1. AQUACROP Model Name/Host Institution/ URL AQUA CROP UN FAO:
Land and Water Division
Domain/Objective
Simulate climate-specific crop yield and
development in response to water stress.
Assumptions
Pests, Diseases and Weeds not considered
Carbon partitioning limited to yield and biomass.
Canopy cover instead of LAI.
Evaporation limited to non-shaded soil.
No direct relationship between root and canopy biomass.
Temporal/Spatial Scale
Daily timestep (GDD), designed for field, farm or regional scale.
Extension offices,
Developed Objective increase efficiency and effectivity of ag water use.

2. Main equation of Paper 33, “Yield Response to Water” (1979)
A direct relationship between relative yield loss and relative reduction in evapotranspiration with proportional factor, Ky.
Adaptations from (a) to AquaCrop:
Division of evaporation and transpiration
Calculation of biomass as product of water productivity and cumulative crop transpiration over time it takes for biomass to be produced:
iii. Final yield product of biomass and
harvest index:
HI: Y = HI * B
Important for when canopy cover not complete
ii. Water productivity is normalized for climate by the evaporative demand and level of CO2
iii. HI increases with time and temperature-decreases under stress

3. INPUT DRIVERS STRESSORS KEY OUTPUTS
Climate: min/max temperature, daily precipitation, daily evaporative demand of atmosphere (ETo) (Penman-Montieth Equation), mean annual CO2 concentration
Soil: type, water balance, salinity, fertility stress, depth of groundwater
Cultivar: Affects physiological processes and development
Management: Irrigation type and schedule, fertilization, mulching and soil mounds.
STRESSORS
Water
Temperature
Nutrient
Aeration
Salinity
KEY OUTPUTS
Biomass
Yield
Soil Water Content
Soil Salt Content
Canopy Growth
Transpiration rates
Daily evap demand Eto (reference ET is max ET of site if soil-water not limited)
Penman Montieth Equation uses solar radiation, temperature, humidity (VPD) and wind
CO2 from Mauna Lau observatory in Hawaii-affects normalized water productivity
Irrigation types: sprinkler, surface, drip surface and underground
Soil mounds affect infiltration and reduce runoff-relates to my research last semester about holding water on land-slow, sink and spread.
Model converts daily transpiration into biomass using normalized water productivity and reference evapotranspiration of location
Water stress triggers canopy growth reduction, stomatal closure, and acceleration of senescence. Use a harvest index, HI to convert biomass into yield. Need to establish parameters of water productivity for each major crop. First maize then cotton.

4. Parameterization and Testing
*Chosen Cultivar: Maize, Zea Mays L.
*Field Data: Compilation of six sets of data from a farm near Davis, CA (6 years of field data and 4 years of canopy data)
*Treatment variable: Irrigation (5 different schedules)
*Four different cultivars
*Compared and adjusted 19 parameters of AquaCrop to match the data:

5. Results used for Parameterization
Canopy cover and biomass dots measured, line simulated under three different irrigation regimes
Soil water content measured with a neutron probe under different time periods and irrigation regimes.

6. Validation Bushland, TX:
Davis parameters were then applied to simulate data from three different climates: Bushland TX , Gainsville, FL , and Zaragoza Spain.
Bushland, TX:
Semi-arid, high wind and high evapotranspiration
Irrigation: Overhead sprinklers
Five different cultivars, different soils types and planting dates.
Study used a variety of climates and irrigation schedules.
Compared canopy development, biomass accumulation, yield, evapotranspiration and water use efficiency

7. Zaragoza, Spain:
Semi-arid-wide basin surrounded by mountains
Irrigation: Flood
Gainsville, FL Humid, subtropical, high precipitation and sandy soil Irrigation: Overhead sprinkler
*High correlations in biomass, yield and canopy cover in no or low water stress scenarios
*Less satisfactory results in high stress scenarios, especially when water stress occurs during senescence.

8. Applications: Rainfed Rice in the Lower Mekong Basin (LMB)
Rainfed rice accounts for 90% of total rice production of lower basin.
Two climate scenarios used from IPCC SRES, scenarios A2 and B2
Echam 4 Global Climate Model to formulate future climate data.
PRECIS model used to scale climate data down to regional geographic scale
Region divided into 14 agricultural zones.
Aquacrop used to evaluate rice yield and adaptation strategies such as supplemental irrigation, fertilizer, and planting date.
T,C V . Labout 60 million people in basin. Simplified extreme weather events that are also likely under climate change such as salinity intrusion, sea water rise, flooding and extreme droughts.
Staple food for half the world’s population-one of primary areas of cutivation in the mekong delta. Farmers in Mekong region produce enough rice to feed 300 million people a year. Over half of world rice exports come from this area. Affect on on the people who reside in these riparian areas and the entire world food market and security.

9. Comparison of climate scenarios (2010-2050)
*Temperature increase varies from 1 to 1.5° C under both scenarios
A2 CLIMATE
SCENARIO
Co2 increases
linearly from ppm
B2 CLIMATE
SCENARIO
Co2 increases
linearly from
ppm
Rainfall varies more than PET across regions. PET calculated from min/max temp, solar rad, wind speed directly related to plant water requirements which is supplied by rainfall in this case. PET generally increases except a few cases in Thailand.
Keep an eye on L2-high rainfall

10. Results: Yield and Rainfall
Percent change in average rainfall and yield from
Values compared with location-specific baseline values taken from
Results: Potential yield increase in upper part of basin (Laos and Thailand)
Potential yield decrease in lower part of basin (Cambodia and Vietnam)
Yield results due to net water availability (rainfall-increase in potential evapotr) and rainfall timing-areas prone to drought benefit from increased rainfall predicted from climate change. Yield generally follows trend of increased or decreased rainfall except in a few sites.
C1 and V3 minimal increase in yield from change in planting dates-> affect of 10% fertilizer addition and supplemental irrigation, which both resulted in positive increases in yield
L2 example-rainfall decreases, PET increases, yet yield also increases, yet overall rainfall already exceeds rice water requirements.
C4 example, rainfall increase and yield decreases-most likely due to timing at key stages in growth.
Other areas of rice production are predicted to result in higher temperatures than LMB, temps that exceed max for rice production.

11. Affect of CO2 on Yield 2000 reference CO2 level is 369.47 ppm.
Varied CO2 increases linearly from
A2 CO2 increases linearly from ppm.
B2 CO2 increases linearly from ppm.
Overall, projected yield is about 25% higher with
varied than with constant CO2.

12. More Climate Change Applications: Kharif Maize in New Delhi
Irrigation Variables:
Full Irrigation (FI),
75% (FI), 50% FI, Rainfed
Nutrient levels: poor (N1),
moderate limiting (N2),
Non-limiting (N3)
Cropwat predicted the date and depth of irrigation
Rice experiencing decreasing yields due to water scarcity, wheat production will likely be limited by rising temperatures. Therefore corn great alternative for market and climate adaptation. Increasing demand for maize due to wide array of uses: animal and human feed, beverages and candy, packaging, film and cosmetics.
Research Location:
Indian Agricultural
Research Institute
New Delhi, India

13. CLIMGEN and CROPWAT RESULTS
2012
CLIMGEN
Total rainfall depth=739 mm.
2013
CLIMGEN
Total rainfall depth=374 mm
CROPWAT
One irrigation at 51 DAS for a total irrigation depth of 56 mm.
CROPWAT
Three irrigations at 47, 66, 75 DAS
for a total irrigation depth of 191 mm.

14. AQUACROP RESULTS 2011: Total rainfall depth=432 mm.
Three irrigations at 42, 72, 92 DAS
for a total irrigation depth of 153 mm.
2012:
Total rainfall depth=739 mm.
One irrigation at 51 DAS
for a total irrigation depth of 56 mm.
2013:
Total rainfall depth=374 mm.
Three irrigations at 47, 66, 75 DAS
for a total irrigation depth of 191 mm.
2014:
Total Rainfall depth=625 mm.
One irrigation at 64 DAS
for a total irrigation depth of 52mm.
Ton to kg?

15. Conclusions List of parameterized crops:
Balance between accuracy and simplicity
Need to improve accuracy of high water stress (rainfed scenarios)
Wide applicability to a variety of climatic conditions and cultivars
High applicability, especially in combination with other global climate models.
List of parameterized crops:
Maize, barley, cotton, potato, quinoa, rice, soybean, sugar beet, sugar cane, sorghum, sunflower, teff, tomato, wheat, millet, bamabara groundnut