Knowledge gaps trees, deep soil resources and rainfed crop production in dryland

production systems

Jan de Leeuw ICRAF Nairobi

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

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?

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

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

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

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

Supporting service: trees and soil fertility • Nitrogen fixation associated to roots and moisture • Redistribution nutrients from lower soil horizons

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?

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

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

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

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

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