Soil erosion in Nigeria,Land use intensification in pilot villages varying in length of cropping season and linkage to erosion features,Impact of soil conservation technologies in the Savanna of Nigeria, Benin, and Ghana assessed,New approaches for on-farm monitoring of short and long-term benefits from soil conservation technologies developed and tested

1. Soil conservation options in the Savanna of
West Africa:
new approaches to assess their potential
Overview of activities and results of the BMZ/GTZ-Project
conducted at IITA from 2005-2008
Birte Junge
International Institute of Tropical Agriculture– www.iita.org

2. Outline
- Introduction
Term: Soil
Problem: Soil erosion in Nigeria
- Activities and Results of studies on
1. Remote sensing + GIS
2. Adoption of soil conservation technologies
3. Measurement of erosion
- Conclusions

3. Introduction
Soils in West Africa
- Age: old
- Material: sand / gravel / clay Ah
(Lal 1995)
Soil degradation (Oldeman 1991) 2 Bt
- Soil erosion by water
- Soil erosion by wind
- Chemical deterioration
3 Ct
- Physical deterioration
Luvisol
Soil conservation (Gibbons 1988)
- includes whole program of studies for preventing + reducing soil degradation

4. Introduction
Problem: Soil erosion in Nigeria
Sheet erosion
Gully erosion
Wind erosion
Federal Surveys of Nigeria (1992)
General Soil Erosion Map of Nigeria 1:6,000,000

5. Output 1:
Land use intensification in pilot villages varying in length of cropping season
and linkage to erosion features established.

6. O1: Methods
Pilot villages:

7. O1: Methods
Remote sensing data:
Aerial photograph IKONOS QuickBird
Date 1962/1981 2000 2005/06/07
Spatial resolution (panchromatic image): 1m 0.6 m

8. O1: Methods
Interpretation:
Land use/land cover
Cowpea
Maize
Compound
Millet / Sorghum

9. O1: Results
Badume: Kano State
Change of village area
Year Area (ha)
1949 265
2000 402
Total Increase + 137
An. increase + 2.7
Today:
NO land available any more

10. O1: Results
Kayawa: Kaduna State
Change of farmland
Sept. 1962
Dec. 2006
2000
Maize
Cowpea
Year 1962 2000 Change 2006 Change
Arable land (ha) 49.7 266.1 + 216.4 286.6 + 20.5

11. O1: Results
Gadza:
Change of settlement, forest, uncultivated land
Oct. 2000
Jan. 2005
Sorghum Millet Fallow
Year 2000 2006 Change
Settlement (ha) 1.2 1.5 + 0.3
Rice
Tree, shrub (ha) 13.3 8.5 - 4.8
Uncult. Land (ha) 104.0 77.5 - 26.5

12. O1: Summary
Land use intensification:
- Expansion of settlements areas
- Expansion of villages areas
- Expansion of farmland
Rate of increase higher in former times
No expansion possible any more today (land scarcity)
Conversion of other land use types into farmland
- Reduction, elimination of fallow
- Deforestation
- Decrease of uncultivated areas in surroundings

13. O1: Results
Badume: Kano State
Present gully erosion
2000 2006
Measurement: Calculation:
Year 2006 Year 2000 2006 Increase
Area (ha) 1.2 Area (ha) 37.9 45.1 7.2
Soil loss (t) 7708

14. O1: Results
Badume: Kano State
Future gully erosion
2006
Estimation:
R = 0.36 (A)0.46 (P)0.20
R = Rate of headward advancement (m yr-1)
A = Tributary watershed area (ha)
P = Annual precipitation (mm)
Morris and Fan (1997)
Badume: R = 0.5 m yr-1
Depth line
Year 2006 2016 2026 Gully border 2006
Area (ha) 4.3 5.1 5.9 Gully border 2016
Gully border 2026

15. O1: Results
Kayawa: Kaduna State
Sheet erosion
1962 2000
Year 1962 2000 Change 2006 Change 2016
Sheet erosion (ha) 7.9 25.6 +17.7 32.3 + 6.7 42.3
Annual rate (ha yr-1) 0.5 1.1

16. O1: Results
Gadza: Niger State
Gully erosion
2005
Settlement
1m
River
Measurement:
Year 2006 Year 2000 2005 Change 2015
Area (ha) 1.2 Gully length (km) 12.8 58.4 + 45.6 91.2
Soil loss (t) 4184

17. O1: Results
Eglime: Dept. Mono
Gully erosion
2007
Cotton
Gully
Year 1982 2000 2007 Change 2017
Gully length (km) ? 4.4 42.4 + 38.0
Gully area (ha) 2.3 18.7

18. O1: Summary
Soil erosion:
- Increase of gully and sheet erosion in Badume, Kayawa, Gadza, Eglime
- Reduction of arable land
Decrease of crop production
- Reduction of uncultivated area in surroundings of farmland
Decrease of grazing land
Rising conflicts among various users deriving from competition
for limited resources in the future

19. O1: Conclusions
Use of thematic maps:
Agenda 21 (UN 1992)
- more effective use of land and natural resources
by improved planning, management and evaluation systems
Nigerian Department of Agricultural Land Ressources, Abuja
- Implementation of appropriate policies
Environmental Management Support System
- Database for inventory of natural resources
Problems: missing equipment, no trained staff, …

20. O1: Conclusions
Use of thematic maps:
Land use planning
- Reservation of areas
with fertile soils for farming
with degraded soils for reforestation, settlements
with minerals for mining
Soil conservation
- Field maps for installation of
soil erosion control measures
Tree, Shrub
Vetiver
Stone barrier
Badume

21. O1: Outcome
Farmer Field Hour:
- Presentation of study on land use change
and soil degradation
- Discussion of possible soil conservation
measures
Kayawa 31 Oct. 2007
Publications:
Junge B., Alabi T., Sonder K., Abaidoo R., Chikoye D., Stahr K. (2008):
Remote sensing and GIS for monitoring changes of land use/land cover and environmental degradation
in different agroecological zones of West Africa
Manuscript for Int. J. Remote Sensing
Junge, B., Abaidoo, R., Chikoye, D., Alabi, T. & Stahr, K. (2006):
Monitoring of land use intensification and linkage to soil erosion in Nigeria and Benin.
Conference proceedings, Deutscher Tropentag (DTT), 11-13 October 2006, Bonn, Germany

22. Output 2:
Impact of soil conservation technologies in the Savanna of Nigeria, Benin,
and Ghana assessed.

23. O2: Methods
Literature
Search for literature on soil conservation:
- Internet
- Research Institutes
- Universities
- Gov. organizations
- NGOs
Location for
search
of literature
Generation of database:
~ 1200 references

24. O2: Results
History of soil conservation in Nigeria:
- Pre-colonial era: indigenous technologies (Slaymaker & Blench 2002)
e.g. ridging, terracing, fallowing
- Colonial era: large-scale projects in areas of high agricultural potential
often failed due to inappropriate technologies
- After 1960: more emphasis put on soil fertility issues
- Today: FGN plans to spend US$ 0.5 mio on soil erosion projects (FGN 2007)

25. O2: Results
Strategies of soil conservation:
Erosion control strategies
On Farm strategies Off Farm strategies
Agronomic Soil Mechanical
Measures Management Methods Mechanical Biological
Mulching Conservation Terracing Waterways Tree Planting
Tillage Planting Shrubs
Crop Waterways Dams & Grasses
Management
Structures
Structures
Wind &
Fire Breaks
El-Swaify et al. (1982)
(changed)

26. O2: Results
Mulching
Benefits Constraints
reduces erosion through soil coverage
Odunze (2002) large amount required: (4-6 t ha-1)
Lal (2000)
increases infiltration, aggregate stability
Hulugalle et al. (1995) extra costs for purchase, transport
of brought-in material, labour for
increases activity of soil fauna distribution on the field
Tian et al. (1997)
Lal (1995)
increases level of organic matter, nutrients,
and crop yield Esa Oke
Mbagwu (1991)
Mulching is a useful SCT

27. O2: Results
Crop management
Intercropping, Alley cropping, Cover cropping, Fallowing, Planting pattern...
Benefits Constraints
reduces erosion through canopy cover
and by acting as runoff barrier special knowledge required on
Lal (1989) compatible species, spacing to
avoid competition for use of growth
maintains and improves soil structure resources
Tian et al. (1999) Tarawali et al. (1999)
improves ability to recycle nutrients (A)
Kang et al. (1995)
Crop management is a useful SCT
Ibadan

28. O2: Results
Conservation tillage
Minimum tillage, No-till + Ridge Tillage
Benefits Constraints
M, N: M, N:
reduces soil loss through soil coverage difficult to perform on shallow land
Kirchhof & Salako (2000) Eziakor (1990)
maintains and improves physical, chemical, poor aeration of root/tuber crops
and biological soil properties in soils with poor drainage
Osunbitan et al. (2005) Kowal and Stockinger (1973)
R: R:
reduces erosion by acting as runoff barrier reduces soil coverage
Lal (unpubl.) Lal (1989)
improves infiltration by destroying surface
crusts and reducing compaction Badume
Chiroma et al. (2006)
Specified tillage operations are useful SCT

29. O2: Results
Other approaches
Modelling
to determine areas with potential erosion hazard
Universal Soil Loss Equation (USLE) Igwe (1999)
Remote sensing + GIS
to monitor erosion within space, time
NIGERIA SAT-1 Ayeni et al. (2004)
IKONOS, QuickBird Junge et al. (unpubl.)
… are useful tools for improving soil conservation

30. O2: Results
Choice of SCTs in dependence of…
Climate: AEZ Mulch. Interc. Coverc. No-till Ridg. TRidg.
Sahel S. X X X X
Sudan S.. X X X X
Nigeria
Guinea S. X X X X
Derived S. X X X X
Humid F. X X X X
Soil: Texture Mulch. Interc. Coverc. No-till Ridg. TRidg.
Sand x x x X
Clay x x x X X
Site specific choice

31. O2: Results
Performance of soil conservation:
e.g. Conservation Tillage
Author Location
Aina, O.A.; Lal, R. and E.J. Roose (1991) (review)
Amezquita, E., Lal, R., Greenland, D.J. and D. Payne (1993) IITA, Ibadan
Armon, M.N. (1980) IITA, Ibadan
Chiroma, A.M., Yakubu, H. and M.K. Sandabe (2002) University in Maiduguri
Chiroma, A.M., Folorunso, O.A. and A.M. Kundiri (2005) University in Maiduguri
Couper, D.C., Lal, R. & S. Claassen (1980) IITA, Ibadan
Franzen, H., Lal, R. and W. Ehlers (1994) IITA, Ibadan
Juo, A.S.R. (1995) IITA, Ibadan
Kirchhof, A.C. and F.K. Salako (2000) IITA, Ibadan
Lal, R. (1974, 1985, 1997) IITA, Ibadan
Maurya, P. R. and R. Lal (1980) IITA, Onne, Port Harcourt
Ogunremi, L.T. and R. Lal (1986) IITA, Onne
Ogunremi, L.T., Lal, R. and O. Babalola (1986) IITA, Ibadan
Onwualu, A.P. and U.G.N. Anazodo (1989) University in Nsukka
Opara-Nadi, O. A. and R. Lal (1987) IITA, Ibadan
Osunbitan, J.A., Oyedele, D.J. and K.O. Adekalu (2005) University in Ile-Ife
Most of research done on-station

32. O2: Methods
Questionnaire
Adoption of Soil Conservation Technologies by farmers:
Questions:
- experience with implementation of SCTs
Individual interview
Respondents: Group discussion Field survey
20 farmers per village
(trained + not trained)
Locations:
Nigeria: 3 villages
Benin: 4 villages
Ghana: 3 villages

33. O2: Results
Nigeria
Known SCTs: Practiced SCTs:
▪ Mulching ▪ Mulching
▪ Intercropping
▪ Cover cropping ▪ Cover cropping
▪ Fallowing
▪ Agroforestry
▪ Contour tillage ▪ Contour tillage
▪ Cut-off drainage ▪ Cut-off drainage
Reasons:
Criteria Mulching Cover Contour Cut-off
cropping tillage drainage
labour intensive no no no yes
tool available yes yes yes no
compatible yes yes yes no
easy to learn, practice yes yes yes no

34. O2: Results
Nigeria
Adoption of SCTs: 51 % rejected all SCTs
38 % adopted 1 SCT
10 % accepted 2-3 SCTs
Continuity
of adoption
Installation Installation Mainte- Implementation
started completed nance interrupted

35. O2: Results
Nigeria
Correlation between personal and socio-economic characteristics
and number of SCTs adopted: (* significant at 0.05 level)
Characteristic rSp
Age - 0.08
Level of education 0.13
No. of memberships in organizations 0.40*
No. of SCTs aware 0.32*
No. of labourer on the farm 0.36*
Total annual income 0.06
Knowledge on SCTs + labourer availability
have positive influence on adoption of SCTs

36. O2: Summary, Conclusions
Nigeria
Soil conservation :
Literature review:
- Mulching, crop management, conservation tillage are useful SCTs
- Much research on-station, few projects on-farm
Bring SCTs on the farmers’ fields
Questionnaire:
- Mulching, cover cropping, contour tillage adopted by farmers
- Knowledge on SCTs, labour availability influence adoption rate
Bring SCTs to the farmers

37. O2: Outcome
Publications:
Junge B., Deji O., Abaidoo R., Chikoye D., Stahr K. (2008):
Farmers’ adoption of soil conservation technologies:
Examples from a survey in Osun State, Nigeria
Manuscript submitted to J. Agric. Techn. Educ.
Junge B., Deji O., Abaidoo R., Chikoye D., Stahr K.,
Kirchhof, G. (2008):
Overview about soil conservation technologies and their
perception by farmers in Nigeria.
Manuscript submitted to Technical Reports of ACIAR
Junge B., Deji O., Abaidoo R., Chikoye D., Stahr (2007):
Soil conservation in Nigeria: Assessment of past and
present initiatives. Proceedings of AfNet, TSBF,
17-21 September 2007, Arusha, Tanzania, 20 pp.

38. Output 3:
New approaches for on-farm monitoring of short and long-term benefits
from soil conservation technologies developed and tested.

39. O3: Methods
Measurement of soil erosion
Traditional technique: Erosion plots
Advantage:
- Data on runoff, soil loss
- Comparison of different crops
under natural conditions
Campus: A23 Disadvantage:
- Size: 4 x 20 m
- Slope gradient: 4 %
A23
- Measurement after each rain
- Time-consuming, labor-intensive,
huge scope for faults
- No data on deposition

40. O3: Methods
Measurement of soil redistribution
Alternative: Radionuclide technique
Nuclide 137Cs 7Be
Source nuclear-weapon spallation of O, N in
tests tropo-, stratosphere Advantage:
Fallout began in 1950s, constant over years - Data on erosion, deposition
max. 1963 -1964, at different time scales
decrease since then - Min. disturbance of sites
Half life 30.2 yr 53.3 d
Soil medium-term short-term
redistr. Disadvantage:
- No data on runoff
- rapidly, strongly adsorbed by fine soil particles
- distributed across surface by physical processes
- valuable sediment tracer
(Zapata 2002)

41. O3: Methods
Field trial 2007: Location
Alternative: Radionuclide technique
Reference Site Arable land
- No soil movement - Soil erosion + deposition
BS16
Forest
IKONOS
2000

42. O3: Methods
Field trial 2007: Sampling
Reference Site Arable land
Slope (5%)
Coring Method
Core
5 cm
Ridge
Vertical distribution Furrow
Spatial distribution
Topsoil + sediment

43. O3: Results
Field trial 2007:
Vertical distribution
Reference Site Arable land
Y = 38.1 (1-0.55x)
R2 = 0.9
- max. concentration below surface - uniform concentration in ploughed layer
- gradually decrease with depth
Spatial distribution
Range 403.0 - 839.6 Bq m-2 Range 96.9 - 1494.4 Bq m-2
Mean 569.3 150.1 Bq m-2 Mean 496.3 272.5 Bq m-2
(n = 9) (n = 44)

44. O3: Results
Field trial 2007:
Particle size dependence
Arable land
- increase of 137Cs concentration
with decreasing particle size

45. O3: Methods, Results
Field trial 2007:
Conversion Model
to convert radionuclide inventories (Bq m-2) to erosion/deposition rate (t ha-1)
Proportional model (Walling and He 1997)
B = soil bulk density (kg m-3)
BdX d = depth of cultivation layer (m)
Y 10 P = ratio of 137Cs in mobilized sediment to that of original soil
100TP P’= ratio of 137Cs in deposited sediment to that of mobilized sediment
T = time elapsed since the initiation of 137Cs accumulation (yr)
BdX X = % reduction in total 137Cs inventory (Bq m-2)
Y 10 X’= % increase in total 137Cs inventory (Bq m-2)
100TP Y = mean annual soil loss rate (t ha-1 yr-1)
Y’= mean annual deposition rate (t ha-1 yr-1)
Sampling 1 2 3 4 5 6 7 8 9 10 11 Total Balance
point
Position Upper slope Middle slope Lower slope
Rate -18.3 -23.9 -29.0 -19.7 -18.2 -10.6 -7.3 -3.1 -10.7 -14.8 +7.1 -155.6
-148.5
(t ha-1 yr-1)
Lal (1976): soil loss 43.5 - 156.2 t ha-1 yr-1

46. Ongoing Activities
Field trial 2008: in cooperation with IAEA, Austria
Measurement of
Medium-term soil redistribution (137Cs) - Onigambari, 50 km S Ibadan
Short-term soil redistribution (7Be) - Campus, A23
O3: Outcome
Publications:
Poster
Junge, B., Dercon G., Walling D., Abaidoo, R., Chikoye, D. & Stahr, K. (2008):
Use of the 137Cs technique under tropical conditions: Estimation of medium-term soil redistribution rates
in Ibadan, Nigeria. EUROSOIL, 25-29 August 2008, Vienna, Austria

47. Conclusions
BMZ/GTZ-Project:
1. Remote sensing + GIS
What is going on?
Why is it going on?
2. Adoption study
What can be done?
How can it be done?
3. Measurement of soil erosion
Does it work in the tropics?
→ Contribution to soil conservation in the savanna of West-Africa
WHO does it?

48. Robert
Tunrayo, Kai, Subash
Computer
Diakalia, Olanike, Sam
Ibrahim, Jean, Michael Sunday