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Soil Quality / Soil Health Assessment

Overview

conservationists learn how to assess soil qualitySoil quality is an assessment of how well soil performs all of its functions now and how those functions are being preserved for future use. Soil quality or health cannot be determined by measuring only crop yield, water quality, or any other single outcome.

Soil quality cannot be measured directly, so we evaluate indicators. Indicators are measurable properties of soil or plants that provide clues about how well the soil can function. Indicators can be physical, chemical, and biological properties, processes, or characteristics of soils. They can also be morphological or visual features of plants. Useful indicators:

  • are easy to measure,
  • measure changes in soil functions,
  • encompass chemical, biological, and physical properties,
  • are accessible to many users and applicable to field conditions, and
  • are sensitive to variations in climate and management.

Indicators can be assessed by qualitative or quantitative techniques. After measurements are collected, they can be evaluated by looking for patterns and comparing results to measurements taken at a different time or field.  

Examples of soil quality indicators

Indicator Relationship to Soil Health
Soil organic matter (SOM) Soil fertility, structure, stability, nutrient retention; soil erosion
Physical: soil structure, depth of soil, infiltration and bulk density; water holding capacity
 Retention and transport of water and nutrients; habitat for microbes; estimate of crop productivity potential; compaction, plow pan, water movement; porosity; workability
Chemical: pH; electrical conductivity; extractable N-P-K Biological and chemical activity thresholds; plant and microbial activity thresholds; plant available nutrients and potential for N and P loss
Biological: microbial biomass C and N; potentially mineralizable N; soil respiration. 
 Microbial catalytic potential and repository for C and N; soil productivity and N supplying potential; microbial activity measure 

 

Soil Quality Indicator Information Sheets

Soil Quality Indicator Guide Sheet (PDF, 740KB) - A How-to Guide

Physical Properties

Aggregate Stability (PDF, 380KB)
Available Water Capacity (PDF, 210KB)
Bulk Density (PDF, 340KB)
Infiltration (PDF, 315KB)
Slaking (PDF, 500KB)
Soil Crusts (PDF, 250KB)
Soil Structure and Macropores (PDF, 480KB)

Chemical Properties

Soil pH (PDF, 265KB)
Soil Electrical Conductivity (PDF, 210KB)

Biological Properties

Earthworms (PDF, 485KB)
Particulate Organic Matter (PDF, 1.8MB)
Respiration (PDF, 329KB)
Soil Enzymes (PDF, 220KB)
Total Organic Carbon (PDF, 210KB)

Note: Soil Quality Kit Guides that serve as soil property lesson plans for teachers and educators are available at Soil Quality for Educators.

 

Soil Quality / Soil Health Assessment Guidelines

"Guidelines for Soil Quality Assessment in Conservation Planning" describes a step-by step process for assessing soil quality. It will help you decide whether to do an elaborate or simple assessment, which tools to use, and what management practices to use to address soil quality concerns. While the guidelines are presented in the context of the NRCS 9-step conservation planning process, they are also useful in informal assessments, or as an educational resource for teaching soil quality concepts. This guide uses the terms soil quality, soil health, and soil condition interchangeably.

Guidelines for Soil Quality Assessment in Conservation Planning (PDF, 564KB)

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