## 1 Introduction  
Saudi Arabia is a desetric land exposed to extreme temperatures and an arid climate, with limited groundwater resources [1]. Despite the harsh environmental conditions, such as high levels of evapotranspiration and low levels of precipitation, the Kingdom has managed to become self-sufficient in the production of some vegetables and food crop products [2]. With the rapid growth of the population, there is a rising demand for vegetables and tomatoes. Hence, the sustainability of agriculture and water resources in Saudi Arabia is essential for food and water security [3]. Soil and water resources, along with the application of agricultural inputs, determine the production potential of agricultural ecosystems. Increased crop yields are associated with an increased use of water and fertilizer, and modern research has focused on maximizing the water and fertilizer use efficiency (WFUE) of crops [3; 4; 5]. The quickly dwindling global supply of fresh water and renewable water resources, coupled with increasing demands for water from the agricultural sector, is threatening the food and water security of nations around the world. As a result, approaches to water resource management are also changing dramatically [6]. The long-term annual precipitation in Saudi Arabia is recorded as 114 mm. The annual water demand has been steadily rising due to increases in developmental activities and essential services in proportion to the growing population. The agricultural sector utilizes around 80 percent of the total quantity of water used in the Kingdom [7]. Limited water resources, sparse and low rainfall, higher temperatures, evapotranspiration, and ecological conditions pose significant challenges to agricultural activities. The sustainability of the agroecosystems of Saudi Arabia depends heavily on the efficient management of available soil and water resources. However, the steady decline in the finite water resources and the continued degradation of soil resources make the task much more challenging [8; 9]. In addition, the external inputs required for agricultural production are becoming more scarce and costly. Thus, the conservation of water and soil resources via the transformation of traditional agricultural practices into modern agricultural practices for self-sustainability is an essential matter in Saudi Arabia. The construction of greenhouses and protected cultivations alter microclimate conditions to favor the productivity of plants, and they also predominantly reduce transpiration and increase water productivity [10; 11]. In traditional agriculture, soil is a medium of plant growth that offers mechanical support to plants, stores water, and provides plants with the required nutrients. However, continuous and intensive use of soil in greenhouses has led to infestation by plant pathogens and deficiencies in essential nutrients. This has resulted in the use of soil disinfections, leading to the pollution of the environment and damage to fertigation systems [12]. Hydroponics, a smart agricultural technique involving the cultivation of plants without soil, which is also referred to as soilless culture and nutriculture, among other terms, is a viable system that overcomes these problems [13; 14]. The production of crops in hydroponic greenhouses results in increased food production, improved food quality, conservation of resources, and protection of the environment. In Saudi Arabia, water is not only scarce but also precious. Since saline water can be used as an alternative for irrigating salt-tolerant crops, especially under hydroponic conditions, the country is planning to use desalinated sea (saline) water as an alternative to groundwater resources [15; 16]. In such a situation, studies on the use of saline water without sacrificing the yield and quality of crops are very much necessary to determine appropriate water management practices.