Risk to soil and water quality from agriculture indicator: data sources and methods, chapter 4

4. Methods

A complete description of how each agri-environmental performance index is calculated is available in Agriculture and Agri-Food Canada's Agri-Environmental Indicator Report Series - Report #4.

The Soil Quality Agri-Environmental Performance Index comprises performance indicators for risk of soil erosion by wind, water and tillage; soil organic carbon change; risk of soil salinization; and contamination by trace elements:

• The Soil Erosion Risk Indicator presents the combined risk of water, wind and tillage erosion when climate, soil, topography and farming practices are considered.
• The Soil Organic Carbon Change Indicator assesses how organic carbon levels in soils are changing over time as a result of land use and management changes.
• The Risk of Soil Salinization Indicator estimates the risk of soil salinization associated with changes to land use and management practices.
• The Risk of Soil Contamination by Trace Elements Indicator considers the risk associated with arsenic, cadmium, copper, lead, selenium and zinc inputs to soil if the current use of fertilizers, manures and municipal biosolids continued for 100 years. Projected trace element concentrations, corrected for loss by leaching, crop removal and volatilization, are compared to the guideline for the health of soil organisms or human health, to estimate risk.

The Water Quality Agri-Environmental Performance Index components are performance indicators for the risk of water contamination by nitrogen, phosphorus, coliform bacteria and pesticides:

• The Indicator of the Risk of Water Contamination by Nitrogen links the amount of excess nitrogen expected to be in the soil after harvest to climatic conditions and soil characteristics to assess the risk of nitrogen leaching to surface water and groundwater.
• The Indicator of the Risk of Water Contamination by Phosphorus estimates the relative risk of agricultural phosphorus reaching surface water bodies in Canadian watersheds. It is based on estimates of source levels of phosphorus and the likelihood of phosphorus transport.
• The Indicator of the Risk of Water Contamination by Coliforms assesses the relative risk of enteric micro-organisms from agricultural sources contaminating surface water bodies using coliform bacteria as a marker.
• The Indicator of the Risk of Water Contamination by Pesticides estimates the relative risk of pesticides reaching surface- and groundwater in agricultural areas as a result of agricultural management practices, taking into account the physical-chemical properties of the pesticides.