**1. Introduction**

Drought and soil salinity are two of the world's dominant abiotic stresses that severely restrict crop production, and it is expected that these challenges, along with accelerating climate change, will drive universal food insecurity [1]. In parallel, the 933 million people affected by the water crisis in 2016 are expected to increase to 1.693–2.373 billion people in 2050 [2] as a consequence of the global increasing population and an additional rise in water demand [3]. Despite the fact that agriculture receives more than 70% of water supplies [4], most governments lack precise irrigation water usage statistics [5]. Irrigation processes waste 25–30% of fresh water, resulting in a loss of \$14 billion. Therefore, proper water management is critical

[6, 7]. Otherwise, growers are compelled to use saline water for irrigation owing to water shortages that lead to soil salinity expanding [8]. Soil salinity is one of the most damaging agents to cropland in more than 100 countries [9, 10]. Salinity affects more than 25% of the world's terrestrial lands and a third of the world's irrigated fields [11]. The total area of saline soils is reported to be 1060.1 million hectares, with climate change driving this estimate to rise [12].

The factors that cause natural or primary salinity include parent materials and saline minerals in the soil. Anthropogenic factors, such as conventional irrigation techniques and weak drainage systems, cause secondary salinity [13]. Complications of the accumulation of excess soluble salts, specifically chloride sulfate [14] in the root zone of plants [15], include reducing plant growth, groundwater pollution, and diminishing soil fertility, ultimately degrading farmlands [11, 16]. High soil salinity decreases crop productivity, especially vegetables, which are extremely sensitive during the ontogeny stage. The salinity tolerance of most vegetables is low [17]. Castanheira et al. [18] observed that along with increasing the salinity of irrigation water to 5 ds.m−1, the average solute concentration in the root zone reaches a level higher than the corn tolerance. Moreover, high salinity negatively impacts the physicochemical and biological traits of soils, such as the diversity and abundance of microbes and animals [19], consequently leading to adverse consequences for farmers' livelihoods, and the regional and national economy [20]. The financial loss caused by salinity-induced land degradation in 2013 was estimated at \$441 per hectare, equivalent to \$27 billion annually [21]. Hence, improper water management and subsequent salinization threaten the sustainability of agriculture [22]. Many investigations have been carried out to cope with the obstacles of water deficit and salinity. Irrigation water management strategies and drainage techniques as the most prevalent solutions [23, 24], specifically in arid and semiarid regions, can face numerous challenges such as high costs and inefficiency [11, 19, 25]. Notwithstanding investments in countering the salinity spread, farmers are still challenged by the consequences of soil salinity [26]. Food security is threatened whenever efficient management actions are not exerted to maintain agricultural production [27]. **Figure 1** shows the salinity and water stress situations in various regions of the world.

The uninterrupted monitoring of soil moisture and salinity in agriculture is accepted in order to limit water and salinity crises. After sea level temperature, soil moisture as a significant climatic determinant is the second prominent factor influencing evapotranspiration, sensible surface heat, and latent heat flux, as well as water, carbon, and energy cycles on a global scale [30, 31]. Changes in soil moisture alter both agricultural and municipal soils [32]. This essential variable is employed in order to improve weather forecasting, rainfall estimation, drought monitoring, and landslide and flood prediction [31]. There are multiple methods to measure soil moisture, which is directly correlated with irrigation efficiency [33]. Indirect methods estimate soil moisture using a gravimetric, gamma-radiation probe, neutron probe, and porous blocks based on gravitational sampling or time-domain reflectometry (TDR) in a small soil bulk. Direct methods also evaluate soil moisture using weighted moisture *in vitro* [34, 35]. In most circumstances, soil moisture is not directly measurable; instead, it is measured indirectly through moisture-related characteristics [36]. TDR is extensively employed to identify the soil water content according to the connection between dielectric constant and moisture content [34]. However, a study in the USA ascertained that only 1.2 out of 10 farms use soil moisture sensors for irrigation planning. This quantity is lower globally due to a lack of systematic support, sensor inconsistency, and high costs, resulting in the rejection of these systems [37].
