where \(w_{\text{target}}\) is the irrigation target SM (mm),\(w_{\text{wilt}}\) is the SM at wilting point (mm), and ๐‘“๐‘กโ„Ž๐‘Ÿ๐‘’๐‘ โ„Ž is a tuning parameter. If \(f_{\text{thresh}}\)= 1 (default), irrigation will be triggered once the available SM is below \(w_{\text{target}}\). If \(f_{\text{thresh}}\) = 0, irrigation is only triggered once the available SM falls below \(w_{\text{wilt}}\). Target SM is determined as the sum of SM at the target SM of each soil layer: