25 Pags.- 5 Tabls.- 5 Figs. The definitive version is available at: http://jast.modares.ac.ir/High efficiency and uniformity of water and fertilizer application are usually, considered as the ultimate goals of an appropriate design and management of irrigation and fertigation systems. The objective followed in this paper was to present a simulation-optimization model for alternate vs. conventional furrow fertigation. Two simulation models (surface fertigation and SWMS-2D models) along with an optimization approach (genetic algorithm) were employed. Inflow discharge, irrigation cutoff and start times as well as duration of fertilizer injection were chosen as decision variables to be optimized for maximizing two objective (fitness) functions based on water and nitrate application efficiency plus uniformity. Experiments were conducted to collect field data (soil water content, soil nitrate concentration, discharge and nitrate concentration in runoff, as well as advance and recession times) in order to calibrate the simulation models. The simulation-optimization model indicated that variable and fixed alternate furrow fertigations benefited from higher water and nitrate efficiencies than the conventional furrow fertigation. However, minor differences were observed between these types of furrow irrigation regarding water and nitrate uniformity. This approach substantially improved water and nitrate application efficiency as well as uniformity, taking into account the field experimental conditions. Water and nitrate application efficiencies ranged from 72 to 88% and from 70 to 89%, respectively. Christiansen uniformity coefficients for water and nitrate varied between 80 and 90% and from 86 to 96%, respectively. A higher improvement was observed in conventional furrow fertigation than those in both alternate furrow fertigation treatments. The potential of the simulation-optimization model to improve design and management of furrow fertigation is highlighted.Peer reviewe
