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Soil microorganisms and organic
fertilization history in relationship to
Striga hermonthica (Del.) Benth. seed
bank density
S. Bökle, T.A. van Mourik, M. Cotter, J. Sauerborn
seboekle@uni-hohenheim.de
Garbenstr. 13, 70599 Stuttgart, Germany
Striga and organic matter
Striga appearance
2/15
Village
~2kmSauerborn et al. 2003
Introduction Objective Material&Methods Results Outlook
Objective
Which soil parameter induces lower Striga infestation
under high organic fertilization practice?
Investigation of:
• Microbial communities via PLFA- Analysis
(Phospholipid fatty acids)
• Soil characteristics
• Field history
Introduction Objective Material&Methods Results Outlook 3/15
Material and methods
• Sindala, Mali (40km SW from
Bamako, near Siby)
• Guinean agro-ecological zone
with 1043mm annual rainfall
• Sandy silty to sandy loamy
Leptosols
• Highly infested area
Introduction Objective Material&Methods Results Outlook4/15
Material and methods
• Mapping the territory
• Interviews with farmers
• Field history
• Crops
• Fertilization
• Striga development
Introduction Objective Material&Methods Results Outlook5/15
Material and methods
Field selection:
• At least 5 out of 10 years sown with host crops
• Organic fertilization
• high ( > 6 out of 10 years)
• low ( < 2 out of 10 years)
• 28 fields
• 2- 6 samples/ field
• 100 soil samples in total
Introduction Objective Material&Methods Results Outlook6/15
Material and methods
Data collection:
• Emerged Striga and seed bank density
• Soil parameters (Corg, Mic C, -N & -P,
N, P, K, CEC, pH, texture)
PLFA Analysis
• PLFAs: components of microbial
membranes
• Peak patterns indicate microbial
community composition.
8/15Introduction Objective Material&Methods Results Outlook7/15
Material and methods
PLFA Analysis :
• Phospholipid fatty acids as bioindicators for microbial
communities (Kandeler et al. 2008)
9/168/15
Introduction Objective Material&Methods Results Outlook
Preliminary resultsNo clear gradients in any directions from the village
9/15Introduction Objective Material&Methods Results Outlook9/15
Preliminary results
10/15
Negative relation of Striga and Gram- bacteria bioindicator
p= 0.0151
R²= 0.0596
Introduction Objective Material&Methods Results Outlook10/15
0.0 0.1 0.2 0.3 0.4 0.5
Preliminary results
11/15
Negative relation of Striga and bacterial bioindicator
p= 0.0457
R²= 0.0389
Introduction Objective Material&Methods Results Outlook11/15
0.0 0.2 0.4 0.6 0.8
Field
Preliminary results
13/15
3 fields with high spacial variability :
• high and low Striga emergence in close vicinity
~20m
Introduction Objective Material&Methods Results Outlook12/15
Preliminary results
13/15
Gra
m+
Fun
giGra
m-
Gra
m-G
ram
+
Gra
m+
Gra
m+
bac
teri
al
bac
teri
al
Bacteria dominate in low Striga spots
Introduction Objective Material&Methods Results Outlook13/15
2
1.5
1
0.5
0
Conclusions & outlook• Statistical analysis show that Striga seed bank density
and bacterial abundance (especially Gram-) are negatively
related.
Examples: Azospirillum brasilense, Pseudomonas putida
(Hassan, M.M. 2009)
• Soil chemical analysis are on-going and will be
integrated in the database and in further statistical
analyses
• Future investigations on soil born Striga control should
focus on bacterial strains especially Gram- ones.
Introduction Objective Material&Methods Results Outlook 14/1514/15
Thanks for your attention!
Acknowledgements: To all my supervisors and the EWRS for the scholarship
15/1515/15
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