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AquaCrop

AquaCrop is a crop water productivity model developed by the Land and Water Division of FAO.

It simulates yield response to water of herbaceous crops, and is particularly suited to address conditions where water is a key limiting factor in crop production.

AquaCrop attempts to balance accuracy, simplicity, and robustness. It uses a relatively small number of explicit and mostly-intuitive parameters and input variables requiring simple methods for their determination.

Applications of AquaCrop include:

AquaCrop is mainly intended for practitioners such as those working for extension services, governmental agencies, NGOs, and various kinds of farmers associations. It is also of interest to scientists and for teaching purposes, as a training and education tool related to the role of water in determining crop productivity.

AquaCrop results from the revision of the FAO Irrigation and Drainage Paper No. 33 “Yield Response to Water” (Doorenbos and Kassam, 1979), a key reference for estimating the yield response to water. AquaCrop evolves from the fundamental equation of Paper No. 33, where relative yield (Y) loss is proportional to relative evapotranspiration (ET) decline, with Ky as the yield response proportional factor.
AquaCrop advances from the Ky approach by:
(i) dividing ET in soil evaporation (E) and crop transpiration (Tr), to avoid the confounding effect of the non-productive consumptive use of water (E),
(ii) obtaining biomass (B) from the product of water productivity (WP) and cumulated crop transpiration,
(iii) expressing the final yield (Y) as the product of B and Harvest Index (HI),
(iv) normalizing Tr with reference evapotranspiration (ETo), to make the B-Tr relationship applicable to different climatic regimes, and
(v) running with daily time steps (either calendar or growing degree days), to more realistically account for the dynamic nature of water stress effects and crop responses.
As the Ky approach, AquaCrop is water-driven, meaning that the crop growth and production are driven by the amount of water transpired (Tr). AquaCrop focuses on the fundamental relation between B and Tr rather than Y and ET (as in the Ky approach), relying on the conservative behaviour of WP. A schematic representation of these evolutionary steps is reported in the figure below.

AquaCrop includes the following sub-model components: the soil, with its water balance; the crop, with its development, growth and yield; the atmosphere, with its thermal regime, rainfall, evaporative demand and CO2 concentration; and the management, with its major agronomic practice such as irrigation and fertilization. AquaCrop flowchart is shown below.

Soil salinity and capillary rise from shallow water tables are not yet implemented in AquaCrop 3.1+

AquaCrop version 3.1+, issued in February 2011, is written in Borland DELPHI (Version 4.0, 1998). It runs under Microsoft Windows operating system (Version 98 and higher) and no special hardware or supporting software is required. The program is available in English, and it is distributed together with a Reference Manual. AquaCrop software and Reference Manual can be freely downloaded.

AquaCrop version 3.1+ represents the third official release of the software, after AquaCrop 3.0 (January 2009). Users are kindly requested to report any errors or deficiencies to FAO. Users are encouraged to provide suggestions, that will be considered in the development of future versions of AquaCrop. For feedbacks and further information on AquaCrop, please contact us

   
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