Developing an optimization model in drip fertigation management to consider environmental issues and supply plant requirements

Recently, groundwater contamination has increased due to incorrect use of nitrogen fertilizers so that it has caused public concern. To solve the problem, the most appropriate approach is to manage on-time and correct application of water and fertilizer. The objective of this study was to provide an optimization program of drip irrigation and fertigation to maximize the nutrients uptake by plants and minimize water and solute losses in field by optimizing the design and management parameters of drip fertigation. In this research, the HYDRUS (2D/3D) model was used to simulate water and nitrogen transport in soil. For this purpose, the requirement data for calibration and validation of the model were collected by carrying out corn field experiments and performing drip irrigation and fertigation. Then, the calibrated model was used to simulate water and nitrogen behavior in soil and optimization process. To optimize the design and management parameters of fertigation, a two-stage optimization program was considered. In the first stage, the amount of irrigation flow rate, duration of fertilizer injection, and the start time of the injection were simultaneously optimized with the aim of minimizing nitrate leaching in a fertigation cycle. The results showed that by selecting the irrigation rate of 0.8 L h−1 and minimum duration of fertigation at the end of irrigation, nitrate leaching was minimum in the period of fertigation. In the second stage, the amount of fertilizer injection at each stage of fertigation was optimized throughout the growth season using the optimum values of the previous step. In fact, in addition to supplying nitrogen requirement of the plant, the amount of nitrate leaching and its accumulation at the end of each fertigation, especially at the end of the growing season, were also minimized to prevent leaching by post-harvest rainfall.