69th SWCS International Annual Conference “Making Waves in Conservation: Our Life on Land and Its Impact on Water” July 27-30, 2014 Lombard, IL

1. Influence of Conversion of CRP land to Cropland on Soil
Quality, Metabolic Capacity and Microbial Diversity
Jennifer Moore-Kucera, Veronica Acosta-Martinez,
Chenhui Li, Lisa Fultz, Mamatha Kakarla,
Francisco Calderon, Juske Horita,
John Zak, and David Weindorf
Depart of Plant & Soil Science
Depart of Geosciences
Depart of Biological Sciences
Award #:
2012-67019-30183

2. TX enrolled area:
1.3 million ha
Enrolled area for 7 major Texas
High Plains counties: 249,000 ha
(27% of THP area)
Total: 11 million hectares
Acres enrolled:
WEI: > 80 tons/ac/yr!
Coarse-textured soil
Low soil organic matter (<2%)
Semi-arid climate
High winds
Frequent intense drought

3. Annual row crops Native RangelandCRP
With increasing time under grassland restoration
In collaboration with NRCS agents in 7 counties, we identified:
0 yrs (annual crop); 6-26 yrs CRP enrollment; Native Rangeland
Our study is evaluating Soil Quality
changes in Amarillo fine sandy loams
Objective 1:
But what happens when CRP contracts expire?

4. Converted CRPCRP
Objective 2: Evaluate short-term changes in soil quality,
microbial activity, & community structure after CRP conversion
Mild, semi-arid climate:
• Avg. annual temp:16°C
• Avg. annual ppt: 470mm
Soil: Amarillo fine sandy loam
• pH: 7.6 (0-30cm)
• SOM: 1.4%
• Sand: 71%
Split-plot RCB:
• Main plot: System (CRP vs. Converted)
• Split: 3 depths (0-10, 10-30, 30-50)
• Block: 3 counties; 2 sampling years
Field histories:
• CRP ages 23-25 yrs enrolled
• Converted fields were 22-25 yrs
enrolled; converted in 2010 or 2012
• Fall sampling with a Giddings probe

5. Soil Quality & Ecosystem Functions From Soil Microbes
Soil is the MOST biologically
diverse ecosystem on Earth!
GHGs, C sequestration
regulated by microbial
processes
Microbes help aggregate soil
to resist erosive forces
C, N,P, S cycling, H2O, pH, EC
Regulates
Climate
Bio-
diversity
Soil
Stability
Plant
Growth
GHG fluxes,
SOC pools
AMF;
bulk
density
Enzyme assays,
chemical analyses
Tools used (e.g.)
TOC,TIC,
13C/12C,
POM-C,
FTIR
MBC, FAMEs, Sequencing
CO2 flux

6. Microbial Community Composition
FAME profiling (all depths; both years)
CRPConverted
CRP
Lower AMF
Higher Gram + bacteria
 Higher AMF
Microbial community composition was altered
following conversion

7. Microbial Biomass C
(CHCl3 fumigation-extraction)
1st sampling year
(2012):
• MBC higher in
converted system
• Resource incorporation?
2nd sampling year
(2013):
• No difference between
systems
• But MBC was 35%
lower in the converted
system
• Resource depletion?
CRP
Converted
CRP
Converted

8. Soil Respiration
(Field measurements with LiCOR 8100 chamber system)
CO2 fluxes:
• Similar fluxes in
both systems
• Sensitive to
moisture/ temp
• Fluxes highest Jun-
Sep
• Combine with
MBC to calculate
metabolic quotient

9. Metabolic quotient
CO2-C released per unit biomass
1st sampling year (2012):
• No difference between
systems
2nd sampling year (2013):
• Converted system >> CRP
• Significant increase
between years
• Microbial community
using more E for
maintenance and less for
growth and production
• Indication of terrestrial
community stress

10. Enzyme activities: When system effect significant:
Converted CRP << CRP
-glucosidase
(cellulose 
glucose)
 35% lower
activity in 2nd
sampling year.

11. Enzyme activities:
Different substrates degrade at different rates
CRP Converted CRP
-glucosaminidase
chitin  amino sugars
Strong decline in
soil properties in
CRP with depth Similar values in top 2
depths for converted CRP
 Incorporation of plant
residues

12. Enzyme activities: When system effect significant:
Converted CRP << CRP
CRP
Converted
Asparaginase
(Amino acid  NH4
+)
 33% lower activity
(average over both years)

13. Alkaline and Acid Phosphatase
(Monophosphate esters  phosphate)
28% and 46% lower activity, respectively
Enzyme activities: When system effect significant:
Converted CRP << CRPCRP
Converted
Acid PhosphataseAlkaline Phosphatase
CRP
Converted

14. Biological properties important to ecosystem
functioning were impacted negatively:
Annual crop
CRP
20+ yr restored grassland Microbial community composition
was altered
Lower AMF; Higher GM+ bacteria
Lower microbial metabolic efficiency
i.e., higher metabolic quotient
Reduced enzymatic activity in top
depth for some enzymes (C, N, P)
Redistribution of organic C, MBC,
and enzymatic activity in the 10-30
relative to 0-10cm depth
Hypothesize that increased levels
will be depleted rapidly
Within 1-2 years

15. Thank You!
?Questions?
Jennifer.moore-Kucera@ttu.edu

16. C&N cycling enzyme:
-glucosaminidase (chitin  amino sugars)
CRP Converted CRP
Only signif with depth
No system effect

17. N cycling enzyme:
Asparaginase Activity (amino acid  NH4
+)
*Converted field < CRP
Note strong decline in soil
properties in CRP with depth
Note similar values in top 2 depths
for converted CRP
 Incorporation of plant residues

18. Bulk
density,
H2O, pH,
EC Microbial
Biomass
C , N
Microbial
Composition
(FAME)
& Diversity
(DNA)
Soil
Respiration
Enzyme
Activities
C,N,P,S
cycling
C
substrates
POM-C,
13C/12C
ratio
TOC,
TIC &
TN
Chemical and Physical
Functions
Soil
Quality
Soil Quality Assessments

19. P cycling enzymes:
Phosphate esters phosphate
Acid PhosphataseAlkaline Phosphatase
Phosphatase enzymes were sensitive to system:
Converted CRP < CRP

20. C-cycling enzyme:
-glucosidase activity (cellulose  glucose)
CRP Converted CRP
1st yr:
No difference between systems

21. Soil Quality Index (Soil Management Assessment Framework)
Bulk density, TOC, pH, EC, MBC, -glucosidase
CRP Converted CRP
0
20
40
60
2012 2013 2012 2013
Sampling year
SoilQualityIndex
Depth (cm)
0-10
10-30
30-50
CRP Converted CRP
*
*
* Converted CRP
slightly higher SQI
in d2 only in 2013

22. C-cycling enzyme:
-glucosidase activity (cellulose  glucose)
CRP Converted CRP
2nd yr: Converted
system 45% lower
than CRP fields
In CRP: -glucosidase
increased from 2012-13
In Converted CRP: no
change from 2012-2013

23. Annual row crops
Converted CRP
Native RangelandCRP
CRP
With increasing time under grassland restoration
0 yrs (annual crop); 6-26 yrs CRP enrollment; Native Rangeland
After CRP conversion to annual cropland
Our study is evaluating Soil Quality changes: