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

We All Want Food that isWe All Want Food that is

PlentifulPlentifulNutritiousNutritious

SafeSafe

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

It’s a Matter of Life andIt’s a Matter of Life and ??

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

Raised Bed Gardening – Noble Raised Bed Gardening – Noble FoundationFoundation

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

A Noble SoilA Noble Soil

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 ?