Tests and indicators of soil health
Soil assessment methods cover physical, chemical and biological indicators.
Integrated soil health assessments
In a healthy soil, the interactions between physics (soil structure and water balance), chemistry (pH, nutrients and contaminants), and biology (including earthworms, microbes and plant roots) are optimal for the conditions in that place. Measuring soil health requires an integrated approach that combines the assessment of the chemical, physical and biological properties of soil.
At a minimum, combine visual evaluation of soil structure (VESS) and earthworm counts with sampling for pH, nutrient status, and organic matter.
Physical soil condition
The physical condition of soil is an essential component of its health. Developing and maintaining a good soil structure depends greatly on good soil management, including cultivation at appropriate times and depths, and minimising traffic over the soil when it is too wet. Soil texture (type) is an inherent property, and management needs to adapt to it.
Chemical analysis and nutrient balance
The nutrient status of a soil is an important component of its health. Tests should be chosen based on the production system and its perceived challenges. The basic parameters – pH and nutrient status – should be tested regularly.
Biological soil tests
Earthworms are useful indicators of soil condition. Counts from several fields over a number of years or crop rotations can indicate long-term trends in soil condition.
Methods to assess soil biological activity by laboratory analysis are available, but need careful consideration and interpretation.
Some other soil biological tests – such as assessments of the soil food web, or molecular indicators of soil bacterial and fungal communities – are relatively new, and information on interpretation and how to improve the values in soils can be lacking.