriculture takes place due to its ability to grow food products. The agricultural land resource and the products that can be grown are based on a soils and climate combination which can vary across the landscape. Typically occurring on farms, agricultural activities are undertaken upon agricultural land to produce agricultural products. Although agricultural land is primarily required for the production of food for human and animal consumption, agricultural activities also include the growing of plants for fibre and fuels (including wood), and for other organically derived products (e.g. pharmaceuticals, etc).
Not all agricultural lands are created equal and not all agricultural land is capable of or suitable for producing all agricultural products. Some agricultural land is more suitable for certain crops than others. British Columbia’s diverse agriculture industry needs all classes of land to thrive. There are three dominant limiting factors in British Columbia:
- Climate – Climate is defined by the heat energy and moisture inputs available for agricultural production.
- Soil variability – Soil properties and characteristics affect the land’s ability to sustain agricultural products.
- Topography – Topography can limit access and the ability to use cultivation equipment.
Physical, chemical and biological inputs are essential to agricultural systems, and are ultimately supplied by the soil, moisture, the sun (in the forms of light and heat energy), plants, animals and biological agents. In productive agricultural systems these inputs are necessarily controlled, to the extent possible, through appropriate agricultural practices. The more capably the land base provides and sustains these inputs, the more capable and productive the land is as agricultural land.
The decision to put a particular parcel into agricultural production is not a sole reflection of its agricultural capability or suitability. Agricultural business costs, physical accessibility and market vagaries may result in a certain block of land being used or left fallow and this may vary over time.
Agricultural Land Capability Classification System
There are two land capability classification systems used in BC depending on the availability of maps for a particular area of the province.
- Canada Land Inventory (CLI)
CLI maps are 1:50 000 scale and are used throughout Canada.
- BC Land Inventory (BCLI)
BC has developed a classification system known as Land Capability Classification for Agriculture in British Columbia. BCLI maps are 1:20 000 scale and are specific to BC.
The agriculture capability classification consists of two main components: (1) the capability class and (2) the capability subclass. The capability class and subclass together provide information about the degree and kind of limitation for agricultural use. In addition to land capability designation, they are also useful for land use planning and assessing management practices.
Both systems describe seven land capability classes, ranging from Class 1, applied to land that has the climate and soil to allow a farmer to grow the widest range of crops, to Class 7, land that is considered non-arable, with no potential for soil bound agriculture. The intermediate classes may be inappropriate for some agricultural uses, while being highly suitable for others. Even Class 6 land, while precluding conventional, arable agricultural activities, may still sustain native and/or perennial uncultivated agriculture, often used for animal grazing
Each of the seven classes also has a subclass that identifies limitations or special management practices needed to improve agricultural capability. Limitations include such factors as topography, stoniness, soil moisture deficiency and low fertility. Management practices include such things as drainage, irrigation, stone picking and fertilization.
Factors on which the classification is based
- The soils will be managed and cropped under a largely mechanised system.
- This classification provides most lands with two ratings — one under improved conditions and one for improved conditions. Unimproved ratings are based on the conditions that exist at the time of the survey, without irrigation. Improved ratings indicate the capability after existing limitations and/or hazards have been adequately alleviated. Improvements which are to be considered include drainage, irrigation, diking, stone removal, salinity alleviation, subsoiling, and/or the intensive addition of fertilizers or other soil amendments.
- In determining improved ratings, irrigation water is assumed to be available. Other types of improvement are considered drainage, stone removal, fertilization, diking, salinity alleviation, subsoiling and the addition of soil amendments. The extent to which these improvements can increase the land capability is determined from site specific assessments.
- The following are not considered in the classification: distance to market, available transportation facilities, location, farm size, type of ownership, cultural patterns, skill or resources of individual operators, and hazard of crop damage by storms.
Classification takes into account the relative degree and type of limitation or hazard to agriculture; use and/or the range of possible crops. It also indicates the type and intensity of management practises required for good management of the soil resource to maintain sustained production. Productivity (i.e. yield per hectare) of any specific crop is not considered.
Increasingly, innovations in drainage and irrigation, tillage, nutrient replenishment, and pest management, as well as closed environmental systems, allow for agricultural production on land once deemed unusable. The recognition of ‘arable’ agricultural activities is also significant in that Class 6 and 7 lands may still be agriculturally productive, where topography and climate allow, and/or where the agricultural activities are dedicated to closed environmental systems (i.e. greenhouses).
Agricultural Land Capability Classes
Class 1 — Land in this class either has no or only very slight limitations that restrict its use for the production of common agricultural crops
Land in Class 1 is level or nearly level. The soils are deep, well to imperfectly drained under natural conditions, or have good artificial water table control, and hold moisture well. They can be managed and cropped without difficulty. Productivity is easily maintained for a wide range of field crops
Class 2 — Land in this class has minor limitations that require good ongoing management practises or slightly restrict the range of crops, or both
Land in class 2 has limitations that constitute a continuous, minor management challenge or may cause lower crop yields compared to Class 1 land but do not pose a threat of crop loss under good management. The soils in Class 2 are deep, hold moisture well and can be managed and cropped with little difficulty.
Class 3 — Land in this class has limitations that require moderately intensive management practices or moderately restrict the range of crops, or both
The limitations are more severe than for Class 2 land and management practises are more difficult to apply and maintain. The limitations may restrict the choice of crops or affect one or more of the following practises: timing and ease of tillage, planting and harvesting, and methods of soil conservation.
Class 4 — Land in this class has limitations that require special management practises or severely restrict the range of crops, or both
Land in Class 4 has limitations which make it suitable for only a few crops, or the yield for a wide range of crops is low, or the risk of crop failure is high, or soil conditions are such that special development and management practises are required. The limitations may seriously affect one or more of the following practises: timing and ease of tillage, planting and harvesting, and methods of soil conservation.
Class 5 — Land in this class has limitations that restrict its capability to producing perennial forage crops or other specially adapted crops
Land in Class 5 is generally limited to the production of perennial crops or other specially adapted crops. Productivity of these suited crops may be high. Some Class 5 lands can be used for cultivated field crops provided unusually intensive management and/or the use of particularly well-adapted crops. Where adverse climate is the main limitation, a broader range of cultivated field crops may be grown, but periodic crop failure can be expected under average conditions. Note that in areas that are climatically suitable for growing tree fruits and grapes, stoniness and/or topography are not significant limitations.
Class 6 — Land in this class is nonarable but is capable of producing native and or uncultivated perennial forage crops
Land in Class 6 provides sustained natural grazing for domestic livestock and is not arable in its present condition. Land is placed in Class 6 for various factors: severe climate; terrain that is unsuitable for cultivation or use of farm machinery; or soils that do not respond to intensive improvement practises. Some Class 6 lands can be improved by draining and/or diking.
Class 7 — Land in this class has no capapbility for arable or sustained natural grazing
Class 7 comprises all lands not included in Classes 1 to 6. Class 7 lands may have limitations equivalent to Class 6 land but they do not provide natural sustained grazing by domestic livestock due to climate and resulting unsuitable natural vegetation. Also included are rockland, other nonsoil areas, and small water-bodies not shown on maps. Some Class 7 land can be improved by draining or diking.
Agricultural Land Capability Sub-Classes
Except for Class 1 lands, which have no significant limitations, the capability classes are divided by subclasses on the basis of the types and extent of limitations to agricultural use. For detailed definitions and guidelines refer to the Land Capability Classification for Agriculture in British Columbia.
A — Soil Moisture Deficiency
Crops are drought prone due to soil and/or climate characteristics. Improved by irrigation.
*C — Adverse Climate
Thermal limitations to plant growth. Minimum temperature near freezing and/or insufficient heat during the growing season and/or extreme minimum temperatures during the winter season. NOT IMPROVABLE.
D — Undesirable Soil Structure And/Or Low Perviousness
Soils are difficult to till, require special management for seedbed preparation, pose trafficability problems, have insufficient aeration, absorb and distribute water slowly, and/or have root-zone depth restrictions such as high water table, bedrock, or permafrost. Improvement practises vary; no improvement is assumed in the absence of local experience.
E — Erosion
Past damage from erosion limits agricultural use due to loss of productivity and hampering of access by gullies. NOT IMPROVABLE.
*F — Fertility
Lack of available nutrients, low cation exchange capacity or nutrient holding ability, high acidity or alkalinity, high levels of carbonates, presence of toxic elements or compounds, or high fixation of plant nutrients. Usually improvable through fertilizers and amendments.
*I — Inundation
Overflow by streams, lakes or marine tides causes crop damage or restricts agriculture use. Improvable by diking if a major reclamation project is not required.
M — Moisture
A low moisture holding capacity, caused by adverse inherent soil characteristics, limits crop growth. (Not to be confused with climatic drought.)
*N — Salinity
Soluble salts in the soil reduce crop growth or restrict the range of crops. The success of improvement practises varies depending on site and soil conditions.
P — Stoniness
Coarse fragments significantly hinder tillage, planting and harvesting. Note that in areas that are climatically suitable, a Class 5 level stoniness may not be a significant limitation to the growing of tree fruits and grapes.
R — Depth To Solid Bedrock
Bedrock near or at the surface restricts rooting depth and cultivation. NOT IMPROVABLE.
T — Topography
Steepness or the pattern of slopes hinders the use of farm machinery, decreases the uniformity of growth and maturity of crops, and/or increases the potential for water erosion. NOT IMPROVABLE. Note that in areas that are climatically suitable, a Class 5 level topography limitation may not be a significant limitation to the growing of tree fruits and grapes,
*W — Excess Water
Excess free water, other than from flooding, limits agricultural use and may be due to poor drainage, high water table, seepage, and/or runoff from surrounding areas. Improvable by drainage; feasibility and level of improvement is assessed on a site-specific basis.
*Z — Permafrost
Permafrost maintains undesirably cold soil temperatures and causes drainage and subsidence problems when near the surface. NOT IMPROVABLE.
Land Capability Subclasses for Organic Soils
B — Wood In The Profile
Layers of wood interfere with cultivation and/or with ditching and drain installation. No improvement is assumed in the absence of local expertise.
H — Depth Of Organic Soil Over Bedrock And/Or Rockiness
Bedrock near the surface restricts rooting depth and the feasibility of subsurface drainage, and/or rock outcrops restrict agricultural use. NOT IMPROVABLE.
L — Degree Of Decomposition — Permeability
Degree of decomposition affects drainage, permeability, capillary rise of water and rate of subsidence. Layers of mineral soil in an organic profile may pose a limitation to optimum crop yield and to drainage. NOT IMPROVABLE.
* These subclasses are the same for both organic soils and mineral soils.
- soils publications are available through the J. T. Fyles Natural Resources Library
- some soils reports are available through Crown Publications
- some maps and reports are available from the Pacific Regional Soil Science Society
- federal soils information can be found through the Canadian Soil Information Service (CanSIS)
- agricultural capability maps of BC can be found through Terrestrial Ecosystems Information (TEI), Ministry of Environment