Page 89 - Ecuador's Banana Sector under Climate Change

chapter 4: assessment of climate change impact on banana production and suitability in ecuador, and general assessment of global banana trends under climate change scenarios
2.2.4 Actual evapotranspiration
Actual evapotranspiration (AET) is the quantity of water that is removed from the soil due to evaporation and transpiration processes (Allen et al., 1998). AET is dependent on the vegetation characteristics, quantity of water available in the soil and soil hydrological properties (mainly soil water retention curves):
AET = Ksoil * Kc* PET (mm/month)
where: Ksoil = reduction factor dependent on volumetric soil moisture content (0-1),
Kc = banana crop coefficient dependent on the development of the crop (0.3-1.3). The crop coefficient (Kc) is used to estimate the crop water use form reference PET for different crops or vegetation types. Kc values for bananas were taken from the literature (Allen et al., 1998; Freitas et al., 2008; Silva and Bezerra, 2009).
2.2.5 Effective rainfall
Rain interception is the process by which precipitation is intercepted by the vegetation canopy (canopy interception losses), where it is subject to evaporation. Interception has an important role in the water budget, as it reduces the amount of precipitation available for soil moisture. The losses due to interception depend on vegetation type, vegetation cover and the intensity, duration and frequency of precipitation (Siles et al., 2010). The vegetation interception is a purely mechanic function of the storage space of vegetation structure. The effective rainfall
(ERain) in this study was estimated using the FAO/AGLW equation. FAO/AGLW developed an empirical formula, based on analyses undertaken for different climatic data to determine the dependable effective rainfall (FAO, 2001; FAO, 1992):
For each month, ERain is calculated as:
ERain = 0.6*Raintot - 10 for Raintot <= 70 mm
ERain = 0.8*Raintot - 25 for Raintot > 70 mm
Where: ERain is the effective rainfall and Raintot is the total month rainfall.
Table 13 Banana crop coefficients (Kc) found in the literature for different cultivars
Banana cultivar
Kc at different stages
Reference
Initial
Medium
Final
Prata Ana
Pacovan
Cavendish
Pacovan
Cavendish
Pacovan
0.8 (0-100 d)
0.9 (0-100 d)
0.4
0.6
0.5
1.0 (100-160 d)
1.0 (100-160 d)
1.2
1.1-1.3
0.8
1.1 Final 1st
1.1-1.4
0.8-0.7
Silva and Bezerra 2009
Silva and Bezerra 2009
Allen 2006
Freitas et al. 2008
Freitas et al. 2008
Bassoi et al. 2004
0.65
0.9-0.95
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