Towards accurate estimation of crop water requirement without the crop coefficient Kc: new approach using modern technologies

Modern technologies to measure actual evapotranspiration, ETa, were implemented at an experimental farm near Bologna, Italy. Large-aperture scintillometer and eddy covariance instruments were installed. The results showed significant differences between actual evapotranspiration measured by eddy covariance and scintillometer when compared with the potential reference evapotranspiration, ET0, calculated from meteorological data using the Penman–Monteith equation and the crop potential evapotranspiration, ETc, which is based on the ET0 and the crop coefficient, Kc. The ETc and ET0 showed higher values than those of ETa obtained by eddy covariance and scintillometer. On average the actual evapotranspiration measured by eddy covariance and scintillometer for the cropping seasons 2014 and 2015 represented 45 and 35% of the ET0 or the ETc, respectively. The ET0, or the ETc, represent the atmospheric water demand while, fundamentally, the crop water requirement should be based on crop water demand better represented by the actual evapotranspiration. At present, the results indicate that the actual crop water requirement based on modern technologies could save at least 50% of irrigation water for this region. Another benefit is that these modern technologies do not need the crop coefficient Kc, which for many irrigation practitioners is difficult to obtain.