Soil BiologyHealth: How to Improve Your Soil

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Soil Biology/Health How to Improve Your Soil
2006 Organic Gardening Conference Canandaigua, NY

• B.K. Gugino and G.S. Abawi
• Department of Plant Pathology

4 Nov. 2006
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Overview

• Concept of soil health
• Soil biology 101
• Microbial diversity
• Microbial interactions soil food web
• Functions of microbes
• When microbes go awry.....and cause disease
• How to manage the soil microbial
  community......improve your soil health!

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Soil Health Concept
Emphasizing the integration of biological with
chemical and physical measures of soil quality as
they affect grower profits and the environment
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Aspects of Soil Health

• Inherent soil quality
• Results from natural soil forming processes and
  factors

interaction
Dynamic soil quality Changes due to human use
and management
(Pierce and Larson, 1993)
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A healthy soil has....

• High populations of beneficial organisms
• Low weed pressure
• Free of chemicals and toxins that may harm plants
• Resistant to degradation
• Resilient when unfavorable conditions occur

• Good soil tilth
• Sufficient depth
• Sufficient but not excess supply of nutrients
• Good soil drainage
• Low population of plant pathogens and other pests

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Actinomycetes
Nematodes
Microarthropods
Bacteria
Fungi
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In 1 teaspoon of soil there are
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In one square meter of soil....
Organisms increase in size and number
From soil biology lecture notes found at
http//snr.osu.edu/current/courses/ss300.html
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Relative sizes of soil microorganisms
From soil biology lecture notes found at
http//snr.osu.edu/current/courses/ss300.html
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Soil Food Web
Organic matter food source Primary consumers
From soil biology lecture notes found at
http//snr.osu.edu/current/courses/ss300.html
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The Soil Food Web
USDA-NRCS
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Principle Soil Microorganisms
TOTAL MICROBIAL COMMUNITY Bacteria, fungi,
algae, actinomyces, nematodes, microarthropods,
etc.

• BENEFICIAL ORGANISMS (majority)
• Mycorrhiza, rhizobia, earthworms, various
  biocontrol agents, decomposers of organic matter,
  etc.
• PLANT PESTS (minority)
• Pathogens, parasitic nematodes, insects, weeds,
  animals, etc.

Healthy soils have large highly diverse
population of beneficial organisms but only small
population of active plant pests.
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Functions of Soil Organisms

• Decomposition of organic matter
• Mineralization and recycling of nutrients
• Fixation of nitrogen
• Detoxification of pollutants
• Maintenance of soil structure
• Biological suppression of plant pests
• Parasitism and damage to plants

Healthy soils have a large highly diverse
population of beneficial organisms but only small
population of active plant pests.
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Different stages of organic matter decomposition
Living
Dead
Very Dead
www.mr-damon.com/experiments/6sv/soil/leaf_litter.
htm
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Basic Plant Anatomy 101
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Decomposition of organic matter
Different groups of organisms can degrade
different portions of the organic matter
Humus-like substances
Cellulose, lignin
Waxes and phenols

• Simple sugars, starches, proteins

Quickly fuels microbes
Up to 10 years
Several years
Very stable
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Soil organic matter is important for
Moderating soil pH Providing nutrients for
microbes Increases microbial populations Maintaini
ng soil structure Providing nutrients to
plants Stimulate root development Protect against
harmful chemicals (e.g. Al)
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Sources of organic matter...

• Leaf debris
• Grass clippings
• Compost (home-made or commercially produced)
• Crop debris (disease free)
• Animal manures (aged or composted)
• Fall planted green manure cover crop

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Not all organic matter is created equally...
Modified from Magdoff, F. and van Es, H. Building
Soils for Better Crops 2nd ed.
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Functions of Soil Organisms

• Decomposition of organic matter
• Mineralization and recycling of nutrients
• Fixation of nitrogen
• Detoxification of pollutants
• Maintenance of soil structure
• Biological suppression of plant pests
• Parasitism and damage to plants

P.R. August
Healthy soils have a large highly diverse
population of beneficial organisms but only small
population of active plant pests.
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Functions of Soil Organisms

• Decomposition of organic matter
• Mineralization and recycling of nutrients
• Fixation of nitrogen
• Detoxification of pollutants
• Maintenance of soil structure
• Biological suppression of plant pests
• Parasitism and damage to plants

P.R. August
G. Vrdoljak
Healthy soils have a large highly diverse
population of beneficial organisms but only small
population of active plant pests.
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Nematode
Plant root hair
Bacterial colonies
Clay OM
Mycorrhizal hyphae
Flagellate
Actinomycetes
Fungal hyphae
Cillate
Amoeba
Drawing by S. Rose and E.T. Elliott
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Functions of Soil Organisms

• Decomposition of organic matter
• Mineralization and recycling of nutrients
• Fixation of nitrogen
• Detoxification of pollutants
• Maintenance of soil structure
• Biological suppression of plant pests
• Parasitism and damage to plants

P.R. August
G. Vrdoljak
Healthy soils have a large highly diverse
population of beneficial organisms but only small
population of active plant pests.
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The Rhizosphere

• rhizo root
• sphere zone

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Plant pathogen suppression

• Competition
• Antibiosis
• Hyperparasitism
• Induced SAR

Fungal spore
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Nematode-trapping fungi
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Mycorrhizae

• Fungi that develop a symbiotic association with
  plant roots
• Fungus receives energy and nutrients from plant
• Plant receives improved access to water and some
  nutrients

• Most plants form associations except brassicas
  and chenopods (beets, spinach, lambs quarters)

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Functions of Soil Organisms

• Decomposition of organic matter
• Mineralization and recycling of nutrients
• Fixation of nitrogen
• Detoxification of pollutants
• Maintenance of soil structure
• Biological suppression of plant pests
• Parasitism and damage to plants

P.R. August
G. Vrdoljak
Healthy soils have a large highly diverse
population of beneficial organisms but only small
population of active plant pests.
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Healthy roots Healthy soils
Unhealthy roots Unhealthy soils
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Roots can be unhealthy due to...

• Poor soil drainage
• Poor nutrient availability
• Soil compaction
• Plant pathogen infection by
• Rhizoctonia
• Fusarium
• Pythium
• Thielaviopsis

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Root rot of bean
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Severe root rot
Good bean roots
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Pythium on Beans
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Rhizoctonia on Beans
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Thielaviopsis on Beans
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Fusarium on Beans
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Beet Root Rot
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Rhizoctonia on Beets
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Rhizoctonia on Carrots
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Lettuce drop (Sclerotinia minor)
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White mold (Sclerotinia sclerotiorum)
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Sclerotinia head rot (Sclerotinia sclerotiorum)
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Lesion nematode (Pratylenchus spp.)
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Galled lettuce roots
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Northern Root-Knot Nematode (Meloidogyne hapla)
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Tillage
Crop rotation
Cover crops
Organic amendments
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Root Pathogens and Disease Management

• All production practices impact root diseases
• Pathogens and their diseases are most damaging in
  poor soils and on stressed hosts
• Many pathogens have a wide host range and/or
  survive for several years in the absence of a
  host crop
• Garden scale management with an IPM strategy is
  most appropriate against root pathogens
• Accurate diagnosis and monitoring of the root
  pathogen(s) is critical for determining
  management options

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Happy and healthy soil building!