This document discusses soil profile rebuilding as a technique for rehabilitating compacted urban soils. It begins by explaining the problems caused by compacted soil, such as reduced water infiltration and carbon storage. Soil profile rebuilding is then presented as a solution that involves using a backhoe to till compost deep into the soil profile. Studies found this technique increased water infiltration rates, reduced bulk density, and doubled tree canopy areas after 7 years compared to untreated soils. The document concludes by providing references for further information on soil profile rebuilding specifications and research.

1. Soil Profile RebuildingSoil Profile Rebuilding
A Technique for Rehabilitating CompactedA Technique for Rehabilitating Compacted
Urban SoilsUrban Soils
Dr. Susan D. DayDr. Susan D. Day
Forest Resources & Environmental Conservation, Virginia TechForest Resources & Environmental Conservation, Virginia Tech

2. • The problem:
Compacted Soil
• Why Rehabilitate
• Technique: SPR
• Emerging
Techniques:
Surface Treatments
and Infiltration
• The problem:
Compacted Soil
• Why Rehabilitate
• Technique: SPR
• Emerging
Techniques:
Surface Treatments
and Infiltration Photo: P.E. WisemanPhoto: P.E. Wiseman
Brief AgendaBrief Agenda

3. Why Rehabilitate?Why Rehabilitate?

4. American Elms
Worcester, Mass. 1912
The fallback
solution

8. Photo: Robert Llewellyn—Magnolia acuminata (Cucumber Tree)
The Remarkable Trees of Virginia

9. Sustainable Land Development?Sustainable Land Development?
Prime farmland soil was
graded down 3 ft to
redirect stormwater to
bioinfiltration swale

10. At “peak” time of year (May) 3 years later, tree
dieback, thin turf, thin canopies, nutrient deficiencies

12. Photo: Rachel M. LaymanPhoto: Rachel M. Layman
• At 5-10 cm macroaggregates were reduced byAt 5-10 cm macroaggregates were reduced by
44%44%
• Lost 35% of total soil organic carbon (0-10 cm)Lost 35% of total soil organic carbon (0-10 cm)
• Lost 47% of mineral-bound carbonLost 47% of mineral-bound carbon
• Subsurface drainage reduced from about 3” anSubsurface drainage reduced from about 3” an
hour to less than ½” an hour.hour to less than ½” an hour.

13. Photo: Jeannette E. Spaghetti (CC)

14. What is my actionWhat is my action
threshold for addressingthreshold for addressing
compaction?compaction?

15. As compaction increases
Growthdecreases
increases
14-year old Tilia tomentosa in a silty clay loam
(Day & Amateis 2009)

16. You can’t interpret
soil bulk density
without soil texture

17. Bulk density = 1.4 g•cm-3
sandy loam—no worriesno worries
silty clay loam—watch outwatch out

19. Will not correct your soilWill not correct your soil
pH problemspH problems

20. Not for use around large treesNot for use around large trees

21. WillWill reduce compaction, increase tree growthreduce compaction, increase tree growth
improve permeability, increase soil carbon storesimprove permeability, increase soil carbon stores
and set long-term soil formation processes onand set long-term soil formation processes on
tracktrack

22. Photo: Jeannette E. Spaghetti (CC)

23. Apply 4 inches of compost to graded subsoilApply 4 inches of compost to graded subsoil
Soil Profile Rebuilding—
A rehabilitation
technique

24. Backhoe to 2 ft, scoop up and drop to createBackhoe to 2 ft, scoop up and drop to create
compost veins to 2 ft.compost veins to 2 ft.

25. • Return topsoil as usual (4” min.) and till 8”
• Plant trees or other woody veg
• Treat surface to reduce erosion and maintain
infiltration

26. 8 cm
33cm
53 cm
18 cm
1.51
1.77
1.76
1.91 (9 mos)
1.76 (5 yrs)
Low Resistance
(Topsoil)
High Resistance
(Compacted subsoil)
Medium Resistance
(Subsoil)
Typical
Practice
Loam Soil—Soil Bulk Density g/cm3
1.28
1.75
1.69
1.35 (9 mos)
1.49 (5 yrs)
Profile
Rebuilding

28. Adaptation of Daddow and
Warrington, 1983
by Sustainable Sites Initiative
Soil in Tree Root Zone
Without Rehab yr 1 = 1.91 g cm-3
With Rehab yr 1 = 1.35 g cm-3
Without Rehab yr 5 = 1.76 g cm-3
With Rehab yr 5 = 1.49 g cm-3

29. Canopy Area approximately
doubled after 7 years in
controlled experiments

30. Arlington County Street Medians
David Mitchell, 2014

31. Surface
UN
TP
ET
PR
25 cm
SoilTreatments
UN
TP
ET
PR
40 cm
Hydraulic Conductivity (cm/hr)
0 5 10 15 20 25
UN
TP
ET
PR
a
a
a
a
a
ab
b
b
a
ab
ab
b
Ksat
Atypical surface
treatments for
research purposes
result in restricted
flow
Bottleneck in “typical
developed land” has
rapid water flow
Aggregate-associated C

32. Site-level Effects Subsurface
Permeability 10-40 cm (Ksat)
Agricultural Soil—4 to 5 cm/hr
Compare to HSG B
Simple grading, urban land development—1 to 2 cm/hr
Compare to HSG C or D
Rehabilitated soil—10 to 11 cm/hr
Compare to HSG A or B
Chen et al. Science of the Total Environment 2014.
Urban land
development
Soil
Management

34. The urban forest systemThe urban forest system

35. Chen, Y., Day, S. D., Shrestha, R. K., Strahm, B. D., Wiseman, P. E., 2014.
Influence of urban land development and soil rehabilitation on soil–atmosphere
greenhouse gas fluxes. Geoderma 226, 348-353.
Chen, Y., Day, S. D., Wick, A. F., McGuire, K. J., 2014. Influence of urban land
development and subsequent soil rehabilitation on soil aggregates, carbon, and
hydraulic conductivity. Science of the Total Environment. 494–495, 329-336.
Chen, Y., Day, S. D., Wick, A. F., Strahm, B. D., Wiseman, P. E., Daniels, W. L.,
2013. Changes in soil carbon pools and microbial biomass from urban land
development and subsequent post-development soil rehabilitation. Soil Biology
and Biochemistry 66, 38-44.
Layman, R.M., Day. S.D., Mitchell, D.K., Chen, Y., Harris, J.R., Daniels, W.L.
2015. Below ground matters: Urban soil rehabilitation increases tree canopy and
speeds establishment. Under review at Urban Forestry & Urban Greening
Journal Articles for SPR
urbanforestry.frec.vt.edu

36. Want more info?
• Recent Article
City Trees (Sept/Oct)
• Download Specifications
urbanforestry.frec.vt.edu/SRES
• Details under production

37. Thank you
Collaborators: J. R. Harris, Joseph Dove, Qingfu Xiao, E.G. McPherson, N. Bassuk,
Brian Strahm, AbbeyWick, W. Lee Daniels, P. EricWiseman, Kevin McGuire,Tess
(Wynn)Thompson, andVincentVerweij
Graduate Students: Rachel Layman,Yujuan Chen, Julia Bartens, and David
Mitchell
Soil Profile Rebuilding Specifications available at urbanforestry.frec.vt.edu/SRES
Partial support provided by the
USDA-Forest Service National Urban and Community Forestry Advisory Council,
Tree Research & Education Fund, the Institute for CriticalTechnology and Applied
Science atVirginiaTech, and the USDA’s McIntire-Stennis program