IOIA Pre-Course

Soils Training Understanding Soil Health, Soil Tests, Crop Fertility I nputs and Organic Fertility M anagem ent

Compiled by Steve Diver,

Agriculture Specialist, Fayetteville, AR

For the International Organic Inspectors Association 1 © IOIA

Objectives At the completion of the module, participants will have: • a basic understanding of the soil ecosystem • be able to recognize the key components of crop management that effect soil quality and health. 2 © IOIA

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

Soil Quality em erges from a ..

Chemical

Biological … .. balance betw een 5 the three soil com ponents. © IOIA

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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Soil texture relates to the size of the individual particles – the texture designations range from Sand Loamy Sand Sandy Loam Fine Sandy Loam Loam Silty Loam Silt Silty Clay Loam Clay Loam Clay

Coarse to Fine textured soils

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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. 9 © IOIA

Texture and Structure • 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.

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Water stable aggregate test on rotation plots.

20 yrs of bluegrass, then 5 yrs CT corn

25 yrs of CT corn

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After adding water to soils from the rotation plots.

25 yrs of 20 yrs of bluegrass, conventional then 5 yrs corn conventional corn 12 © IOIA

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 13 © IOIA

pH level

Effect of soil pH on plant nutrient availability width of the bar indicates availability

Graphic: www.ca.uky.edu/agc/pubs/agr/agr19/fff00009.gif 14 © IOIA

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 OHHigh pH - alkaline Liming ??

eg. 8.5 [H+]-8.5

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

Uses up the [H+] ions

OH- + H+ = H2O 15 © IOIA

Acidifying and Liming materials approved for use in organic farming.

Acidifying

Liming

• Elemental sulfur

• Agricultural limestone • Dolomitic limestone

The OMRI Products List is a “key” guide to approved sources of crop fertility inputs and soil amendments. OMRI Products List - w w w .om ri.org © IOIA

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

Carbon (C) Oxygen (O)

Secondary elements

(intermediate requirement)

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

Trace elements

(needed in very small amounts)

Copper (Cu) Zinc (Zn) Molybdenum (Mb) Chlorine (Cl)

Iron (Fe) Boron (B) Manganese (Mn) Nickel (Ni) 17

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Essential Elements for Plant Growth

Cationic elements

(+ positive charged ions)

Calcium (Ca) Magnesium (Mg) Potassium (K)

Anionic elements

Copper (Cu) Iron (Fe) Sodium (Na)

(- negative charge on soil forms )

Nitrogen (N) Phosphorus (P) Sulfur (S)

Boron (B) Selenium (Se) Chlorine (Cl)

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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 (hum us) content.

Base saturation

is the percentage of soil CEC occupied by base cations. 19 © IOIA

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

Microfauna