Soil The basis of the living skin of the planet.

Four components Air Water Minerals Organic matter Traditionally, they are seen as : Air, Water, Earth and Fire (as Biomass represents the capture of solar energy)

Air Atmospheric gasses, present in spaces created by interstices of soil particles Atmospheric gasses, conducted into passages and pores created by macroorganisms Atmospheric gasses, transported into the soil through the action of vegetation. Atmospheric gasses, transported into the soil through the action of extra fossorial events

Water 1. Water is gained by the soil through rainfall or flood. 2. Water is lost by the soil through gravitational action, transpiration and evapotranspiration 3. Microorganisms and plants influence the retention of water in the soil 4. The capacity to retain water influences the biodiversity of the soil ecosystem and vice versa 5. Water composition of the soil is impacted by compression or disturbance. 6. The water composition of the soil is greatly influenced by short-term climate events

Earth Earth is represented by minerals that constitute the non-organic solid component of soils. This mineral fraction of soil is described in terms of the size of particulate matter. Ranging from rock, sand to clay. Minerals are usually transported by wind, water or other geologic agency or are found in situ where they were formed. The mineral fraction of soil usually takes many thousands of years to form

Fire Solar energy that sequesters organic matter Geothermal energy that sequesters organic matter Nuclear energy that sequesters organic matter.

Organic Matter Truly the Cinderella. The wonder of the world of soil carbon has generally been ignored by much of soil science. Ranging from about.01 to 10 % in proportion. This diminutive fraction is really the engine that drives all of agriculture. The principal property of soil fertility is determined by biological factors, mainly by microoganisms. The development of life in the soil endows it with the property of fertility.Krasil’nikov 1958.

Soil Biodiversity One gram of soil may contain 1-2 billion individual bacterial cells. This accounts for a mass of about kg of bacteria per hectare in the upper 15 cm of soil. Similarly it has been found that actinomycetes may reach populations of 200 million or more individuals per gram of soil. This group which falls between the bacteria and fungi are able to decompose organic matter at moisture levels too low for either bacteria or fungi to operate effectively. The fungi are present in similar numbers and often have a kilometre of hyphae in a gram of soil (Allison, 1973).

The combined biomass of all soil organisms in one hectare is equal to that of twenty horses The daily operation of these organisms yield the power of about 20 HP per hectare. This energy goes into maintaining the productivity and sustainability of the soil ecosystem.

As this component is reduced, the biological power component to sustaining the soil is reduced. The process if allowed to continue leads to desertification and complete loss of soil productivity.

Regenerating soils How can we design an active soil ecosystem that is analagous to the mature soils that once existed in the area ? The living soil should be supported by a terrestrial ecosystem that provides it with the critical OM increment What is missing in terms of mineral matter and biodiversity should be replaced exogenously but in a seral sequence, that is analogous to the native systems.

Techniques in regenerating soils Ramial chopped wood Remineralization Revegetation MSI Mulching Composting

Roots and Soil Tree Roots provide up to 20% of their total root weight as exudates into the surrounding soil. Each Species of tree provides differing chemical compounds Many species of trees have distinct species of associated soil organisms

Water is a critical part of soil

The thermal regime of soils is determined by the vegetation cover and OM content of soils Absorption of solar radiation Chernozerms86% Gray soils80% White soils20%