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Alternate-furrow fertigation has shown potential to improve water and fertilizer application efficiency in irrigated areas. A combination of simulation and optimization approaches permits researchers to identify optimum design and management practices in furrow fertigation, resulting in optimum cost, irrigation performance, or environmental impact. The objective of this paper is to apply one-dimensional (1D) surface and two-dimensional (2D) subsurface simulation-optimization models to the minimization of nitrate losses in two types of alternate-furrow fertigation, as follows: (1) variable alternate-furrow irrigation, and (2) fixed alternate-furrow irrigation. For comparison purposes, optimizations are also reported for conventional furrow irrigation. The model uses numerical surface fertigation and soil-water models to simulate water flow and nitrate transport in the soil surface and subsurface, respectively. A genetic algorithm is used to solve the optimization problem. Four decision variables (inflow discharge, cutoff time, start time, and duration of fertilizer solution injection) were optimized to minimize the selected objective function (nitrate loss) for two fertigation events performed during a maize-growing season. The simulation-optimization model succeeded in substantially reducing the value of the objective function as compared with the field conditions for all irrigation treatments. In the experimental conditions, optimization led to decreased inflow discharge and fertilizer injection during the first half of the irrigation event. This was because of the high potential of the field experiment to lose water and nitrate through runoff. In the optimum conditions, alternate-furrow fertigation strongly reduced water and nitrate losses compared with conventional furrow irrigation. The simulation-optimization model is a valuable tool for alleviation of the environmental impact of furrow irrigation.

This data set contains the results of the experimental evaluation of two alternate and conventional furrow fertigation events. Experiments were performed at the College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. Three irrigation treatments were considered: Variable Alternate Furrow Irrigation (AFI), Fixed Alternate Furrow Irrigation (FFI) and Conventional Furrow Irrigation (CFI). Liquid fertilizer was injected in the irrigation water during part or the irrigation event. The data set contains advance and recession, soil water and nitrate, inflow and outflow discharge and nitrate concentration, and meteorological data.

Alternate furrow irrigation and surface fertigation have been known as techniques to control water and fertilizer losses. The main goal of this field study was to characterize the combined effect of these techniques on water and nitrate losses and on soil water and nitrate concentration. Two types of alternate furrow irrigation, i.e., variable alternate furrow irrigation (AFI) and fixed alternate furrow irrigation (FFI), as well as conventional furrow irrigation (CFI) were considered in the experiments. Results evidenced higher infiltration at irrigated furrows under AFI and FFI as compared to CFI. Increased lateral water movement under alternate irrigation resulted in lower water and nitrate losses via runoff and deep percolation. Water application efficiency for the CFI, FFI and AFI strategies amounted to 61.3%, 71.8% and 77.0% in the first fertigation and 36.4%, 58.8% and 60.7% in the second fertigation, respectively. Nitrate runoff for the CFI, FFI and AFI strategies amounted to 32.4%, 31.2% and 25.7% in the first fertigation and 44.3%, 35.1% and 32.7% in the second fertigation, respectively. Soil water content and nitrate concentration at the upstream part of the experimental field were larger than at the middle and downstream parts for all three irrigation regimes. Overall, alternate furrow fertigation, particularly AFI, stands as a simple and practical management practice for water and fertilizer conservation in agricultural fields.