The Soil Foodweb Approach to Soil and Compost

Managing the Biology to Design Compost

Soil Foodweb Canada East Ltd.Halifax, Nova Scotia

We know more about the movement of celestial bodies than about the soil underfoot.

- Leonardo da Vinci circa 1510

SOIL ORGANISM INTERACTIONS = SOIL FUNCTIONS = SOIL BIOLOGY

Healthy soil performs the following functions:– Holds nutrients and prevents leaching into water sources– Cycles nutrients from organic to plant available forms– Decomposes organic matter (coupled to nutrient cycling)– Suppresses and prevents soil-borne diseases – Maintains porous structure to allow air and water movement– Binds or detoxifies pesticides and other toxic substances– Sequesters carbon in humus and stable forms of organic

matter

All of these healthy soil functions are a result of healthy soil biology.

Role of Plants in Soil Food Webs

• Provide large quantities of plant matter to soil (food for the food web)• Provide up to 60% of their photosynthetically fixed carbon dioxide as

food to soil organisms through their roots as root exudates (sugars, amino acids, proteins, shed root cells)

• By providing a rich source of exudate foods, plant roots are surrounded by a thin layer of intense biological activity – the rhizosphere – where most soil biology is found

• By selectively secreting specific foods a plant can stimulate specific organisms to grow and perform a required function for the plant (facilitated by high biodiversity)

• By regulating microbial growth in the rhizosphere, plants exert a very sophisticated influence on the structure of soil food webs and patterns of nutrient flow

SOIL BACTERIA• One acre of healthy soil contains the weight of a cow in bacterial biomass• One gram of healthy soil contains over 25,000 species and a billion

individual bacteria• High bacterial biodiversity is required to sustain soil functions under a variety

of soil conditions• Engage in nitrogen fixation (rhyzobia, Azotobacter), chemical detoxification

(pseudomonads), promoting root growth and mycorrhizal associations• Decompose organic matter and dissolve minerals and hold these nutrients• Cover leaf and root surfaces to provide pathogen protection• Secrete polysaccharide glues that stick soil particles together, increase

water holding capacity and improve soil structure• Serve as a primary food source for protozoa and bacteria-feeding

nematodes that (bacterial nutrient cycling channel)• While most bacteria are beneficial, a small number are plant pathogens and

usually occur in unhealthy and unbalanced soils• Recent research has discovered numerous bacteria species inside plants

and performing beneficial functions

SOIL FUNGI

• Important decomposers of high-carbon and resistant materials (lignins, woody materials) – including toxic organic chemicals

• Efficiently retain nutrients/micronutrients in their biomass and prevent them from leaching (N, P, S, Ca, Fe and others)

• Build soil structure by holding soil particles (glued by bacteria) together in aggregates with their long hyphal strands

• Improve air and water infiltration and the water holding capacity of soil• A small number are pathogenic in contrast to large numbers of beneficial

fungi that perform essential soil functions, including suppression of pathogenic species and the soil conditions permitting their appearance

• Can trap and digest nematodes• Serve as a food source for fungal feeding nematodes and microarthropods

that then excrete plant available nutrients (fungal nutrient cycling channel) • Easily damaged by high-till and chemical agriculture

Soil Protozoa

• Single-cell flagellates, amoebae and ciliates living in water films on soil and organic particles, feed on bacteria and small bits of organic matter

• Feed almost exclusively on bacteria and in this process take in more nitrogen and nutrients than they need and excrete these in plantavailable form (Key discovery by Elaine Ingham in the 1980s)

NUTRIENT CYCLING RATES are proportional to protozoa populations.

• Activity and movement helps maintain soil structure

Soil Nematodes

• Small round worms living in water films, inside plant roots and inside insects or their larvae

• Movement through soil spreads bacteria and fungi• Classified as bacterial, fungal or root feeders - or as predators• Participate in both bacterial and fungal nutrient cycling

channels• Provide food for other soil fungi, insects and worms

Soil Food Web Structure and Plant Growth

• Different plants require different soil biology and food webs• The ratio of soil FUNGI:BACTERIA is very important to plant growth

and to supply balanced food resources to protozoa and nematodes• Strong populations of mineralizers (protozoa and nematodes) are

required for high rates of nutrient cycling from organic matter decomposition by way of bacteria and fungi

• Soil biology can be managed by using :– Bacterial or fungal specific foods– Compost (bacterial, fungal, balanced)– Compost Teas– Compost Extract

Bare Parent

Material

100% bacterial

CyanobacteriaTrue BacteriaProtozoaFungiNematodesMicroarthsF:B = 0.01

“Weeds”- high NO3- lack of oxygen

F:B = 0.1

Early GrassesBromus, Bermuda

BRASSICA FAMILYF:B = 0.3

Mid-grasses, VEGETABLESF:B = 0.75

Late successionalgrasses, row crops

F:B = 1:1CEREAL GRAINS

Shrubs, vines,Bushes

F:B = 2:1 to 5:1FRUIT CROPS

Deciduous TreesF:B = 5:1 to 100:1

Conifer, old-growth forests

F:B = 100:1 to 1000:1

Soil Foodweb StructureThrough Succession,Increasing Productivityand Fungal Dominance

What does your plant need?

Basic Program

• Measure the soil biology to determine deficiencies or imbalances

• Apply compost and compost tea to supply deficient biology and provide food for the soil food web (Compost must be tested; its biology must be known.)

• Robust and healthy soils resist disease and provide plant available nutrients from organic and mineral matter in composts and soils.Soluble fertilizers and synthetic pesticides are not required. Healthy soil food webs are absolutely required.

Components of Soil Nutrient Pools Tests used for each pool

Total Extractable

Exchangable

Soluble

Biology

Biology

RootsBacteria and Fungi

Grind; Conc. Nitric acid, combustion10% HCl, H2NO3

Melich IIIBray 2Amm. Cl / BaCl

ColwellOlsen, Bray 1Melich IMorgan (Reams)1 M KCl, Universal

Designer Compost

Compost produced to contain specific food webs for specific soil management applications:

– Correct biomasses of highly diverse bacterial and fungal populations in the correct ratio to provide high levels of decomposition and nutrient cycling

– Correctly balanced mineralizer populations to provide robust nutrient delivery capacity with the correct pattern of nutrient flow

All design principles are based on understanding soil andcompost biology and how to integrate them into healthy andproductive soil food webs.