9/19/2014 1 Alternative Media Components and their Potential Advantages and Limitations Todd Cavins, Ball Horticultural Co. Michael Evans, University of Arkansas Why do we need new components? • Always on the look out for something better and cheaper! PHYSICAL CHEMICAL BIOLOGICAL ECONOMIC structure stability water capacity air capacity bulk density wettability pH nutrient content organic matter noxious substances buffering capacity weeds, seeds and viable propagules pathogens pests microbial activity storage life availability consistency of quality cultivation technique plant requirements price Properties of growing media and their constituents that pertain to “quality”. * * G. Schmilewski , 2008 • Far fewer options for alternatives with plugs and cuttings. • Smaller substrate volume. • More “sensitive” cuttings and seedlings. • Most common component still used and most effective in most situation is peat. • Type and grades of peat vary with respect to properties and best use. Coconut Coir • Coir with minimal fiber is typically best for plugs and cuttings. • Be careful of high E.C. and remember pH is different from Sphagnum peat. • Coir typically holds more water and has less air space than a typical sphagnum peat. • Coir may be disease suppressive.
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Alternative Media Components and their Why do we need ......• Probably very limited use in substrates for plugs and cuttings. Rooting “Cubes” Numerous types including ^Oasis
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9/19/2014
1
Alternative Media Components and their Potential Advantages and Limitations
Todd Cavins, Ball Horticultural Co. Michael Evans, University of Arkansas
Why do we need new components?
• Always on the look out for something better and cheaper!
PHYSICAL CHEMICAL BIOLOGICAL ECONOMIC
structure
stability
water capacity air capacity bulk density wettability
• Some grind sizes have physical properties very similar to sphagnum peat.
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• Differences in chemical properties from sphagnum peat but at 30 - 40% of substrate are within acceptable ranges.
Composted Rice Hulls
• Hull has been broken down to produce a
small particle size.
•Dark brown to black in color.
•Physical properties vary with degree of
composting.
Composted
Hulls Peat
Total pores 85% 85% Air-filled pores 18% 15% Water-holding 67% 69% Bulk density 0.2 0.1
• Chemical properties varying with degree of composting and composting method.
• composting method
• amount and source of N
• pile age
• Typical pH of 5.4 to 5.7 and E.C. of 0.5 to 0.7 mmho/cm. •Macro- and microelements usually within acceptable ranges and not problematic so long as acceptable pH maintained. •Important to know source. •Test new batches of material.
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Biochars
• Oxidized (burned) organic matter under low oxygen conditions.
• Process using various methods including torification (torrefacation), pyrolysis and gasification.
• Processes varying in temperature and time and impact properties
Biochars
• The feedstock and the process greatly impact the products properties.
• Therefore, highly variable in physical and chemical properties.
• Various types have been
used successfully in trials and a mix component.
Biochars
Feed stock pH E.C. (mS/cm)
Poultry litter 6.8 28.0
Poplar 5.8 0.1
Miscanthus 9.3 1.7
Cotton gin 7.1 4.6
Rice hull 7.2 0.2
Pine shavings 4.6 0.9
Biochars
Vinca (L) and Geranium (R) in biochar-containing mixes fertilized with 200 ppm N and overhead irrigation.
• Variability and consistency can be a problem.
• Chemical properties of some can be a problem.
• Do not tend to absorb water very well.
• Probably very limited use in substrates for plugs and cuttings.
Rooting “Cubes”
• Numerous types including “Oasis” foam, rockwool and peat-based materials.
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• Push out of seedlings can be a problem in some types of cubes.
• Especially problematic with spinach, lettuce and some other types of greens.
Worm Casting & Vermicompost
• The practice of using worms to degrade organic materials
– Vermicompost = poop plus the bedding, etc.
– Worm Castings = just poop (finished)
– pH: 6.0- 7.0
– EC: 5+ mS/cm (SME)
– Bulk Density: 10 – 15 lbs/ft3
Worm Casting & Vermicompost
• The feed and bedding used can be highly variable, so the end
product can be highly variable
• Vermicompost is not acceptable to be used as the major
component in a mix (Mota et al., 2007)
• As vermicompost is increased, bulk density increases, water
holding capacity increases, and aeration decreases (Bachman & Metzger, 2007)
• Levels greater than 15% provide high levels of P limiting
mycorrhizal activity and potentially causing plant stretch. (Miller et al,
1997)
Worm Casting & Vermicompost
• Target volume of vermicompost: 10% (volume)
• Minimal impact on EC and pH
• Still provides some level of nutrient and biological activity
• Moisture retention
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Greenwaste Compost
Vital Earth, Ashbourne, UK
Greenwaste Compost
Vital Earth, Ashbourne, UK
Greenwaste Compost
Vital Earth, Ashbourne, UK
Greenwaste Compost
Vital Earth, Ashbourne, UK
Greenwaste Compost
• Composted yard waste
– Ideally grass, leaves and limbs
• Caution! What else?
– Herbicides, CCA wood, plastic, coat hangers
– pH: 7.0 – 8.0
– EC: 1.0 – 5.0 + mS/cm (SME)
– Bulk Density: 25-31 lbs/ft3
Greenwaste Compost
• Good microbial activity
• Good CEC
• Heavy – Shipping, aeration
• Micronutrients and pH – Some are good suppliers some are not
• Stability and N-draw down
• Limited substitution
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Wood Fiber Wood Fibers
• Two thermo-screw presses shred wood chips under pressure using steam
• Can be impregnated with nutrients
– pH: 6.0 – 6.5
– EC: 1.5 - 2.5 mS/cm (SME)
– Bulk Density: 5.5 – 6.5 lbs/ft3
Wood Fibers blended with Peat*
* G. Schmilewski , 2008
Wood Fibres
• Good physical properties • “Sustainable” • Prevents shrinkage
• Now readily available in the U.S. • $$$ for manufacturing equipment • N draw down • “Splinters”
Bill Carlile, Bord Na Mona
Available for Growing-on mixes Silicon is a beneficial plant nutrient