A biotic approachto erosion control by building soil
without importing topsoil
Construction Engineering Design
• Always attempt to minimize amount of earthwork to minimum necessary
• Is intended to reduce risks as much as possible
After Construction
the erosion control part of the project start and ……
• Organic Matter Lost (usually due to removal) • Loss of micro and macro pores (air/water exchange)
The Biotic Approach Ask:
Is importing topsoil really needed for establishing vegetation and therefore
control erosion?
Natural Soil Profile
Topsoil is imported only to add the ORGANIC MATTER needed
Why Topsoil is Added?
Conventional approach to Erosion Control
A typical Standard Specifies a Minimum of 5 cm Topsoil. To achieve this it is required to transport and manage the equivalent of 25 trucks per hectare loaded each one with 20 cubic meters of soil
Biotic Approach to Erosion ControlJust what is needed
Construction Engineering Design
• Always attempt to minimize amount of earthwork to minimum necessary. However, when the Agronomic part of the project starts (erosion Control) the design criteria changes, why?
• Because the designers are usually civil engineers and because this part of the project is typically the smallest
Biotic Approach• Amend the existing soil with the right organic matter
and fertilizer and tillage the soil if needed to improve the physical conditions. By doing this vegetation can be established without the need of importing TOPSOIL.
• The Biotic Approach follows the design criteria of minimizing the amount of earthwork and Is intended to reduce risks as much as possible.
What sources of organic matter are available?
– Compost (although it can contain some nutrients, frequently it is not consistent in texture and quality and might import contaminants such as hydrocarbons, metals, pathogens, pesticides and weeds
– Peat Moss (the best source of organic matter available and the best growing medium)
Compost Sock in Toronto
Why Peat Moss is the best?This photomicrograph of a peat moss particle shows it’s natural capillary and porous structure (natural sponge). It increases many times the water and nutrient retention as compared with any other source of organic matter (compost, manure, wood, etc. The peat absorbs inside water and nutrients and avoid the leachate and loss of nutrients to the environment.
This is why it is the Most popular green house growing medium of the world.
HONEYCOMB STRUCTURE
Peat Moss• Most popular green house growing
medium in the world. • Consistent in texture and quality• Honeycomb structure holds inside water
and nutrients• Weed and contaminants free
What prevents the Peat Moss to be washed away?
Peat Moss in combination with Straw, Flexible Flax Fibers and a stabilizing emulsion or tackifier creates a stable matrix which temporarily protects exposed soil from erosion and fixes the peat on place, and works as an excellent growing medium that accelerates the grass growth that eventually will protect permanently the soil.The source of these materials?Biotic Earth ™ Growth Medium
Flexible Flax Fibers
Straw
Why Biotic Earth ™ Growth Medium
• Other mulches look for increasing the temporal protection of the soil by making the mulch last longer using synthetic materials
• Biotic Earth™ Growth Medium protect the soil but additionally are excellent growing mediums that make the grass to establish faster, reducing the risk because the planted area will be totally vegetated sooner.
The Biotic Earth ™ Growth Medium Family
• Biotic Earth™ Black
• Biotic Earth™ HGM
• Biotic Earth™ BFM
CASE STUDY
• 70% Straw with FFF (flexible flax fiber)
• 30% Canadian Sphagnum Peat Moss (growth medium)
• By volume.
Hydro Quebec James Bay
• Northern Canada• Boreal Forest• No topsoil • Short Growing
Season
We just added what was needed, THE BEST SOURCE OF ORGANIC MATTER
One Year Later
One Year Later
To mimic nature a seed mix was used
• Creeping Red Fescue• Timothy• Bent Grass• Birdfoof Trefoil• White Clover Barley• Reed Canary Grass
Bird River
Success adding just what was needed, the best source of ORGANIC MATTER
CASE STUDY
• 60 % Sphagnum Peat Moss• 40 % Straw with FFF• Mycorrhizae• Tricontonal Growth Stimulant • Micro Nutrients
Bird River Manitoba
• Manitoba, Infrastructure and Transportation Cut Slopes
• Done in 2003
2250kg/ha or 2000lbs/acre
Black HGM requires erosion protection on slopes 3:1 or steeper. C32 was used for it’s longevity.
40 days after seeding
Milner Ridge Manitoba• Government of Manitoba• Medium Security Jail• 70,000 square meter waste water pond
• PROBLEM– Very sandy material– marginal natural topsoil – not reclaimable
Very Erodible Sand
Challenge
• 70,000 square meters pond• $6.00 per square meter to import topsoil
= $420,000• Plus seeding and erosion control cost
Marginal topsoil layer
3900kg/ha 3500lbs/acre
Seed, fertilizer added right in the mix
Complete Ground Cover
Biotic Approach Building the O Horizon (mimic nature)
2 weeks later
3 weeks later
7 weeks later
13 Weeks later
Effects of mycorrhizea (a strong root system)
Biotic Layer mimic the natural O horizon
“Our Expectations of the finished product has been far exceeded”
Harry Schroeder, P.Eng, LEED AP
• 70% Straw with FFF• 20% Canadian sphagnum peat moss• 10% Tackifier and growth stimulants
Glue added during manufacturing
Peat moss added
Biotic Earth™ BFM
• Used in slopes up to 1:1• Where you need effective erosion
control and a biotic HGM
To maximize biotic performance
• Conduct a minimum of 3 soil tests to determine– Soil pH (to know if you need to add lime or sulphur)– Fertility requirements (Slow release fertilizers optimal)
– Organic content and requirements.
In challenging situations conducting these tests is critical to helping improve your vegetation in the short and long term.
Venezuela Case Study 2009A rail road embankment was constructed using sub soil in Venezuela by Astaldi (Italian company). It needed slope protection in 80 kilometres. Topsoil was specified for the construction. Because there were no sources of adequate topsoil in adjacent areas, the cost of the topsoil addition was far away out of budget.
The embankment soil characteristics were:
• pH 5 (acid)• Organic Matter less than % 2• Fertility extremely poor (P < 4 ppm, K = 10 ppm, Mineral N (traces),
Mg = 47 ppm)• Soil Particles: Sand 54.8%, Silt 18% and Clay 27.2%
SOLUTIONThe solution was to spray a layer of organic matter composed of a biotic growing medium. Before it, soil samples were taken and the soil was limed accordingly to the low pH. With the biotic growing medium, appropriate amounts of fertilizer and seeds of two varieties of grasses adapted to tropical conditions were added.
RESULTS
BEFORE AFTER AERIAL VIEW
Slope Soil Erosion was avoided due to fast vegetation growth without the addition of a topsoil layer, therefore saving a lot of money
Summary• Mimic nature (building soil)• Faster growth = lower risk• Using a Growth Medium helps • Peat moss – consistent organic material• Straw – natural wide mulch• FFF- Flexible Flax Fiber• Topsoil is not needed in most cases