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Understanding Bark, Peat, and Pumice in Your Soilless Substrate
J.S. Owen Jr., M. Zazirska-Gabriel, and D. SullivanOregon State University, Aurora, OR
J.E. AltlandApplication Technology Research Unit, USDA-ARS, Wooster, OH
J.P. Albano US Horticultural Res. Lab, USDA-ARS, Fort Pierce, FL
Douglas Fir BarkDouglas Fir Bark
AGED FRESH
Altland
Data CollectionData Collection3-inch coresPorometers
Total porosity (TP)Container Capacity (CC)Air Space (AS)Bulk Density (Db)
15-bar plate (1.5 inch cores)Unavailable waterAvailable water
General TrendsGeneral Trends
ShrinkAged 5.63 mmFresh 0.08 mm
Total porosity remained constant
Year 1Year 1
0
20
40
60
80
100
0 3 6 12 0 3 6 12
Per
cen
t vo
lum
e
FreshAgedTime (months)
46%»29%
59%»50%
Air Space (AS)
Per
cen
t vo
lum
e
FreshAged
Time (months)
42%»58%
27%»34%
Container Capacity (CC)
Year 1Year 1
Year 2Year 2P
erce
nt
volu
me
FreshAged
Time (months)
47%»59%
34%»47%
Container Capacity (CC)
Year 2Year 2P
erce
nt
volu
me
FreshAged
Time (months)
Up to 80% unavailable water
Container Capacity (CC)
Up to 60% unavailable water
Corresponding Research
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
o2 (taxa) x 7 (substrate treatments)
oRandomized complete block design
oWeigela florida 'Polka' and Azalea ‘Girard’s Fuchsia’
o4 containers per 4 replications
o2 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
Material & Methods
Initial physical properties
Initial physical properties
Initial physical properties
Initial physical properties
Weigelia crop response
Peat
Weigelia crop response
Peat Peat Pumice
Percent addition (by vol.)
Dry
weig
ht
(g)
Significant (p < 0.05 ) linear and quadratic response for peat and pumice, respectively
peat vs pumice **bark vs peat **bark vs pumice NS
45%
Control(100% DFB)
Percent addition (by vol.)30%15%
Pu
mic
eP
eat
Water applied to Weigelia (0.2 LF)
Significant (p < 0.05 ) linear response for peat.
Peat Pumice
Percent addition (by vol.)
Wate
r ap
plied
(L)
peat vs pumice **bark vs peat **bark vs pumice NS
Weigelia water status as ƒ(leaf length)
*Significant (p < 0.05 ) linear and quadratic response for peat and pumice, respectively
Peat Pumice
Percent addition (by vol.)
peat vs pumice NSbark vs peat **bark vs pumice **
Azalea crop response
Azalea crop response
Peat Peat Pumice
Percent addition (by vol.)
Dry
weig
ht
(g)
peat vs pumice NSbark vs peat **bark vs pumice NS
Significant (p < 0.05 ) linear response for peat.
Azalea water use efficiency (WUE)
Peat Pumice
Percent addition (by vol.)
WU
E (
g m
L-1)
peat vs pumice NSbark vs peat **bark vs pumice NS
Significant (p < 0.05 ) linear response for peat.
45%
Control(100% DFB)
Percent addition (by vol.)30%15%
Pu
mic
eP
eat
Significance to IndustrySignificance to IndustryLinear 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
Jim Owen: 503.678.1264 or [email protected] Owen: 503.678.1264 or [email protected]
