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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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Phytotophthora nicotiana

peat; unautoclaved peat; autoclaved

coir; unautoclaved

coir; autoclaved seed treatment

Phytotophthora capsici

peat; unautoclaved

peat; autoclaved

coir; unautoclaved

coir; autoclaved seed treatment

Ground Cork Vermiculite is often used as a top coating substrate for plug production.

Various issues have promoted a desire for alternative top coating materials.

Ground cork is a by-product from the production of various cork-based products.

Cork may be ground and screened to produce several sizes.

Frequent misting used to maintain moist top coat.

Plugs fertilized with 50 ppm N after first true leaves began to develop.

Placed in polycarbonate-glazed greenhouse at temperature set points of 19 C and 22 C.

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Physical Properties

**

Physical Properties

‘Orbital Cardinal Red’ Geranium ‘Orbital Cardinal Red’ Geranium

‘Orbital Cardinal Red’ Geranium

‘Score Deep Red’ Geranium

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‘Dazzler Lilac Splash’ Impatiens ‘Rutgers Select’ Tomato

‘Better Belle’ Pepper

Ground Parboiled Fresh Rice Hulls • Physical properties depends on grind size.

• 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

• Thicker, stronger stems

• Increased drought tolerance

• Resistance to insects and diseases

• Dense, more compact plants

• Increased tolerance to pH drift

S. Kamenidou, 2002

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Typical Silicon Results Brussels Sprouts Week 19: 4 weeks after sowing

Standard

Brussels Sprouts Week 19: 4 weeks after sowing

• Brussels sprouts plugs produced in Resilience mix developed earlier than those grown in the standard mix.

Standard

Brussels Sprouts Week 19: 4 weeks after sowing

• Brussels sprouts rooted better in Resilience mix than in standard mix.

Standard

Pepper ‘Tomcat’ Week 23: 7 weeks after sowing

• Peppers rooted better in Resilience mix than in standard mix.

Standard

Tomato ‘Bobcat’ Week 19: 4 weeks after sowing

Standard

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Tomato ‘Bobcat’ Week 19: 4 weeks after sowing

• Tomato plugs produced in Resilience mix developed earlier than those grown in the standard mix.

Standard

Tomato ‘Bobcat’ Week 19: 4 weeks after sowing

• Tomatoes rooted better in Resilience mix than in standard mix.

Standard

Sunflower ‘Sunny Smile’ Week 19: 4 weeks after sowing

• Sunflower rooting was about the same in both mixes.

Standard

Zinnia ‘Magellan Cherry’ Week 19: 4 weeks after sowing

• Zinnias rooted better in Resilience mix than in standard mix.

Standard

Miscanthus Ornamental Grass Week 25: 9 weeks after sowing

Standard

Miscanthus Ornamental Grass Week 25: 9 weeks after sowing

• Miscanthus rooted better in Resilience mix than in standard mix.

Standard

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Ground Cedar Ground Cedar

• Historically – we have said Cedar (Juniperus

virginiana) is allelopathic.

• Likely not – Kansas State and Auburn

Universities say otherwise.

• Nursery and finished greenhouse focus – not

plugs

Ground Cedar Table 3. Physical properties of bark mixes with distilled cedar chips replacing bark or perlite components.

Treatment Total Porosity

(%) Container

Capacity (%) Air Space (%)

Dry Bulk Density (g/cc)

Control 94.2% 75.2% 19.0% 0.10

10 BR 83.3% 61.5% 21.9% 0.11

20 BR 40.1% 8.2% 31.9% 0.11

30 BR 41.7% 10.3% 31.4% 0.10

Table 4. Physical properties of peat mixes with distilled cedar chips replacing perlite.

Treatment Total Porosity

(%) Container

Capacity (%) Air Space (%)

Dry Bulk Density (g/cc)

Control 86.4% 60.2% 26.2% 0.09

5 PR 87.9% 51.3% 36.5% 0.09

15 PR 36.3% 12.7% 23.6% 0.10

25 PR 39.9% 7.6% 32.2% 0.09

35 PR 43.1% 10.5% 32.5% 0.10

Cedar will work!

Figure 1. ‘Freedom Red’ poinsettias 8 weeks after transplant into bark-based substrates with 0% and 30% bark replaced with cedar.

Figure 3. ‘Pinto™ Red’ geraniums 5 weeks after transplant into peat-based substrates with 0% and 35% perlite replaced with cedar.

Lots of others… Little Info or Limitations

• Composted Manure

• Nut shells/hulls

• Straws

• Kenaf

• Bagasse

• Grape Marc

• Plastic foams

Todd Cavins Ball Horticultural Company

tcavins@ballhort

Michael Evans University of Arkansas

mrevans@uark.edu