Soil Ecology: whole system approach

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Soil Ecology whole system approach

• Sherrilyn Phelps, SAFRR
• Jill Clapperton, AAFC
• Stu Brandt, AAFC

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• When you are standing on the ground you are
  really standing on the roof top of a whole other
  world.
• Dr. Jill Clapperton

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• We stand in most places on Earth, only six
  inches from desolation, for that is the thickness
  of the topsoil layer upon which the entire life
  of the planet depends.
• R. Neil Sampson

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• For in the end we will conserve only what we
  love. We will love only what we understand. And
  we will understand only what we are taught.
• Baba Dioum
• African Conservationist

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What is soil?

• Complex mixture of mineral matter, organic
  matter, living organisms, air, water
• Product of the environment constantly changing,
  constantly evolving
• Develop over time
• Supports life
• skin of the land

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Physical properties (soil physics)

• Texture
• sand, silt, clay
• Structure
• aggregates, held together
• Colour
• All influenced by OM

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Texture

• Determines bulk density and porosity
• Organic matter also influences

Texture Bulk Density (gm/cm3) Porosity ()
Sand 1.6 40
Loam 1.2 55
Clay 1.05 60
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Depth of moist soil
Soil Texture Available Water (inches water per foot soil)
Coarse (Sand) 1
Medium (Loam) 1.5
Fine (Clay) 2
3 feet of moisture in sandy soil 3 inches of
available water
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Color

• Influences gain and loss of radiant energy
• Useful for predictions
• Mineral weathering
• OM content
• State of aeration

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Organic Matter

• All humus is OM but not all OM is humus
• Raw OM waste products or remains of organisms
  not yet decomposed
• Humus decomposed
• OM is the primary food source for most soil
  organisms/animals
• Quantity and quality of OM is what drives
  nutrient cycling

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Effects of Organic Matter/Humus

• Bulk density decreases bulk density
• Pore space increases pore space
• Structure provides crumb structure that resists
  compaction
• Oxygen diffusion increases oxygen diffusion
  rate
• Field capacity improves soil structure

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Humus

• Stable humus
• Long chained, bonded to clay particles
• Long-term nutrient storage
• Increases CEC
• Chelates toxic substances
• Effective humus
• Soluble (small)
• Mobile and readily releases nutrients to plants
• Holds nutrient anions in form available to plants
  but safe from leaching
• Increases CEC

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Chemical properties

• Breakdown of rocks, minerals, OM
• Transformations of mineral nutrients
• Cation exchange capacity (CEC)
• pH
• salinity

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OM Constituents (plant)

• Carbon 42
• Oxygen 42
• Hydrogen 8
• Ash 8
• Macronutrients (N, P, K, S, Ca, Mg)
• Micronutrients (Fe, Mn, B, Zn, Cu, Cl, Co, Mo, Ni)

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Macronutrients sources

• Air and water
• C, H, O
• Soil
• N, P, K, Ca, Mg, S
• Complex organic compounds (CO2, H2O, NO3, NH4-,
  H2PO4-, S042-)
• CNPS ratio is 1001011 approximate
  proportions in humus and therefore target for soil

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Carbon

• Building block of life

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Nitrogen

• Component in protein, amino acids
• N2 from air/rain is fixed by soil MO
• CN ratio is important to OM cycle
• Influences rate of minerlization and release of
  nutrients
• Too high CN slow decomposition, binds N
• 20 301 is ideal for nutrient cycling

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Organic Matter CN Organic Matter CN
Spruce sawdust 600 Paper mill sludge 61
Newspaper 120 Rotted manure 20
Wheat straw 80 Household compost 15
Rye (anthesis) CC 37 Digested sewage 7
Rye (veg) CC 26 MO bacteria 5
Hairy vetch CC 11 MO fungi 10
Adapted from The Nature and Properties of Soils
by Brady Weil
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Phosphorus

• Complex chemical reactions
• Easily immobilized fixed with Al, Fe, Ca
• Most of the available P is in the form of OM,
  released by microbial activity
• P comes from rocks/soil

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Sulfur

• Critical for microbial nutrition
• When OM is adequate it will usually be present in
  proper proportions
• Organic sulfur is transformed to sulfate by
  microbes

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Other Macronutrients
Major Cation Forms in soil Function in plants
Calcium Ca, high pH binds P N uptake, protein synthesis, enzyme activation and cell reproduction
Magnesium Mg Chlorophyll, P metabolism, enzyme activation
Potassium K CHO metabolism, cell division, absorption of Ca, Na, N
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Micronutrients

• Important in small amounts
• Fe, Mn, Cu, Co, Ni ()
• Mo, Bo, Cl (-)
• Chelated forms generally (ring)

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Cation Exchange Capacity

• Ability to store cations (nutrients)
• 1/1000th of a gram of H per 100 grams of soil
• Higher CEC more nutrients it can hold
• Humus increases CEC

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CEC (at pH 7.0)
Exchangeable Material CEC
Organic matter 100 300
Clay Vermiculite 100 150
Clay Montmorillonite 60 100
Clay Chlorite or Illite 20 40
Clay Kaolinite 2 16
Sand 2
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pH

• Measure of soils acidity or alkalinity
• Concentration of H in solution
• Acid high H
• Basic low H

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Biological Properties

• Life in out of the soil
• Soil Ecosystem system made up of parts
• Animals people unless wastes are returned to
  soil the whole life-supporting process is
  undermined
• Soil organisms perform vast array of fertility
  maintenance tasks
• One part of system influences other part

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Soil Organisms

• Microorganisms
• Fungi, actinomycetes, bacteria, algae
• Microfauna
• Nematodes, protozoa, rotifers
• Insects mullulsks
• Mites, springtails, spiders, sowbugs, ants,
  beetles, centipedes, millipedes, slugs, snails
• Earthworms
• Mammals
• Moles, mice, groundhogs
• Plant roots

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1 teaspoon of soil

• 100 million to 1 billion bacteria
• Several yards of fungal hyphae
• 1000s of protozoa
• 10 to 20 nematodes
• Insects mullusks 100s / cubic foot
• Earthworms 5 30 per cubic foot
• Plant roots 4000 kg/ha in top 120 cm SK

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Bacteria and fungi

• Principle agents of decomposition
• Make nutrients available from organic matter
  (nutrient cycling)
• Fungal hyphae and bacterial exudates bind smaller
  soil particles into larger soil aggregates

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Bacteria

• Decompose OM simple C compounds
• Consume/immobilize simple nutrients from soil
• azotobacter, rhizobia, nitrobacter
• N-fixers, S-oxidizers, nitrifiers

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Photo by Dr. J. Clapperton, AAFC
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U of S
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Bacteria N fixation

• Rhizobia Bradyrhizobia
• symbiotic with legumes
• Actinomycetes
• symbiotic with angiosperms
• Cyanobacteria
• Associative with various higher plants and MO

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PHOTO Philom Bios Inc
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Crop (bacteria) N fixed (kg N/ha/yr)
Alfalfa 150 200
Clover 100 150
Vetch, Soybean 50 150
Alders (actinomycetes) 50 150
Cyanobacteria 10 50
Pangola grass (Azospirillum) 5 30
Bahia grass (Azobactor) 5 - 30
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N fixed (lbs/acre/year)
Legume Range Typical
Alfalfa 50-300 200
Beans 20-80 40
Chickpeas 20-100 50
Clovers 50-300 150
Lentils 40-130 60
Peas 30-180 70
Red Clover 70-160 115
Sweet Clover 20-160 20
Trefoil 30-150 105
Vetch 80-140 80
White Clover 30-150 100
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Type of N fixation N fixed (MMT)
Non-biological Industrial Combustion Lightning 50 20 10
Biological Agricultural land Forest/non ag land Sea 90 50 35
Data complied by DF Bezdicek AC Kennedy, in Microorganisms in Action (eds. JM Lynch JE Hobbie). Blackwell Scientific Publications 1998 Data complied by DF Bezdicek AC Kennedy, in Microorganisms in Action (eds. JM Lynch JE Hobbie). Blackwell Scientific Publications 1998
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Fungi

• Carry out largest share of decomposition in
  cultivated soils
• cellulose, starch, gums, lignin, proteins,
  sugars
• C is energy source
• Major role in humus formation and aggregate
  stabilization (hyphae, exudates)
• Yeasts, mushrooms, molds
• Some are predators of soil animals (ie., some
  trap nematodes)

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Dr. Jill Clapperton, AAFC
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Photo by Dr. J. Clapperton, AAFC
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Fungi Benefits

• Mycorrhizae association (fungus root)
• Team up with plants
• Sugars from root cells energy source
• Provide extension of root system nutrient
  availability
• Increase uptake of P and other nutrients
• Prevent uptake of toxic levels of some nutrients
• Evidence for protection against soil borne
  diseases

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Vesicular Arbuscular Mycorrhizae (VAM)
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Vesicular Arbuscular Mycorrhizae (VAM)
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Dr. Jill Clapperton, AAFC
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The relationship between some crop species and
VAM fungi
Potatoes and other root crops Most tropical
plants and trees
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Photo obtained from Dr. Jill Clapperton, AAFC
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Phosphate solubilizing fungi - Penicillium

• Enhances root growth
• Acidification/ solubilization of P
• Root surface only
• Different bacteria and fungi solubilize at
  different rates

Source Philom Bios Inc
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Effect of JumpStart on wheat yield. 2 site years
of data
Wheat yield ( of control)
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Fungi effect on more than nutrients
With P. bilaii
Without P. bilaii
Root hairs were 33 longer with inoculation over
all P levels Kevin Vessey, U of M
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Fungi negative aspects

• Mycotoxins (aflatoxin by Aspergillus flavus on
  corn or peanuts)
• Plant diseases such as wilts (Verticillium,
  Fusarium) and root rots (Rhizoctonia)

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Mites and nematodes

• Regulate populations of bacteria and fungi
  increasing nutrient turnover
• Chew larger pieces of organic matter into smaller
  pieces stimulating microbial activity
• Increase nutrient release from decomposition by
  eating and burying organic matter
• Create biopores for better rooting, water
  infiltration and aeration
• Indicator species

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Estimated Nitrogen Balance(N supplied minus N
removed kg/ha)
Stu Brandt, Alternative Cropping Study, AAFC Scott
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Estimated Phosphorus Balance(P supplied/P
removed kg/ha)
Stu Brandt, Alternative Cropping Study, AAFC Scott
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Oribatid Mites Olfert

• - Feed on microbial and higher plants
• decomposer/recycler pooping pellets
• move up and down roots, move nutrient, carry
  other organisms, great tunnels
• - Respond negatively to cultivation

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Oribatid Mites
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Nematodes

• Indicator species
• Feed off bacteria and fungi, plants, insects, etc
• Under tillage see more bacterial feeders because
  that is what dominates

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Ants, termites, and insect larvae

• Mix organic matter and faecal matter into the
  deeper mineral soil
• Stimulate microbial activity
• Create deeper nutrient rich soil
• Affect N and C cycling
• Create larger biopores for better rooting, water
  infiltration and aeration

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Earthworms

• 10 to 10,000 per sq m (30 to 300 arable soils)
• 7000 species (13 on prairies)
• Grouped according burrowing habits and habitats
• Epigeic group
• Edogeic group
• Anecic group

Photo obtained from Dr. Jill Clapperton, AAFC
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Influence of Earthworms

• Eat their way through the soil
• Ingest soil in amount of 2 to 30 times their own
  body weight in a day
• At 100 to 1500 kg/ha 200 to 45000 kg soil
  /ha/year
• Burrows, Casts, Nutrients

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Burrows

• continuous macropores
• Increase aeration and drainage
• Increase infiltration of water
• Fungal hyphae that proliferate in burrows help
  bind soil particles into stable aggregates
• Mixing reduce compaction

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Casts
Characteristic Casts Soil
Silt and Clay () 38.8 22.2
Structural Stability 849 65
CEC (cmal/kg) 13.8 3.5
Exchangeable Ca2 8.9 2.0
Exchangeable K 0.6 0.2
Soluble P (ppm) 17.8 6.1
Total N () 0.33 0.12

• soil aggregates of mineral soil and shredded
  organic matter
• Higher in bacteria, OM and nutrients than bulk
  soil

Vleeschauwer Lal, 1981
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Nutrients

• Reduce loss of nutrients by incorporation of
  surface residues into the soil
• increase availability due to
• ground up physically
• digested (chemical)
• assimilate into body tissue

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Factors affecting activity

• Positive
• Moist, well-aerated environment
• Principal food source is fungi bacteria that
  grow on decaying organic matter
• pH 5.5 to 8.5
• Abundant supply of calcium (slime excretions)

• Negative
• Predators (moles, mice, mites)
• Very sandy soil (abrasive)
• Saline soils
• Ammonia fertilizer
• Carbamate insecticides
• Tillage

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Number of earthworms per m2
1, 3 and 5 are organic rotations 2, 4, 6 are low
input rotations 7 is continuous wheat with all
inputs
Data from Dr. Jill Clapperton, AAFC
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Seasonal variation in the percent species
composition of earthworms under three different
types of tillage.
autumn
no tillage
spring
Sampling month
Data from Dr. Jill Clapperton, AAFC
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Variation in the number and size of earthworms
under conventional tillage and no tillage after
winter wheat (ww), fallow (sf), and canola (cn).
Crop and tillage
Data from Dr. Jill Clapperton, AAFC
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Photos from Dr. Jill Clapperton, AAFC
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The activities of soil biota

• Drive nutrient cycling
• Stabilise the soil structure
• Creating a more stable and continuous soil pore
  network
• Diverisity and abudance is key for success

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Plant Roots

• Morphology
• Fibrous vs tap
• Rooting depth
• Water extraction
• Exudates

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Rooting depths
Deep Moderate Shallow Alfalfa Barley Pea Buckwh
eat Canola Flax Sunflower Wheat Lentil
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Water Extraction from differentsoil depths
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Crop Water Use (Swift Current, 1998-2000)
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Water Use Efficiency
Argentine Canolamustardsunflower least
Wheatwinter wheat Barleydurumkabuli Polish
canola desi Flaxlentil Pea most
Yantai Gan AAFC Swift Current
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How do we have an Impact on Soil Ecology?
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Negative Impacts

• Industrial wastes/heavy metals
• Tillage
• Monocropping
• Row crops
• Residue burning/removal

• Fumigants
• Nematicides
• Some insecticides
• Compaction
• Soil erosion
• Plastic mulches

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Positive Impacts

• Balanced fertilizer use
• Lime on acid soils
• Proper irrigation
• Improved drainage and aeration
• Animal manure or composts
• Organic mulches
• Green manure

• Domestic sewage sludge
• Reduced tillage
• Crop rotations
• Grass-legume pastures
• Cover crops
• Residue return to soil

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Summary

• Everything is connected system
• Fertility is a balancing act
• Soil organisms are good indicators of soil health
• Tillage is disruptive to natural systems
• Biodiversity is key

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• For in the end we will conserve only what we
  love. We will love only what we understand. And
  we will understand only what we are taught.
• Baba Dioum
• African Conservationist

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THANK YOU

• Jill Clapperton, AAFC
• Stu Brandt, AAFC