1. The FAO’s crop model AquaCrop
Pasquale STEDUTO
Gabriella IZZI & Jippe Hoogeveen
Water Unit, Land and Water Division
21/01/2010 FAO, Rome

2. Background Revision of the 1979 FAO I & D Paper no.33,
“Yield Response to Water” (Doorenbos & Kassam)  
Consultative process with experts
Separation between herbaceous-crops and
trees: AquaCrop & Guidelines
AquaCrop as one model with crop-specific
parameters

3. { Evolution from Paper 33 HI E Solar Radiation Biomass=WP · ΣT Canopy
AquaCrop
(c’)
Canopy
Transpiration
BIOMASS WP HI E
daily time-steps
Crop
Evapotranspiration
Paper 33
(c)
YIELD Ky
long-term sums

4. AquaCrop Conceptual Framework
Atmosphere
Crop
Management
Soil

5. CLIMATE | Atmosphere AquaCrop Conceptual Framework Rain T (oC) ETo CO2
RS, T, RH, u
ETo
CO2

6. | Crop Biomass Phenology Canopy Cover Yield Rooting depth HI
AquaCrop Conceptual Framework
| Crop
CO2
T (oC)
ETo Es Ta
Biomass WP
Phenology
Canopy Cover
Leaf expansion gs
Yield HI
Senescence
Rooting depth

7. CC follows the exponential
growth during the first half
of the full development (Eq. 1)
and an exponential decay
during the second half of the
full development (Eq. 2)
(1)
(2)

8. WP
Water Productivity
(g m-2)
(g m-2 mm-1)

10. Soil water (& salt) balance
AquaCrop Conceptual Framework
| Soil
Rain
Irrig.
Senescence
Leaf expansion gs HI Es Ta
Runoff
Runoff Ks
Soil water (& salt) balance
Texture 1
Ksat
Infiltration
Texture 2 FC
Redistribution
Uptake
Texture …
PWP
capillary
rise
deep
percolation

11. + aeration & T stresses Ks leaf expansion gs senescence HI
Ks for leaf expansion, maize
(1)
leaf expansion
Ks for stomata, maize
Ks for senescence, maize
(2) gs Ks
(3)
senescence HI
(4)

12. upward or downward adjustment
Harvest Index Y HI
(biomass) B
(yield)
adjusted for:
water and/or
temperature stress
Y = HIadj x B
multiplier x HIo (reference)
upward or downward adjustment

13. | Management AquaCrop Conceptual Framework Field Management
Fertility level (non-limiting; moderate; poor)
Field-surface practices (mulching; soil bunds)
Water Management
Rainfed
Irrigation
User defined schedule (timing and depth)
Model-generated schedule (fixed interval; fixed depth;
% of RAW)
Irrigation method (drip; sprinkler;
surface » basin; border; furrow)

14. Soil water (& salt) balance
Summing up
CLIMATE
T (oC) Es Ta
Phenology
Canopy Cover
Leaf expansion gs
Senescence
Biomass WP
Yield HI
CO2
Soil water (& salt) balance
Infiltration
Uptake
Redistribution
deep
percolation
capillary
rise
Rooting depth
ETo
Rain
Runoff
Atmosphere
Soil
Crop
Management

15. Conclusions
AquaCrop is explicit and mostly intuitive, and maintains an
optimum balance between simplicity, accuracy and robustness
AquaCrop differs from other models for being water-driven, using CC instead of LAI, not having partitioning except than HI, not attempting nutrient balance but relate to fertility regimes, and for its relatively lower number of parameters
AquaCrop is aimed at practical end-users, as those in farmers and irrigation associations, extension services, governmental agencies and NGOs, planners and economists, for devising water management and saving strategies, and productivity analysis as well
AquaCrop is also particularly suited for perspective studies
(e.g., under different climate change scenarios)

16. Main scientific publications

17. Crops dealt by AquaCrop
About to be
released
(January 2010)
Already calibrated
For the future
Wheat
Maize
Rice
Sugarbeet
Soybean
Cotton
Potato
Quinoa
Sunflower
Sugarcane
Tomato
Teff
Bambara Groundnut
Forage crops (Alfalfa)
Millet
Barley
Chickpea
Sorghum
NO TREE CROPS

18. Thank You