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Understanding Soil Health, Soil Tests, Crop Fertility Inputs and

Organic Fertility Management

Compiled by Steve Diver, Agriculture Specialist, Fayetteville, AR

For the International Organic Inspectors Association

IOIA Pre-Course

Soils Training

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Objectives

• a basic understanding of the soil ecosystem

• be able to recognize the key components of crop management that effect soil quality and health.

At the completion of the module, participants will have:

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Topics

• Soil Quality and Soil Health – Physical – Chemical – Biological

• Soil Organic Matter and Crop Management • Soil Tests and Fertility Management

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Soil Fertility Goals in Organic Farming

• Soil Quality & Soil Health

• Crop Fertility & Crop Vitality

• Food Quality & Nutritional Health

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Soil Health is the fitness or capacity of soils to support crop growth and maintain environmental quality.

Physical Chemical

Biological Soil Quality emerges from a .. … .. balance between

the three soil components.

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Three components of soil quality

• Physical (structural) – tilth, infiltration, porosity, bulk density,

aggregation, texture (mix of sand, silt and clay) • Chemical (mineral)

– nutrient content, salinity, pH, organic matter, clay, mineral content (parent material)

• Biological (flora and fauna) – living biota, biomass, biodiversity, biological

activity, biological control

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Sand Loamy Sand Sandy Loam Fine Sandy Loam Loam Silty Loam Silt Silty Clay Loam Clay Loam Clay

Coarse

to

Fine textured

soils

Soil texture relates to the size of the individual particles

– the texture designations range from

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Soil Texture Triangle What is the % mixture of a loam soil at this location?

Sand - 0.05 2.0mm

Silt - 0.002 0.05 mm

Clay - < 0.002 mm

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Soil structure • refers to the clumping together or “aggregation” of sand, silt, and clay particles into larger, secondary clusters. • these aggregates form roundish granules, cube-like blocks, plate-like

sheets, or prism-like rectangles.

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• determine pore space for air and water circulation, erosion resistance, ease of tillage, and root penetration.

• Texture is related to mineral components of the soil and does not change, but

• Soil structure can be improved or destroyed by choice and timing of farm practices.

Texture and Structure

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25 yrs of CT corn

20 yrs of bluegrass, then 5 yrs CT corn

Water stable aggregate test on rotation plots.

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25 yrs of conventional corn

20 yrs of bluegrass, then 5 yrs conventional corn

After adding water to soils from the rotation plots.

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Soil pH refers to its acidity or alkalinity, which is determined by the concentration of hydrogen (H+) and hydroxyl (OH-) ions in soil.

Soil pH determines the solubility and availability of essential nutrient elements to plants. Graphic: extension.missouri.edu/explore/agguides/soils/g09102.htm

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Effect of soil pH on plant nutrient availability

Graphic: www.ca.uky.edu/agc/pubs/agr/agr19/fff00009.gif

pH level

width of the bar

indicates availability

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pH - the negative log of

the Hydrogen Ion Concentration [H+]

Low pH or acidic - eg. 4.5 1/ [H+]4.5 or [H+]-4.5

Neutral pH of 7 balance of H+and OH-

High pH - alkaline eg. 8.5 [H+]-8.5

Liming ?? CaCO3 + H20 = Ca2+ + HCO3- + OH-

OH- + H+ = H2O Uses up the [H+] ions

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Acidifying and Liming materials approved for use in organic farming.

The OMRI Products List is a “key” guide to approved sources of crop fertility inputs and soil amendments.

OMRI Products List - www.omri.org

Acidifying • Elemental sulfur

Liming • Agricultural limestone • Dolomitic limestone

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Essential Elements for Plant Growth Major elements (required in large quantities) Nitrogen (N) Carbon (C) Phosphorus (P) Oxygen (O) Potassium (K)

Secondary elements (intermediate requirement)

Calcium (Ca) Magnesium (Mg) Sulfur (S)

Trace elements (needed in very small amounts) Copper (Cu) Iron (Fe) Zinc (Zn) Boron (B) Molybdenum (Mb) Manganese (Mn) Chlorine (Cl) Nickel (Ni)

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Cationic elements (+ positive charged ions)

Calcium (Ca) Copper (Cu) Magnesium (Mg) Iron (Fe) Potassium (K) Sodium (Na) Anionic elements (- negative charge on soil forms )

Nitrogen (N) Boron (B) Phosphorus (P) Selenium (Se) Sulfur (S) Chlorine (Cl)

Essential Elements for Plant Growth

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Cation exchange capacity (CEC) is a measure of the soil’s ability to store base cation nutrients (e.g., Ca, Mg, K, Na, trace elements).

CEC is affected by clay and organic matter (humus) content.

Base saturation is the percentage of soil CEC occupied by base cations.

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Table of Cation Exchange Capacities Don Schriefer - Agriculture in Transition

Sand + 2 -3 CEC

Silt = 5 - 7 CEC

Clay = up to 60 CEC

Humus = 250 CEC

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Soil Biota

Classification Body Width Examples

Microflora < 10 µm • bacteria • fungi • actinomycete • algae

Microfauna <100 µm • protozoa • nematode

Mesofauna 100 µm to 2 mm • mites • springtails

Macrofauna 2 mm to 20 mm • earthworms • millipedes

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Number of organisms in 1 cubic centimeter of agricultural soil: Bacteria 90,000,000 Actinomycetes 4,000,000 Fungi 200,000 Algae 30,000 Protozoa 5,000 Nematodes 30 Earthworm < 1

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Soil Life Under a Microscope, UV Light w/ Acridine Orange

Photo: Siegfried Luebke, CMC Group, Austria

Each glowing spot is a microbe

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Resources on Soil Biology & Microbial

Ecology

• Life in the Soil video • Soil Biology Primer

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Diagram: Elaine Ingham, Soil Foodweb, Inc.

Soil Food Web

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Soil Foodweb Influence on Crops Bacterial Dominated • Turfgrass • Vegetables • Row crops

Fungal Dominated • Fruit trees • Vineyards • Forests

Food Sources • Green plant material • High nitrogen • Easily decomposed

Food Sources • Brown plant material • High in cellulose, lignin

• Slow decomposition

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Diagram: Soil Biology Primer

Plants Determine Biology

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Bare Parent Material 100% bacterial

Cyanobacteria True Bacteria Protozoa Fungi Nematodes F:B =.01

“Weeds” -- High nitrates -- Lack of oxygen F:B =.1

Early Grasses -- Bromus -- Bermuda F:B =.3

Mid-grasses, vegetables F:B =.75

Late successional grasses & row crops F:B =1.1

Shrubs, vines, bushes F:B = 2 to 5 Deciduous trees

F:B = 5 to 100

Coniferous trees Old-growth forests F:B = 1000 to 10,000

Soil Food Web Structure Through Succession,

Increasing Productivity

Concept: Soil Foodweb, Inc.

F:B Fungal to Bacteria Ratio

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VAM Mycorrhizal Fungi This is a special kind of symbiosis between roots and fungi known as vesicular arbuscular mycorrhizae. The fungi live inside the plant, but they also send hyphae into the surrounding soil to gather water and nutrients for delivery to the plant. In exchange, the plant provides carbon to the fungi. The Rhizosphere The 3-dimensional zone at the interface between plant roots and bulk soil -- is home to a diverse microbial community that lives in association with plant roots. Plants slough-off tissue and excrete plant-manufactured substances like amino acids and sugars that feed and stimulate a microbial community that surrounds plant roots. In turn, these microbes make nutrients and microbial substances available to the plant, directly or indirectly. Rizobacteria that live in association with plant roots exude bacterial slimes and glues to benefit their own survival, but as a result these substances help release soil nutrients for plant uptake. These rhizobacteria function as biocontrol organisms by suppressing soil-borne plant pathogenic fungi that cause plant disease such as fusarium, phythium, and rhizoctonia. Mycorrhizal fungi that live in symbiotic association with plant roots obtain nutrients from several centimeters or even several meters further out into the bulk soil, thus extending the mycorrhizosphere.

The Root-Soil interface

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Soil Life Under a Microscope, VAM Mycorrhizal Fungi

Photo: Sara Wright, USDA

The yellow stain is a fungal glue (glomalin) that helps build soil structure and soil

organic matter.

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Rhizosphere Benefits for Microorganisms Root Excretions 1. Amino acids 2. Organic acids 3. Carbohydrates = Sugars 4. Nucleic acids 5. Growth factors 6. Sloughed-off tissue

Key: Food + Shelter + Energy for microbes

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Soil Organic Matter (SOM) is part of each component and binds and weaves them together.

Physical Chemical

Biological

… the binding thread Organic Matter

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Soil Composition

20-30% Water 45% Mineral

20-30% Air

50% Pore Space 50% Solids

5% Organic Matter

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Soil Organic Matter

Organic matter is 1-6% of total soil mass

living biomass 10-20%

active fraction 10-20%

humus 60-80%

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Pools of Soil Organic Matter Active or Labile SOM — fresh OM (litter, manure), living organisms, microbial biomass, partially stabilized OM; half-life in days to a few years

Slow or Intermediate SOM — stabilized OM derived from above; half-life of a few years to decades

Passive or Stable or Recalcitrant SOM — extremely recalcitrant molecules, humus; half- life of decades to centuries

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2% Organic Matter 4% Organic Matter

Effect of 20 years of conventional vs. organic management in the Rodale Farming Systems Trial

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Humus Management • Biological Farming Practices: Cover crops, rotations, compost,

tillage system, manures, microbials • Purpose: Soil organic matter

Food and Shelter for soil foodweb Clay-humus crumb

• “Feed the Soil” Number & Diversity of soil organisms

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Crop Rotations

Soil Depleting Row crops Soil Neutral Cereal Crops Soil Building Sod-forming grasses & legumes

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Crop Rotation: What does the inspector do?

• Is the grower following their plan?

• Is the same crop being repeated?

• Is there a balance of- Soil building crops Soil depleting crops Soil neutral crops?

• Do you see signs of the past year’s rotation (crop residues, etc)?

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Clover plant with

Rhizobium root nodules

Crimson Clover

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Crops vary based on:

• Regional climates:

- Cool season or warm season

• Type of plant

- Cereals, Legumes and Broadleaves

Cover Crops & Green Manures

Spader incorporating green manure

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Green Manures: What does the inspector look for?

• Is the seed for the green manure or cover crop organic?

• How much biomass is actually incorporated?

• How is it incorporated?

• Are their photos or records of dates of application?

• Did the green manure crop get planted and did it germinate?

• Inoculants?

Effects of OM additions Add

organic matter

Increase biological activity (& diversity?)

Decomposition

Nutrients released

Aggregation increased Pore

structure improved Humus formed

May reduce soil-borne disease

Improved tilth

HEALTHY PLANTS

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Composting a managed process of organic matter decomposition & humification C:N ratio Particle size

Mixing Porosity Temperature Moisture Aeration Microbes

Management Factors

“Humus is to OM,

as Bread is to Flour”

Compost Turner

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Material Carbon to Nitrogen Seaweed 20 (e.g., 20:1) Poultry Manure 5-15:1 Dairy Manure 5-25:1 Fall Leaves 30-80:1 Legume Hay 50:1 Corn Stalks 60:1 Grass Hay 80:1 Sawdust 200-700:1 Compost 10-30:1

Optimum OM digestion 10-30:1

C:N – Carbon:Nitrogen Ratio of Organic Materials

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Compost Rate of Application

Low 2-3 tons per acre

Regular 5 tons per acre

High 10-20 tons per acre

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Three Pillars of Organic Farming Fertility

• Compost – Compost, organic amendments, manures

• Cover Crops – Cover crops, green manures, living mulches

and intercrops, crop rotations, mulch

• Rock Minerals – Limestone, gypsum, rock phosphate,

activity, sul-po-mag, rock dusts

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Organic Soil Fertility

Main Concepts • Soil Test • Mineral Balancing & Remineralization • Humus Management & Soil Biology • Organic Fertilizers & Supplements

(Fertigation, Foliar Feeding, Biostimulats)

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Soil Test Report • pH • Buffer Index (lime rate) • OM (organic matter) • CEC – varies with soil type/texture • Base saturation – % for each cation • Nutrients:

- Major, - Secondary,

- Micronutrients • Nutrient Levels (depends on the crop)

- Low - Med - High - Excess

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Microbial - Humus • ABC Organics • BBC Labs • Microbial Matrix • Soil Foodweb, Inc. • Woods End

Minerals - Fertilizers • Agri-Energy Resources • Brookside Labs • Kinsey Ag Services • Midwestern Bio-Ag • Midwest Bio-Systems • Texas Soil & Plant Lab

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Three Pillars of Eco-Farming

• Mineralization – Soil tests, rock minerals, rock dusts, mineral

balancing, foliar fertilization, fertigation

• Humus Management – Composts, cover crops, crop rotations,

grazing, proper tillage, microbial inoculants

• Energetics (not included in this module)

– Photosynthesis, homeopathics, paramagnetism, sound

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Dr. William Albrecht Paths to Eco-Farming Fame 1. Univ. of MO

2. Brookside Labs 3. Acres USA 4. Base Saturation &

Mineral Balancing 5. Humus Management

1888-1974

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The Mineral Balancing Approach

• Balanced Fertilization provides Soil Structure and Soil Nutrients, supporting the work of Soil Microbes. • Ex. Calcium flocculates the soil, expands clay, increases porosity, facilitating oxygen transfer to roots. • A focus on interactions and Ratios Between Nutrients based on a soil test.

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The Albrecht Ratios

Ca++: 60-70%

Mg++: 10-20% H+: 10-15%

K+: 2-5%

Na+: 0.5-2%

Base Cation Saturation Ratio

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Remineralization Rock Minerals

Rock dusts (72 elements)

Sea solids and Seawater (52 elements)

Broad diversity + low concentration Secondary elements, Trace elements

Rare earth elements

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Rock Minerals examples of products used as soil amendments and fertilizer inputs

Rock phosphate

Sul-po-mag (K-Mag)

Limestone

Oyster shell

Greensand

Gypsum

Granite meal

Rock dusts

Granular humates

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Organic Fertilizers

Plant & Animal Byproducts Feather meal Fish meal Soybean meal Pelletized poultry litter Liquid Organic-Biological Fertilizers

Products & Suppliers:

OMRI Products List

ATTRA Organic Fertilizer List

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Seven Steps to Organic Soil Fertility

1. Cover crops & crop rotations 2. Compost 3. Rock minerals

4. Bagged organic fertilizer 5. Sidedress or fertigate

6. Foliar fertilization 7. Bioaugmentation with

biological inoculants and microbe teas

Fertilize the Crop

Supplemental Fertility & Biological Inoculation

Feed the Soil

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Landscape Overview - including fence rows

Crop Rotation - simple or complex

Soil Texture and Structure

Crop and Weed species - patterns

Nutrient Deficiency

Soil Test results

Biological activity

Evaluating Soil Fertility and Quality during a Farm Inspection

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Tatsoi

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Review ?’s 1. What is Soil Health? 2. What was the % sand, silt and clay for the loam soil? 3. What is the difference between soil texture and soil structure? 4. What can you observe about texture and structure as an inspector? 5. What is the optimum pH range for Phosphate availability? 6. List three trace elements. 7. Which will have a higher CEC – sand or clay? 8. What is an example of a microflora? – an example of mesofauna? 9. What is the Rhizosphere? What is a mycorrhizal fungi? 10. What are the three pools of Soil Organic Matter (SOM)? 11. Give a specific crop example for each of

– Soil depleting, Soil Neutral and Soil building. 12. What does C:N mean and what is a “good” number for compost? 13. What is a high rate of compost application? 14. What is “good” ratio for Ca:Mg? (based on Albrecht’s Theory) 15. What is Sul-po-mag?

Cont’d

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Humus

Structure

Texture

Soil fauna

Plant roots

Microbes

Colloids

pH

CEC

Anions & Cations

Aeration Drainage

Nutrients

Mycorrhizae

Biological

Physical Chemical

The Soil Ecosystem

16. Place the terms in one of the four areas

Tilth

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Soil Biology Primer - a question for each chapter

1. Soil Food Web - what’s missing?

2. Where do red wigglers fit in?

3. What causes the “Good Earth Smell”?

4. How do nitrogen fixing bacteria operate?

5. How can protozoa feed a crop with high N requirements?

6. What group of organisms play a significant role in P nutrition?

7. How can nematodes be both beneficial and pathogenic?

8. What is a more proper name for soil “Bugs”?

17. Complete the Pre-course Assignment and submit by deadline.