Abstract
This study analyzed the temporal and spatial features of cassava evapotranspiration from 1985 to 2015 in Benin using linear regression, Mann-Kendall trend test, Sen’s slope estimator, and interpolation. The study used basic meteorological data from the Met office of Benin and the Terra/MODIS vegetation index. The estimated crop coefficients (Kc) from FAO and NDVI have shown a strong and positive linear relationship with a correlation coefficient of r = 0.968, while NDVI-Kc presented values slightly lower than FAO-Kc. The rates of crop evapotranspiration (ETc) varied from 1.23 to 7.63 mm/day and 2.92 mm/day on average. At the local level, there were significant upward trends in the seasonal ETc for stations located in the bimodal rainfall pattern area (Cotonou, Bohicon, and Save) and non-significant for stations in the unimodal rainfall pattern area (Kandi, Parakou, and Natitingou). At the country level, both methods revealed a non-significant positive trend in cassava evapotranspiration in the study area while showing a strong and positive linear relationship in variations throughout the growing season, r = 0.956. Cassava’s growth in Benin may encounter in the future the risk of water deficit.
Highlights
Cassava is one of the major food crops in Benin both for its direct consumption and for processing into gari, tapioca, cassava chips, and lafun, as well as for its economic implications as an important trade product
The crop coefficients were estimated from FAO-56 default values and Normalized Difference Vegetation Index (NDVI) on daily basis over the length of the cropping cycle
The crossing of the two Kc lines between the days 174 and 177 showed that the two sources Kc have the same values during those days, while the FAO-Kc decreased faster than the NDVI-Kc over the period laying between day 150 and day 210
Summary
Cassava is one of the major food crops in Benin both for its direct consumption and for processing into gari, tapioca, cassava chips, and lafun, as well as for its economic implications as an important trade product. Since the warning of the Intergovernmental Panel on Climate Change about global increase in evapotranspiration as result of a warming climate (IPCC, 2014), and the recent study of (Ndehedehe et al, 2018) on evapotranspiration dynamics over Sub-Sahara Africa which indicated an increasing trend of evapotranspiration in Benin, much more attention are drawn on how this may affect major crops of the country including cassava. Understanding the mechanism of evapotranspiration is vital in hydrological and agricultural studies at the global, regional, and local scales (Xu et al, 2014). Crop water requirement (CWR) should be equal to the ET under ideal crop growth conditions. The FAO-56 method has been the most widely and practical approach used for estimating crop water requirement and the operational jas.ccsenet.org
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