This document discusses how trees can positively impact annual food crop production by reducing various challenges. It provides examples of how trees can increase water availability for crops through reduced evaporation, hydraulic lift, and improved soil water retention. Trees can also fix nitrogen and recycle nutrients through organic acid exudation and mycorrhizal partnerships, benefiting crops. Additionally, trees may help control pests and rodents, and reduce heat and water stress for crops. The effects depend on tree and crop species selection and spacing, as well as soil fertility management. Measuring environmental, productivity and stress indicators can help understand these impacts. The goal is to answer practical questions for maize farmers on how to best integrate trees and crops.

1. Frédéric Baudron
CIMMYT Ethiopia
f.baudron@cgiar.org
Agroforestry &
Food Security:
Assessing the Direct Effects
of Trees on Annual Food Crops

2. Challenges faced by Annual
Food Crop Production
 Water scarcity
 Nutrient scarcity
– N, P
 Climate change
 Pests and diseases
 Energy scarcity
– Labour, ADP, fuel
 Slow yield gains
– Yield gap
– Land scarcity
– Undernourished people
(Water scarcity in 2050, from Wallace, 2000)(from Cairns et al., 2012)
(from FAO, 2009)

3. A Question of Efficiency?
 Only 10-30% of water is used by
the crop (Wallace, 2000)
 Only 20-50% of N ferilizers
applied is used by cereal crops
(Cassman, 2002)
 Less than 0.1% of pesticides
applied reach their pest target
(Pimentel, 1995)
Management response: Precision
agriculture
Genetic response
Management response: Exploiting
positive interactions between species

4. (from Cox et al., 2006)
An Example of Genetic Response:
Developing Perennial Grain Crops

5. Precision Agriculture: when,
where, how much?

6. 1.When does it occur?
2.What are the
mechanisms?
3.How to maximize it?
Tree - Annual Food Crop facilitation

7. Increasing Water Availability
The problem: high water loss
through runoff, evaporation and
deep drainage; shallow root
distribution of annuals
Reduced
evaporation (from
Ong et al., 2000)
Increased soil water (from Joffre and
Rambal, 1993)
Hydraulic lift (from Emerman and
Dawson, 1996)

8. N Fixation and Recycling
The problem: production of N
fertilizers dependant on fossile
energy; highly mobile nutrient,

9. P Mobilization & Acquisition
The problem: poorly mobile
nutrient, mainly in non-available
forms in the soil
(from Cox et al., 2006)
Exudation of organic acids by proteoid roots of
e.g. Grevillea robusta (Watt & Evans, 1999)
Ectomycorrhizae of e.g.
Caesalpinioideae (Högberg, 1992)

10. Heat and water stress
(from Ong et al., 2000)

11. Pest control
Rodents: 0.1-0.5 t/ha of field
damage in Tigray (Yonas et al., 2010)
(from Koh, 2008)

12. Interactions
Effect of water availability on heat stress of
maize (from Lobel et al., 2011)Effect of nutrient application on
water productivity (from Penning
de Vries and Ditèye, 1991)

13. Minimizing Competition
 Tree species selection
– Phenology
– Pattern of root activity
– Plasticity of the root system
 Management
– Spacing
– Supply of limiting factors
– Shoot pruning
– Tillage
(from Burges et al., 1998)
(from Schroth et al., 1995)

14. (Gc × Gt) × E × M
 Gc: Diversity of maize varieties
– Productivity (e.g. land, water)
– Resistance or sensitivity to e.g. heat,
drought, low N, pests & diseases
 Gt: Diversity of tree species
– Morphology (above and below ground)
– Phenology (inverse or not)
 E: Diversity of environments
– Climates (semi-arid vs. sub-humid)
– Soils (N limited vs. P limited)
 M: Diversity of management options
– Geometry
– Fertilization
– No-till vs. Ploughing
0%
20%
40%
60%
80%
100%
0 100 1000 3000
Waterusebysorghum
Surface mulch (kg DM ha-1)
Transpiration Runoff
Soil evaporation Drainage
(from Baudron et al., in prep)

15. What to measure (near and
away from trees)?
 Environmental parameters
– Radiation and temperature
– Soil water content
– N and P balance
 Productivity
– Crop yield
– Biomass production (crop & trees)
 Crop stress indicators
– NDVI
– Canopy temperature
 Crop damage inside and outside bird-
exclosures
 Fate of biocides - phytoremediation

16. Conclusion: Answering Practical
Questions for Maize Farmers
 What happens near trees?
 What to plant near trees?
 What management is needed
near trees?

17. Thank you!