Soil conservation options in the Savanna of                 West Africa:  new approaches to assess their potentialOverview...
Outline- Introduction        Term: Soil        Problem: Soil erosion in Nigeria- Activities and Results of studies on     ...
IntroductionSoils in West Africa  - Age: old  - Material: sand / gravel / clay                            Ah              ...
Introduction                   Problem: Soil erosion in Nigeria                                                      Sheet...
Output 1:Land use intensification in pilot villages varying in length of cropping season              and linkage to erosi...
O1: MethodsPilot villages:
O1: Methods                    Remote sensing data:  Aerial photograph                  IKONOS          QuickBirdDate     ...
O1: Methods                   Interpretation:                           Land use/land cover                               ...
O1: ResultsBadume: Kano State     Change of village area                              Year           Area   (ha)          ...
O1: Results                   Kayawa: Kaduna State                         Change of farmland                             ...
O1: Results                    Gadza:                             Change of settlement, forest, uncultivated land         ...
O1: SummaryLand use intensification:       - Expansion of settlements areas       - Expansion of villages areas       - Ex...
O1: Results                     Badume: Kano State                          Present gully erosion                         ...
O1: Results                          Badume: Kano State                               Future gully erosion                ...
O1: Results                Kayawa: Kaduna State                      Sheet erosion                               1962     ...
O1: Results                    Gadza: Niger State                           Gully erosion                                 ...
O1: Results         Eglime: Dept. Mono                Gully erosion                         2007                          ...
O1: SummarySoil erosion:     - Increase of gully and sheet erosion in Badume, Kayawa, Gadza, Eglime     - Reduction of ara...
O1: Conclusions               Use of thematic maps:Agenda 21                                               (UN 1992)- more...
O1: Conclusions                       Use of thematic maps:Land use planning- Reservation of areas                  with f...
O1: OutcomeFarmer Field Hour:- Presentation of study on land use change  and soil degradation- Discussion of possible soil...
Output 2:Impact of soil conservation technologies in the Savanna of Nigeria, Benin,                          and Ghana ass...
O2: Methods                      LiteratureSearch for literature on soil conservation:  - Internet  - Research Institutes ...
O2: ResultsHistory of soil conservation in Nigeria:   - Pre-colonial era: indigenous technologies                (Slaymake...
O2: ResultsStrategies of soil conservation:                              Erosion control strategies             On Farm st...
O2: Results                                     Mulching             Benefits                                   Constraint...
O2: Results                              Crop management      Intercropping, Alley cropping, Cover cropping, Fallowing, Pl...
O2: Results                                     Conservation tillage                                 Minimum tillage, No-t...
O2: Results             Other approaches  Modelling  to determine areas with potential erosion hazard    Universal Soil Lo...
O2: Results                     Choice of SCTs in dependence of…Climate:           AEZ           Mulch. Interc.    Coverc....
O2: ResultsPerformance of soil conservation:   e.g. Conservation Tillage   Author                                         ...
O2: Methods                           QuestionnaireAdoption of Soil Conservation Technologies by farmers: Questions: - exp...
O2: Results                 Nigeria             Known SCTs:              Practiced SCTs:             ▪   Mulching         ...
O2: Results                 NigeriaAdoption of SCTs:       51 % rejected all SCTs                        38 % adopted 1 SC...
O2: Results                  NigeriaCorrelation between personal and socio-economic characteristicsand number of SCTs adop...
O2: Summary, Conclusions                   NigeriaSoil conservation :      Literature review:      - Mulching, crop manage...
O2: OutcomePublications:                Junge B., Deji O., Abaidoo R., Chikoye D., Stahr K. (2008):                   Farm...
Output 3:New approaches for on-farm monitoring of short and long-term benefits   from soil conservation technologies devel...
O3: Methods                        Measurement of soil erosionTraditional technique: Erosion plots                        ...
O3: Methods                     Measurement of soil redistributionAlternative: Radionuclide techniqueNuclide 137Cs        ...
O3: Methods                     Field trial 2007: LocationAlternative: Radionuclide technique    Reference Site           ...
O3: Methods                        Field trial 2007: Sampling     Reference Site                              Arable land ...
O3: Results                   Field trial 2007:                                Vertical distributionReference Site        ...
O3: Results              Field trial 2007:                    Particle size dependenceArable land                         ...
O3: Methods, Results                              Field trial 2007:Conversion Modelto convert radionuclide inventories (Bq...
Ongoing ActivitiesField trial 2008: in cooperation with IAEA, AustriaMeasurement of    Medium-term soil redistribution (13...
Conclusions           BMZ/GTZ-Project:1. Remote sensing + GIS                          What is going on?                  ...
Robert             Tunrayo, Kai, Subash                                             ComputerDiakalia, Olanike, Sam      Ib...
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Soil conservation options in the Savanna of West Africa: new approaches to assess their potential

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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

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Soil conservation options in the Savanna of West Africa: new approaches to assess their potential

  1. 1. Soil conservation options in the Savanna of West Africa: new approaches to assess their potentialOverview 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. 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. 3. IntroductionSoils 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 LuvisolSoil conservation (Gibbons 1988) - includes whole program of studies for preventing + reducing soil degradation
  4. 4. Introduction Problem: Soil erosion in Nigeria Sheet erosion Gully erosion Wind erosionFederal Surveys of Nigeria (1992)General Soil Erosion Map of Nigeria 1:6,000,000
  5. 5. Output 1:Land use intensification in pilot villages varying in length of cropping season and linkage to erosion features established.
  6. 6. O1: MethodsPilot villages:
  7. 7. O1: Methods Remote sensing data: Aerial photograph IKONOS QuickBirdDate 1962/1981 2000 2005/06/07Spatial resolution (panchromatic image): 1m 0.6 m
  8. 8. O1: Methods Interpretation: Land use/land cover CowpeaMaize Compound Millet / Sorghum
  9. 9. O1: ResultsBadume: 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. 10. O1: Results Kayawa: Kaduna State Change of farmland Sept. 1962 Dec. 2006 2000 Maize CowpeaYear 1962 2000 Change 2006 ChangeArable land (ha) 49.7 266.1 + 216.4 286.6 + 20.5
  11. 11. O1: Results Gadza: Change of settlement, forest, uncultivated land Oct. 2000 Jan. 2005 Sorghum Millet FallowYear 2000 2006 ChangeSettlement (ha) 1.2 1.5 + 0.3 RiceTree, shrub (ha) 13.3 8.5 - 4.8Uncult. Land (ha) 104.0 77.5 - 26.5
  12. 12. O1: SummaryLand 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. 13. O1: Results Badume: Kano State Present gully erosion 2000 2006Measurement: Calculation: Year 2006 Year 2000 2006 Increase Area (ha) 1.2 Area (ha) 37.9 45.1 7.2 Soil loss (t) 7708
  14. 14. O1: Results Badume: Kano State Future gully erosion 2006Estimation: 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. 15. O1: Results Kayawa: Kaduna State Sheet erosion 1962 2000Year 1962 2000 Change 2006 Change 2016Sheet erosion (ha) 7.9 25.6 +17.7 32.3 + 6.7 42.3Annual rate (ha yr-1) 0.5 1.1
  16. 16. O1: Results Gadza: Niger State Gully erosion 2005 Settlement 1m RiverMeasurement: 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. 17. O1: Results Eglime: Dept. Mono Gully erosion 2007 Cotton GullyYear 1982 2000 2007 Change 2017Gully length (km) ? 4.4 42.4 + 38.0Gully area (ha) 2.3 18.7
  18. 18. O1: SummarySoil 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. 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. 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 miningSoil conservation- Field maps for installation of soil erosion control measures Tree, Shrub Vetiver Stone barrier Badume
  21. 21. O1: OutcomeFarmer Field Hour:- Presentation of study on land use change and soil degradation- Discussion of possible soil conservation measures Kayawa 31 Oct. 2007Publications: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 SensingJunge, 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. 22. Output 2:Impact of soil conservation technologies in the Savanna of Nigeria, Benin, and Ghana assessed.
  23. 23. O2: Methods LiteratureSearch for literature on soil conservation: - Internet - Research Institutes - Universities - Gov. organizations - NGOs Location for search of literatureGeneration of database: ~ 1200 references
  24. 24. O2: ResultsHistory 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. 25. O2: ResultsStrategies of soil conservation: Erosion control strategies On Farm strategies Off Farm strategies Agronomic Soil Mechanical Measures Management Methods Mechanical BiologicalMulching 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. 26. O2: Results Mulching Benefits Constraintsreduces 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 forincreases 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. 27. O2: Results Crop management Intercropping, Alley cropping, Cover cropping, Fallowing, Planting pattern... Benefits Constraintsreduces erosion through canopy coverand by acting as runoff barrier special knowledge required on Lal (1989) compatible species, spacing to avoid competition for use of growthmaintains 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. 28. O2: Results Conservation tillage Minimum tillage, No-till + Ridge Tillage Benefits ConstraintsM, 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. 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. 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 XSoil: Texture Mulch. Interc. Coverc. No-till Ridg. TRidg. Sand x x x X Clay x x x X X Site specific choice
  31. 31. O2: ResultsPerformance 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. 32. O2: Methods QuestionnaireAdoption of Soil Conservation Technologies by farmers: Questions: - experience with implementation of SCTsIndividual interview Respondents: Group discussion Field survey 20 farmers per village (trained + not trained) Locations: Nigeria: 3 villages Benin: 4 villages Ghana: 3 villages
  33. 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 drainageReasons:Criteria Mulching Cover Contour Cut-off cropping tillage drainagelabour intensive no no no yestool available yes yes yes nocompatible yes yes yes noeasy to learn, practice yes yes yes no
  34. 34. O2: Results NigeriaAdoption 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. 35. O2: Results NigeriaCorrelation between personal and socio-economic characteristicsand 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. 36. O2: Summary, Conclusions NigeriaSoil 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. 37. O2: OutcomePublications: 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. 38. Output 3:New approaches for on-farm monitoring of short and long-term benefits from soil conservation technologies developed and tested.
  39. 39. O3: Methods Measurement of soil erosionTraditional technique: Erosion plots Advantage: - Data on runoff, soil loss - Comparison of different crops under natural conditionsCampus: 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. 40. O3: Methods Measurement of soil redistributionAlternative: Radionuclide techniqueNuclide 137Cs 7BeSource 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 sitesHalf life 30.2 yr 53.3 dSoil medium-term short-termredistr. Disadvantage: - No data on runoff- rapidly, strongly adsorbed by fine soil particles- distributed across surface by physical processes- valuable sediment tracer (Zapata 2002)
  41. 41. O3: Methods Field trial 2007: LocationAlternative: Radionuclide technique Reference Site Arable land - No soil movement - Soil erosion + deposition BS16Forest IKONOS 2000
  42. 42. O3: Methods Field trial 2007: Sampling Reference Site Arable land Slope (5%) Coring Method Core 5 cm RidgeVertical distribution FurrowSpatial distributionTopsoil + sediment
  43. 43. O3: Results Field trial 2007: Vertical distributionReference 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 distributionRange 403.0 - 839.6 Bq m-2 Range 96.9 - 1494.4 Bq m-2Mean 569.3 150.1 Bq m-2 Mean 496.3 272.5 Bq m-2(n = 9) (n = 44)
  44. 44. O3: Results Field trial 2007: Particle size dependenceArable land - increase of 137Cs concentration with decreasing particle size
  45. 45. O3: Methods, Results Field trial 2007:Conversion Modelto 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 BalancepointPosition Upper slope Middle slope Lower slopeRate -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. 46. Ongoing ActivitiesField trial 2008: in cooperation with IAEA, AustriaMeasurement of Medium-term soil redistribution (137Cs) - Onigambari, 50 km S Ibadan Short-term soil redistribution (7Be) - Campus, A23 O3: OutcomePublications:PosterJunge, 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 ratesin Ibadan, Nigeria. EUROSOIL, 25-29 August 2008, Vienna, Austria
  47. 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. 48. Robert Tunrayo, Kai, Subash ComputerDiakalia, Olanike, Sam Ibrahim, Jean, Michael Sunday

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