Garden

Biochar Trial Photos

Empty Planting Trays on Rack	Fine Wet Processed Charcoal Settling in Flask	Bamboo Feedstock	Softwood Chip Feedstock
Charcoal Production in Woodgas Stoves	Charcoal Grades	Char Measurement
Amended Pots Prior to Mixing	Pots Mixed and Seeds Sown	Growth After 9 Days	Wheat and Peas Seperated to Avoid Shading

Some design features below:
Exploring interaction effects of feedstock type, soil, char application
rate, crop species, char size, fertilization, and mycorrhizal fungi.
No repetition (n=1), this loses the ability to assign a statistical
significance level to results, but allows more interactions (96 unique
combinations, 96 pots) to be tried given limited resources.

Charcoal produced in WoodGas stoves.
Char yield 12-18% (char mass/air dry biomass mass) (ie not adjusted to conventional dry weight yield unit, yet).
Fine Char - Blended and sieved to 230 mesh (<63 micron).
Coarse Char - Blended and sieved to between ~24 mesh - 8 mesh.
Fertilizer - 4-4-4 NPK Organic (bone meal, feather meal...)
Potting Soil - Potting Mix
Sandy Soil - Mixture of Horticultural Sand and Sandy Loam from Central Valley

Pots arranged in random spatial order (to randomize light/watering variation). Trays rotated to limit effects of light/watering variation.
Automatic drip emitter watering. Pots grown in enclosed cage outdoors.

Blocks - ( 8 pots/block)
    Fertilizer {Yes,No}
    Plant {Wheat, Pea}
    Soil {Sandy, Potting}

Blocks - (12 blocks * 8 pots/block = 96 pots)
    B1 -    Char (0 g)
    B2 -    Char (1 g, Pine, Fine)
    B3 -    Char (1 g, Pine, Coarse)
    B4 -    Char (1 g, Bamboo, Fine)
    B5 -    Char (1 g, Bamboo, Coarse)
    B6 -    Char (5 g, Pine, Fine)
    B7 -    Char (5 g, Pine, Coarse)
    B8 -    Char (5 g, Bamboo, Fine)
    B9 -    Char (5 g, Bamboo, Coarse)
    B10 -   Char (0 g) + Mycorrhizae
    B11 -   Char (5 g, Pine, Coarse) + Mycorrhizae
    B12 -   Char (10 g, Pine, Coarse)
 

Bear Kaufmann. Initially posted April 7, 2008. Updated August 5, 2008.

Images showing trial preparation and radish germination
(Select image to enlarge in Gallery.)

Materials/Methods

Char was Lazzari Brand mesquite BBQ char (due to availability), crushed and screened to 1/8".
No nutrients were added to the char itself or to the soil.
Soil was FoxFarm OceanForest Potting Soil.
Sand used was horticultural sand.
No mycorrhizal fungi were added.
Mixtures range from 0-100% sand, soil, and char in ~16% increments by volume. 90 pots total. 28 combinations with 3 pots each + 6 additional pots at 33%/33%/33% composition. Pots were placed randomly within the tray. Tray was rotated 180° occasionally.
Plants were watered daily by a drip irrigation system.
Plants were removed from pots ~1 month after first watering. Soil was rinsed from roots and roots were patted dry with a towel. Wet weight of roots+shoots was measured (Acculab VI-3mg, 0.001 g precision).

Figure 1. Box Plots Showing Effect of Composition Across Three Transects

Figure 2. Pictures of Radishes at Important Compositions

Results

Plant growth was stunted even for the best preforming plants, likely due to the small pot size. Leaf color varied across different compositions.
A mixture of 33% charcoal and 67% soil had the best growth (176% of pure soil). Aside from mixtures around this level (Figure 1b), high levels of charcoal showed a generally negative effect on plant growth (Figure 1c).

Discussion

The positive interaction effects of charcoal and soil (Figure 1a,1b) are interesting. Assuming charcoal itself provides no integral nutrients to the soil (eg. nitrogen), increasing amounts of charcoal reduce nutrients available from the soil mixture. The effects at 33% char/67% soil, however, show beneficial effects. This could be explained by increased mineralization rates caused by the charcoal causing soil nutrients to be more available to plants. Beyond 33%, the Cation Exchange Capacity of the charcoal may have held the nutrients produced by mineralization, making them less plant available. Since the charcoal was not amended/soaked in a nutrient bearing solution it likely had a low Base Saturation leading to adsorption of nutrients as they became available. Other potential explanations for increased growth along the soil/char transect include alterations to pH or limiting nutrients (eg potassium(?)) provided by the charcoal. The speculative mineralization/CECi model could also explain the effects seen along the sand/char transect. Here, since the sand lacks organic materials and bound nutrients for soil microorganisms to make plant available, the increasing unsaturated CEC may have made any nutrients less plant available.

Author: Bear Kaufmann bear at ursine-design.com

Gardening with Biochar FAQ (Wiki)
Philip Small, May 21, 2008

Welcome to a Gardening with Biochar FAQ!
... a work in progress...

When gardeners add biochar to garden soil, we are, in effect attempting to follow in the footsteps of the originators of Terra Preta. Because we don't know exactly how that process worked, nor how we can best adapt it outside its area of origin, we are left to discover much of this by experimenting with our own gardens and comparing observations within our own communities.

See:

Gardening with Biochar FAQ (Wiki)

Partially burned material a boon to plants: Sandy (Oregon) resident sees biochar as a way to fertilize and capture carbon
By Garth Guibord, The Gresham Outlook, Mar 30, 2007

When most people see a pile of sticks and wood, all they see is sticks and wood. Sandy resident Paul Elmore, 39, sees possibilities. He sees biochar – burned organic material that can be used to make plants grow.

Richard Haard: Affinity of fungi and crop plant roots to charcoal
Richard Haard, February 12, 2007

The image below illustrates the affinity of fungi and crop plant roots to charcoal.

Charcoal placed in a fertile garden for a few months showing how crop roots (Swiss chard) and fungi are attached to this medium as habitat