Crop Responses to Elevated CO2 and Interactions with H2O ...
Tree-Crop Interactions
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Transcript of Tree-Crop Interactions
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Frédéric BaudronCIMMYT Ethiopia
Agroforestry &Food Security:
Assessing the Direct Effectsof Trees on Annual Food Crops
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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)
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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
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(from Cox et al., 2006)
An Example of Genetic Response: Developing Perennial Grain Crops
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Precision Agriculture: when, where, how much?
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1.When does it occur?
2.What are the mechanisms?
3.How to maximize it?
Tree - Annual Food Crop facilitation
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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)
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N Fixation and Recycling
The problem: production of N fertilizers dependant on fossile energy; highly mobile nutrient,
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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)
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Heat and water stress
(from Ong et al., 2000)
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Pest control
Rodents: 0.1-0.5 t/ha of field damage in Tigray (Yonas et al., 2010)
(from Koh, 2008)
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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)
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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)
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(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
0 100 1000 30000%
20%
40%
60%
80%
100%
Transpiration Runoff
Soil evaporation Drainage
Surface mulch (kg DM ha-1)
Wate
r use b
y s
org
hum
(from Baudron et al., in prep)
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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
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Conclusion: Answering Practical Questions for
Maize Farmers
What happens near trees? What to plant near trees? What management is
needed near trees?
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Thank you!