**1. Introduction**

## **1.1 Human, food and plants**

Almost all life forms on the Earth fundamentally depend on plants and/or plantbased (food and non-food) resources. Human being, in particular, are indebted (directly or indirectly) to the diversity of plants for oxygen, food, fuel, fiber, medicines, and even for shelter. Being sessile by nature, plants have to closely interact with the immediate environment (growing conditions comprising air, water, soil, energy/ light) to sustain their own lives and accomplish the aforementioned notable contributions to human life. As an enigmatic, heterogeneous, multiphasic and porous system, soil acts as a natural growth environment/medium for diverse land plants. The health of soil is closely linked with the health of plants and that of their immediate and longterm consumers. Interestingly, 80% of average calorie consumption comes from crop plants grown directly in soil. Hence, healthy soil has been widely argued vital both as a resource for feeding the burgeoning global population via agriculture, and also for realizing most of the United Nations Sustainable Development Goals [1–5].

### **1.2 Soil salinization: concept and types**

The health of soil is being significantly impacted by increased salinization due to excess accumulation of varied salts (e.g., cations: Na+ , Ca2+ and Mg2+; anions: Cl− , SO4 2−, CO3 2− and HCO3 − ). Based mainly on the soil properties, namely electrical conductivity (EC), pH, exchangeable sodium (Na+ ) percent (ESP), Na+ adsorption ratio (SAR), total soluble salts (TSS), and total dissolved solids (TDS), soils can be categorized in three major types: saline, sodic and saline-sodic. EC of the saturation paste extract (ECe) is the measure of salinity, whereas the measure of sodicity is the exchangeable sodium (Na+ ) percentage (ESP) or the sodium adsorption ratio (SAR). Soils can be saline (ECe > 4 dS m−1 (decisiemens per meter)) at 25°C and ESP < 15 (high soluble salts and low exchangeable Na+ ; pH 7.0–8.5), sodic (Ece < 4 dS m−1 and ESP > 15; with a high amount

of exchangeable Na+ ions on the cation-exchange sites; weak bond between soil particles; pH > 8.5) or saline-sodic (Ece > 4 dS m−1 and ESP > 15; both salts and exchangeable sodium are high). According to the first ever country-driven global map of salt-affected soils (GSASmap, V1.0.0), which comprised over 118 countries with 257 and 419 locations (covering 85% of global land area), 85% of salt-affected top-soils are saline, 10% are sodic and 5% are saline-sodic, 62% of salt-affected subsoils are saline, 24% are sodic and 14% are saline-sodic (FAO-GloSIS 2023 [6]; **Figure 1**). Major consequences of sodicity and salinity on soil health are summarized in **Figure 2**.

The building-up of elevated level of varied salts (e.g., cations: Na+ , Ca2+ and Mg2+ ; anions: Cl− , SO4 2−, CO3 2− and HCO3 − ) in the soils may be caused naturally (*leading to primary salinity*) or human-induced (or anthropogenic activities) (*leading to secondary salinity*). Interestingly, the natural climate conditions; different geological, hydrological and pedological processes; wind; rainfall; parent rock weathering; long-term natural accumulation of salts (including Cl− of Na+ , Ca2+ and Mg2+ and sometimes SO4 2− and CO3 2−); and higher evapotranspiration (versus precipitation) largely contribute to the primary or natural salinity in the soil or surface water. On the other hand, the humaninduced (or anthropogenic) activities done in agricultural management practices are largely inappropriate, which cause poor drainage and arbitrary irrigation, disrupt the hydrologic balance of the soil between water applied (irrigation or rainfall) and water used by crops (transpiration), leading ultimately to the secondary salinization, the major cause of the loss of agricultural soils (**Figure 3**) [6, 8]. Both primary and secondary

**Figure 1.** *Global map of salt-affected soils (GSASmap) [6].*

*Introductory Chapter: Making Plant Life Easier and Productive under Salinity – Updates… DOI: http://dx.doi.org/10.5772/intechopen.113407*

**Figure 2.**

*Schematic representation of the major impacts of sodicity and salinity on soil health [7].*

**Figure 3.** *Schematic representation of the major factor contributing to natural and human-induced soil salinization [7].*

salinization of soils mainly occurs in arid and semi-arid regions, where precipitation to evapotranspiration ratio is low. Notably, climate change is among the major factors known to influence the global distribution of salt-affected soils [9–13].

Notably, soil salinization is at the top among the major climate change-influenced abiotic stress factors and is also known to bring severe consequences at both agricultural soil and agricultural crop plant levels. It significantly changes the major physiochemical and biological characteristics (including soil structure, soil microbial activity, etc.). These soil-level changes culminate in the inhibition of absorption of water and nutrients by plants and severely impairing the physiological/biochemical, molecular and yield (≈50% reduction) attributes of crop plants. On the other hand, agriculture, in particular, is under pressure to accelerate crop plant yield (by >70%) in order to feed the burgeoning world population that is projected to stabilize at around 9.7 billion by the year 2050 [14].

Given above, efforts must be made to make crop plant life easier and more productive under rapidly increasing soil salinity. It is required to consider a multi-level approach comprising monitoring, assessment, and the management of soil salinization; getting insights into the crop plant physiological/biochemical and moleculargenetic responses to soil salinity; and dissecting the strategies for strengthening plant/crop salinity-tolerance mechanisms.
