Indoor Science : Soil / Substrates & "Best Practices" from Nurseries.

[Rev. Green Genes]

Most of you will not care, but here is some compiled information from the nursery industry that can be applied while making decisions about media, containers, and some basic practices that pros don't usually talk about.

Carbon-to-Nitrogen (C:N) Ratio
C:N Ratio
Microbes . . . . . . . . . . . . . . . . . 8:1
Soil humus (organic matter). . . . . . . ..10:1
Grass clippings . . . . . . . . . . . . . .10:1
Tree leaves . . . . . . . . . . . . . . . 50:1
Uncomposted bark . . . . . . . . . . . 300:1
Sawdust . . . . . . . . . . . . ............ 400 to 700:1
Hardwood chips . . . . . . . . ...............600 to 1,000:1

Bulk density –
dry weight of media given as lb/yd3
–Nursery media: 12-24 lb/yd3 ( = 0.2-0.5 g/cc)
–Mineral soils: 40-50 lb/yd3
–Greenhouse potting media: 8-18 lb/yd3

Common Nursery Substrate Mixes Bulk density
–100% composted pine bark 14 lb/yd3 –3
pine bark:1 sand 36 lb/yd3–1
pine bark:1 sand (heavier mix) 56 lb/yd3–2
pine bark:1 sand:1 peat 45 lb/yd3–100%
sand (propagation mixes) 97 lb/yd3

Cation Exchange Capacity (CEC) of Nursery Media Mixes
Substrate Composition CEC meq/100 mg
•100% Composted Pine Bark 52
•3 Pine Bark:1 Sand 15
•1PB:1Sand 6
•100% Coarse Builder’s Sand 1*
•100% Peat 100
meq = “milliequivalents”



Percolation Rates of Various Nursery Media Mixes
Substrate Composition cm/15 min
•100% Composted Pine Bark 91
•3 Pine Bark:1 Sand 62
•1PB:1 Sand 35
•100% Coarse Builder’s Sand 15



• Cation Exchange Capacity (CEC) of Nursery Media Mixes
• 100% Composted Pine Bark 52
• 3 Pine Bark:1 Sand 15
• 1PB:1Sand 6
• 100% Coarse Builder’s Sand 1*
• 100% Peat 100
• Silt-loam 12-16
• Sandy loam 5-10

• Lowering pH Levels

• elemental sulfur (S), aluminum sulfate, ammonium sulfate [(NH4) 2SO4] & ferrous sulfate (FeSO4) have been used.
• Caution: if using ammonium sulfate or ferrous sulfate, you must account for extra nitrogen and iron that comes with these materials.
• Growers can also use high ammoniacal nitrogen-based fertilizers.
• This fertilizer source lowers media pH with time
• ammonium must be converted to nitrate to be used by the plant
• Done by soil microbial & chemical activity

• Raising pH Levels

• Use either calcined lime (CaCO3) or dolomitic limestone (mixture of CaCO3 and MgCO3 )
• Works best if pre-plant incorporated
• Is immobile in soil
• Typical rates range between 5 to 15 lbs/yd
• Small particles of crushed lime act faster than large ones
• CAUTION: pelletized granular limestone materials are actually fine powders glued with a binder • Fast-acting, can burn roots
• When these granules are exposed to water they fall apart into a fine powder
• may wash out of coarse media
• Other liming materials include:
• calcium oxide (CaO) = “quick” or burned lime• is very reactive, caustic & expensive • hydrated lime (Ca(OH)2) • fast-acting, caustic & expensive• egg/oyster shells • wood ash

• Raising pH Levels by “Fertigation” If you are using liquid fertilization (fertigation) you can also increase media pH • Switch from an acid-based fertilizer (i.e., high % nitrogen in ammoniacal form) • To a basic fertilizer (i.e., high % nitrogen in the nitrate form)



Effect of Container Depth on Air Spaces& Water Content
Pot Size - Aeration : Water
6-inch pot 21 % 49 %
4-inch pot 15% 56 %
Bedding Plant Cell (48/tray) 9% 61%
Plug TrayCell(273 cells) 3% 68%



PAR Range
• 400 to 700 nm wavelengths
• PAR is expressed in “millieinsteins per square meter per second”
– umol/m2/s
• Also use “foot candles” to describe light
– 5 fc = about 1 umol/m2/s
• Middle USA, Noon, Full Sun
– 10,000 fc or 2000 umol/m2/s – Shade ~1,000 fc (200 umol/m2/s)


• “Green” light
– little effective PAR for plant use
– Safelight to limit growth

• “Blue” light
– Phototropic responses
• Orientation to light

• “Red” light
– Photoperiodism
• e.g., daylength effects

Plants grown in sun become saturated at light levels ~2,000 - 3,000 fc. – Or, 400 - 600 umol/m2/s
Plants grown in shade become saturated at light levels ~ 500 - 1,000 fc. – Or, 100 - 200 umol/m2/s

How a Plant “Tells” You about Low Light Levels

• Long, thin stems
• Weak stems
• Pale foliage
• Widely separated leaves or internodes

Enjoy.

 

[Rev. Green Genes]

sorry, a lot of my tables lost the formatting somehow. Thats a bit hard to read.

 

[Dr. Babnik]

Cool!



This I will study. Questions will follow.

 

[Rev. Green Genes]

Cool!



This I will study. Questions will follow.

Thank you, I will post more on CEC, and about pH. There are actually two relevant pH measurements for outdoor use.. This was geared towards all the things I was considering when deciding what potting systems to use. I left out a bit about perched water table also.

 

[Dr. Babnik]

Thank you, I will post more on CEC, and about pH. There are actually two relevant pH measurements for outdoor use.. This was geared towards all the things I was considering when deciding what potting systems to use. I left out a bit about perched water table also.

Please do post more, Professor. I'll take my seat in your auditorium and listen carefully.

 

[Rev. Green Genes]

Like it!!

Science ... makes the world go round!

Let me know if you'd like the title changed to something catchy and informative! (may get some more sciencey types clicking if it was more decriptive)

Sure, dress her up and let's take her for a spin.

 

[Rev. Green Genes]

I think more people would take notice of the word soil than media, but ya, that sounds much better.

 

[Rev. Green Genes]

Thanks!

 

[pop22]

Excellent post! I look forward to more!

 

[Rev. Green Genes]

Soilless Media

Organic
Decomposed, pH stable
Organic & inorganic components
Holds moisture
Peat, bark, moss, coconut husk “coir”

Peat or Peat Moss
Partially decomposed aquatic, marsh, bog, or swamp vegetation
High water-holding capacity (15x dry)
High acidity (pH 3.2+)

Sphagnum Moss
Dehydrated acid-bog plants, Sphagnum spp.
Fungistatic
High water-holding capacity, up to 20x dry
High acidity (pH 3.5+)

Vermiculite
Heated, expanded mica
Magnesium-aluminum-iron silicate
Porous and light-weight
High water-holding capacity
High cation exchange capacity (CEC)

Perlite
•Gray-white silica, of volcanic origin
Heated, expanded
•Lightweight, pH neutral
•Good drainage
•Low water-holding capacity & CEC

Shredded bark & coconut fiber “Coir”
More research needed. I don't know much about it yet.... to come later.



Inorganic
Coarse, porous, improves drainage & aeration to roots
Sand, perlite, vermiculite, rockwool, Turface™


Sand
best forHardwood cutting propagation
Great drainage
Holds the least amount of nutrients
Very heavy-consideration if used in mix
Sterilization recommended
Organic or inorganic?




Environmental Factors and management of propagation:


Quality of irrigation & misting water
Low salinity tolerance of unrooted cuttings and germinating seeds
Salt = ionic bond between a cation(+) & anion(-)
Ca+2Cl-, MgSO, CaCO, Na+Cl-243
Hard water (high Ca++, Mg++) buildup
Irrigation system--clogs lines & misters
On leaves-reduces photosynthesis (Pn)

Overwatering (change soil environment)
 Root rots & damping off organisms
 Suffocation (lack of oxygen)
 2 stress-related phytohormones
Too-high humidity = excessive condensation
 Promotes fungi & other pests
 In media & directly on plants
 Foliage leached of nutrients
 Reduces cutting propagule health

Intermittent fog & mist
Provide conditions that reduce wilting of cuttings until established
relative humidity (RH) at 90% or higher
leaf temperature via
evaporative cooling
intercepting light intensity
Fog better than mist, Mist-falls quickly
Fog-remains suspended until evaporation
Maintains zero-transpiration without over wetting

Every plant process is temperature-driven
 up & down extremes: detrimental to plants. ie. Wilted cuttings
Germination, rooting, graft union formation, growth, disease incidence…
Bottom heat allows efficient root zone heating and does not encourage wilting

Light intensity
How strong
Duration
Day length (Photoperiod)
Quality
Wavelengths
Quantity
How much over a period of time

Influence of intensity, duration, quality, quantity
Growth (photosynthesis (Pn), transpiration)
Delay or increase flowering
Stretching/etiolation
Stock plant health
Root initiation of cuttings
Germination
carb reserves
winter survival & spring growth

Manipulated via:
Greenhouse filters & coverings
Supplemental light

Seed germination, plug development, rootingare all high respiration processes
Ethylene emitted by cuttings can cause Stress in a closed environment, or in shipping.

Fertilization after cutting propagation
Liquid; Soluble
Immediately released
Automatic injection application
Dry granules weighed
Concentrated solution

A fertilizer grade or analysis that appears on the bag gives the percentages of nitrogen (N), phosphate (P2O5) and potash (K2O) in the material. A 5-10-15 grade fertilizer contains 5 percent N, 10 percent P2O5 and 15 percent K2O. A 50-pound bag of 5-10-15 fertilizer contains 2.5 pounds of N (50 x 0.05 = 2.5), 5 pounds of P2O5 (50 x 0.10 = 5) and 7.5 pounds of K2O (50 x 0.15 = 7.5).

Environmental Effects on Organic Nutrient Uptake Soil Temperature
– Early Spring is cool and soil temperatures rise slowly to the point where microorganisms are active. Until the soil warms sufficiently and the organic fertilizer materials are broken down into their useable form, these fertilizers may not successfully stimulate plant growth.

Soil Moisture – In addition to warmer temperatures, soil microorganisms need a moist soil to grow and thrive. If rainfall is not adequate, crops may need to be irrigated for good nutrient release.

EC testing.

PourThrough test

Extraction Procedure:
The PourThru extraction procedure does not disturb plant roots as is necessary with other extraction procedures such as the Saturated Medium Extract procedure used at many commercial testing labs or the 1 to 2 procedure previously used by growers. In brief, 30 minutes to two hours after irrigation, pour approximately 1/2 cup (120 milliliters; 4.0 fl.oz.) of water over the surface of a 1 gallon container or 1.5 cups (360 milliliters; 12 fl.oz.) over a 3 gallon container for pine bark : sand potting mixes. More water may be required if the container mix contains sphagnum peat moss or other organic substrate amendments. Distilled water is recommended for determining existing leachate concentrations, however using water from irrigation risers for most production conditions is acceptable since the irrigation water contributes to the pH, EC and nutrient levels in the container. Reading the EC of the irrigation water and subtracting it’s EC value from the container leachate EC indicates soluble salt concentrations in the container derived from fertilizer.

Leachate solution can also be obtained by picking up containers and tipping the container to drain leachate from drainage holes. Tipping the container 30 to 60 minutes after irrigation of containers provides a true reading of EC and pH levels in the container solution available to plant. It is important to remember that the PourThru extraction procedure provides an average of EC and pH concentrations in the container. If fertilizer is placed in one spot on one side of the plant in the container, the Pour Thru will not provide an accurate reading for the concentrated zone around the fertilizer; it will provide an average reading for the container.

* Irrigate nursery containers to container capacity (10% to 20 % leaching expected).
* Wait 30 minutes to 2 hours for equilibration of nutrients in container solution.
* Place containers to be tested in a shallow saucer to collect leachate.

Pour 1/2 cup (120 milliliters; 4.0 fl.oz.) of water over the surface of a 1 gallon container
Pour 1 1/2 cups (360 milliliters; 12 fl.oz.) over the surface of a 3 gallon container