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» General Soil Ecology
» What are the roles of soil organisms?
» How does organic matter fuel the soil food web?
General Soil Ecology
Soil ecology refers to the complex interactions of all soil dwelling organisms with one and other, plants and the physiochemical soil properties.
These interactions can be explained by using a soil food web example. Organisms within the soil food web range from the smallest bacteria, fungi,
algae and protozoa to small micro-invertebrates (rotifers to nematodes), larger invertebrates (earthworms, millipedes, centipedes and insects)
and small mammals. However, the most important element of soil ecology is the plant community that lives within the soil system.
Essentially, interactions between organisms create a healthy and productive environment; they eat organic matter and each other, releasing nutrients through
fecal deposition. Nutrients are up-taken by plant roots and in return plants release simple organic compounds into the soil. This provides the bulk of energy
required for soil microorganisms to grow and reproduce. There are various types of soil organisms providing a multitude of plant-beneficial tasks.
Some organisms may aid in the breakdown of various pesticides preventing them from entering the food web or ground water.
Properties affecting the biodiversity of soil organisms include pH, electrical conductivity, water-holding capacity, soil structure,
organic matter content and pore size. Biodiversity is greatly effected by the above factors.
Soil organisms can be defined as any organism living all or part of its life in the soil system. The basis of soil life comes from the
primary producers (photosynthetic organisms). These organisms include photosynthetic bacteria, algae, mosses, lichens and higher plants.
Photosynthetic organisms capture carbon dioxide from the atmosphere and convert it into simple and complex sugars, powered by sunlight.
Although there are some bacteria that derive energy from nitrogen, sulfur or other compounds, these organisms represent a minority of the soil food web.
As soil organisms consume decomposing organic matter and each other, nutrients are transferred and converted into various forms,
ultimately becoming available for plant uptake. All plants (grasses, trees and shrubs alike) rely on the nutrients released by
soil organisms for growth and reproduction.
What are the roles of soil organisms?
The ultimate goal of all organisms is to grow and reproduce. In order to achieve this goal soil organisms rely on each other for food sources.
Root exudates (sugars and other by-products) released by plants feed soil organisms and in turn soil organisms release locked up nutrients,
create more suitable soil structure and control pest populations. Some organisms produce plant beneficial hormones and enzymes
to aid in times of stress.
How does organic matter fuel the soil food web?
Organic matter in the soil contains the energy and nutrient supply that most soil organisms require. Bacteria, fungi and a diverse array of other
organisms transform and release valuable nutrients from organic matter.
Organic matter is comprised of many different compounds, some more useful than others. In general, organic matter is a mixture of humus and active
organic debris. Active organic debris is the main food source for soil organisms. Bacteria feed mainly on fresh root exudates and plant debris,
whereas most fungi prefer more woody lignified plant tissues and humus as a food source.
Many other organisms utilize necrotic plant tissue as a food source, such as earthworms, which are considered the most important
group of soil dwelling organisms.
So, it is important to realize that your soil is a diverse ecosystem made up of organisms from all facets of life. As synthetic fertilizers
and pesticides are often deadly to soil organisms, we should consider alternative means of agricultural management practices. By
understanding how the biological elements of healthy soil work we can unlock the secret to ecologically sustainable management practices.
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