Abstract
Cassava is an important crop in the developing world. The goal of this study was to review published cassava models (18) for their capability to simulate storage root biomass and to categorize them into static and dynamic models. The majority (14) are dynamic and capture within season growth dynamics. Most (13) of the dynamic models consider environmental factors such as temperature, solar radiation, soil water and nutrient restrictions. More than half (10) have been calibrated for a distinct genotype. Only one of the four static models includes environmental variables. While the static regression models are useful to estimate final yield, their application is limited to the locations or varieties used for their development unless recalibrated for distinct conditions. Dynamic models simulate growth process and provide estimates of yield over time with, in most cases, no fixed maturity date. The dynamic models that simulate the detailed development of nodal units tend to be less accurate in determining final yield compared to the simpler dynamic and statistic models. However, they can be more safely applied to novel environmental conditions that can be explored in silico. Deficiencies in the current models are highlighted including suggestions on how they can be improved. None of the current dynamic cassava models adequately simulates the starch content of fresh cassava roots with almost all models based on dry biomass simulations. Further studies are necessary to develop a new module for existing cassava models to simulate cassava quality.
Highlights
Cassava (Manihot esculenta Crantz) is the fourth most important source of calories in Africa (FAO, 2020)
The spill-over model just considers eight crop param eters for calibration including carbon concentration when the light saturated rate of photosynthesis is reduced to 50 %, the number of apices and primary stems, internodal length of the stems and branches, inhi bition factor of the photosynthesis based on the substrate concentration, and maximum leaf senescence rate
For example, if the processes in the model have separately been developed for cool temperatures and large vapor pressure deficits, even though no field data are available for the combination of hot summers with large vapor pressure deficits and cool winter temperatures, the model could simulate these conditions reasonably well
Summary
Cassava (Manihot esculenta Crantz) is the fourth most important source of calories in Africa (FAO, 2020). Cassava has long been a staple crop for most of the countries in Africa, it is increasingly considered as a cash crop (Nweke, 2005). It is a major source of starch with highly industrialized extraction in countries like Vietnam and Thailand in Asia (Howeler, 2012) and Brazil and Paraguay in the Americas (Aristizabal Galvis et al, 2017).
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