Upper North Shore Sydney Australia

Microflora & Microfauna of our Topsoil

Compost Dirt

Topsoil is defined as the humic (derived from decomposed plant and animal remains and animal excrement) upper fertile layer of soil.Root connections

Soil Structures

The roots of plants bind the soil together interlacing with other roots to form a more solid mass that is less susceptible to both water and wind erosion. Nitrogen is obtained by plants, through their roots, from inorganic or organic sources. In garden settings nitrogen deficiency may be a limiting factor for plant growth and yield. A plant deficient in nitrogen will shunt resources away from its green shoots in order to expand its root system so that it can acquire more nitrogen.


Nitrogen (N) is a vital macronutrient for plants, necessary for the biosynthesis of many basic cellular components, such as DNA, RNA and proteins. Bacteria are concentrated forms of Nitrogen. No other living creature has a higher concentration of N in its body than bacteria. Nitrogen-fixing bacteria convert initrogen gas (N2) into organic nitrogen species that can then enter the water cycle and be taken up by plants.


Conventional gardening practices such as; digging, overturning topsoil, using fertilizers and fungicides, poor crop rotations and selecting plants that survive these poor conditions, hinder the ability of plants to form a symbiotic (cooperative) relationship with fungi.

Mycorrhizal fungi help plants to capture macronutrients and micronutrients from the soil by using a loose network of hyphae, (delicate, microscopic, cobweb-like threads). These hyphae consist of the feeding and growing body (mycelium) of the fungus. Each fungus will have vast numbers of these hyphae, all intertwining and helping to bind soil particles, contributing to soil structure and erosion control.

NOTE: Fungi have differing functions for example;

all species of the mushroom genus Agaricus are decomposers of soil organic matter and good for perennials whereas

all members of the genus Amanita are mycorrhizal partners of plants increasing nutrient and water uptake and good for annuals.

Soil Glue Compost soil

Surface topsoil particles are held together by various organic substances acting as a soil ‘glue’ to create stable soil aggregates. The ‘gluing’ of soil particles together into aggregates helps maintain pores and channels in the soil for air and water to enter and move through it. Soil aggregates are more stable and harder to wash away than individual soil particles during rain storms. Erosion of your precious top soil is less likely.

Do Not Disturb

When the soil is not disturbed, more animals, plants, fungi, and microorganisms thrive in the soil. In undisturbed soils the amounts of soil ‘glue’ increases and your soil holds together better. Soil organisms’ increase in abundance and more variety of species are represented when soil is not disturbed.

Soils are disturbed in the production of underground crops, such as potatoes and beetroot, and the construction of furrows for planting. When soil is heavily cultivated (tilled) or dug up during garden construction, the surface layer (topsoil) is often drastically altered, buried, or removed. Change takes place when oxygen gets into the newly exposed soil and decomposers, (animals, plants, fungi, and microorganisms), convert the organic matter into energy, carbon dioxide, and water. This reduces the amount of organic matter in the soil and the amount of ‘glue’ that is available to hold soil together. Soil structure is altered and live soil creatures are reduced in number and possibly variety, or they are eliminated altogether.

Helping Nature

Planting quick growing green cover crops and always covering disturbed soils with a thick layer of mulch provides protection from raindrops and food for soil ‘glue’ producing organisms. Increasing Australian native vegetation increases mycorrhizas. Abundant networks of fine fungal mycelium occur in woodland soil, and many woodland plants have mycorrhizas. Worm castings are another excellent source of bacteria and help create mycorrhizas. Actively aerated compost teas are very high in beneficial microbes.