Soil biology and system

managementLisa M. Fultz

Assistant Professor Soil Microbiology of Cropping Systems

LSU AgCenter

Baton Rouge, LA

Award #: 2012-67019-30183

1

Ecosystem Functions from the Soil Perspective

Soil texture, compaction, PAW, aggregate stability

pH, SOM, CEC, nutrients

Microbial biomass and activity, SOC, nutrient cycling, diseases

Physical

Chemical

Biological

2

To Understand Soil Health We MustUnderstand Soil Biology

Soil Biota

Plant growth enhancement

Photo credit: Lisa M Fultz, LSU AgCenterSlide design: Jennifer Moore-Kucera, NRCS-SHD

Nutrient cycling

N fixation

Plant protection

Pathogen supression Detoxify

pollutants

Influence atmosphere composition

Decompose residues

Water filtration

Water storage

Water flow

Aggregate formation

3

Resist erosion

Soil Health Identifies the Importance of Soil Biology To Enhance Ecosystem Services

Increase H2O infiltration and storage

Enhance water/air quality

• Increase amount, types and availability of plant residues.

• Minimize disturbance

C sequestrationClimate mitigation Release plant

available nutrients

Plant Growth, Productivity

Aggregate Stability

Increase #s and types of soil organisms

OM TransformationsHumus Formation

Biogeochemical Cycling

4

Ecological Challenges to Soil Resilience

Abiotic Variables:• Depleted water sources• Changes in precipitation

patterns• Extreme weather• Erodibility indexes

(>200 tons ha-1 y-1)

Cultural Practices:• High disturbance

agronomic systems• Intensive/ frequent tillage• Low diversity• Fallow periods• Low residue return

5

Management Practices to Enhance Soil Health and Combat Soil Degradation

• Increase plant residues returned to the soil• Perennial grasslands/forage lands• Use crop rotations or cover crops• Integrate cattle into cropping system

• Convert to conservation or no-till • Enroll in conservation management

programs

6

Integrated Crop-Livestock Agroecosystems

• Great flexibility

• Divide fields to suit needs/skill/resources

CottonMonocultures

Grass-cattle

Grain - Cotton

Pullman clay loam soilspH = 7.4SOM = 1.5 – 3.3%34% clay

7

0

2

4

6

8

10

12

14

1997 CTN_1 ICL_1 CTN_2 CTN_3 ICL_2 ICL_3 ICL_4

Soil

orga

nic

C (g

kg-1

)

System

Gra

ssla

nd

Def

icit

irrig

ated

co

ntin

uous

cot

ton

Def

icit

irrig

ated

bl

uest

em &

cro

p ro

tatio

n

Dry

land

fora

ges &

co

tton

Def

icit

irrig

ated

per

enni

al

gras

ses

Blu

este

m a

nd fu

lly ir

rigat

ed

row

cro

ps

Def

icit

irrig

ated

co

ntin

uous

cot

ton

Def

icit

irrig

ated

co

ntin

uous

cot

ton

Fultz, L.M., Moore-Kucera, J., Zobeck, T.M., Acosta-Martinez, V, & Allen, V.G. (2013) 77:1659-1666.

• 31% increase in SOC following 13 years under ICL management

8

Water use and productivity-Allen et al. 2012. Agronomy Journal

Integrated system compared to continuous cotton

Per hectare 25% less irrigation 36% less N fertilizer Decreased chemical inputs (pesticides and plant growth

regulators) Avg. over 10 years profitability was similar when

comparing the two systems

9

0

2

4

6

8

10

12

14

1997 CTN_1 ICL_1 CTN_2 CTN_3 ICL_2 ICL_3 ICL_4

Soil

orga

nic

C (g

kg-1

)

System

Gra

ssla

nd

Def

icit

irrig

ated

co

ntin

uous

cot

ton

Def

icit

irrig

ated

bl

uest

em &

cro

p ro

tatio

n

Dry

land

fora

ges &

co

tton

Def

icit

irrig

ated

per

enni

al

gras

ses

Blu

este

m a

nd fu

lly ir

rigat

ed

row

cro

ps

Def

icit

irrig

ated

co

ntin

uous

cot

ton

Def

icit

irrig

ated

co

ntin

uous

cot

ton

• ICL’s increased aggregate stability 2-3x’s that in continuous cotton

10

SOM and Aggregate Stability

y = 0.04e0.09x

r² = 0.73***

0.0

0.5

1.0

1.5

2.0

2.5

0 10 20 30 40

Mea

n w

eigh

t dia

met

er (m

m)

Soil organic matter (g kg-1)

Relationship between increasing SOM and MWD (proxy for stability)

0.000.200.400.600.80

Annualcrops

PerennialMea

n w

eigh

t di

amet

er

(mm

)

Critical SOM value for enhanced aggregate stability

Annual crops

Perennials

11

Relative abundance of arbuscular mycorrhizal fungi (mol%)

0 5 10 15 20 25 30 35 40

Mea

n w

eigh

t dia

met

er (m

m)

0.0

0.5

1.0

1.5

2.0

2.50-5 cmY= 0.05x + 0.24

r ² 0.357r = 0.597p < 0.0001

5-20 cmY= 0.02x + 0.30

r ² 0.370r = 0.608p < 0.0001

12

What are the ecological impacts of increased fungal richness?

Fungal Diversity

CTN_1CTN_2

FRG_CTN

OWB_BERFRG_RC

Fung

al o

pera

tiona

l tax

onom

ic u

nits

(p

ropo

rtion

al to

syst

em a

rea)

0

200

400

600

800

1000

1200

1400

1600

1800

Davinic, M. 2014, Ph.D. DissertationMonoculture

Cotton

Increased Fungal Richness

Rotations/Perennial Systems

Fungal richness (diversity)

Converting part or all of the field to rotation or perennial-based agroecosystems

Rotations/PerennialSystems

Monoculture Cotton

Fungal richness (diversity)

Increased SOM

13

Do these shifts in microbial groups influence nutrient cycling?

Bacterial Phylum Acidobacteriay = 16.852x + 2.4869

R² = 0.213

Fungal Class Onygenalesy = 27.467x + 38.791

R² = 0.248

0

50

100

150

200

250

0.00 2.00 4.00 6.00 8.00 10.00

Avai

labl

e So

il P

(ppm

; Meh

lich3

)

Relative abundance (%) Onygenales or Acidobacteria

Microbial composition influences the release of plant-available nutrients

14

Field Design

Cereal radish + rye mix

Radish (Raphanus sativus var. longipinnatus)

Fallow

Hairy vetch (Vicia villosa Roth)

Crimson clover (Trifolium incarnatumL)

Cereal rye (Secale cereale)

Winter pea (Pisium sativum L)

Berseem clover (Trifoliumalexandrinum)

• Split plot design: Cover crop (CC) as main plot and N rates as sub plots• 32 treatments: 8 cover crops and 4 N rates, with 4 reps for each CC*N

treatment within a cover crop main plot

N rates: 0, 235, 268, 302 kg Urea ha-1

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Cover crop dry weight biomass

[CELLRANGE]

[CELLRANGE]

[CELLRANGE]

[CELLRANGE][CELLRANGE]

[CELLRANGE]

[CELLRANGE]

[CELLRANGE]

0

500

1000

1500

2000

2500

3000

Fallow BerseemClover

CrimsonClover

Hairy Vetch Winter Pea Cereal Rye Radish Rye+Radish

Biom

ass

wei

ght

(g)

16

Soil organic matter – 14.6% increase Fall 2014 to Fall 2015

17

[CELLRANGE]

[CELLRANGE]

[CELLRANGE]

[CELLRANGE][CELLRANGE]

2.1

2.2

2.3

2.4

Fallow Legume Grass Brassica Rye/Radish

Soil

Org

anic

Mat

ter

(% L

OI)

C cycling enzyme greater in spring, fallowing cover crops

0

10

20

30

40

50

60

70

80

90

Fallow Legumes Grass Brassica Rye/Radish

B-gl

ucos

idas

e (m

g p-

nitr

ophe

nol

g-1

hr-1

)

Fall 2014 Spring 2015 Fall 2015 Spring 2016

18

N cycling enzymes increasing over time

0

5

10

15

20

25

Fallow Legumes Grass Brassica Rye/Radish

B-gl

ucos

amin

idas

e (m

g p-

nitr

ophe

nol g

-1 h

r-1)

Fall 2014 Spring 2015 Fall 2015 Spring 2016

19

y = 52.938x + 7.3273R² = 0.2542

0

50

100

150

200

250

300

350

0 1 2 3 4

Tota

l Mic

robi

al B

iom

ass

(nm

ol g

-1)

Soil Organic Matter (% LOI)

y = 0.1413x - 5.789R² = 0.3082

0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300

Nit

rate

-N (

mg

kg-1)

Total Microbial Biomass (nmol g-1)

y = 0.2147x + 6.0442R² = 0.1687

0

20

40

60

80

100

120

0 50 100 150 200 250 300

Soil

P (m

g kg

-1)

Total Microbial Biomass (nmol g-1)

Total microbial biomass increased with SOM

20

Fallow Berseem Crimson Hairy vetch Winter pea Cereal rye Radish Rye+Radish

Fallow Berseemclover

Crimsonclover

Hairy vetch Winter pea Cereal rye Radish Rye+Radish

76%

85%77% 85% 82%

81%

75% 74%

64%

93% 123%70%

132% 128%

67% 69%

21

0

20

40

60

80

100

120

140

160

180

200

Corn

gra

in y

ield

(bu

/A)

ABC

ar 3 – Corn yields increased following asses and legumes

F

DECD

AAB

BCD

E

22

nter annuals overseeded on a perennial stureouthern Mississippi

eef cattle operation

Winter annual mixture

Oats

Triticale

Annual ryegrass

Hairy vetch

Red clover

Crimson clover

White clover

Turnip

Radish

23

y = 57.9x - 23.55R² = 0.4532

0

100

200

300

400

500

600

700

0 2 4 6 8 10

Tota

l Mic

robi

al B

iom

ass

(nm

ol g

-1)

Soil Organic Matter (% LOI)

y = 0.0839x + 7.4626R² = 0.2816

y = 0.0552x + 7.8822R² = 0.2939

0

10

20

30

40

50

60

70

80

90

Soil

P (m

g kg

-1)

ial pastureeded wither annuals

24

MF, P, and O3

25

26

Thank you!

Lisa M. Fultz

lfultz@agcenter.lsu.edu

27

Large macroaggregate roots

Fibers

28

What is the impact of ICLs on the ratio of ungi to bacteria (F:B)?

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

• Highest F:B (18:2/Bac) ratio in continuous cotton

• Marker common for saprophytic fungi• No change between ICLs

Type of ratio impacts interpretation!

g(

,)

29

What is the impact of ICLs on the ratio of fungi to bacteria (F:B)?

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

AMF/Bac ratio:cotton < rotation < perennial-

based systems

Type of ratio impacts interpretation!

30

CRP

ctive: Evaluate short-term soil health changes ng conversion of CRP back to cropland

tems (CRP vs. Converted CRP)ths (0-10, 10-30, 30-50cm)rs (2012, 2013, 2014)

histories:P ages 23-25 years enrolledverted CRP were 22-25 s enrolled and converted 011 2012

Semi-arid climate:• Avg. annual temperature :16°C• Avg. annual PPT : 475mmSoil: Amarillo fine sandy loam • pH: 7.6 (0-30cm)• SOM: 1.4%• Sand: 71%

WEI 200 t /h /

Converted to annual crops

-3.8

22.7

-56.8

-26.8 -22.4

23.2

M-C POM-N MBC α-galac/MBC

β-gluc/MBC

β-glm/ MBC

qCO2

10cm Converted CRP change percent (%) Reference line is CRPLabile OM Specific Metabolic ActivitiesMBC

36.1 -53.9 -38.5

5.9

-9.1

31.0

111.7

46.614.2 27.5

125.6

Actinomycetes

Gram+

Totalbacteria

Totalfungi

Fungi:Bacteria

Gram‐AMF

Gram‐

TotalbacteriaGram

+

Actinomycetes

Totalfungi

Fungi:Bacteria

AMF

33

Increased soil organic matter increased total microbial biomass

y = 74.9x - 44.232R² = 0.73

0

0

0

0

0

0

0

0

0 2 4 6 8 10

Annual corn w/cover crops

Perennial grasses over seeded w/winter annuals

34

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