Rev. Green Genes
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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.
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.
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