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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
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