Soil Management Assessment Framework SMAF

This document is not a method, but rather a framework for selecting and applying indicators to assess soil quality. It does not specify detailed procedures for measuring the indicators, so those must be chosen or developed locally. Its primary strength is the depth with which it describes procedures for modeling and integrating the soil quality indicators.

Purpose: To enhance and extend current soil assessment efforts by presenting a framework for assessing the impact of soil management practices on soil function.

Method Description: The tool consists of three steps: indicator selection, indicator interpretation, and integration into an index. First, users are to select indicators by applying a series of decision rules to a soil measurements database. This selection is based on soil functions important to management goals for a site, associated soil functions, and site factors such as regional sensitivity. Next, users interpret indicators using non-linear scoring curves, such as those used by the “Habitat Evaluation Procedure” (HEP) (USFWS 1980) and “Hydrogeomorphic (HGM) Approach” (Smith et al. 1995). Finally, researchers use the data to integrate into an index of soil quality.
SMAF recognizes 3 management goals: Maximize Productivity, Waste Recycling, or Environmental Protection. Associated with these are 6 soil functions: Nutrient Cycling, Water and Solute Flow, Physical Stability and Structural Support, Filtering and Buffering, Resistance and Resilience, Biodiversity and Habitat. These functions are predicted by 81 indicators and 169 selection rules. Examples of indicators are: bulk density, soil test phosphorus, total organic carbon, microbial biomass carbon, potentially mineralizable nitrogen, macroaggregate stability, available water capacity, electrical conductivity, sodium absorption ratio, nematode maturity index, and metabolic quotient.

Method Specific Categories:

Habitat (e.g., habitat suitability, biological integrity) 

• Biodiversity and habitat: nematode maturity index
• Resistance and resilience

Biogeochemistry and water quality for aquatic life

• Filtering and buffering (e.g. electrical conductivity, sodium absorption ratio)
• Nutrient cycling (e.g. soil test phosphorus, total organic carbon, microbial biomass carbon, potentially mineralizable nitrogen, and metabolic quotient)
• Resistance and resilience

Hydrologic integrity

• Filtering and buffering (e.g. electrical conductivity, sodium absorption ratio)
• Resistance and resilience
• Water and solute flow (e.g. available water capacity)

Physical structure or geomorphic integrity

• Filtering and buffering (e.g. electrical conductivity, sodium absorption ratio)
• Physical stability and structural support (e.g. bulk density, macroaggregate stability)
• Resistance and resilience