Understanding Bark, Peat, and Pumice in Your Soilless Substrate

Understanding Bark, Peat, and
Pumice in Your Soilless Substrate
J.S. Owen Jr., M. Zazirska-Gabriel, and D. Sullivan
Oregon State University, Aurora, OR
J.E. Altland
Application Technology Research Unit, USDA-ARS, Wooster, OH
J.P. Albano
US Horticultural Res. Lab, USDA-ARS, Fort Pierce, FL
AGED
FRESH
Altland
!!3-inch cores
!!Porometers
"!Total porosity (TP)
"!Container Capacity (CC)
"!Air Space (AS)
"!Bulk Density (Db)
!!15-bar plate (1.5 inch cores)
"!Unavailable water
"!Available water
!!Shrink
"!Aged 5.63 mm
"!Fresh 0.08 mm
!!Total porosity remained
constant
Percent volume
Air Space (AS)
59%»50%
46%»29%
Aged
Fresh
Time (months)
Percent volume
Container Capacity (CC)
42%»58%
27%»34%
Aged
Fresh
Time (months)
Percent volume
Container Capacity (CC)
47%»59%
34%»47%
Aged
Fresh
Time (months)
Percent volume
Container Capacity (CC)
Up to 60%
unavailable water
Up to 80%
unavailable water
Aged
Fresh
Time (months)
Corresponding Research
Material & Methods
Dougals fir bark (<3/8 in) (DFB) with:
•!0, 15, 30, 45% (by vol.) screened pumice
•!0, 15, 30, 45% (by vol.) sphagnum peat
Chemical Amendments
•!15-9-12 CRF
•!Dolomite + Micromax
Physiochemical Analysis
•!Porometer
•!Particle size
•!Pourthru (pH and EC)
Material & Methods
o!2 (taxa) x 7 (substrate treatments)
o!Randomized complete block design
o!Weigela florida 'Polka' and
Azalea ‘Girard’s Fuchsia’
o!4 containers per
4 replications
o!2 gallons containers
Material & Methods
Crop Response
•!Root and shoot dry weight
•!60 and 120 days
Water Relations
•!Water use efficiency of
productivity
•!Water use efficiency of
photosynthesis
•!Leaf area and length
Initial physical properties
Peat
Pum
ice
Percent addit
ion (by vol.)
Initial physical properties
Peat
Pum
ice
Percent addit
ion (by vol.)
Initial physical properties
Peat
Pum
ice
Percent addit
ion (by vol.)
Initial physical properties
Peat
Pum
ice
Percent addit
ion (by vol.)
Weigelia crop response
Weigelia crop response
Dry weight (g)
peat vs pumice **
bark vs peat
**
bark vs pumice NS
Peat
Pumice
Percent addition (by vol.)
Significant (p < 0.05 ) linear and quadratic response for peat and pumice, respectively
Pumice
Peat
Control
(100% DFB)
15%
30%
Percent addition (by vol.)
45%
Water applied to Weigelia (0.2 LF)
Water applied (L)
peat vs pumice **
bark vs peat
**
bark vs pumice NS
Peat
Pumice
Percent addition (by vol.)
Significant (p < 0.05 ) linear response for peat.
Weigelia water status as ƒ(leaf length)
peat vs pumice NS
bark vs peat
**
bark vs pumice **
Peat
Pumice
Percent addition (by vol.)
*Significant (p < 0.05 ) linear and quadratic response for peat and pumice, respectively
Azalea crop response
Azalea crop response
Dry weight (g)
peat vs pumice NS
bark vs peat
**
bark vs pumice NS
Peat
Pumice
Percent addition (by vol.)
Significant (p < 0.05 ) linear response for peat.
Azalea water use efficiency (WUE)
WUE (g mL-1)
peat vs pumice NS
bark vs peat
**
bark vs pumice NS
Peat
Pumice
Percent addition (by vol.)
Significant (p < 0.05 ) linear response for peat.
Pumice
Peat
Control
(100% DFB)
15%
30%
Percent addition (by vol.)
45%
!!Linear increase in air space and
container capacity (0.6 to 1.3% vol. month-1)
!!Water Management
(0.2L to 0.5L per 3.8L cont.)
!!Growth appears to correlate
with available water

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