organic and sustainable farming - uf/ifas ociconference.ifas.ufl.edu/smallfarms12/pdfs and handouts...
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Organic and Sustainable Farming 11:00-12:30 Capturing the Organic Market
2:00-3:00 Organic Pest Management
4:30-5:30 Alternative Soil Management
The 2012 Educational Program Committee is pleased to share conference educational materials with you under the condition that they are used without alteration for educational and non-commercial use only. All materials are protected by copyright law. The authors kindly request their work is properly cited, including the date of publication. For more information on Small Farms, visit our website at: http://smallfarms.ifas.ufl.edu or contact your local County Extension Agent. For inquiries about this topic, please contact: Danielle Treadwell, Educational Program Chair. Phone: (352)-273-4775 E-mail: [email protected] Suggested Citation: Author Full Name. Title of Presentation or Handout. 2012 University of Florida-IFAS and Florida Agricultural and Mechanical University-CAFS Florida Small Farms and Alternative Enterprises Conference. July 27-29, Kissimmee, FL.
Soil Health and Disease Suppression in organic versus conventional plant production
Prof. Dr. Ariena van Bruggen Emerging Pathogens Institute and Plant Pathology Dept. University of Florida in Gainesville, FL
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Outline:
Organic and conventional crop management, soil quality and soil health
Root disease suppression in organic compared to conventional soil
Root diseases in crop mixtures versus pure stands Nematode suppression in organic soils Suppression of human pathogens in organic soils Reasons for pathogen suppression in organic soils Conclusions
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Differences between conventional and organic management Conventional synthetic pesticides
synthetic fertilizers
short rotation
rarely cover crops
rarely plant mixtures
sometimes biological control
(fungi, bacteria) applied
sometimes soil disinfestation
Organic
natural and mineral pesticides
organic amendments
longer rotation
frequently cover crops
more frequently plant mixtures
rarely biocontrol applied
rarely soil disinfestation
(by heat)
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Differences between conventional and organic management: agrobiodiversity
Differences in plant diversity in time and space can have a major influence on plant diseases
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Org - Conv Org - Conv
Photographs by Frans Smeding
Differences between conventional and organic soils
Conventional pesticide residues high NO3 and P2O5 contents low organic matter content poor structure lower microbial diversity and activity lower soil animal diversity and numbers conduciveness to root diseases
Organic no pesticide residues low NO3 and P2O5 contents higher organic matter content sometimes better structure higher microbial diversity and activity higher soil animal diversity and numbers suppressiveness to root diseases
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Soil quality and soil health
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Quality: mainly physical and chemical characteristics Health: mainly biological characteristics; diversity, ability to withstand stress
Left: old grassland, no fertil. Right: reseeded, fertilizer
Left: good quality soil, crumbly Right: poor quality soil, blocky
Photo’s on the right by Jan Bokhorst
Tomato corky root severity in organic, low-input and conventional plots in California
ORG, LOW and CONV 4-yr rotations, CONV2 a 2-yr rotation Effects of rotation and of management were significant
Corky root
0
4
8
12
16
20
Year 8 Year 9
Lesi
ons/
root
sys
tem
ORG LOW CONV CONV2
EPI Van Bruggen et al., unpubl.
Tomato root rot by Pythium in organic, low-input and conventional plots in California
0
10
20
30
40
1997 1998
% ro
tted
tips/
root
sys
tem
Pythium root rot
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ORG, LOW and CONV 4-yr rotations, CONV2 a 2-yr rotation Effects of rotation and of management were significant
Year 8 Year 9
Van Bruggen et al., unpubl.
Take-all disease on barley in conventional and organic soils
BARLEY 0% INOCULUM
0
2
4
6
C-C C-S O-C O-S
DIS
EASE
RA
TIN
G
BARLEY 0.5% INOCULUM
0
2
4
6
C-C C-S O-C O-S
DIS
EA
SE
RA
TIN
G
Hiddink et al., 2005
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Less disease in organic than in conventional soil
Pseudomonas fluorescens was not responsible for disease suppression in organic soils
Relation between take-all disease on triticale and bacterial diversity in conventional, transitonal and organic soil
0
2
4
6
C-L CO-S O-S
Dis
ease
ratin
g
0
50
100
85 90 95 100Relative diversity index
Rel
ativ
e di
seas
e
Hiddink et al., 2005
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Greater microbial diversity in organic soil
was associated with less take-all disease
Effects of plant diversity on root diseases
0.0
20.0
40.0
60.0
80.0
100.0
2001 2002 2003
% D
isea
sed
root
s
TriticaleTriticale-clover
0.0
1.0
2.0
3.0
4.0
5.0
2001 2002 2003
NO
3 m
g/kg
soi
l TriticaleTriticale-clover
Take-all disease severity on triticale alone or in a mix with clover
Soil NO3 content in a triticale crop or in a mix with clover
Hiddink et al., unpubl.
EPI Hiddink et al., unpubl.
Effects of plant diversity on root diseases
0.010.020.030.040.050.060.070.080.0
2001 2003
% D
iseased p
lants B.SPROUTS
MIX
Clubroot incidence on Brussels sprouts grown alone or in a mix with barley
Hiddink et al., unpubl.
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Effects of soil heating by steam on relative survival of J2 juveniles of root knot nematode (Meloidogyne incognita) in organic greenhouse soils
Berkelmans et al., unpubl.
EDECDCDCDCCC
BAB
ABABAAA
00,10,20,30,40,50,60,70,8
N M E Q B I X Y S G D O F C LGreenhouse soils
J2 s
urvi
val (
unpa
st/p
ast)
Steamed in past Never steamed
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Root knot nematode larvae were more suppressed in nonsterilized soil
Slow-growing predatory nematodes did not come back in steamed soil
Effects of soil heating by steam on root knot nematode index (RKI) in pots inoculated with J2 of M. incognita
Berkelmans et al., unpubl.
00,5
11,5
22,5
33,5
44,5
55,5
control L O M S F I
Farmers
RK
I (m
ed
ian
)
A
B BC
D C
C BC
Steamed in past
Never steamed
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Root knot nematode index was lower in nonsterilized soil
Slow-growing predatory nematodes did not come back in steamed soil
Risk of human pathogens in food production systems
Most cases/outbreaks linked to animal products
Increased association between food-borne diseases and fresh vegetables
manure
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Franz et al., 2008
Klerks et al., 2007
Salmonella
Reservoirs: cows pigs chickens Salmonella low medium high E. coli O157:H7 high low low Campylobacter low medium high
Survival of E.coli O157:H7 in manure and soil
Risk of human pathogens in food systems
Time (days)
0
1
2
3
0 20 40 60 Time (days)
log
CFU
/gdw
org/sand conv/sand org/clay conv/clay
0
1
2
3
4
5
6
7
log
CFU
/gdw
GMH
GH
SH
GML
GL
SL
0 20 40 60
EPI Franz et al., 2005
E. coli O157:H7 declined faster in fibrous manure from cows on a high fiber diet (with straw) than on a low fiber diet (with corn silage)
E. coli O157:H7 declined faster in organic than in conventional soil
Internalization of Salmonella in tomato plants
Salmonella declined faster in leaves of plants in organic than in conventional soil
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BSL II greenhouse
0 1 2 3 4 5 6 7 8 9
One-week post inoculation
Two-week post inoculation
log
CFU
/gdw
Salmonella Typhimurium inside inoculated leaflets. Green=sand; Red=conventional soil; Yellow=organic soil
Gu et al., 2011
Internalization of Salmonella in tomato plants
Salmonella declined faster in organic soils Decline rates were higher at higher bacterial diversity and Ca and Mg
concentrations in soil
Correlation of decline rates with bacterial diversity and soil nutrients
EPI Gu et al., 2012
Internalization of Salmonella in tomato plants
A trichome (leaf hair) and a stomate (leaf opening) with Salmonella cells
The tip of a leaflet with hydathode; Salmonella cells inside leaf and conducting vessels
Water droplets emerging through hydathodes (openings) on the margins of leaflets
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Salmonella enters a leaf through stomates or hydathodes (different kinds of openings for movement of gas and liquid)
Gu et al., unpubl.
Internalization of Salmonella in tomato plants
Conducting tissues: xylem on left and phloem on right (in box)
Phloem cells with Salmonella cell inside
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Salmonella moves from leaves into stems (phloem) and fruit
Gu et al., 2011
Internalization of Salmonella in tomato plants
contaminated fruits control fruits
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Salmonella inside tomato fruits on leaf-inoculated plants
Gu et al., 2011
Internalization of Salmonella in tomato plants
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Gu et al., 2012
1 Number of plants with internally contaminated leaves 2 Number of fruits that were internally contaminated, 9 fruits on 1 plant 3 Number of fruits that were internally contaminated, 5 fruits on 1 plant,
2 fruits on another plant.
Reasons for pathogen suppression in organic soils
In the soil and rhizosphere Greater diversity of microbiota (bacteria, fungi, nematodes etc.) ->
a greater chance of the presence of antagonists and predators Root exudates consumed by abundance of microbes -> no
rhizosphere effect -> pathogens cannot find roots Fewer nutrients and substrate available for pathogens to grow
In the plants Lower nitrogen levels, higher Mg and Ca levels -> sturdier plants Greater induced resistance throughout the plants Better soil structure, drainage, water-holding capacity -> less
stressed plants
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Similarity of microbial communities in rhizosphere versus bulk soil from organic and conventional farms ‚‚3ˆB‚‚BRR‚R2ˆBBRR‚BBBRR‚BRBBRRBR‚BBRRRRR1ˆBBBBRBR‚BBBBBR‚BBBRBBRRRR‚BRRR0ˆRRR‚RRRR‚RRRB‚RB‐1ˆRRRRBRR‚RBBR‚R‚B‐2ˆB‚‚BBBB‚B‐3ˆ‚‚BB‚‐4ˆBB‚B‚B‚‐5ˆ‚B‚‚‐6ˆ‚Šƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒ‐6‐4‐202468
R Conventional Rhizosphere samples B Conventional Bulk Soil samples R Organic Rhizosphere samples B Organic Bulk Soil samples
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Bacterial composition 1
Bac
teria
l com
posi
tion
2
Van Diepeningen et al., 2006
Each dot is a soil sample
Conclusions
Usually: root disease severity is lower in organic than in conventional farms
Frequently: a positive correlation of root disease severity with N availability, and a negative correlation with microbial activity and diversity
Usually: soil sterilization has a long-term negative effect on natural pathogen and nematode suppression
Commonly: enteric pathogens are suppressed in fibrous manure and well aerated (organic) soil
Rarely: enteric pathogens can enter through roots or leaves, move inside the plant and contaminate a plant internally
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Conclusions
Survival and movement of Salmonella in tomato plants is less in organic than conventional soil
Greater bacterial diversity in plants grown in organic soils may lead to greater resistance to internal colonization of Salmonella as well as plant pathogens
It is important to maintain soil health by diverse cropping systems, addition of organic matter to soil, and avoidance of any kind of soil sterilization (soil solarization and biological soil disinfestation are ok)
It is important to prevent contamination with human pathogens: properly composted manure, clean water
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Acknowledgements
University of California Davis: all people of the SAFS project, especially Howard Ferris, Kate Scow, Sean Clark
Wageningen University: Aad Termoshuizen, Wim Blok, Gerbert Hiddink, Anne van Diepeningen, Robert Berkelmans, Eelco Franz, Michel Klerks, Oscar de Vos
University of Florida: Ganyu Gu, Juan Cevallos-Cevallos, Ellen Dickstein
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