There are several technical terms that are described in the digital soil map, the soil analysis and the Tea Bag index. A glossary of some common terms that are used can be found here. For further details please refer to the resources page or feel free to contact us.
The term “organic” refers to something that is composed of carbon-based compound and is usally derived from living things.
Microbes or microorganisms describe tiny living organisms that cannot be viewed with the naked eye. Microbes in soil can include bacteria, fungi, viruses, protozoa and nematodes.
A microbial community refers to a group of microorganisms that are living in the same environment. These microbes interact with each other and the population can vary based on a range of environment and internal factors.
Decomposition rate (k)
The decomposition rate is a measure of turnover of carbon in plant material and describes the initial breakdown which is important to release organic nutrients and carbon. A “healthy” soil is predicted to have a lower k indicating that the microbes decomposing the organic materials are more efficient in using the carbon enabling greater carbon storage.
Factors that increase the decomposition rate includes temperature and moisture.
Stabilisation Factor (s)
Stabilisation factor describes a measure for stabilization of organic carbon in plant material. A high stabilization factor indicates a greater carbon storage capacity. Like the decomposition rate, the stabilization factor is influenced by temperature and moisture. S values decrease as temperature and moisture increase.
Tea bag index
The Tea Bag Index is a measure of decomposition and stabilization of organic matter in soil. The index consists of two parameters – decomposition rate and stabilisation factor.
Soil pH is an estimation of soil acidity and alkalinity. It varies along a scale between 0 and 14 with neutral soil being at pH 7. In nature, soil pH can range from pH 3 to 10. Soil pH affects the fertility of soil as it affects the microbial activity with most of the activity estimated to occur at pH levels between 5 and 7. Soil pH also affects the availability of nutrients with nutrients like phosphorus becoming less available at a low pH.
Inorganic carbon in the soil comprises of the carbon from soil minerals such as carbonates
Organic carbon in the soil can be derived from organic materials such as plant materials and microbial biomass (living and dead).
Total carbon describes all the carbon in the soil including organic and inorganics forms. Soil carbon can tell us about the fertility of the soil – particularly organic carbon. Total carbon can vary based on a number of factors including soil texture and the extent of human interaction with a site.
Electrical Conductivity is a measurement of the amount of salt in the soil, this is also known as soil salinity. It is an important indicator of soil health as it can affect nutrient availability, microbial activity and soil-water balance. As the EC increases, the activity of the microorganisms decreases.
Soil texture describes a physical property of the soil which is dependent on the percentage of different particle sizes in the soil. These particles can be arranged by size. Clay is the smallest (<0.002mm) followed by silt (0.002mm-0.05mm) and sand (0.05mm-2mm). Different soil textures affect the way soil can be worked, its aeration and the movement of water through it. For example, sandy soils are well aerated but do not hold much water and is low in nutrients. In contrast, clayey soils are better ay holding water and supplying nutrients.
Soil Slaking Index
Soil Slaking is a measure of soil aggregate stability. Soil aggregates describes a group of soil particles that bind together. These aggregates are important because they create pore space that allow air and water to circulate allowing plant roots to grow.
Therefore, soil aggregate stability refers to the ability of the soil aggregates to resist external forces, mainly from water. Soil aggregate stability can be affected by the amount and type of soil organic matter and the type and size of the soil microbial community.