Calibration and Evaluation of Three CROPGRO Models under Different Water Regimes in a Semi-Arid Tropical Environment Kindie Tesfaye Haramaya University, Ethiopia 16 Dec 2008
Outline of presentation • Introduction • Ethiopia • Subject • Methodology • Results • Conclusion
Introduction The topic presented is result of research conducted in Ethiopia Ethiopia is one of the ancient civilized countries Has its own calendar (Julian) and Alphabets Federal administration (14 states)
Country profile Location: 8o 00 N, 38o 00 E Area: 1.13 million sq km (437,794 sq miles) Elevation: -125 to 4620 m Population: 75 million (UN, 2007) Capital:Addis Ababa Major languages:Amharic, Oromo, Tigrinya, Somali, English (schools) Major religions:Christianity, Islam Main exports:Coffee, hides, cereals, oilseeds, grain legumes, beeswax, sugar, cotton, cut flowers, livestock products Natural recourses: reserves of gold, platinum, copper, potash, natural gas, petroleum, hydropower Tourist attractions: National game reserves (parks), historical places, the oldest human fossils found (e.g. Lucy-3.18 m yrs old).
Endemic Animals and Plants 23 endemic birds Chilada Baboon Walia Ibex Red fox Mountain Nyala Colobus Monkey Oryx Spps. Many plant genetic resources
Country profile-historical places Blue Nile Water Falls Negash Mosque- 2000 yrs old Sofamar Natural cave Axum Stelle- > 2000 yrs old Lalibela rock hewn churches-built in the 12th C. Axum Zion- the oldest church Fasilede Palace –built in 16th C
Challenges Climate variability Recurrent drought Crop failures Deforestation Soil Degradation
Challenges… • Almost half of the country is in the semi-arid climate belt • Agricultural decision making is difficult • Climate variability • Climate change • Poor research and extension coverage • lack of interdisciplinary approach • Grain legumes (drybean, chickpea, cowpea) are relegated to marginal areas • the majority of the production of these crops comes from the semi-arid parts of the country
Crop models could play an important role in managing agricultural production in the these areas because: • Involve integrated approach (climate, soil, crop, management) at once • fast results • Inexpensive
The CSM-CROPGRO model has been used to study and evaluate several production problems including: • climate change (e.g. Mera et al., 2006; Challinor and Wheeler, 2008) • spatial yield variability (Paz et al., 2001) • water related constraints (e.g. Ruiz-Noueira et al., 2001) • plating date and cultivar selection ( Cooper et al., 2006) • plant population and fertilizer interactions (Meirles et al., 2002) • optimum irrigation optimization (Faria et al., 1997; Heinemann et al., 2000).
Objective To calibrate and evaluate CROPGRO-drybean, chickpea and cowpea under three water regimes in a semi-arid tropical environment
Methodology • Site: Dire Dawa • latitude 9o6’N • longitude 41o8’ E • altitude 1197 m • Season: Three seaosns • Dec, 2001-March, 2002 • April-July, 2002 • Oct, 2002-March, 2003 • Treatments: Three water regimes • Well-irrigated control (C) • Mid-season water deficit (MS) • Late-season water deficit (LS) • Three crops (drybean, chickpea, cowpea) • Design: Split-plot in RCBD (WR: main plot; • Water regimes: main-plot; Crops: sub-plot
Data collection • Phenology • Growth, Yield & YC • Soil water • Physiology (PS, SC, LWP) • Canopy and soil temp. • Radiation interception • Weather • Soil (initial, profile) • Crop management
Methodology… • Data organization for DSSAT format • data were organized and all the required files created (Soil.Soil, WTH files, Xfiles, A files, T files) • Calibration • the 2001/2003 well-irrigated treatment of the respective spps. • Stepwise calibration followed • First phenological parameters using Gencalc • Growth and yield: sensitivity analysis using the data in the Tfiles • Evaluation • Comparing simulated and measured phenology, growth and yield parameters with using • RMSE • MAD • CV (%) • Willmot’s Index of agreement (d) • Coefficient of determination (R2)
Results-Calibration Table 1. Calibrated genetic coefficients of drybean, chickpea, cowpea using data from a well-irrigated experiment
Results-Model Evaluation 1. Soil water
Results-Model Evaluation… 2. Days to flowering (dap)
Results-Model Evaluation… 3. Physiological maturity
Results-Model Evaluation… 4. Growth-drybean
Results-Model Evaluation… 4. Growth-chickpea
Results-Model Evaluation… 4. Growth-cowpea
Results-Model Evaluation… 4. Grain yield (kg ha-1)
Results-Model Evaluation… 5. Relative yield reduction
Results-Model Evaluation… 5. Simulated WSF vs. Measured LWP
Conclusion • The CSM-CROPGRO- drybean, chickpea and cowpea models accurately simulated: • soil water dynamics in the root zone layer and the duration and intensity of water deficit occurrence during the growing seasons • the seasonal pattern of LAI, biomass accumulation and pod growth under different water regimes although accuracy is less in the MS treatment, and • grain yield variability with water supply. • The models overestimated the duration of physiological maturity under water deficit conditions suggesting the need for further improvement in this regard.
Conclusion… • If properly calibrated, the models have shown their ability to be used as decision support tools in: • irrigation water management, • choice of cultivars to different water supply environments, • prescreening of genotypes for drought tolerance and • determining the occurrence and severity of agricultural drought in the semi-arid tropical environments.