Towards Sustainable Irrigation Water Management in a Semi-arid Climate: Quantifying Evapotranspiration and Crop Coefficient for Citrus Orchards Based on Eddy Covariance Measurements
Résumé
This work aims to determine the citrus water requirements in the semi-arid region of the Souss-Massa, Morocco, where citrus plays a high strategic socio-economic role. The adopted approach consisted of quantifying 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. 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. The derived seasonal mean crop evapotranspiration (ETa) was about 2.56 mm/day 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. 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 40 percent overestimation of water requirements. This excess can be saved by optimizing the irrigation water.