Author(s): Asma Abou Ali; Lhoussaine Bouchaou; Salah Er-Raki; Jamal Ezzahar; Said Khabba; Youssef Brouziyne; Mohammed Hssaissoune; Adnane Chakir; Adnane Labbaci; Ghani Chehbouni

Linked Author(s): Asma ABOU ALI, Lhoussaine Bouchaou, Salah Er-Raki, Youssef Brouziyne

Keywords: Citrus; Crop coefficients; Evapotranspiration; Irrigation management; Souss-Mass

Abstract: Climate and land-use change are the most pressing medium- and long-term challenges affecting water availability in the agricultural sector. One way to mitigate this vulnerability is to understand when, where, and how much water is needed for agricultural production. This study contributes to water planning and management in semi-arid climates, where irrigation is mandatory, especially during the dry season, to compensate for plants’ water requirements. Specifically, this work aims to determine the citrus water requirements in the semi-arid region of the Souss-Massa, Morocco, where this crop plays a high strategic socio-economic role. The adopted approach consisted of o determining the total amount of water needed to meet the water loss through evapotranspiration. For this purpose, an eddy covariance (EC) tower was placed over a commercial citrus orchard in Souss-Massa that was planted with the Esbal clementine variety to measure sensible and latent heat fluxes. This tower was also equipped with sensors to measure net radiation, soil heat fluxes, and meteorological data. Soil moisture was measured continuously at different soil depths to monitor its changes in the root zone. The energy balance closure (EBC) approach was performed to ensure a quality check for the EC data, resulting in a good closure of 92 and 83 percent for daily and half-hourly scales, respectively. Later, actual crop evapotranspiration (ETa) was inferred from daily latent heat flux (LE) measurements for an eventual computation of crop coefficients (Kc) values. These values are used to optimize irrigation management in the specific conditions of Souss-Massa. The derived seasonal mean crop evapotranspiration (ETa) was about 2.56 mm/year with an annual value of about 938 mm. On another side, seasonal Kc values varied from 0.49 in February, corresponding to the pre-flowering phenological stage, to 0.72 in October, with an average value of 0.62. October corresponds to the ripening period and requires significant water volume, not covered by the erratic rainfall. Measured crop coefficient values were then compared to the values tabulated by the FAO-56 paper usually used by the local farmers and other values reported by the literature. The comparison showed a significant discrepancy between the collected results in terms of the pattern and the values. The bottom line of this study is to suggest crop and region-specific Kc values for farmers and evaluate their added value. That is why the standard irrigation strategy adopted by the farmer was assessed, resulting in a 20 percent overestimation of water requirements. This excess can be saved by optimizing the irrigation water while maintaining profitable yields. The adopted approach and methodology revealed significant potential for more sustainable water use in the irrigation sector within the experiment conditions.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221718

Year: 2022