Climate Change in Arid Lands: Effects on Soil Biota and Ecosystem Processes
Management of Soil Biota - Welcome | Field Crops of the Soil Biota •Plant Pathogens & Disease...
Transcript of Management of Soil Biota - Welcome | Field Crops of the Soil Biota •Plant Pathogens & Disease...
Importance of the Soil Biota
Interactions with Physical Environment
• Nutrient Cyclingand Storage
• Aggregation and Aggregate Stabilization
• Biomass Contribution to Organic Matter
• Residue Incorporation and Breakdown
Interactions with Plant Community
• Nutrient Access
• Plant Growth Promotion
• Plant Establishment
• Plant Disease
• Plant Disease Suppression
Ecosystem services: Water purification, Toxin breakdown, C sequestration
Plant Disease: Soil-Borne Pathogens
• Fungal: e.g. Rhizoctonia, Verticillium
• Bacterial: e.g. Streptomyces, Ralstonia, • Residue-borne issues such as Clavibacter michiganensis
sub nebraskensis or Erwinia chrysanthemi pv. zeae
• Oomycetes: Pythium, Phytophthora,
• Viruses: • SBWMV (vector: protozoan), • Tomato Black Ring Virus, Grapevine Fanleaf Virus
(vectors: nematodes)
• Nematodes: Meloidogyne, Heterodera
Management of the Soil Biota
• Plant Pathogens & Disease• Management Considerations
in Relation to Soil Health
• General Principles for Managing Soil Biological Health
• Plant and Soil Biodiversity
• Key Manageable Symbioses
Management of the Soil Biota
• Plant Pathogens & Disease• Management Considerations
in Relation to Soil Health
• General Principles for Managing Soil Biological Health
• Plant and Soil Biodiversity
• Key Manageable Symbioses
Fusarium Head Blight Disease Cycle
Fusarium head blight - Disease Cycle (Courtesy A. Schilder and G. Bergstrom) apsnet.org
Fusarium head blight in wheat. (Photo: G. Bergstrom)
Management of the Soil Biota
• Plant Pathogens & Disease• Management Considerations
in Relation to Soil Health
• General Principles for Managing Soil Biological Health
• Plant and Soil Biodiversity
• Key Manageable Symbioses
Management Strategies
Target the pathogen:
• Fungicides, nematicides, fumigants
• Some quite effective
Systemics, cf. Protectants
• Risk of non-target effects
Host
Pathogen Environment
Disease
Management Strategies
Target the pathogen:
• Fungicides, nematicides, fumigants
• Some quite effective
Systemics, cf. Protectants
• Risk of non-target effects
A complex food web is needed for releasing mineral nutrients
Management Strategies
Target the pathogen:
• Fungicides, nematicides, fumigants
• Some quite effective
Systemics, cf. Protectants
• Risk of non-target effects
• Sometimes High Toxicity
• Environmental Impact
• Blank Slate Effect
(Blank Slate = Blank Check)
Management Strategies
Target the pathogen:
• Biocides
• Overwintering Structures• Tillage to incorporate residue
Management Strategies
Target the pathogen:
• Biocides
• Overwintering Structures• Tillage to incorporate residue
Management Strategies
Target the pathogen:
• Biocides
• Inoculum Source
• Sanitation!
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Management Strategies
Target the pathogen:
• Biocides
• Overwintering Structures• Tillage to incorporate residue
• Subsoil compaction
• Saturated conditions
• Stressed roots
Host
Pathogen Environment
Disease
Management Strategies
Target the pathogen:
• Biocides
• Overwintering Structures• Tillage to incorporate residue
May create conducive environment
• Subsoil compaction
• Saturated conditions
• Stressed roots
Management Strategies
Improve Soil Environment:• Reduce disease-conducive conditions
• Improve drainage• Many pathogens exacerbated by wet and
waterlogged conditions
• Decrease / Avoid compaction• Improves drainage and decreases root
stress
• Residue / Mulch / Soil Cover• Decrease lower-canopy humidity
Host
Pathogen Environment
Disease
Strategies for Disease Control
• Resistance: host plant genetics reduce susceptibility
• Exclusion: prevent pathogen from coming in contact with plants
• Protection: chemical or physical barriers between plant and pathogen; environmental manipulation to favor plant growth, disfavor pathogen
• Eradication: eliminate pathogen inoculum directly at its source
• Avoidance: planting in time or space to avoid pathogens and/or conducive environments
• Therapy: treat individual diseased plants to reduce or eliminate pathogen
Plant Resistant Varieties
Two wheat varieties showing differing levels of Fusarium head blight. (apsnet.org)
Partial resistance to Phytophthora sojaemeasured in a layer cup test. (apsnet.org)
Management Strategies
Manage the Host
• Resistance
• Diversity of Hosts• Spatially
Host
Pathogen Environment
Disease
Management Strategies
Manage the Host
• Resistance
• Diversity of Hosts• Spatially
• Temporally• Rotation
• Cover Cropping
Host
Pathogen Environment
Disease
Management of the Soil Biota
• Plant Pathogens & Disease• Management Considerations
in Relation to Soil Health
• General Principles for Managing Soil Biological Health
• Plant and Soil Biodiversity
• Key Manageable Symbioses
per 40 ft of row Root Rot
Severity
Rating
(1-9)*Rotation
Emerg-
ence Stand
Total Wt.
(kg)
Pod
Wt.
(kg)
Pod Wt.
(tons/A)
Cn-Cn-Cn-Bn 106 90 12.4 6.7 3.2 4.1
Cn-Bn-Cn-Bn 125 93 10.3 5.5 2.6 4.5
Bn-Bn-Bn-Bn 77 76 4.6 2.4 1.1 5.0LSD (P = 0.05) 39 16 2.3 1.3 0.6 0.6
Rotation trial with snap beansNYSAES Research Farm 2001 through 2004
*Mean rating of 40 plants dug at flowering.
Higher numbers indicate more disease pressureDr. George Abawi
Effect of incorporated cover crops on root rot severity of beans
Lower rating means better disease suppression
1 2 3 4 5 6 7 8 9
White clover ' New Zealand'
Check
Hairy vetch
White mustard 'Mantegena'
Alfalfa 'Iroquois'
Ryegrass 'Pennant'
Oats
Sudangrass
Rye grain
Wheat 'Geneva'
Crown vetch
Rapeseed
Root Rot Severity (1-9)Dr. George Abawi
0 250 500 750 1000 1250 1500 1750 2000
Hairy Vetch
Alfalfa
White clover
Rye grain
Alsike clover
Phacelia
Radish
Crown vetch
Red clover
Wheat
Oats
Buckwheat
Mustard
Ryegrass
Rapeseed
Sudex
Number of P. penetrans/g bean root
Incorporation of cover crops as green
manures against Pratylenchus penetrans
Dr. George Abawi
Management Strategies
Manage the Host
• Resistance
• Diversity of Hosts• Spatially
• Temporally• Rotation
• Cover Cropping
Host
Pathogen Environment
Disease
General Principles
• Diversity aboveground Diversity belowground
• Diverse inputs Diverse soil community
• Diversity Robustness and Resilience• Return to proper functioning after perturbation
• Simpler communities are easier to invade & less resilient
• Diverse crops & inputs encourage beneficial organisms(cover crops, manures, green manures, composts,
vermicomposts, chitin-amended composts, etc…)
Why add different kinds of organic matter?Different types of organic matter perform different important roles
• Nutrient release (N if low C:N ratio)
• Aggregation
• Accumulation of OM in soil
• Diverse soil microbial community
• Balanced effects (over-application of same thing can be a problem)(Building Soils for Better Crops)
Beneficial Organisms and Processes Encouraged
• Antagonists of Disease
Competition for nutrients or space
Mycoparasitism
Antibiosis
Inactivation of the pathogen enzymes
Induced resistance
Beneficial Organisms and Processes Encouraged
• Antagonists of Disease
• PGPR• Phosphate solubilizers
• Plant hormone (mimic) producers
• ISR/SAR triggers
Biotechnol. Agron. Soc. Environ. 2011 15 (2), 327-337
http://vro.depi.vic.gov.au
Beneficial Organisms and Processes Encouraged
• Antagonists of Disease
• PGPR• Phosphate solubilizers
• Plant hormone (mimic) producers
• ISR/SAR triggers
• Primed nutrient cycling
• N fixers (symbiotic, associative, free-living)
• AM Fungi (with associated MHB)
Management of the Soil Biota
• Plant Pathogens & Disease• Management Considerations
in Relation to Soil Health
• General Principles for Managing Soil Biological Health
• Plant and Soil Biodiversity
• Key Manageable Symbioses
Management of Soil Biota:Key Mutualisms
N Fixing Bacteria
• Transform N2 gas (unavailable) to NH3 and derivatives (plant available)
• Free-living, Associative, and Symbiotic bacteria
• Energy intensive process
Arbuscular Mycorrhizal Fungi
• Trade nutrients for sugars with plants
• Increase access to poorly available nutrients and water
• Increase disease resistance
• Contribute greatly to aggregation and OM
N Fixing Bacteria: Management
• Grow Legumes• In rotation and as cover crops• Alone or in mixtures
• Inoculate with Appropriate bacterial strains
• Check for Nodulation
• Assess Effectiveness
Cross-inoculation groups of legumes and rhizobia.
Legume group Inoculation group code Rhizobia species
Alfalfa and Sweet Clover A Rhizobium meliloti
True clovers B R. trifolii
Peas and vetch C R. leguminosarum
Soybean S Bradyrhizobium japonicum
Birdsfoot trefoil K R. loti
Crown Vetch M Rhizobium spp.
J. Grossman (on www.extension.org)
Importance of Soil Biota:Special Cases
N Fixing Bacteria
• Transform N2 gas (unavailable) to NH3 and derivatives (plant available)
• Free-living, Associative, and Symbiotic bacteria
• Energy intensive process
Arbuscular Mycorrhizal Fungi
• Trade nutrients for sugars with plants
• Increase access to poorly available nutrients and water
• Increase disease resistance
• Contribute greatly to aggregation and OM
Mycorrhizae
• The normal condition for most plant roots is to be associated with symbiotic fungi – mycorrhizae are their normal joint absorptive structures
• Plant disease susceptibility is increased when this association is absent
• Conversely, disease resistance is generally increased when the plant is mycorrhizal
• Competition for infection and colonization space• Better nutrient status• Plant defenses primed – but not fighting the AMF
• AM Fungi cultivate a surrounding beneficial bacterial community
Mycorrhizae: Function
• Mycorrhizae important for plant establishment• Particularly in mixed-species stands
• Decrease competition, increase interspecies facilitation
• Fungal diversity important for maintaining plant diversity
• Fungal growth is important for soil quality• Aggregation
• Organic Matter
• Carbon sequestration
• Harbor ‘mycorrhizosphere’ communities
• Inoculum commercially available but of extremely limited diversity
• Growing medium or in-furrow application
• Inoculation of root zone directly more useful than surface application – spores large
• Management to maintain native populations recommended
• On-farm production possible• Area of active extension work
Mycorrhizal Fungal Management
Mycorrhizal Fungal Management
Dr. D. Douds (USDA-ARS) and Rodale Institute On-farm Arbuscular Mycorrhizal Fungal Management
Management of Key Mutualisms
AM Fungi
• Know and Grow Hosts
• Rotate
• Use Cover Crops
• Reduce Tillage
• Inoculate if Transplanting
• Don’t overload P
Rhizobia
• Inoculate Legume Seeds
• Check for (pink) nodules
• Keep pH high enough
• Keep P high enough
Wrapup / General Principles
Good environmental ConditionsConducive to plant health, not disease developmentDrainageCompactionHealthy Root Growth
Robust, Diverse Soil Biotic CommunityMainly through plant communitySome inoculation and specific
direct management possible
Target acute biological dysfunction
Best Defense is a Good Offense