Organic Agriculture: Organic Agriculture: Microbial Activity and Soil Microbial Activity and Soil
HealthHealth
Warren RobertsWarren RobertsJim ShreflerJim Shrefler
Merritt TaylorMerritt TaylorLane Agricultural CenterLane Agricultural Center
OSUOSU
Why Have Organic Food?Why Have Organic Food?
Public Concern about Public Concern about Food SafetyFood Safety
– Perception that Organically Grown Foods Perception that Organically Grown Foods are Safer & More Nutritiousare Safer & More Nutritious
Microbial Activity and Soil HealthMicrobial Activity and Soil Health
Define Microbial Define Microbial – Micro-organismsMicro-organisms
Define ActivityDefine Activity– Growth, Reproduction, FunctionGrowth, Reproduction, Function
Define Soil HealthDefine Soil Health– Ability of a Soil to Function Ability of a Soil to Function
Chemistry, Physics, BiologyChemistry, Physics, Biology
Define BiologyDefine Biology– Study of Life and Life ProcessesStudy of Life and Life Processes
Purpose of Soil HealthPurpose of Soil Health
Promote Plant and Animal SystemsPromote Plant and Animal Systems
Promote Clean WaterPromote Clean Water
Prevent Soil ErosionPrevent Soil Erosion
Promote Human HealthPromote Human Health
Promote Life !Promote Life !
Soil MicroorganismsSoil Microorganisms
Larger AnimalsLarger Animals
Bacteria (Often Single Cell)Bacteria (Often Single Cell)
Fungi (Often Long Filaments or Hyphae)Fungi (Often Long Filaments or Hyphae)
Actinomycetes (Properties of Both)Actinomycetes (Properties of Both)
MicroorganismsMicroorganisms
Affected byAffected by– MoistureMoisture– TemperatureTemperature– AerationAeration– Food Supply (Organic Matter)Food Supply (Organic Matter)– AcidityAcidity
Location in SoilLocation in Soil
Mostly in top inchMostly in top inch
Almost all in top 6 inchesAlmost all in top 6 inches
RhizosphereRhizosphere– Adjacent to plant rootsAdjacent to plant roots– High microbial activityHigh microbial activity– Contains root exudatesContains root exudates
Soil AnimalsSoil Animals
EarthwormsEarthworms
MitesMites
NematodesNematodes
ProtozoaProtozoa
BeetlesBeetles
TermitesTermites
BacteriaBacteria
Mostly Single CellMostly Single Cell
Millions per GramMillions per Gram
Millions of Billions per AcreMillions of Billions per Acre
Roles of BacteriaRoles of Bacteria
Nitrogen FixationNitrogen Fixation
MineralizationMineralization
Organic Matter DecompositionOrganic Matter Decomposition
Soil StabilizationSoil Stabilization
AerationAeration
TilthTilth
Nitrogen FixationNitrogen Fixation
Bacteria (Rhizobium and others)Bacteria (Rhizobium and others)
Symbiotic Symbiotic – Bacteria gets carbon from plantsBacteria gets carbon from plants– Bacteria supplies Nitrogen to plantsBacteria supplies Nitrogen to plants– Usually with LegumesUsually with Legumes
MineralizationMineralization
Conversion from Organic Substance to Conversion from Organic Substance to Molecular Level MineralsMolecular Level Minerals
DecayDecay
Physical and ChemicalPhysical and Chemical
Organic Matter Organic Matter DecompositionDecomposition
Physical changesPhysical changes– Organisms eat, crunch, rip, tear Organisms eat, crunch, rip, tear – Earthworms, mites, ants, etcEarthworms, mites, ants, etc
Chemical changesChemical changes– Digestion with enzymesDigestion with enzymes
What Controls Rate of DecayWhat Controls Rate of Decay
TemperatureTemperature
MoistureMoisture
Food Supply Food Supply
OxygenOxygen
C:N RatioC:N Ratio
C:N RatioC:N Ratio
Microbes Need CarbonMicrobes Need Carbon
Microbes Need Nitrogen Microbes Need Nitrogen
Nitrogen is Often the Limiting FactorNitrogen is Often the Limiting Factor
C:N RatioC:N Ratio
SawdustSawdust 300:1300:1
NewspaperNewspaper 175:1175:1
Corn StalksCorn Stalks 75:175:1
LeavesLeaves 60:160:1
IDEAL RATIOIDEAL RATIO 30:130:1
Vegetable ScrapsVegetable Scraps 25:125:1
Grass ClippingsGrass Clippings 20:120:1
CloverClover 20:120:1
ManureManure 15:115:1
AlfalfaAlfalfa 12:112:1
Slo
wS
tin
ky
Soil StabilizationSoil StabilizationSoil AggregationSoil Aggregation
Clumps of ParticlesClumps of Particles– Organic MatterOrganic Matter– Bacterial ResiduesBacterial Residues– Fungal HyphaeFungal Hyphae
Aeration & TilthAeration & TilthHigh Organic MatterHigh Organic Matter
Low CompactionLow Compaction
High AggregationHigh Aggregation
FungiFungi
Hundreds of Thousands per GramHundreds of Thousands per Gram
Perform Functions Similar to BacteriaPerform Functions Similar to Bacteria– DecompositionDecomposition
Important in Plant NutritionImportant in Plant Nutrition– Mycorrhizae (fungus root)Mycorrhizae (fungus root)
MycorrhizaeMycorrhizae
Mutualism or SynergismMutualism or Synergism
Benefits Plant and FungusBenefits Plant and Fungus– EctomycorrhizalEctomycorrhizal
Hyphae do not penetrate root cellsHyphae do not penetrate root cells
– EndomycorrhizalEndomycorrhizalHyphae do enter root cellsHyphae do enter root cells
ArbuscularArbuscular
Very CommonVery Common– 90+ % of plant families90+ % of plant families
EctomycorrhizaeEctomycorrhizae
Ecto- (outer)Ecto- (outer)
Hyphae form sheath Hyphae form sheath around root tiparound root tip
Promotes nutrient Promotes nutrient absorptionabsorption
Promotes nutrient Promotes nutrient translocationtranslocation
EndomycorrhizaeEndomycorrhizae
Endo – (inner)Endo – (inner)
Hyphae Penetrates Cell WallHyphae Penetrates Cell Wall
Promote Nutrient Uptake and ExchangePromote Nutrient Uptake and Exchange
Increase Surface Contact AreaIncrease Surface Contact Area
To Your Good Health (Soil)To Your Good Health (Soil)
Keep pH near neutral Keep pH near neutral
Avoid Compaction Avoid Compaction
Maintain Good MoistureMaintain Good Moisture
Promote DrainagePromote Drainage
Good TemperatureGood Temperature
Organic MatterOrganic Matter
ProBioticsProBioticsCultures of Beneficial Cultures of Beneficial MicroorganismsMicroorganisms– Compost TeasCompost Teas– InoculantsInoculants
Organism FoodOrganism Food– SugarSugar– MolassesMolasses– NitrogenNitrogen
Where We AreWhere We Are50 + years of Chemical 50 + years of Chemical ResearchResearch
What If ?What If ?– 50 + Years of Biological 50 + Years of Biological
Research ?Research ?