Idea Transcript
Soil Foodweb Canada East Ltd. Halifax, Nova Scotia
Jason Hofman PhD Laboratory Director
The Soil Foodweb: Optimizing the Life in Your Soil Soil Biology and Soil: the Foundation of Agriculture
ECO Farm Day 23 February 2008
We know more about the movement of celestial bodies than about the soil underfoot. - Leonardo da Vinci circa 1510
Soil Health Is the Foundation of Our Health • Human and animal health is related to the quality of their food. • The quality of food is related to the health of the soil it was grown in. • The health of the soil is related to the health of the biology living in it.
SOIL ORGANISM INTERACTIONS = SOIL FUNCTIONS 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 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) Provide large quantities of plant matter to soil (food for the food web) 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 plant available 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
. . . And The Rest . . .
• • • •
Mites Small insects Worms Centipedes, millipedes
What does your plant need? Bare Parent Material 100% bacterial
Conifer, oldgrowth forests F:B = 100:1 to 1000:1
Cyanobacteria True Bacteria Protozoa Fungi Nematodes Microarths F:B = 0.01
Soil Foodweb Structure Through Succession, Increasing Productivity and Fungal Dominance
“Weeds” - high NO3 - lack of oxygen F:B = 0.1
Early Grasses Bromus, Bermuda BRASSICA FAMILY F:B = 0.3
Mid-grasses, VEGETABLES F:B = 0.75
Deciduous Trees F:B = 5:1 to 100:1
Shrubs, vines, Bushes F:B = 2:1 to 5:1
FRUIT CROPS
Late successional grasses, row crops F:B = 1:1
CEREAL GRAINS
Fungal:Bacterial Ratios of Selected Crop Species Brassicas (broccoli) Carrots, lettuce Corn, tomatoes Barley, oats, rye Potatoes Pastures, turf
0.3 – 0.7 0.5 - 0.8 0.8 - 1.0 0.8 – 1.0 0.8 – 1.2 0.9 – 1.5
Strawberries Blueberries Cranberries
2-5
Grapes
3-5
Apples, orchard crops 5 – 10 Pine 50 - 100 Conifers 100 - 1000
SOIL FOODWEB APPROACH TO SOIL MANAGEMENT •
Measure the biomasses of soil/compost organisms: bacteria, fungi, protozoa, nematodes • Determine Fungal:Bacterial Ratios and sufficiency/deficiency levels of the major soil groups. • Identify biologically active compost/compost tea as a corrective remedy to supply deficient organisms and food to feed them. • Apply compost/compost tea and re-measure the foodweb in the following spring or fall. • Evaluate foodweb results to guide further compost/compost tea applications. Compost and compost teas are the primary management tools in a soil foodweb approach to soil management.
Components of Soil Nutrient Pools
Grind; Conc. Nitric acid, combustion 10% HCl, H2NO3
Total Extractable
Melich III Bray 2 Amm. Cl / BaCl
Exchangable Biology Biology Soluble
Roots
Tests used for each pool
Bacteria and Fungi
Colwell Olsen, Bray 1 Melich I Morgan (Reams) 1 M KCl, Universal
• •
•
•
Biology Releases Nutrients Available nutrients may be lacking A reserve of nutrients (total extractable) exists in MOST soils that are more than adequate to grow any plant. ACTIVE, functioning organisms must be present to move nutrients from one pool to the next. Organisms killed by pesticides or high levels of inorganic fertilizers must be replaced
SOIL FOODWEBS and TILLAGE PRACTICES
Total Fungi 2000
T o ta l F u n g i (u g / g )
1800 1600 1400 1200 1000
Total Fungi
800 600 400 200 0 0
5
10
15
20
Years After Clearing
25
30
NO-TILL
COMPOST
What Compost Can Do • Suppress Disease (no more pesticides!) • Retain Nutrients (stop run-off, leaching) • Make Nutrients Available at rates plants require (eliminate fertilizer) • Decompose Toxins • Build (re-build) Soil Structure • Reduce Water Use, increase water holding capacity, rooting depth • Supports and restores soil foodweb health
Biological Compost Standards Full Foodweb Compost • 15 to 30 or more µg active bacteria /g (dw) • 150 µg (fungal compost) to 300+ µg (bacterial compost) total bacteria /g (dw) • 2 to 10 µg or more active fungi/g (dw) • 150 (bacterial compost) to 500 or more (fungal compost) µg total fungi/g (dw) • Hyphal diameters on average 2.5 micrometers or greater • 50,000 or more protozoa per gram (dw) 25,000 or more flagellates 25,000 or more amoebae 50 - 100 ciliates. Higher numbers indicate anaerobic conditions resulting from compaction, water-logging, discontinuities in soil • 20 to 100 BENEFICIAL nematodes per gram (dw)
Organism numbers after compost addition Organism Assays Total bacteria (#/gram dry soil) # of bacterial species/g soil
Agricultural Field 1 X 106
Compost (1ton/ac) 6 X 109
Ag soil with compost 17 X 108
5,000
25,000
25,000
Total fungi (ug per g dry soil)
5
150
500
# of fungal species /g soil
500
8,000
8,000
F, A C
0, 0 1,450
12,000, 31,000 29
6,000, 17,000 67
How to select for beneficial organisms • Foods • Conditions in piles – Temp – Moisture – Disturbance
• Chemistry • Structure (physics)
Bacterial Foods Fungal Foods Simple
Complex
More Complex
Amino Acids
Proteins
Hormones Vitamins
Carbohydrates Chlorophyll Sugars Coal
Fats
Polysaccharides
Very Complex
Fulvic acids (Minerals) Humic Acids
Lipopolysaccharides
Amino sugars Organic Acids
Fatty Acids
Cellulose Waxes
Lignin
Commercial Compost Temperature Cycle Temperature ( C)
80 60 40 20 0 0
2
5
8 11 14 17 20 23 26 29 32 35 38 41 44 47 Days
Bacterial Starting Materials: Commercial Compost 25% Hi N – alfalfa, beans, peas, manures • Salts, Antibiotics, Heavy Metals • Cow < poultry < pig = human
45% Green Diversity desired
30% Woody
Fungal Starting Materials: Commercial Compost 25% Hi N 30% Green 45% Woody
The Standard “FIX” Compost – 1 to 5 tons/ac fall and spring; VAM Crops - Broadcast (inoculum, non-soluble nutrients) Vines – Under row (inoc, nutrients, soil protection) Trees – 2 inch to drip line, vertical mulching -----------------------------------------------------------------Compost Tea – 5 gal/ac foliar for each 6 ft height; 15 gal/ac soil drench fall and spring Pasture – Hay, soil drench, seed treat Crops – drench, seed, 1st true leaf, flower bud, postseed-set Vines and Trees - 2 wks before bud break, every 10-14 days for first three months, assess disease, once a month. Understory, fungal cover crops
2001 Compost Trial New Brunswick Dept of Agriculture and Forestry Check
1 Ton Compost
2 Ton Compost
4 Ton Compost
Total Yield
404cwt/acre
455 cwt/acre
427 cwt/acre
437 cwt/acre
Mrkt. Yield
342 cwt/acre
384 cwt/acre
365cwts/acre
371 cwt/acre
Large
10.0% (>3”)
11.5% (>3”)
12.2% (>3”)
10.1% (>3”)
Smalls
12.6% (