Sweet and Sour Dirt

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Sweet and Sour Dirt
Sweet and Sour Dirt

• A little understanding of pH
• to help you use
• biochar better

Contains animation. View in Slide Show mode
Contains animation
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Soils Have Flavors!
Its possible to taste a difference between
different types of soil

• Acidic soils taste sour
• Basic (alkaline) soils taste slightly sweet

Mike Lieberman of UrbanOrganicGardener.com

• The flavor of a soil affects
• How well different plants grow
• What kind of microbes thrive in the soil
• How well the solid holds on to various minerals
• We talk about soils flavor as pH

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What Exactly is pH?
hydrogen ions (H)
power of
pH
in water

• Water allows some hydrogen ions to escape from
  their molecules
• pH tells the concentration of H in the solution
• pH is a logarithmic (not linear) scale

compare with distilled water
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Finding the pH (without tasting)
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Strength of pH
Acids

• Acids release H
• Bases suck up H
• Acids and bases neutralize each other

Acids
Biochar is basic (alkaline). It can neutralize
acidic soil.
acidic
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Soils Natural pH Varies
Heavy rainfall forest ? acidic soils
Light rainfall prairie ? neutral soils
Cultivated developed soils often differ from
native soils
Natural limestone bedrock ? alkaline soils
Drought desert ? alkaline soils
But soils can also differ from one yard to
another.
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Different Plants Like Different Soils
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Soil Ecology and pH
Soil is a Living Community
Resident What it does Effect of pH
Fungi Decompose dead plants, animals, and bacteria into nutritious molecules Some live in plant roots to help plants take up nutrients Prefer slightly acidic pH
Bacteria Decompose dead plants, animals, and fungi into living molecules Exude nutritious molecules Become food for higher organisms Prefer slightly alkaline pH
Insects worms Excrete plant fertilizer Open spaces in soil to let in air and water to support soil life Become food for bacteria and fungi Dont like extreme pH Worms avoid acid pH
Supports Plants
Supports Animals
Unbalanced pH upsets the whole community
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Soils and Mineral Availability

• Plants need many minerals to thrive
• Plant roots only absorb minerals dissolved in
  water.
• If solution is too acidic or alkaline, H
  chemistry locks up some nutrients.

Nitrogen Phosphorus Potassium Sulfur Calcium Magne
sium Iron Manganese Boron Copper and Zinc
Examples pH lt 6.00
Near neutral pH is best for most minerals
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Most Plants Like Near-Neutral Soils
Best for minerals
Best for fungi
Best for bacteria
Most plants grow in this range.
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Neutralizing
Because pH scale is not linear, neutralizing
different strengths takes very different
quantities
Equal distances from neutral, use equal
concentrations
neutral
? more acidic
more basic?
0
1
2
3
4
5
6
7
8
9
10
11
12
13
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One pH number further from neutral, use 1/10th
as much of the stronger
Two pH numbers further from neutral, use 1/100th
as much of the stronger
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How to Modify Soil pH
Adding organic matter to the soil makes both acid
and alkaline soils more neutral.

Add one of the following Ground limestone lasts
a long time Hydrated Lime works quickly easy to
over-do Wood Ashes fast-acting a little goes a
long way
Add one of following Granular sulfur slow
acting Aluminum Iron Sulfate faster need a
lot Acidifying fertilizer Doesnt work well for
pH gt 7.5 May contain a large amount of calcium
carbonate
Lower Soil pH (improve alkaline soil)
Raise Soil pH (improve acid soils)
ALWAYS FOLLOW DIRECTIONS
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Biochar and pH

• Biochar is usually alkaline
• Biochar pH depends on the pyrolysis temperature

typical pH range
typical formation temperature range
neutralizes
Biochars neutralizing power diminishes after a
few years.
Note ash created by pyrolysis is strongly
alkaline (pH 12-13)
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Using Biochar to Change Soil pH

• If your soil is already alkaline,
• dont use biochar!
• Because biochar is a pretty strong base, use it
  sparingly

2 by volume per application

• To keep pH moderate, add small amounts
• of biochar every few years, not all at once.
• If your soil is strongly acidic (ltph 5),
• you can mix a small amount of ash into the
  biochar.
• Ash adds important minerals (calcium, sulfur,
  potassium, phosphorus, magnesium)

strongly acidic