Soil Microclimate and Degradation of Biodegradable Plastic ...
1
Soil Microclimate and Degradation of Biodegradable Plastic Mulch Henry Sintim 1 , Marie English 2 , Andy Bary 1 , Mustafa Saglam 1 · 3 , Sean Schaeffer 2 , and Markus Flury 1 1 Department of Crop & Soil Sciences, Washington State University, Puyallup, WA · 2 Biosystems Engineering and Soil Science, The University of Tennessee, Knoxville, TN · 3 Department of Soil Science & Plant Nutrition, Ondokuz Mayis University, Samsun, Turkey Introduction There has been increased interest in biodegradable plastic mulch in recent decades due to the limited disposal options for polyethylene mulch. However, sustainable application of biodegradable plastic mulch will depend on how well they maintain microclimate to support plant growth and undergo complete degradation. Objectives 1. Evaluate the effects of biodegradable plastic mulch on soil microclimate 2. Evaluate the degradation of biodegradable plastic mulch in soil and in compost 3. Determine whether micro-residues are released upon degradation of biodegradable plastic mulch Materials & Methods Sites: I Knoxville, TN and Mount Vernon, WA Plant: I Pie pumpkin (Cucurbita pepo L.) Mount Vernon Knoxville Map showing field sites Mount Vernon field site under pie pumpkin production Mulch treatments: I Bareground (control treatment) I Biodegradable plastic mulch (PLA/PHA; Metabolix Inc., Cambridge, MA) I Polyethylene plastic mulch (Filmtech, Allentown, PA) Soil Microclimate Soil water content: I Measured at 10cm and 20cm depths Soil temperature: I Measured at 0cm, 10cm, and 20cm depths Light illuminance: I Light illuminance (soil surface and directly underneath mulch) Mulch Degradation Degradation in soil and in compost: I Harvested mulch samples and cut into 10cm×12cm I Placed mulch samples in Nylon meshbags (250μm opening) I Buried meshbags in soil at 10cm depth and retrieved every six months I Placed meshabgs in compost pile at 60cm depth and retrieved every two weeks I Determined mulch degradation by image analysis (ImageJ software) Release of micro-residues: I Visual observation of meshbags I Electron Microscopy I Electrophoretic mobility test Burial of meshbag in soil Meshbags retrieved after two weeks of composting Results: Light Intensity g Light illuminance as affected by mulch: Jul Aug Sep 10 0 10 1 10 2 10 3 10 4 10 5 Bareground PLA/PHA Polyethylene Date Light illuminance (lux) I Light Illuminance reduced by 2 orders of magnitude below mulch I Comparable light illuminance of Polyethylene and PLA/PHA Results: Soil Water Content g Soil water content as affected by mulch: Jul Aug Sep 0.0 0.2 0.4 Date Water content (m 3 m -3 ) Bareground PLA/PHA Polyethylene Knoxville Jun Jul Aug Sep 0.0 0.2 0.4 Date Water content (m 3 m -3 ) Bareground PLA/PHA Polyethylene Mount Vernon I Increased soil water conservation of Polyethylene and PLA/PHA Results: Soil Temperature g Soil temperature as affected by mulch: Jul Aug Sep 0 10 20 30 40 Date Soil temperature ( o C) Bareground PLA/PHA Polyethylene Knoxville Jun Jul Aug Sep 0 10 20 30 40 Date Soil temperature ( o C) Bareground PLA/PHA Polyethylene Mount Vernon I Increased early season soil warming of Polyethylene and PLA/PHA Results: Mulch Degradation g Degradation in soil: Polyethylene PLA/PHA Initial Knoxville 12-month Mt. Vernon 12-month Degradation in compost: Polyethylene PLA/PHA Initial Week 8 Week 18 I Minimal degradation of PLA/PHA in soil I >99% degradation of PLA/PHA after 18 weeks of composting Results: Release of Micro-residue g Electron Microscopy: 500μm 500μm 500μm Unused meshbag Composted PLA/PHA Composted Polyethylene 50μm 50μm 50μm Electrophoretic mobility: ï ï ï 0 4 8 Time (week) ● Carbon black PLA/PHA Polyethylene Electrophoretic mobility (μm s / V cm ) -1 -1 ● ● ● I Micro-residues observed after composting for 18 weeks I Some micro-residues may be carbon black Conclusions g I Microclimate of biodegradable plastic mulch comparable to polyethylene mulch I Incomplete breakdown of biodegradable plastic mulch Acknowledgement g Washington State University fl[email protected] [email protected] University of Tennessee
Transcript of Soil Microclimate and Degradation of Biodegradable Plastic ...
Soil Microclimate and Degradation of Biodegradable Plastic MulchHenry Sintim1, Marie English2, Andy Bary1, Mustafa Saglam 1·3, Sean Schaeffer2, and Markus Flury1
1Department of Crop & Soil Sciences, Washington State University, Puyallup, WA · 2Biosystems Engineering and Soil Science, The University of Tennessee,Knoxville, TN · 3Department of Soil Science & Plant Nutrition, Ondokuz Mayis University, Samsun, Turkey
IntroductionThere has been increased interest in biodegradable plastic mulch inrecent decades due to the limited disposal options for polyethylenemulch. However, sustainable application of biodegradable plastic mulchwill depend on how well they maintain microclimate to support plantgrowth and undergo complete degradation.
Objectives1. Evaluate the effects of biodegradable plastic mulch on soil
microclimate2. Evaluate the degradation of biodegradable plastic mulch in soil and
in compost3. Determine whether micro-residues are released upon degradation of
biodegradable plastic mulch
Materials & MethodsSites:I Knoxville, TN and Mount Vernon, WA
Plant:I Pie pumpkin (Cucurbita pepo L.)
Mount Vernon
Knoxville
Map showing field sites Mount Vernon field site under piepumpkin production
Mulch treatments:I Bareground (control treatment)I Biodegradable plastic mulch (PLA/PHA; Metabolix Inc., Cambridge,
MA)I Polyethylene plastic mulch (Filmtech, Allentown, PA)
Soil MicroclimateSoil water content:I Measured at 10cm and 20cm depths
Soil temperature:I Measured at 0cm, 10cm, and 20cm depths
Light illuminance:I Light illuminance (soil surface and directly underneath mulch)
Mulch DegradationDegradation in soil and in compost:
I Harvested mulch samples and cut into10cm×12cm
I Placed mulch samples in Nylonmeshbags (250µm opening)
I Buried meshbags in soil at 10cm depthand retrieved every six months
I Placed meshabgs in compost pile at60cm depth and retrieved every twoweeks
I Determined mulch degradation byimage analysis (ImageJ software)
Release of micro-residues:I Visual observation of meshbagsI Electron MicroscopyI Electrophoretic mobility test
Burial of meshbag in soil
Meshbags retrieved after twoweeks of composting
Results: Light Intensity gLight illuminance as affected by mulch:
Jul Aug Sep10
0
101
102
103
104
105
Bareground PLA/PHA Polyethylene
Date
Lig
ht illu
min
ance (
lux)
I Light Illuminance reduced by 2 orders of magnitude below mulchI Comparable light illuminance of Polyethylene and PLA/PHA
Results: Soil Water Content gSoil water content as affected by mulch:
Jul Aug Sep
0.0
0.2
0.4
Date
Wate
r con
tent (m
3m
−3)
Bareground
PLA/PHA
Polyethylene
Knoxville
Jun Jul Aug Sep
0.0
0.2
0.4
Date
Wate
r con
tent (m
3m
−3)
Bareground
PLA/PHAPolyethylene
Mount Vernon
I Increased soil water conservation of Polyethylene and PLA/PHA
Results: Soil Temperature gSoil temperature as affected by mulch:
Jul Aug Sep
010
20
30
40
Date
Soil tem
pe
ratu
re (
oC
)
Bareground
PLA/PHA
Polyethylene
Knoxville
Jun Jul Aug Sep
010
20
30
40
Date
Soil tem
pe
ratu
re (
oC
)
Bareground
PLA/PHA
Polyethylene
Mount Vernon
I Increased early season soil warming of Polyethylene and PLA/PHA
Results: Mulch Degradation gDegradation in soil:
Polyethylene
PLA/PHA
InitialKnoxville
12-month
Mt. Vernon
12-month
Degradation in compost:
Polyethylene
PLA/PHA
Initial Week 8 Week 18
I Minimal degradation of PLA/PHA in soilI >99% degradation of PLA/PHA after 18 weeks of composting
Results: Release of Micro-residue gElectron Microscopy:
500μm 500μm 500μm
Unused
meshbagCompostedPLA/PHA
CompostedPolyethylene
50μm 50μm 50μm
Electrophoretic mobility:0
4 8
Time (week)
� Carbon black
PLA/PHA
Polyethylene
Elec
troph
oret
ic m
obilit
y
(
μm s
/ V
cm )
-1-1
� � �
I Micro-residues observed after composting for 18 weeksI Some micro-residues may be carbon black
Conclusions gI Microclimate of biodegradable plastic mulch comparable to
polyethylene mulchI Incomplete breakdown of biodegradable plastic mulch
Acknowledgement g
Washington State University [email protected] [email protected] University of Tennessee
