70th SWCS International Annual Conference July 26-29, 2015 Greensboro, NC

1. SOIL HEALTH IN A SOD-BASED CROP
ROTATION SYSTEM
SHEEJA GEORGE, J.J. MAROIS, D.L. WRIGHT
UNIVERSITY OF FLORIDA-NORTH FLORIDA RESEARCH AND
EDUCATION CENTER, QUINCY, FL

2. The top 6 inches of our
soil-
• Cycle C and other
nutrients
• Stabilize soil aggregates
• Improve soil structure
• Source of and substrate
for enzymes
• Increasing evidence of
OM being mostly
derived from microbial
activity

3. The 10,000-50,000 species in 1g of soil contribute $1.5
-20 trillion worth of nutrient cycling services in a
year (Dance and Tillman et al.)
Structure and activity/function of microbial
communities are influenced by:
• management practices
• weather patterns
• climate change factors
• Interaction of all the above
Sustainable practices need to focus on fortifying
soils and this in turn depends on keeping a viable
microbial population in the system year-round

4. SBR has it all!
Cover crop
Crop rotation
Livestock integration
Perennial roots

5. Ecosystem services provided by a perennial grass
based system-
• Builds soil organic matter: Average OM in SBR
1.86% and in conventional rotation was 1.72%
• Maintains soil structure through macro-aggregate
formation-increasing stability of organic matter :
>2mm and 2-1mm macroaggregates relatively
higher in SBR than conventional rotation
• Year round cover prevents leaching or emissions of
nitrates; uptake of nitrates and ammonium by
microbes
• Efficiently regulates mineralization and
sequestration processes: mix of different C:N ratio
residues

6. We monitor shifts in soil biological properties in the
shallow depths of soil because these shifts are “Early”
indicators of change-
• Microbial biomass C and N-correlates well with
amount and diversity of crop residues, proportion of
easily decomposable residues returned to soil, root
density
• Soil enzymes-soil structure, microbial activity,
quality and quantity of organic matter
• Microbial communities and diversity-indicate
potential of soil (cropping system) to carry out key
soil functions integral to plant productivity

7. Sod- based rotation Conventional rotation
Bahia-2nd
year
oats
oats
oats
oats
Bahia-1st year
Cotton
Cotton-1st yearCotton-2nd year
oatsPeanut
Peanut
oats
Bahia-2nd year
OVERVIEW OF THE ROTATION SYSTEM

8. Bulk density 1.6 g/cm3
Sand 875 g/kg
Silt 76 g/kg
Clay 49 g/kg
pH (H2O) 5.6
N content 0.45 g/kg
Available water holding
capacity
0.08-0.15 cm3/ cm3
Select soil properties at the North Florida Research and Education Center, Quincy,
FL experimental site at 0-15 cm depth

9. Air-dried soil
Incubate with substrate in buffer and
toluene
60 mins / 37° C
Terminate reaction
Read absorbance at 420 nm
Measure released product P-Nitrophenol

10. 0
20
40
60
80
100
120
140
160
180
200
ACP ALP AS BG BGLM
mgP-Nitrophenol/Kgsoil/h
B1 B2 SP CP SC C1 C2
ENZYME ACTIVITY
Acid phosphatase, alkaline phosphatase, arylsulfatase, Beta-Glucosidase, Beta-Glucosaminidase

11. ACID PHOSPHATASE
77
70
33
155
105
120 119
63 62
39
149
123 122 123
0
20
40
60
80
100
120
140
160
Con. Peanut Con.
Cotton-1st
year
Con.
Cotton-2nd
year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
CONVENTIONAL SOD
mgP-Nitrophenol/Kgsoil/h
IR NIR

12. ALKALINE PHOSPHATASE
0
20
40
60
80
100
120
140
160
Con.Peanut Con.
Cotton-1st
year
Con.
Cotton-2nd
year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
CONVENTIONAL SOD
45
54
43
97
82 77
93
47
59
48
99
90
70
45
mgP-Nitrophenol/Kgsoil/h IR NIR

13. 0
20
40
60
80
100
120
140
160
180
200
Con. Peanut Con. Cotton-
1st year
Con. Cotton-
2nd year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
CONVENTIONAL SOD
106
167
128
173
110
117
137
119 122
133
187
149
96
186
mgP-Nitrophenol/Kgsoil/h
IR NIR

14. 0
20
40
60
80
100
120
140
Con. Peanut Con. Cotton-
1st year
Con. Cotton-
2nd year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
CONVENTIONAL SOD
70
96
80
128
86
95
105
61 58 61
120
92
54
111
mgP-Nitrophenol/Kgsoil/h
IR NIR

15. 0
10
20
30
40
50
60
70
80
Con. Peanut Con. Cotton-
1st year
Con. Cotton-
2nd year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
CONVENTIONAL SOD
mgP-Nitrophenol/Kgsoil/h
IR NIR

16. MICROBIAL BIOMASS CARBON
Extract with
0.5M K2SO4
Estimate Organic
Carbon (OC)
Estimate Organic
Carbon (OC)
Acid digestion with K2Cr2O7
C → CO2
Dichromate → Chromic Acid
MBC = Microwaved OC – Control OC
Field-moist soil
MicrowavedControl

17. MICROBIAL
80
40
140
160
140
100
220
64
38
120
164
86
100
180
0
50
100
150
200
250
Con. Peanut Con. Cotton-
1st year
Con. Cotton-
2nd year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
mgC/Kgsoil
Sum of Summer-IR Sum of Summer-NIR

18. 12.2
14.8
13.8
16
18.4
21.3
19.61
0
5
10
15
20
25
Con. Peanut Con Cotton
1st Year
Con. Cotton
2nd Year
Bahia-1st
year
Bahia-2nd
year
Sod Peanut Sod Cotton
mgN/Kgsoil
MICROBIAL

19. Microbial community analyses using -
• Fatty acid methyl ester analysis-Saponification, methyl
esterification, followed by GC analysis
• GP bacteria: a15:0, i15:0, a17:0, i17:0
• GN bacteria: 17:1w9c, 17:1w8c, 16:1w7c, 18:1w7c, cy17:0,
cy19:0
• AMF: 16:1w5c
• Saprophytic fungi: 18:1w9c, 18:3w6c, 18:2w6c
• Actinomyces: 10Me16;0, 10Me17:0, 10Me18:0

22. Non-Irrigated Irrigated
0.0
5.0
10.0
15.0
20.0
CP C1 B1 B2 SP SC
Gram positive
0.0
5.0
10.0
15.0
20.0
CP C1 B1 B2 SP SC
Gram positive
0.0
5.0
10.0
15.0
20.0
CP C1 B1 B2 SP SC
Gram negative
0.0
5.0
10.0
15.0
20.0
CP C1 B1 B2 SP SC
Gram negative

23. Non-Irrigated Irrigated
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
CP C1 B1 B2 SP SC
Mycorrhizal fungi
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
CP C1 B1 B2 SP SC
Fungi
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
CP C1 B1 B2 SP SC
Fungi
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
CP C1 B1 B2 SP SC
Mycorrhizal fungi

24. Fungal to bacterial ratio
6.2
5.7
4.1
4.3
3.7
4.7
1.87 1.8 1.81
1.57 1.64
2.6
1.64
1.83 1.9 1.88
2.5 2.6
0
1
2
3
4
5
6
7
Ratiooffungalandbacterialfattyacidmarkers

25. 0.8
0.88
0.6
0.92 0.95
0.72
0.45
0.65
0.52
0.6
0.56
0.48
0.42
0.61
0.41
0.31
0.65
0.49
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
ratioofrelativepercentagesofunsaturatedand
saturatedfattyacids Unsaturated to saturated FA ratio

26. ARISA-automated ribosomal intergenic spacer
analysis-amplifies region between16s and 23s
subunits
Most fragments between 150 and 500 bp
Permutational Multivariate Analysis of
Variance (PERMANOVA)

27. Cotton-Bacteria
Permanova P value=0.25
SC-60N
SC-0N
C2-0N
C1-0N
C2-60N
C1-60N
Samples
100
95
90
85
Similarity
Standardise Samples by Total
Transform: Log(X+1)
Resemblance: S17 Bray Curtis similarity
Conventional
Sod

28. Group average
SP-0N
SP-60N
PT-0N
PT-60N
Samples
100
95
90
85
Similarity
Standardise Samples by Total
Transform: Log(X+1)
Resemblance: S17 Bray Curtis similarity
Tillage Type
Conventional
Sod
Peanut-Bacteria
Permanova P value=0.32

29. CROP
TOTAL
SPECIES
SPECIES
RICHNESS
PIELOUS
EVENNESS
SHANNON’
S
DIVERSITY
INDEX
B1 14.4 1.58 0.97 2.6
B2 15.8 1.72 0.98 2.7
SP 14.6 1.6 0.97 2.61
CP 13.8 1.51 0.97 2.54
SC 14.8 1.6 0.97 2.62
C1 13.5 1.47 0.97 2.52

30. • Microbial biomass carbon was higher in the sod
rotated systems
• Enzymes involved in soil organic phosphorus
mineralization, S mineralization, Carbon cycling
and nitrogen cycling and overall plant nutrition
were all significantly higher in the sod rotated
systems.
• Enzymes activity is associated with organic matter
and thus increased enzyme activity in the sod
rotated system is another indicator of organic
matter build-up

31. • Ratio of unsaturated to saturated fatty acids was
higher in SBR
• High ratio of unsaturated fatty acids (contributed by
Gram negative bacteria) is known to:
• Increase proportionally with increasing amounts
and diversity of carbon sources; an indicator of
organic matter build-up
• Associated with nutrient stress
• low levels of unsaturated fatty acids are
attributed to compacted and disturbed soils
• Even though these ratios decrease when rotation
is not in Bahiagrass phase, the soil likely
acquires favorable physical and biochemical
properties benefiting subsequent crop

32. • Fungal to bacterial ratio significantly higher during
both years of bahiagrass and mostly in the sod
rotated crops
• Arbuscular mycorrhizal fungi (known to improve
soil structure, disease resistance, drought
resistance) was significantly higher in the SBR
• Differential microbial activity seems to be
significant factor for better soil characteristics (and
greater productivity) of SBR