Delivery of Hydrologic and Microbial Services by Shrub Rhizospheres to Increase Crop productivity and Stability in the Sahel. Shrubs do hydraulic lift – during night when photosynthesis stops – but water keeps moving up through roots because of low water potential in surface and high water potential in subsoil – so water moves passively through roots because of the structure of roots facilitates faster movement of water then through the soils.

1. Delivery of Hydrologic and Microbial Services by
Shrub Rhizospheres to Increase Crop
Productivity and Stability in the Sahel
Global Forum for Innovations in Agriculture,
Abu Dhabi, 9-10 March, 2015
Richard P. Dick, Director (dick.
78@snr.osu.edu)
Soil Microbial Ecology Laboratory
Ohio State University, Columbus Ohio, USA

2. Senegal
West
Africa

3. Senegal
~ 60% of population
depends on agricultural
economy

4. Overgrazing
Cropping intensification
and disturbance
Landscape
Exploitation
Increasing rural and urban
populations
Scavenging for fuel resources

5. Encroachment of Desert

6. Challenges of Semi-arid
Agroecosystems in the Sahel
Subsistence Faming
Low primary productivity
Efficiency of water and nutrients

7. Sahalian Agroecosystems:
Carbon - A Major Agronomic Constraint
Loss of soil organic matter inputs:
Decreases nutrient/water efficiency and optimal yields
(Badiane et al., 2001; Sanchez et al., 1997)
Even with fertilizer applications yields continue to go
down over the long-term (Sanchez et al., 1997; Merckx et
al., 2001).

8. 1. Unique Research Opportunity
• Shrub-crop rhizosphere interactions/ecology
• Possible because of minimally mechanized
agriculture in the Sahel
• Food security
• Rural poverty
• Buffering capacity for global climate change
• Desert encroachment
2. Potential Applications for Africa
3. Implications for semi-arid regions worldwide

9. Dr. Mateugue Diack, Univ of Gaston
Berger, Decomposition
Dr. Ibrahima Diedhiou, Univ. of Thies,
Senegal, Plant ecology
Dr. Modou Sene, CNRA/ISRA, Senegal,
Hydrology
Dr. Richard Dick, Ohio State University,
Soil biology
Dr. Mamadou Khouma, UNDP (formerly
ISRA), GIS and plant nutrition
Dr. Samba Ndiaye, Univ. Thies, (formerly
ISRA), Agroforestry
Dr. Jay Noller, Oregon State University
C and biomass – landscape level
Dr. Maria Dragila, Oregon State
University, Hydrology
Dr. Aminata Badiane, USAID (formerly
ISRA), Soil biochemistry
Ms. Astou Sene, ISRA, Socio-economics
Phase I – Collaborators
USAID ($US 250,000)
US National Science Foundation Project
(1.2 $US million)
1999-2008

10. Dr. Samba N. Samba
Agroforestry
Ms. A. Sene
Rural Sociology
Dr. Aminata Badiane
Soil Biochemistry
Dr. Modou Sene
Soil Physics
Dr. Mamadou Sene
Agronomy/GIS

11. Research
Coordinator
Dr. Ibrahima Diedhiou
Post doc - Plant ecology
Sire Diedhiou, Senegal
Soil microbiology
Ekwe Dossa, Togo
Soil chemistry
Nutrient cycling
Abel Lufafa
Uganda
Landscape carbon
dynamics
Fred Kizito, Uganda
Hydrology/soil physics
PhD Students

12. Dr. Richard Dick, Ohio State University,
Soil Biology
Dr. Ibrahima Diedhiou, Univ. of Thies,
Senegal, Plant Ecology
Dr. Brian Mcspadden Gardener, Ohio
State University, Plant Pathology
Dr. Hassna Founoune-Mboup, Institut
Senegalais de Recherches Agricole, Plant
Science
Dr. Teamrat Ghezzehei, University of
California, Merced, Hydrology, Soil &
Env. Physics
Dr. Lydie Lardy, IRD Dakar, Molecular
Biology
Dr. Yacine Ndour, Institut de Recherche
pour le Development, Soil Microbiology
Dr. Paul Schreiner, USDA-ARS,
Mycorrhizal Fungi
Dr. Komi Assigbetse, IRD Dakar,
Molecular Biology
Phase II – Collaborators
US National Science Foundation Project
(2.6 $US million)
2011-2016

13. Phase II – Collaborators
Richard Dick
Soil microbiology
Ibrahima Diedhiou
Plant ecology
Brian Mcspadden Gardener
Microbial diversity
Teamrat Ghezzehei
Soil Physics hydrology
Paul Schreiner
Mycorrhizal fungi
Yacine Ndour
Soil microbiology
Komi Assigbetse
Molecular microbiology
Lydie Lardy
Nitrogen cycling
Hassna Founoune-Mboup
Mycorrhizal fungi

14. Students
Nathaniel Bogie, PhD
Rhizpsphere hydrology
Matthew Bright, PhD
Mycorrhizal fungi
Chelsea DeLay, MS
Diazotrophs and
nitrogen cycling
Spencer Debenport, PhD
Beneficial microorganisms
Esther Lattin, MS
Enzymes and
microbial communities
Roger Bayala, Post doc
Fieid research coordinator
hydrology

15. 3 m3 m
Dominant Native Shrubs in Farmers’ Fields
1m
" Northern region, typically sandy
" Mean annual rainfall 300 mm
" Mean annual temperature 30 oC
" Southern region, higher clay content
" Mean annual rainfall 750 mm
" Mean annual temperature 32oC
Guiera senegalensisPiliostigma reticulatum

16. G. Senegalensis
3 Mg dry stem+leaves ha-1
P. reticulatum
3 Mg dry stem+leaves ha-1
Shrub Biomass Study
Factorial Treatments:
Biomass Rate - 1.5 or 3 Mg ha-1
Fertilizer - 0, 0.5, 1.0 or 1.5 X Recommended Rate

17. Effect of Shrub Residue (absence of shrub plant)
and rate of fertilizer in on Crop Yields in Senegal.
‡Values within columns followed by the same superscript letter are not significantly different at P <0.05
Residue Treatment Rate ha-1 2004
Peanut
2005
Millet
2006 Peanut 2007 Millet
--------------------------------------------kg ha-1---------------------------------------
Control No residue 816a 537a
712b 1197c
G. senegalensis
Biomass
1.5 Mg 766a 664a
912b 1296c
G. senegalensis
Biomass
3.0 Mg 857a 755a
1116a 1609a
P. Reticulatum
Biomass
1.5 Mg 615a 583a
908b 1385b
P. Reticulatum
Biomass
3.0 Mg 691a 588a
1116a 1479b
NS NS P<0.05 P<0.05

18. Ekwe Dossa
N and P Cycling
PhD Candidate
Shrub X Fertilizer Rate (Bambey ~500 mm)
Factorial:
1) + and - Shrub
2) 0, 0.5, or 1.0
Rec. Fret. Rate
Plus Shrub
Litter Incorporation
Guiera senegalensis
Minus
Shrub

19. †Rate Shrub No shrub Shrub
Increase
Shrub No shrub Shrub
Increase
------------ kg ha--1
------------- % ---------- kg ha-1
----------- %
2004 season (Arachis hypogaea) 2005 season (Pennissetum glaucum)
0 190a† 78b 143 218a 11a 1818
0.5 135a 103a 32 359a 148b 142
1.0 153a 116a 36 422a 278b 52
1.5 203a 91b 123 605a 503a 20
Mean 170a 97b 400a 260b
2006 season (Arachis hypogaea) 2007 season (Pennissetum glaucum)
0 384a 273b 41 197a 6b 3183
0.5 542a 449b 21 403a 85b 374
1.0 556a 579a -4 378a 200b 89
1.5 708a 532b 33 622a 174b 257
Mean 547a 458b 400a 116b
Effect of shrub (G. senegalensis) and rate of fertilizer on
Crop Yields in the Peanut Basin, Senegal.
‡Values within columns followed by the same superscript letter are not significantly different at
P <0.05
†Fertilizer rate is 0, 0.5, 1.0 or 1.5 the recommended NPK rates appropriate for each crop.
(Dossa et al. Agronomy J. 2012)

20. G. Senegalensis and P. reticulatum are found in farmers’ fields
between < 200 to ~ 1200 mm from Senegal to Niger and Chad

21. Senegal – P. reticulatum

22. Burkina Faso
P. reticulatum
Niger
G. senegalensis
Mali
G. Senegalensis P. reticulatum

23. Dramatic Yield Response to
Shrub Intercrops:
Why?
Improved Water Relations
Improved Nutrient Status
Beneficial Microorganisms

24. Increased Soil Organic Matter
and Nutrient Availability
(Dossa et al., 2008; 2009)
• Root turnover
• Litter inputs from aboveground biomass

26. Shrub Roots go very deep
• Roots grow to 10 meters or more
• Perform hydraulic lift – movement of water through
roots from wet subsoil to surface soil at night when
PS stops (Kizito et al., 2012)

27. Shrub impact on water balance
" Hydraulic lift under dry
conditions
" Ground water recharge with
excess precipitation
" No competition of shrubs with
crops for water
WATER TABLE
ET
P
ΔSW
Gin
DP
Crop
Shrub
?
Kizito et al. 2006; 2012

28. Shrub Rhizosphere
Promotes Beneficial Microorganisms
Harbor bacteria and fungi for crop roots that:
- increase nutrient availability
- provide plant growth promoting hormones
- increase N fixation by free living microbes
Promote mycorrhizal fungi-infecting shrubs/crops:
- common hyphal connections of shrub to crop roots
- improves water relations of crops
- promote P and other nutrients for crops

29. 0 1 2 3 40
20
40
60
80
100
Wet season
Distance from Center of Shrub (R=canopy radius)
Center R/2 1 R 2 R
MicrobialBiomassC(µgg-1)
Dry season
Rhizosphere soil
Non-rhizosphere
soil
Dry season
Wet season
Soil Microbial Biomass C (incubation-fumigation) (0-20 cm
depth) in the Wet and Dry Season of P. reticulatum (n=3).

30. Microbial Diversity with
PLFA Analysis
Variance explained (PCA): 64%
Correlation with Axis 1
! Fungi, 18:2ω6c (0.89)
! Actinomycetes, 10Me 18:0 (0.86)
! 15:0 3OH (0.85)
! Rhizosphere effect (p<0.001)
! Seasonal effect (p<0.02)
PLFA
Axis 1
Axis2
Rainy season Dry season
Rhizosphere
Bulk
Non-rhizosphere
P. reticulatum : red color
G. senegalensis: black color
(18%)
(46 %)
Non-rhizosphere soil
Bulk soil
Rainy season
Bulk soil
Dry season
Rhizosphere
Rainy season Dry season
Rhizosphere
Bulk
Non-rhizosphere
P. reticulatum : red color
G. senegalensis: black color

31. Common
Mycorrhizal
Hyphal
Network
Shrub
Crop

32. Mycorrhizable
Roots
(<
2mm)
Guiera
senegalensis
(dicot)
Millet
(C4
grass)

33.
Hyphae,
Vesicle,
Arbuscule
Spore
AMF
Structure
ExplanaJon
Millet
Root
G.
senegalensis
Root

34. Mescosm for studying hydraulic redistribution relative to
microbial and crop responses in rhizo- vs. mycorrhizo-spheres.
G. senegalensis
Millet
Perforated 35 !m
stainless steel sheet
coated with PTFE
tap root chamber
water container
15 !m air
gap
mycorrhizae
fungi
75 cm
Root
chamber

35. Investigation of Mycorrhizal Hyphal
Connections from Shrub to Millet
Mescosm Study Field Study

36. Millet under water stress in mesocosm:
Effect of Mycorrhizal hyphae
Intact microcosm Turned microcosm
Hyphae connections No hyphal connection

37. Paradigm shift
Biogeochemical processes can proceed in
the dry season of arid regions.
Hydraulic lift maintains microbial
communities and activities – Therefore,
driving processes that can improve crop
yields – notably nutrient release for crop
uptake

38. Overall Conclusions
Shrubs can act as “mother” plant for crops
Shrub Rhizospheres:
ü Increase microbial diversity/activity
ü Harbor beneficial microorganisms
ü Are performing hydraulic lift
ü Increase nutrient availability and decomposition rates
Crop Productivity
P Shrub residues do not inhibit yield & can increase yield
P Shrubs do not compete for water with crops
P Shrubs assist crops through drought periods
P Non-thermal systems with shrub present increase crop
yields dramatically with G. senegalensis
P Shrubs decrease time to maturityb

39. Publications
Diack, M., M. Sene, A. N. Badiane, M. Diatta, and R. P. Dick. 2000. Decomposition of a native shrub (Piliostigma
reticulatum) litter in soils of Semiarid Senegal. J. of Arid Soil Research and Rehabilitation 14(3):205-218.
Iyamuremye, F., V. Gewin, R.P. Dick, M.Diack, M.Sene, A.N. Badiane, and M. Diatta. 2000. Carbon, nitrogen,
and phosphorus mineralization of agroforestry plant residues in soils of Senegal. J. of Arid Soil Research and
Rehabilitation 14:359-371.
Badiane, A.N., A. Faye, C.F. Yamoah, and R.P. Dick. 2002. Compost and mineral fertilizers for millet production
by farmers in semi-arid Senegal. Biol. Ag. Hort. 19:219-230.
Lufafa, A., I. Diédhiou, S. Ndiaye, M. Séné, M. Khouma, F. Kizito, R.P. Dick, and J.S. Noller. 2008. Carbon stocks
and patterns in native shrub communities of Sénégal’s Peanut Basin. Geoderma 146: 75-82
Kizito, F., M. Dragila, M. Sène, A. Lufafa, I. Diedhiou, E Dossa, R.P Dick, M Khouma, A. Badiane, and S.
Ndiaye. 2006. Seasonal soil water variation and root dynamics among two semi-arid shrubs coexisting with
Pearl millet in Senegal, West Africa. J. of Arid Environments 67:436.
Lufafa, A., Wright, D., Bolte, J., Diédhiou, I., Khouma, M., Kizito, F., Dick, R.P., Noller, J.S., 2008. Regional
carbon stocks and dynamics in native woody shrub communities of Senegal’s Peanut Basin. Agriculture,
Ecosystems and Environment 128:1–11.
Kizito, F., M. Senè, M. I. Dragila, A. Lufafa, I. Diedhiou, E. Dossa, R. Cuenca, J. Selker, R. P. Dick. 2007. Soil
water balance of annual crop-native shrub systems in Senegal’s Peanut Basin. Ag. Water Management
90:137 – 148.
Dossa, E.L. M. Khouma, I. Diedhiou, M. Sene, F. Kizito, A.N. Badiane, S.A.N. Samba, and R.P. Dick. 2009.
Carbon, nitrogen and phosphorus mineralization potential of semiarid Sahelian soils amended with native
shrub residues Geoderma 148:251–260
Dossa .E. L., J. Baham, M. Khouma, M. Sene, F. Kizito, R.P. Dick. 2009. Phosphorus Sorption and Desorption in
Semiarid Soils of Senegal Amended with Native Shrub Residues Soil Science 173:669-682.

40. Publications (continued)
Lufafa, A.; Diedhiou, I.; Ndiaye, N.A.S.; Sene, M.; Kizito, F.; Dick, R.P.; Noller, J.S.
Allometric relationships and peak-season community biomass stocks of native
shrubs in Senegal's Peanut Basin. Journal of Arid Environments73:260-266.
Diedhiou, S., A.N. Badiane, I. Diedhiou, M. Khoum, A.N.S Samba, M. Sène and R.P.
Dick. 2009. Succession of Soil Microbial Communities during Decomposition of
Native Shrub Litter of Semi-Arid Senegal. Pedobiologia 52:273—286.
Dossa , E.L.,S. Diedhiou & J. E. Compton, K. B. Assigbetse & R. P. Dick. 2010. Spatial
patterns of P fractions and chemical properties in soils of two native shrub
communities in Senegal. Plant Soil 327:185–198
Kizito, F., M. I. Dragila, M. Senè, R. J. Brooks, F. C. Meinzer, I. Diedhiou, M. Diouf,, A.
Lufafa, R.P. Dick, J. Selker, R. H Cuenca. 2012. Hydraulic Redistribution by Two
Semi-arid Shrub Species: Implications for Sahelian Agro-ecosystems. J. Aird
Environments. 83:69-77.
Dossa, E.L. M. Khouma, I. Diedhiou, M. Sene, F. Kizito, A.N. Badiane, S.A.N. Samba,
and R.P. Dick. 20012. Crop Productivity and Nutrient Dynamics in a Shrub (Guiera
senegalensis) -Based Farming System of the Sahel. Aronomy J. 104:1255–1264.
Diedhiou1, S., E.L. Dossa, A.N. Badiane, K.B. Assigbetsee, I. Diedhiou, N.A.S. Ndiaye5,
M. Khouma, M. Sène and R.P. Dick. 2012. Microbiology and Macrofaunal Activity
in Soil beneath Shrub Canopies during Residue Decomposition in Agroecosystems
of the Sahel. Soil Science Society of America J. Soil Science Soc. Am. J. 77:501-511
Dossa, E.L. I. Diedhiou, M. Khouma,, M. Sene, A.N. Badiane, S.A.Ndiaye, K.B.
Assigbetse, S. Sall, A. Lufafa, F. Kizito, S. Diedhiou, and R.P. Dick, and J. Saxena
2012. Crop productivity and Nutrient Dynamics in a Shrub (Piliostigma reticulatum)
-Based Farming System of The Sahel. Agron. J. 105:1237-1246.

41. WEST AFRICAN SHRUB INTER-
CROPPING INITIATIVE:
ALearning and Observatory Network Focused
on Subsistence Farm Families
Guiding principles
Gender neutral
Locally defined criteria of success
Integrate ‘expert’ and ‘non-expert’ knowledge
World Agroforestry Centre, Nairobi, Kenya
Ohio State University

42. Technology Development
Participating Countries:
Burkina Faso, Mali, Niger, Senegal
Approach
On-farm demonstration and technology development
A. Test and demonstrate:
Optimized shrub-crop system – high shrub density/no burning
vs.
Traditional management – low shrub density/coppicing& residue burning
B. Monitoring: C sequestration, soil quality, crop water stress levels and yield,
and socio-economic impacts of shrub-based farming systems
C. Farmer-researcher data analysis and interpretation

43. Expected Results:
Technology Adaptation and Transfer
Successful shrub-based farming options in the
Sahel documented, and findings made
available to stakeholders (FBO, NGO,
government agencies, ) for decision making.
Farmer-centered decision-support tools will be
developed using focus sessions, workshops,
and field surveys.

44. Expected Products
1. Roadmap for scaling and fundamentals for full
technology transfer campaigns
2. Optimized Shrub-Crop Manuals for agricultural
professionals and policy makers - local language
and French for both literate and illiterate end
users
3. Smart Phone apps and technology transfer
platforms – including real time crop management
information transfer

45. Expected Products (continued)
4. Website Model for farmers and ag professionals
with downloadable and printable extension
instruments - local language and French
5. Carbon Credit Calculator - App for smart phones
that uses easily measurable above ground
measurements to verify C sequestration rates at the
farmer level

46. Richard Dick
School of Environment an Natural Resources
Ohio State University
dick.78@snr.osu.edu
Thank You
Questions?

47. Reestablishment Technology
1. Grow seedling in spring season
P. reticulatum by seed; G. senegalensis by layering mother plant
2. Transplant seedling into farmers fields during
wet season
3. Allow seedlings to grow without further
irrigation over dry season.

48. Stem from mother plant
New seedling growth
Dr. Ibrahima Diedhiou
Cooperating
Farmer
Shrub Reproduction

49. Piliostigma reticulatum
Interplanting for Mango Seedling
Establishment
Plant mango on established P. reticulatum
Hydraulic lift “irrigation”
High mango seedling survival – likely because of
water and improved soil quality

50. 1 Year Mango Seedling

51. Pruned Piliostigma
reticulatum plant

52. Piliostigma reticulatum
1 Year Mango Seedling