Soil Biology


This is an extract of a beautifully written piece for all we citizen soil scientists. It makes sense. For the full and original article, go here.

Soil Biology is the study of the living component of soils – the bacteria, fungi, and soil animals which all have particular soil processing roles. It is distinct from, but linked to the processes involved in Soil Chemistry (nutrient processes) and Soil Physics (soil structure, texture, stability, water movement in soil).

Why is soil biology important?

The activities of the wide range of organisms in soil play a pivotal role in both natural and managed ecosystems. Their processes of organic matter breakdown contribute to the soil’s health – its stability, permeability, ability to retain nutrients and make them available for plant uptake.

Soil biological, physical and chemical processes are interrelated and all contribute to plant productivity. The level of soil biological activity is therefore affected by the soil type, but it also depends on the management practices used, particularly the management of organic matter, especially carbon. Changes that are made to the chemical and physical environment in soil will therefore influence the biological processes and subsequently the contribution they make to the soil’s fertility overall.

What are the issues associated with soil biology?

Knowledge of soil biological processes can support decision making aimed at achieving sustainable use of agricultural land. Soil biology is a complex field, however, and research continues to uncover new facts concerning the organisms themselves, their processes and factors that affect them. Additionally, management of soil biological processes is difficult to do precisely due to the differing parameters of each individual situation, such as soil type and land use. A certain land management practice may also affect one group of organisms, but not others. Consideration of the mass of microorganisms as a whole (microbial biomass) is therefore not sufficient for a complete interpretation of the effects of land management on soil biological fertility.

Measurement of soil health in terms of biological fertility is also a complex and at present, relatively expensive process. More attention has been usually given to the management of the soil chemical and physical environments. As a result, a host of inexpensive and simple tests are available to land managers. Incorporating soil biological processes into farming systems will require a more holistic and longer term approach to agricultural land management.

What are the benefits of understanding and managing soil biology?

Agricultural land management practices alter aspects of soil chemical and physical fertility with consequences for soil biological processes and vice versa. Both fauna and microorganisms contribute significantly to chemical transformations in the soil and influence their physical surroundings to various degrees. Organisms on and around plant roots have major influences on plant nutrient availability and some form specific associations with legumes, which greatly influence the C:N ratio of plant residues in soil. Associations between agricultural plants and fungi known as arbuscular mycorrhizas have the potential to increase the efficiency of use of phosphorus in agricultural ecosystems as well as improve soil structure.

Current research includes understanding some of the undesirable members of the biological population, such as root pathogens. The role of mycorrhizal fungi in preventing and reducing the effects of salinity is also being investigated. Stubble management is another area of research.