With the growth of agricultural production will intensify the pressure on natural ecosystems, water and energy resources (Pastor et al., 2019; Abdelkader and Elshorbagy, 2021). In this regard, the global demand for water, energy and food (WEF) resources is expected to increase by more than 50% on average by 2050 (Zuo et al., 2021 Schull et al., 2020). Furthermore, in the past decades, economic development along with the occurrence of environmental phenomena, such as climate change and land use changes, have led to excessive demand for these key resources (Mabhaudhi et al., 2019; Azarm et al., 2020; Mirzaei et al., 2022b). The continuation of this trend and the ever-increasing demand for WEF resources, while threatening the security of these strategic resources, will be an obstacle to the attainment of sustainable development globally (Feng et al., 2022).
Considering the use of water for irrigation and energy for food production, the concept of WEF nexus can be concretely pursued in rainfed agriculture (Avellan et al., 2018; Hamidov and Helming, 2020). With increasing international concerns and sensitivities of environmental and social damage caused by increasing pressure on water and energy resources for food production, the concept of WEF nexus has received a lot of attention (Karnib, 2018). This concept was proposed at the nexus conference in Bonn (2011) in order to understand the complex relationships and interdependence between the three sectors of water, energy and food (Si et al., 2019; Ma et al., 2021).
Statistics show that 70% of the world's water resources are consumed in the agricultural sector (Bruinsma, 2017). Meanwhile, in dry and semi-dry regions of the world that are facing water shortages, there is intense competition for water use between different sectors (De Odorico et al., 2019). On the other hand, the vital role of energy in the production process of agricultural products, including the transfer and extraction of water for irrigation and the use of agricultural machinery, is significant (Tian et al., 2018; Guan et al., 2020). Therefore, considering the strong interconnection among food production and water and energy resources and the existence of managerial and environmental challenges in this field, it is necessary to evaluate the link of WEF in irrigated agriculture.
In previous studies, various indicators, such as efficiency, productivity and security of water, energy and food resources have been evaluated in the agricultural sector (Echchelh et al., 2018; Sanjuan-Delmas et al., 2018). However, researchers now state that all these criteria should be quantified and combined in the form of the WEF nexus concept (Zhang et al., 2018b; Radmehr et al. 2021; Karamian et al., 2021). In this regard, in various studies, the WEF nexus index has been used as a comprehensive approach in agricultural systems (El-Gafy et al., 2017a, b; Fabiani et al., 2020, Gathala et al., 2020; Sadeghi et al., 2020; Karamian et al., 2021). The review of the literature shows that from a methodological point of view, due to the conflict between the goals of stakeholders in different sectors and complex relationships and feedbacks, the multi-objective programming model has been operationalized as an efficient and powerful tool at the national, regional and global levels in order to assess the WEF nexus. Optimization of the criteria related to the concept of the WEF nexus and the maximization of farmers' gross profit have been the main objectives of these studies (Zhang et al., 2018a; Zhou et al., 2019; Sun et al., 2020; Ji et al. 2020; Radmehr et al. 2021; Mirzaei et al., 2022a).
In the past decades, in addition to mismanagement of water and energy resources have also intensified concerns about the negative effects of the use of chemical fertilizers and pesticides in agricultural productions on human health and environmental conditions (Zhang et al., 2019). By proven significant impact of the use of chemical inputs such as fertilizers and pesticides on maintaining and increasing the productivity of agricultural productions, the use of these inputs has been greatly expanded in the agricultural sector (Mardani Najafabadi et al., 2022b). Therefore, evaluating the WEF nexus approach in the agricultural sector without considering environmental issues will not have enough value and credibility (González-Bravo et al., 2018; Mirzaei et al., 2022a).
Today, the residual amount of chemical fertilizers and pesticides in agricultural products exceeds the permissible limit in many regions of the world (Park et al., 2019). In addition, the role of excessive use of chemical inputs has been proven on the growth of pollutant emissions in the agricultural sector (UNEP, 2011). In this regard, González-Bravo et al. (2018) used the WEF nexus index in order to design of the water distribution network in the agricultural sector. In addition to the goals of maximizing the WEF index and maximizing the gross margin, they added the limitation of greenhouse gas emissions to the optimization model. In the study of Mirzaei et al. (2022a), in addition to the goal of maximizing the WEF index and gross margin, minimizing the consumption of chemical fertilizers and pesticides in agricultural production was included as a goal in the mathematical programming model. At the same time, considering the minimization of the consumption of chemical fertilizers and pesticides in the objective function, regardless of the effects of changes in the consumption of these inputs on the value of agricultural products, cannot make economic development of the agricultural sector possible. Therefore, it is necessary to use an effective and comprehensive index to consider the environmental effects of expanding the use of chemical inputs (Xu et al., 2022). Based on this, by introducing the decoupling index (DEC), researchers considered separating pollution from the growth of agricultural production (Xiong et al., 2016; Li et al., 2019b; Chen et al., 2020, Naghavi et al., 2022, Mardani Najafabadi et al., 2022b). The DEC index discusses the harmonious development of both economic and environmental dimensions and separates agricultural economic growth from pollution (Shi, 2020).
There are various studies that have separately calculated the pollution-agricultural growth DEC index and included it in agricultural production planning without considering the WEF nexus (Wang et al., 2018; Román-Collado et al., 2018; Dong et al., 2021; Wang & Zhang, 2021; Naghavi et al., 2022, Mardani Najafabadi et al., 2022b). The review of the literature on the agricultural growth-pollution decoupling index shows that in none of the past studies, the optimal allocation model has been estimated according to the goals of this index.
To the best of researchers’ knowledge, there was no study that has extracted the optimal and sustainable pattern of resources in the agricultural sector according to WEF and DEC as two emerging indicators. In this regard, the simultaneous consideration of various dimensions and indicators related to WEF and DEC to provide economic goals and sustainability of resources in the agricultural sector is unique. Therefore, the aim of the present study was to design and analyze a new approach so as to alleviate the weakness of the WEF nexus in not paying attention to environmental pollution issues and the weakness of the pollution-agriculture growth DEC index in not paying attention to water and energy issues in optimal economic and sustainable planning of agricultural production. In order to achieve this objective, the integration of two indicators of WEF nexus and pollution-agricultural growth DEC has been used to extract the pattern of optimal consumption of resources in the agricultural sector through multi-objective modeling, which has not been observed in previous studies.