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2014 05 bamako meeting jan de leeuw
1. Knowledge gaps trees, deep soil resources
and rainfed crop production in dryland
production systems
Jan de Leeuw
ICRAF Nairobi
2. Revival of interest groundwater in Africa
• 2012 UCL Research 'Huge'
water resource exists under
Africa
• NERC-UPGRO: Unlocking
Potential of Groundwater in
Sub Saharan Africa
• Renewed interest in
development of irrigated
agriculture
• Argument this should not
compromise benefits from
agroforestry systems
3. Perspectives on Agriculture in Sahelo
Soudanian Zone
• Crops – sorghum millet farming system
• Livestock – pastoral / agro-pastoral systems
• Trees – dryland agroforestry system
• Mixed systems: annual crops, livestock and trees
• Agricultural institutions (incl. research) focus on
crops and livestock
• Do trees merit more attention?
4. Commodity based perspectives
• Agendas agriculture achieving DG’s
• Leading to focus agricultural institutions on
crop and livestock commodities
• Negative side
– Monocultures – diet and health
– Barren unhealthy landscapes
– Unsustainable natural resource management
5. Trees and multifunctional systems
• Agricultural systems can be managed to include trees to
optimize provisioning of multiple functions:
– Water and nutrients
– Dietary diversity
– Healthy human habitat
– Food security / resilience
– Sustainability
• Trees build many of these traits into agricultural production
systems, some are direct many are indirect benefits
• Ecosystem service perspective on benefits from trees
– Provisioning services, food and other goods
– Supporting and regulating services
6. The ecosystem goods: tree products
• Positives –
– Production of tree products more resilient to drought
than crops or livestock
– Food fruits, nuts, edible oils also available dry season
– Construction- and fuel-wood, gum arabica, assets
than can be used in case of shortage
• Negatives –
– Prone to over-utilization and degradation
– Trees in the landscape are a fragile natural capital
7. Regulating service: Trees and
groundwater
• Hydraulic lift and
redistribution
groundwater
• Driven by gradient in
water potential
• Moisturizing dry upper
soil horizons
• Benefiting shallow rooted
species like crops
8. Supporting service: trees and soil fertility
• Nitrogen fixation associated to roots and moisture
• Redistribution nutrients from lower soil horizons
9. Example Faidherbia alibida
• Groundwater dependent in drylands
• Widespread in Africa
• 5 million ha in Niger
• 0.5 million ton increased cereal production
• 1 million people benefiting
• Are these benefits attributable to groundwater?
• What is the potential for upscaling and how does
that relate to groundwater?
10. Knowledge gaps nutrient enrichment and
hydraulic redistribution
• Biophysical principles well understood
• Significance and benefits of poorly not quantified
• Potential for designing more resilient agricultural
systems to be explored
11. Trees and crops
• Positive impact on crop production
– Water balance – shade, hydraulic redistribution
– Nutrients – Upward redistribution, N fixation
• Negative impacts on crop production
– Competition for water and nutrients
• Gap - optimal design of tree - crop systems
12. Trees and livestock
• Positive impacts –
– Food - foliage and seeds as forage for livestock
– Veterenary medicine – trees important
• Negative impacts –
– Livestock degradation tree cover and the sustainability
of benefits derived from trees
• Gap – designing sustainable integration of tree
based forages and crop residues in livestock
production systems
13. Need for a strategic perspective on
groundwater and evergreen agriculture
• Reawakened interest developing
groundwater and irrigation
• Danger of development of
irrigated agriculture ignoring
benefits from AF systems
• Blue water paradigm dominates
groundwater management
• Paradigm shift required towards
blue and green water
management
• Evidence required that trees in
Sahelian landscapes generate
significant social benefits
14. Take home messages
• Trees enhance the production of the system as a
whole, benefits of this poorly recognized
• Trees system builders, multifunctional landscapes
with many desirable traits including support to
crop and livestock production
• Research lacking on optimization and design of
multifunctional landscapes and the role of trees
in there