This study assessed soil health metrics across crop and hay fields in the Piedmont region of North Carolina. Soil samples were taken from 3 depths down to 1 meter across fields under different land management systems. Ten metrics were measured in the field and laboratory to evaluate differences between systems. Most metrics did not detect differences between crop and hay fields. Soil organic carbon and respiration rates differed between depths but not systems. Enzyme assays showed differences between depths and an interaction between system and depth. Standardized soil health measurement protocols need further refinement to be practical and effective at distinguishing management impacts.

1. Assessing Soil Health Metrics in the
Piedmont of North Carolina
Caitlin Caudle, Deanna Osmond, Matthew Ricker,
Joshua Heitman, Rachel Cook
North Carolina State University

2. Importance of Soil Health
• Soil serves many
important roles in
ecosystems
• Defined as:
– “ The capacity of a soil to
function within ecosystem
boundaries to sustain biological
productivity, maintain
environmental quality, and
promote plant and animal
health.” (Doran and Parkin,
1994)
Photos courtesy of USDA NRCS.
2

3. Soil Health Metrics
• Chemical, physical, and/or
biological indicators used to
measure processes within
soils
• Can be measured in the
field or in the lab
• Little standardization in
methodologies used
• Ideal indicators and their
ideal values are unknown
Photo courtesy of USDA NRCS. 3

4. USDA-Natural Resources Conservation Service:
Dynamic Soil Properties for Soil Health
• NRCS provided a standard measurement and sampling protocols to
all universities
4

5. North Carolina Soil Health Objectives
• To identify differences in
soil health status across
Cecil soils under two
extremes of land
management systems
• To assess proposed
indicator variability
between systems, within
the systems, within fields,
and with depth
5

6. Experimental Design
• All fields mapped Cecil
• 3 crop fields; 3 hay fields;
1 forest field
• 1 pit dug in one field of
each system and
characterized
• 3 sample locations in each
field oriented downslope
• Total of 20 sample
locations; 9 crop, 9 hay,
2 forest
6

7. Sampling Methods
• Soils sampled in March
2018
• Cores divided by depth to
100 cm
• Bulk samples homogenized
and air dried
• Natural fabric samples
collected and air dried
7
0 – 5 cm
Bottom of A
Bt1
Bt2
5 – 10 cm

8. Methods
• Total of 10 metrics
measured
– 2 in field
– 8 in lab
• Field metrics completed in
each field June 2018
• Lab metrics completed on
each sample depth
8

9. Indicators
9
Field Methods Metric Measured Units
Cornell Sprinkle Infiltrometer Infiltration (simulated rainfall) cm/min
Single Ring Infiltration Infiltration (ponded head) cm/h
In Field Soil Health Assessment Visual field conditions high/medium/low
Lab Methods Metric Measured Units
Dry Combustion Soil organic carbon % total
Autoclave Citrate Extractable Protein
Content
Soil protein content mg/g soil
p-Nitrophenyl Enzyme Assays (𝛽-glucosidase,
𝛽-glucosaminidase, acid phosphatase, alkaline
phosphatase, phosphodiesterase, arylsulfatase)
C, N, P, and S cycling mg p-Nitrophenyl
/kg soil/hour
Wet Macroaggregate Stability using Yoder
device
Aggregate mean weight
diameter
mm
> 0.5 mm Aggregate Retention Aggregate stability %
CO2 Respiration after 4 day Incubation Mineralizable C mg CO2
Permanganate Oxidizable Carbon using 0.02
M KMnO4 and < 2 mm soil
Active C mg reactive C/
kg soil
Phospholipid Fatty Acid Analysis Microbial community
structure
pmol/g soil

10. Statistical Design
• Split-Strip design
• Fields were replicates
10
C
B
A
0-5 cm
5-10 cm
Bottom A
Bt1
Bt2
C
Shoulder
Slope
Back
Slope
Foot
Slope

11. Results
• Mixed Model
• SAS
• 2 field metrics
• 14 lab metrics
– Included 6 enzyme
assays
11

12. Indicator System Pedon Depth System*
Pedon
System*
Depth
Depth*
Pedon
System*
Depth*
Pedon
SOC NS NS *** NS NS NS NS
CO2 Respiration * NS *** NS NS NS NS
POxC NS NS NS ** ** NS NS
β-Glucosidase NS NS *** NS *** NS NS
β-Glucosaminidase NS NS *** NS NS NS **
Alkaline Phosphatase NS NS *** NS NS NS NS
Acid Phosphatase NS NS *** NS *** NS NS
Phosphodiesterase NS NS *** NS NS NS NS
Arylsulfatase NS NS *** NS *** NS NS
ACE Protein NS NS *** NS NS NS NS
Aggregate Retention * NS *** NS *** NS NS
Mean Weight Diameter NS NS *** NS NS NS NS
Sprinkle Infiltrometer NS NS N/A NS N/A N/A N/A
Single Ring Infiltration NS NS N/A NS N/A N/A N/A
12

13. Soil Organic Carbon Depth
0
0.5
1
1.5
2
2.5
0-5 cm 5-10 cm Bottom of A Bt1 Bt2
%weightC
Depth
a
b
c
d
d
13

14. CO2 Respiration
0
10
20
30
40
50
60
70
80
Crop Hay
mgCO2Respired
System
a
b
14
0
10
20
30
40
50
60
70
80
0-5 cm 5-10 cm Bottom of
A
Bt1 Bt2
mgCO2Respired
Depth
a
b
c
d d

15. 712
713
714
715
716
717
718
0-5 cm 5-10 cm Bottom of
A
Bt1 Bt2
mgC/kgsoil
Depth
System*Depth
Crop Hay
Permanganate Oxidizable Carbon
712
713
714
715
716
717
718
A B C
mgC/kgsoil
Pedon
Pedon*Depth
Crop Hay
a
c
b
ab ab
bc
15
aa a
b b
c
de
cd
ef f

16. Carbon Cycling Enzymes
0
100
200
300
400
500
600
700
0-5 cm 5-10 cm Bottom of A Bt1 Bt2
ugp-nitrophenyl/gsoil/hour
Depth
B-Glucosidase System*Depth
Crop Hay
b
a
c
d
e
ef f f ff
16

17. Phosphorus Cycling Enzymes
0
100
200
300
400
500
600
700
0-5 cm 5-10 cm Bottom of
A
Bt1 Bt2
ugp-nitrphenyl/gsoil/hour
Depth
Alkaline Phosphatase Depth
a
b
c
17
0
50
100
150
200
250
300
350
400
0-5 cm 5-10 cm Bottom of
A
Bt1 Bt2
ugp-nitrophenyl/gsoil/hour
Depth
Acid Phosphatase System*Depth
Crop Hay
a
bc
c
d
de
e e e e
b

18. Structural Stability
0
20
40
60
80
100
0-5 cm 5-10 cm Bottom of
A
Bt1 Bt2
%retention
Depth
Aggregate Stability (NRCS)
System*Depth
Crop Hay
a
a
b
cc c cd
d d d
18
0
0.5
1
1.5
2
2.5
3
0-5 cm 5-10 cm Bottom of
A
Bt1 Bt2
mm
Depth
Mean Weight Diameter (ARS)
Depth
b
a
b
c
c

19. Conclusions
• Many metrics were not sensitive
enough to detect differences
between management systems
• Metrics meant to represent
similar soil processes showed
different results
• Protocols provided by NRCS
required further clarification
and standardization
• Protocols provided were labor
intensive and time consuming,
not suitable for high-throughput
commercial settings
19

20. Acknowledgements
• Thank you my committee: Deanna
Osmond, Josh Heitman, Matt Ricker,
Rachel Cook.
• Thank you to Grady Miller for assistance
with statistics.
• Thank you to Skye Wills and Debbie
Anderson of USDA – NRCS for technical
guidance and assistance with sampling.
• Thank you to the Gardner lab for the use
of the lab space.
• Special thanks to the Adam Howard, Chris
Neiwoehner, and Wes Childres for
technical assistance with sampling.
• Funding was provided by USDA-NRCS Soil
Survey Division.
20

21. Questions
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