Concepts and applications of AquaCrop: The FAO crop water productivity model

Authors: STEDUTO, PASQUALE - Food & Agriculture Organization (FAO); RAES, DIRK - Leuven University; HSIAO, THEODORE - University Of California, Davis; FERERES, ELIAS - Universidad De Cordoba; HENG, LEE - International Atomic Energy Agency (IAEA); HOWELL, TERRY - Retired ARS Employee; Evett, Steven - Steve; ROJAS-LARA, BASILIO - University Of California, Davis; FARAHANI, HAMID - Clemson University; IZZI, GABRIELLA - Food & Agriculture Organization (FAO); OWEIS, THEIB - International Center For Agricultural Research In The Dry Areas (ICARDA); WANI, SUHAS - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India; HOOGEVEEN, JIPPE - Food & Agriculture Organization (FAO); GEERTS, SAM - Leuven University

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/25/2009
Publication Date: 3/30/2009
Citation: Steduto, P., Raes, D., Hsiao, T.C., Fereres, E., Heng, L.K., Howell, T.A., Evett, S.R., Rojas-Lara, B.A., Farahani, H.J., Izzi, G., Oweis, T.Y., Wani, S.P., Hoogeveen, J., Geerts, S. 2009. Concepts and applications of AquaCrop: The FAO crop water productivity model. In: Cao, W., White, J.W., Wang, E., editors. Crop Modeling and Decision Support. Berlin, Germany: Springer, Berlin, Heidelberg. p. 175-191. https://doi.org/10.1007/978-3-642-01132-0_19
DOI: https://doi.org/10.1007/978-3-642-01132-0_19

Interpretive Summary: Water resources for irrigation are declining in the U.S. Great Plains due to both declines in the High Plains (Ogallala) aquifer and competition with urban and industrial users. Meanwhile, climate change is increasing temperatures, which increases evaporative demand and crop water use without increasing yield. Predicting the crop yield that can be produced for a given amount of water is increasingly important to farmers planning their operations and for water district and state water planners as well. USDA ARS scientists and engineers at Bushland, Texas, cooperated with scientists in Texas, California, Spain, Italy, Austria and other countries to test and improve the AquaCrop computer simulation model to closely estimate yield of crops such as grain corn, sorghum, wheat and cotton as a function of rainfall and irrigation applied for different combinations of planting density and fertilizer application. The widely tested model is useful for planning future irrigation activities and implementation of water district plans.

Technical Abstract: Predicting attainable yield under water-limiting conditions is an important goal in arid, semi-arid and drought-prone environments. To address this task, FAO has developed a model, AquaCrop, which simulates attainable yields of the major herbaceous crops in response to water. Compared to other models, AquaCrop has a significantly smaller number of parameters and attempts to strike a balance between simplicity, accuracy, and robustness. Root zone water content is simulated by keeping track of incoming and outgoing water fluxes. Instead of leaf area index, AquaCrop uses canopy ground cover. Canopy expansion, stomatal conductance, canopy senescence, and harvest index are the key physiological processes which respond to water stress. Low and high temperature stresses on pollination and harvestable yield are considered, as is cold temperature stress on biomass production. Evapotranspiration is simulated separately as crop transpiration and soil evaporation and the daily transpiration is used to calculate the biomass gain via the normalized biomass water productivity. The normalization is for atmospheric evaporative demand and carbon dioxide concentration, to make the model applicable to diverse locations and seasons, including future climate scenarios. AquaCrop accommodates fertility levels and water management systems, including rainfed, supplemental, deficit, and full irrigation. Simulations are routinely in thermal time, but can be carried out in calendar time. Future versions will incorporate salt balance and capillary raise. AquaCrop is aimed at users in extension services, consulting firms, governmental agencies, NGOs, farmers associations and irrigation districts, as well as economists and policy analysts in need of crop models for planning and assessing water needs and use of projects and regions.