Updated single and dual crop coefficients for tree and vine fruit crops

The present study reviews the research on the FAO56 crop coefficients of fruit trees and vines performed over the past twenty years. The main objective was to update information and extend tabulated single (Kc) and basal (Kcb) standard crop coefficients. The selection and analysis of the literature for this review have been done to consider only studies that adhere to FAO56 method, computing the reference ET with the FAO Penman–Monteith​ ETo equation and field measuring crop ET with proved accuracy. The crops considered refer to vine fruit crops, berries and hops, temperate climate evergreen fruit trees, temperate climate deciduous fruit trees and, tropical and subtropical fruit crops. Papers satisfying the conditions expressed above, and that studied the crops under pristine or appropriate eustress conditions, were selected to provide for standard Kc and Kcb data. Preference was given to studies reporting on the fraction of ground cover (fc), crop height (h), planting density, crop age and adopted training systems. The Kc and Kcb values obtained from the selected literature generally show coherence relative to the crop biophysical characteristics and reflect those characteristics, mainly fc, h and training systems. The ranges of reported Kc and Kcb values were grouped according to crop density, particularly fc and h, and were compared with FAO56 (Allen et al., 1998) previously tabulated Kc and Kcb values, as well as by Allen and Pereira (2009) and Jensen and Allen (2016), which lead to define update indicative standard Kc and Kcb values. These values are aimed for use in crop water requirement computations and modeling for irrigation planning and scheduling, thus also aimed at supporting improved water use and saving in orchards and vines.