Transcript Biochar and pH

Sweet and Sour
Dirt
A little understanding of pH
to help you use
biochar better
Contains animation
Contains animation.
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Soils Have Flavors!
It’s possible to taste a
difference between
different types of soil
• Acidic soils taste sour
• Basic (alkaline) soils taste
slightly sweet
• The flavor of a soil affects…
We don’t
recommend this!
Mike Lieberman of UrbanOrganicGardener.com
– 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 soil’s “flavor” as pH
~2~
What Exactly is pH?
power of…
…hydrogen ions (H+)…
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
0
1
2
etc.
3
 more acidic neutral more basic
6
4
5
7
8
9
10
10X
100X
1,000X
10,000X
100,000X
Concentration of
H+
~3~
11
12
13
1/
10
1/
100
1/
1,000
1/
10,000
1/
100,000
vs. distilled water
etc.
14
Finding the pH (without tasting)
Litmus paper colors shows pH
Hydrangeas’ colors reflect soil pH
Do-it-yourself
home test kits
Meters read pH directly
4
Strength of pH
• Acids release H+
• Bases suck up H+
• Acids and bases
neutralize each other
Biochar
~5~
Biochar
is basic (alkaline).
It can neutralize
acidic soil.
Soil’s Natural pH Varies
Light rainfall
& prairie 
neutral soils
Heavy rainfall
& forest 
acidic soils
Cultivated & developed soils often differ from native soils
Natural limestone
bedrock 
alkaline soils
Drought & desert 
alkaline soils
Soil pH
Strongly
Acidic
Mildly
Acidic
Neutral
Mildly
Alkaline
But soils can also differ from one yard to another.
6
Different Plants Like Different Soils
blueberry
lilac
ash
hydrangea
azalea
geranium
white birch
pomegranate
eucalyptus
~7~
Soil Ecology and pH
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
• Don’t like
extreme pH
• Worms avoid
acid pH
Supports
Plants
~8~
Supports
Animals
Unbalanced pH upsets
the whole community
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.
Examples: pH < 6.00
Mg deficiency
Mineral availability in solution
Nitrogen
Phosphorus
Potassium
Sulfur
Calcium
Magnesium
Iron
Manganese
Boron
Copper and Zinc
pH
Fe, Zn, Ma
deficiency
~9~
Source: Colorado State Extension
CMG, GardenNotes #222
Most Plants Like Near-Neutral Soils
Best for
minerals
Best for fungi
Best for
bacteria
~10~
Neutralizing
Because pH scale is not linear, neutralizing
different strengths takes very different
quantities
Equal distances from neutral,
use equal concentrations
0
1
2
3
acid = base
 more acidic neutral more basic
6
4
5
7
8
9
10
11
12
13
acid = base
14
acid = base
One pH number further from neutral,
use 1/10th
Two pH numbers further from neutral,
as much of the stronger
use 1/100th
as much of the stronger
~11~
How to Modify Soil pH
First – Test
Your Soil !!!!!
Adding organic matter to the soil
makes both acid and alkaline soils
more neutral.
Lower Soil pH
(improve alkaline soil)
Raise Soil pH
(improve acid soils)
Add one of following:
Add one of the following:
Granular sulfur
slow acting
Aluminum & Iron Sulfate
faster
need a lot
Acidifying fertilizer
Doesn’t work well for pH > 7.5
May contain a large amount
of calcium carbonate
Ground limestone
lasts a long time
Hydrated Lime
works quickly
easy to over-do
Wood Ashes
fast-acting
a little goes a long way
***** ALWAYS
FOLLOW DIRECTIONS ****
~12~
Biochar and pH
• Biochar is usually alkaline
• Biochar pH depends on the
pyrolysis temperature
biochar
neutralizes
acidic soil
typical
pH range
typical
formation
temperature range
NOTE: ash created by pyrolysis
is strongly alkaline (pH 12-13)
~13~
Using Biochar to Change Soil pH
First – Test • If your soil is already alkaline,
Your Soil !!!!! don’t use biochar!
• Because biochar is a pretty
strong base, use it sparingly
• To keep pH moderate, add small amounts
of biochar every few years, not all at once.
• If your soil is strongly acidic (<ph 5),
you can mix a small amount of ash into the biochar.
– Ash adds important minerals (calcium, sulfur,
potassium, phosphorus, magnesium)
~14~