Ted Floyd Creekcare

Urban Soils

Soils, Water and Plants

Ted Floyd Nov. 2014

Keywords: Plants, Soils, Water, Soil Health, Sustainable Soils, Climate Change, Soil Water, Organic Matter.

Life on earth depends on photosynthesis occuring in plants while growing in soils with adequate water.

drawing of tree with roots and kangarooAs ye sow. So shall ye reap.

Plants climbed out of ancient seas onto dry land 0.4 billion years ago and soils were formed under plants.

Plants are essential for the formation of new soils and the maintenance of existing soils.

Soils will degrade when there are no plants.


Plants began growing on land 0.4 billion years ago and soils developed where plants grew. Ecosystems evolved on land with plants growing in soils and microorganisms and animals eating organic matter.

Plants are the center of natural, sustainable, ecosystems on land where energy from the sun, water and carbon dioxide from the atmosphere is synthesized into organic carbohydrates during photosynthesis.

Microorganisms and animals eat organic matter and gain energy by respiration.

Plants growing in soils, with an adequate water supply is neccessary for life on earth and survival of the human race.

diagram of wheatDynamic Carbon in Soils

Soil health and plant growth is improved by the dynamic activity of soil carbon.

  1. Organic matter is produced during photosynthesis by plants.
  2. Root exudates are added to soils.
  3. Plant material is added to soils and increases soil carbon.
  4. Animals and microorganisms eat organic matter.
  5. The percentage of carbon in organic matter decreases during decay.
  6. The nutrient percentage of organic matter increases during decay.
  7. Transpiration draws water from soils by plants into the atmosphere.
  8. Water is needed by microorganisms and soil animals.
  9. Nutrients are converted into inorganic chemicals and are able to be absorbed by plant roots.
  10. Most organic carbon is converted into carbon dioxide and is returned to the atmosphere during respiration.
  11. Humus is resilient carbon formed at the end of the decay chain and remains in the soil for many years.

Plants improve soils.

Physical properties improved by plants.
  1. Protect soils.
  2. Reduce erosion.
  3. Reduce raindrop impact.
  4. Stabilize soils.
  5. Form aggregates.
  6. Increase water infiltration.
  7. Improve aeration.
  8. Increase water holding capacity.

Soil Carbon Cycle.

The dynamic activity in the carbon cycle promotes plant growth and improves soil health. The rate of turnover of carbon during the carbon cycle promotes soil health and is as important, if not more, than the absolute quantity of soil carbon.

Carbon is the natural building block of all living organisms. In natural eco-systems carbon is continually cycled from the atmosphere to plants and then to animals and microorganisms and back to the atmosphere. All living creatures contain carbon and all organic matter found in soils contains carbon. The natural carbon cycle is essentially a closed loop with no carbon added or subtracted from ecosystems.

Soils play an important role in the global carbon cycle. There is more living material in soils than above the soil surface. The mass of plant roots is often greater than the mass of growing plant matterial found above ground level. Bacteria, actinomycetes, fungi, algae and protozoa are microorganisms found in all soils. Insects, mites, worms, and many more animals live in the dark. Rabbits and wombats are larger animals who make their home underground.

a tree surfing on a leaf

Soil organic matter is the decaying remains of plants, microorganisms and animals. Plants are made from sugars, starches, cellulose, fats, oils, proteins, and lignins. Lignin and cellulose decompose slowly and form long-lasting soil humus. Sugars and carbohydrates decompose quickly and disappear from soils.

A bio-carbon sink can only be created in soils by adding organic matter faster than the rate of decomposition of existing organic matter.

Humus is completely decomposed organic matter and cannot be recognized as plant remains. Small humus particles are amorphous colloids, which are smaller than crystalline clay particles. The surface of humus particles is electrically charged and attracts positive charged cations and negative anions. Many essential plant nutrients are stored on the electrically charged surface of humus helping to improve soil fertility.

Soil organisms

A gram of healthy soil contains up to 3,000 million bacteria and 500,000 fungi plus actinomycetes, algae and protozoa. Bacteria have a diameter of approximately 0.001 mm and fungi filaments, 0.005 mm. Clay is less than 0.002 mm.

Bacteria prefer to grow in the thin water layer surrounding clay particles and fungi grow better in large soil pores and can survive dry conditions.

Fungi are able to feed on hard to decompose plant fibers and woody material including cellulose and lignin. Bacteria thrive on sugars and starches, especially in the rhizosphere close to the surface of plant roots.

What is more important, the product or the process?

What is more important for soil health? Humus or the carbon cycle?

The product *is humus.

diagram of wetlands

The process *is the carbon cycle.

Recalcitrant soil carbon contains humus, humic and fulvic acids and charcoal like carbons. It is resistant to decay, and may last in soils for thousands of years.

Labile carbon consists of partly broken down plant remains and living organisms and is active in the carbon cycle.

To obtain humus, with all the desired properties stimulating plant growth, many processes occur beginning with the growing of plants and addition of root exudates to the soil. Bacteria thrive in the nutrient rich rhizosphere of root growing tips. Mychhorizal fungi collect and transport nutrients directly into plant roots. Small soil animals break up and eat organic matter. Animal and microbe faeces contain soluble plant nutrients available for absorption by plant roots.

When soil organic matter is eaten and excreted by microorganisms and animals, the carbon becomes harder to break down and more resilient. The end product is humus which is recalcitrant, very difficult to decompose, and survives in the soil for hundreds of years. Humus is the end product of the carbon decomposition chain.

The organic matter content of soils is often considered to be a measure of soil health. There are many useful physical and chemical soil properties improved by organic matter. Organic matter contains both recalcitrant soil carbon resistant to decomposition and labile soil carbon still available for decomposition.

The dynamic activity of soil organic matter is important. Labile organic matter is active in the carbon cycle. It is a source of food and supports the growth of microorganisms and soil animals. This activity in the carbon cycle promotes plant growth.

Is the cycling of soil carbon more important than attempting to create permanent soil carbon? Recalcitrant soil carbon helps to improve soil health and labile soil carbon improves soil growth while active in the soil carbon cycle.

thistle showing rootsPlants in cities.

  1. Biophilic Cities
  2. Habitat for animals
  3. Shady cool space
  4. Cool the urban heat island
  5. Generate natural biocarbon sinks and ensure climate stability
  6. Increase water infiltration into soils
  7. Reduced flooding
  8. Pollution control
  9. Education of young and old.

Climate change

Renewable energy will reduce additions of Carbon Dioxide to the atmosphere. Natural bio-carbon sinks absorb Carbon Dioxide from the existing atmosphere. Comprehensive programs to establish climate stability should include both natural biocarbon sinks and renewable energy.

Every year 10% of Carbon Dioxide in the atmosphere is converted by photosynthesis to organic matter. Photosynthesis occurs in green chlorophyll of plants and algae. In the ocean, significant amounts of photosynthesis occurs in algae containing chlorophyll. In the total carbon cycle in the Earth, organic matter decomposes and Carbon returnes to the atmosphere.

Dynamic soils in town and country

Soils are continually undergoing formation and erosion.

Plants are fundamental in the formation and loss of soils.

A continual cover of plants over soils reduces erosion and soil degredation.

Urban areas have large impervious areas of buildings, concrete and tar reducing plant growth.

Irrigation, water harvesting and soil moisture management improves plant growth.

Urban spread increases impervious soils and reduces plant growth in outer suburbs.

A compact city has a smaller area and impervious soils in the outer fringe is reduced.

Variable environments.

Variable environments improve biodiversity and increase plant growth. Dry spots, wet spots, rock piles, log piles, trees, shrubs, grasses, bumpy surfaces, depressions, high spots, low spots, uneven land surfaces and contours create variable environments. Water environments, leaky weirs, wetlands, duck ponds and wildlife islands may be established in drainage lines and wet areas.


Plants are essential to maintain a sustainable world. The maximum benefit of plants is obtained by encouraging photosynthesis and plant growth. Healthy sustainable soils and water promote photosynthesis and plant growth.

Plant Plants.

Further information.