A method for managing agricultural irrigation of a crop in an area of a field or a subplot thereof during a growing period, the method comprising: receiving data indicative of an irrigation recommendation function of the crop during a growing period (IR(t)), data indicative of a current crop water potential at a time t S within the growing period, data indicative of an evapotranspiration (ET0) at t S , data indicative of a crop coefficient Kc, and optionally data indicative of a last irrigation time; wherein the data indicative of the current crop water potential are obtained using remote sensing data of said crop canopy and/or direct water potential measurements using in-situ plant sensors; computing a current crop water stress coefficient Ks cur (t S ); computing an actual evapotranspiration (ETa) at t S (ETa(t S )) of said crop by taking a product of Ks cur (t S ) and a corresponding non-stress crop evapotranspiration (ETc) at t S (ETc(t S )), wherein ETc(t S ) = ET0(t S ) * Kc(t S ); and if ETa(t S ) ≥ IR(t S ), setting an optimal irrigation time (t opt ) by: extrapolating a line L passing through or near a first point P 1 and a second point P 2 , P 1 defined by first coordinates (t L , ETc(t L )) comprising a last irrigation time t L , which is earlier than t S , and ETc at t L , and P 2 defined by second coordinates (t S , ETa(t S )); obtaining a third point P 3 , where at line L intersects, or is tangent to, a curve defined by IR(t), wherein t opt is equal to the day of the time coordinate of P 3 ; and setting the forecast irrigation amount (FIA) by: computing a value v indicative of an integral of IR(t), between t L+1 and t opt , wherein t L+1 equals t L plus one day, wherein the FIA is equal to v. receiving data indicative of an irrigation recommendation function of the crop during a growing period (IR(t)), data indicative of a current crop water potential at a time t S within the growing period, data indicative of an evapotranspiration (ET0) at t S , data indicative of a crop coefficient Kc, and optionally data indicative of a last irrigation time; wherein the data indicative of the current crop water potential are obtained using remote sensing data of said crop canopy and/or direct water potential measurements using in-situ plant sensors; computing a current crop water stress coefficient Ks cur (t S ); computing an actual evapotranspiration (ETa) at t S (ETa(t S )) of said crop by taking a product of Ks cur (t S ) and a corresponding non-stress crop evapotranspiration (ETc) at t S (ETc(t S )), wherein ETc(t S ) = ET0(t S ) * Kc(t S ); and if ETa(t S ) ≥ IR(t S ), setting an optimal irrigation time (t opt ) by: extrapolating a line L passing through or near a first point P 1 and a second point P 2 , P 1 defined by first coordinates (t L , ETc(t L )) comprising a last irrigation time t L , which is earlier than t S , and ETc at t L , and P 2 defined by second coordinates (t S , ETa(t S )); obtaining a third point P 3 , where at line L intersects, or is tangent to, a curve defined by IR(t), wherein t opt is equal to the day of the time coordinate of P 3 ; and line L intersects, or is tangent to, a curve defined by IR(t), wherein t opt is equal to the day of the time coordinate of P 3 ; and setting the forecast irrigation amount (FIA) by: computing a value v indicative of an integral of IR(t), between t L+1 and t opt , wherein t L+1 equals t L plus one day, wherein the FIA is equal to v. computing a value v indicative of an integral of IR(t), between t L+1 and t opt , wherein t L+1 equals t L plus one day, wherein the FIA is equal to v. <EOS>