Progress on the cassava model in DSSAT (Decision Support System for Agro-technology Transfer) including a sensitivity and uncertainty analysis and some model testing on the ACAI trials.

1. www.iita.org | www.cgiar.org | www.acai-project.org
Update on PhD:
Modeling the dynamics of
starch content in cassava
Patricia Moreno-Cadena

2. OUTPUTS
INPUT
FACTORS
GLOBAL SENSITIVITY ANALYSIS
A
B
C
A
B
C
Apportions output variance into input factors
UNCERTAINTY ANALYSIS
Propagates input factor variability into output
Uncertainty
*Adapted from Muñoz-Carpena, 2017: Advanced modeling system class
time
Yield
Importance of genetic parameters and uncertainty
16 crop parameters

3. Importance of genetic parameters and uncertainty
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Parameter Parameter description PDF n Source of parameter values
B01ND
Thermal time from planting to first
branching (°Cd)
Triangular 22 (Bolaños, 1987; Irikura et al., 1979; Lian and Cock, 1979; Veltkamp, 1986)
B12ND
Mean thermal time between branching
levels after the first branching (°Cd)
Triangular 22 (Bolaños, 1987; Irikura et al., 1979; Lian and Cock, 1979; Veltkamp, 1986)
LAXS Maximum individual leaf area (cm2) Lognormal 60
(Alves, 2002; Alves and Setter, 2004, 2000; Ceballos and Cruz, 2012; CIAT,
1975, 1978; Connor et al., 1981; Gabriel et al., 2014; Irikura et al., 1979;
Keating et al., 1982; Lian and Cock, 1979; Matthews and Hunt, 1994;
Okogbenin et al., 2013; Pellet and El-Sharkawy, 1993; Pinheiro et al.,
2014; Santhosh Mithra et al., 2013; Streck et al., 2014; Veltkamp, 1986)
SLAS Specific leaf area (cm2/g) Normal 22
(Fukai and Hammer, 1987; Gabriel et al., 2014; Gijzen et al., 1990; Keating
et al., 1982; Matthews and Hunt, 1994; Pellet and El-Sharkawy, 1993;
Rosenthal and Ort, 2012; Vandegeer et al., 2013)
LLIFA
Active leaf area duration in thermal time
(°Cd) after full expansion
Weibull 338
(Alves, 2002; Bolaños, 1987; CIAT, 1978; Connor et al., 1981; Fukai and
Hammer, 1987; Howeler, 2012; Irikura et al., 1979; Lian and Cock, 1979;
Veltkamp, 1986)
LPEFR Leaf-petiole weight fraction (-) Gamma 337
(Cadavid, 1988; CIAT, 2013a; Cock, 2011; De Tafur et al., 1994; Fukai and
Hammer, 1987)
LNSLP
Leaf appearance slope (-) as proportion of
the leaf appearance curve of reference
Uniform 0
NODWT Individual node weight (g) Weibull 72
(CIAT. Unpublished results., n.d.; CIAT, 2013b; Lian and Cock, 1979; Porto,
1983)
NODL Internode length (cm) Lognormal 55 (CIAT. Unpublished results., n.d.)
PARUE
Radiation use efficiency (g dry matter MJ-
1)
Lognormal 27
(De Souza et al., 2016; El-Sharkawy and Mejia de Tafur, 2010; Ezui, 2017;
Leepipatpaiboon et al., 2009; Pellet and El-Sharkawy, 1997; Veltkamp,
1986; Yamamoto et al., 2004)
TBLSZ
Base temperature for leaf development
(˚C)
Uniform 3 (Fukai and Hammer, 1987; Keating et al., 1982; Manrique, 1992)
BR1F-BR4F Branch number per fork at fork 1-4 (#) Uniform 2e (Ceballos and Cruz, 2012; Lian and Cock, 1979)
KCAN
Photosynthetically active radiation (PAR)
extinction parameter (-)
Uniform 12
(Cock, 2011; Ezui, 2017; Fukai and Hammer, 1987; June, 1993; Pellet and
El-Sharkawy, 1993; Veltkamp, 1986)

4. Importance of genetic parameters and uncertainty
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Enhanced Sampling for Uniformity (eSU) Qualitative analysis (408
parameter combinations)

5. Importance of genetic parameters and uncertainty
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Sobol  Quantitative (15360 parameter combinations)

6. Model calibration and evaluation
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PhD Candidate Joy Adiele (NOT trials-Nigeria)
TME 419
Simulated vs. observed harvest weight for the
variety TMS 419 in 39 NOT trials

7. Model calibration and evaluation
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PhD Candidate Rebecca Enesi (SPT trials)
TMS 0581- TME 419

8. Model calibration and evaluation
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PhD Candidate Rebecca Enesi (SPT trials)
TMS 0581- TME 419

9. Next steps
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• Evaluate the performance of the cassava model in Tanzania
• Adding algorithms to modify dry matter content From dry
weight to fresh weight.