The living soil

There are several techniques and methods of making compost for soil amendment. The following information is based on the research conducted by soil microbiologist Dr. Elaine Ingham, which was shared with us by Spero Latchis who has been farming in Bir, and implementing Dr. Elaine’s ideas, while improvising based on his own research and observations.

Common soil terminology and the background of the living soil are included to describe the context of this compost recipe.

THE LIVING SOIL

Our current farming practices are focused on the chemical nature of the soil and are based on extensive use of chemical and nutritive additives to feed the plants. Gradually the soil in commercial farms has deteriorated prompting the farmers to resort to increasing the use of fertilisers to compensate for this deficiency.

This has ended up as a vicious cycle where the farmer has to keep increasing the fertilizer input, the soil depletes continually and the crops grown in these soils lose their vitality and vigour. Most of these changes take generations to become visible and thus our feedback in remedying it often lacks the information and understanding of how the problem arose.

Intensive research in the last couple of decades has made it clear that soil and its properties cannot be understood completely without considering its biological nature. Besides being sand, clay and a mix of elements and minerals, soil is also a habitat to a microbial ecosystem, which forms a symbiotic network with plants in the soil.Products from growing roots and plant residue feed soil organisms. In turn, soil organisms support plant health as they decompose organic matter, cycle nutrients, enhance soil structure, and control the populations of soil organisms including crop pests.

At the same time, the smaller microorganisms become the food for the bigger ones, which eventually die and add to the organic matter of the soil and become food for the smallest microorganisms.

Thus the organisms and plants are connected within an energy cycle in the soil. This is often called the soil food web.

food web

SOIL ANATOMY:

Bacteria (single celled organisms)

Fungi (single and multi celled)

Protozoans (single celled- Ciliates. Amoebae, Flagellates)

Nematodes (non-segmented micro worms)

Micro and macro arthropods (earthworms, small insects)

FUNCTIONS:

Photosynthesizers

Plants/Algae/Bacteria

Major function: Capture Energy

  • Use solar energy to fix CO2
  • Add organic mater to soil (biomass such as dead cells, plant litter, secondary metabolites)

 Decomposers

Bacteria/ Fungi

Major function: Break down residue

  • Immobilise (retain) nutrients in their biomass
  • Create new organic compounds (cell constituents, waste products) that are sources of energy and nutrients for other organisms

Mutualists

Bacteria/ Fungi

Major function: Enhance plant growth

  • Protect plant roots from disease causing organisms
  • Some bacteria fix nitrogen (N2)
  • Some fungi form mycorhizal associations with roots and deliver nutrient (such as phosphorus) and water to the plant

Pathogens – parasites

Bacteria/ Fungi – Nematodes/ Micro-arthropods

Major function: Promote diseases

  • Consume roots and other plant parts causing diseases
  • Prasitise nematodes or insects, including disease causing organisms

 Root feeders

Nematodes/ Macro-arthropods (e.g. cutworm, weevil larvae, symphylans)

Major function: Consume plant roots

  • Potentially cause significant crop yield losses

Bacterial feeders

Protozoa/ Nematodes

Major function: Graze

  • Release plant available nitrogen (NH4+) and other nutrients when feeding on bacteria
  • Control many root feeding or disease causing pests
  • Stimulate and control the activity of bacterial populations

Fungal feeders

Nematodes/ Micro-arthropods

Major function: Graze

  • Release plant available nitrogen (NH4+) and other nutrients when feeding on fungi
  • Control many root feeding or disease causing pests
  • Stimulate and control the activity of fungal populations

Shredders

Earthworms/ Macro-arthropods

Major function: Break down residue and enhance soil structure

  • Shred plant litter as they feed on bacteria and fungi
  • Provide habitat for bacteria in their guts and fecal pellets
  • Enhance soil structure as they produce fecal pellets and burrow through the soil

Higher-level predators

Nematode feeding nematodes/ Larger arthropods, mice, birds, other underground animals

Major function: Control populations

  • Control the populations of lower trophic level predators
  • Larger organisms improve soil structure by burrowing and by passing soil through their guts
  • Larger organisms carry smaller organisms long distances

A NOTE ON MYCORRHIZAL FUNGI

Mycorrhiza = mikès (fungus) + rhiza (roots)

Mycorrhiza is a symbiotic association between fungi and plant roots and most trees and agricultural crops depend on or benefit substantially from mycorrhizae with the exceptions of members of the Brassicaceae family (e.g., broccoli, cabbage, mustard), and the Chenopodiaceae family (e.g. spinach, beets), which do not form mycorrhizal associations.
The plant shares the food (sugars) it synthesises with the mycorrhizae fungi and the fungi shares the nutrients it gathers from the soil. The fungi also increase the uptake of water and nutrients for the plant by forming an extensive hyphal network on the roots, increasing their effective absorptive surface area. A plant with mycorhiza association is often more competitive for nutrients and water and is able to tolerate environmental stresses.

RATIO OF FUNGI TO BACTERIA IN A SOIL

This ratio is characteristic to the type of system and the nature of food web it supports.

Grasslands and agricultural soils usually have bacterial-dominated food webs (F:B=1:1) – that is, most biomass is in the form of bacteria.
Forests tend to have fungal-dominated food webs. The ratio of fungal to bacterial biomass may be 5:1 to 10:1 in a deciduous forest and 100:1 to 1000:1 in a coniferous forest.

The biological view of the soil and microbial activity it supports has far reaching implications for the farming and agricultural practices. It calls for new criteria for qualifying healthy soils and seeing fertility as not just productivity, but as vitality.

Soil microbes can be beneficial to a farmer in the following ways:

  1. Suppress diseases by outnumbering the disease causing organisms
  2. Nutrient retention by bacteria and fungi
  3. Cycle nutrients at rates at which the plant requires – a diversity of microbes makes this possible
  4. Decompose toxins (within a month or so) and plant residues and reincorporate them in the soil and nutrient cycle
  5. Maintain oxygen flow in the soil
  6. Good soil structure- good oxygen diffusion, retention and flow of water
  7. Aerobic conditions for healthy decomposition

ORGANIC MATTER

In general, soil organic matter is composed of equal parts of active organic matter and humified organic matter (humus).

Active organic matter (root exudes, dead organisms, plant litter etc.) is the portion available to soil organisms as food. This changes very quickly in the soil depending on the microbial activity and management practices.

Humus is chemically complex carbon compounds produced after several transformations of the active material by the microorganisms. Because of its chemical complexity, it stays unchanged in the soil for a long time and acts as a long-term source of nutrients for the plant. Humus is important in binding tiny soil aggregates, and improves water and nutrient holding capacity of the soil.

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Website Powered by WordPress.com.

Up ↑

%d bloggers like this: