Abstract

Salinity stress is one of the most vital abiotic stresses which results in significant damages of agricultural production, particularly in arid and semi-arid areas of the world. Salinity causes by high accumulation of soluble salt, especially NaCl in soil and water. Salinity hampers the growth and survival of many field crops such as rice, wheat, maize, cotton, sugarcane, and sorghum. It affects the plant growth by three ways such as osmotic stress linked with an increase of phytotoxic ions, ionic stress e in the cytosol, and oxidative stress facilitated by reactive oxygen species (ROS). These stresses caused by salinity hinder the water uptake, causes ion imbalance, ROS production, and hormonal imbalance, and results in the decline of photosynthesis activities reduce the plant growth and final yield. However, the sensitivity of field crops depends on the nature of cultivar and growth stages. There are many strategies to cope with salinity stress which are the development of salinity tolerant crop cultivators by using genetic and molecular techniques such as QTLs and CRISPR CAS9 technique, nutrients management strategies, use of hormones regulators (AVG, 1-MCP, D-31). This chapter will give a brief idea to the scientist to understand the effects of salinity on field crops and their management strategies.

Keywords: salinity, field crops, physiology, yield, sodium chloride, reactive oxygen species

#### 1. Introduction

The plant growth, development, and yield are negatively affecting by abiotic stresses such as drought, salinity, chilling, and high temperature. About 50% of plant productivity is under the influence of these abiotic stresses [1]. Among these abiotic stresses, salinity is considered as one of the most harmful agents for the plant life cycle. Salinity is an excess amount of salt in the soil, water, and plant. Salinity is frequently an underrated problem in the agriculture sector. It is estimated that salt affected area (sodic and saline) about 6% irrigated and 20% of world's total cultivable land is under the influence of salinity [2]. The irrigated areas of many countries are affected due to salinity in the world (Table 1) [3]. Salinity problem is caused by the natural and anthropogenic activities and increasing with time. It is also estimated that 50% of the cultivable land will effect due to salinity by 2050 [2]. On the contrary side, with the current speed of population increase in the world,


cell sap and tissues. This imbalance causes ion toxicity within plant tissues, and plant shows leaf burn or wilting symptoms due to Na+ and Cl accumulation. Ionic stress also causes nutrients disequilibrium and results in reduce final germination percentage (FG %), decrease vegetative and reproductive growth, decline yield, and yield components of the plant under salinity. Similarly, ionic stress in the plant due to salinity causes reduction of photosynthesis activity, alteration of enzymatic activities, oxidative stress, disrupted the biochemical membrane structure and function, destroy the ultrastructural cellular components, and hormonal imbalance are the primary reason for the reduction of overall plant's growth and development [7, 8].

Salinity Stress in Arid and Semi-Arid Climates: Effects and Management in Field Crops

For better plant performance under salinity stress, natural adaptation responses at physiological, molecular, and cellular levels to tolerate salinity stress is of great concern. These adaptations are an osmotic adjustment, closure of stomata, Na+ exclusion

efficiency, and increased antioxidant defense system are very important for ideal plant growth under salinity. Besides these, various other management strategies have been embraced on a scientific basis to improve plant growth efficiency under salinity. These strategies are genetic modification, identification, sequencing of gene, microarray analysis, and plant transformation, and agronomic strategies to reduce salinity stress by soils reclamation via water and nutrients management, seed priming, and usage of hormone regulator to create homeostasis in hormonal production under salinity. These management strategies are being useful for stress management, including salinity. In this book chapter, we will review the latest information about the 'Salinity Stress in Arid and Semi-Arid Climates: Effects and Management in Field Crops, which could be a good advantage to the scientific community and farmers for

the understanding of salinity issue in the field crops and their solution.

The ecological anxieties (biotic and abiotic stresses) have turned into essential threats to plant growth, development, and survival. Among these ecological anxieties, abiotic stresses, for example, drought, chilling or high temperature, and salinity inactively influencing the growth, biomass generation, and yield of many field crops. These threats are ending up more deteriorated by regular or humanmade activities, which result in the excessive soluble salts accumulation in the underground water and soil. As concern salinity stress, about 20% of the world's land, and about 33% of the world's irrigated zone is under the impact of salinity [9].

Besides, salinity influenced areas are expanding at a rate of 10% yearly. The expanding of salinity issues are because of low precipitation, high surface evaporation, weathering of native rocks, irrigation with saline water, and poor agronomic practices. Salt influenced soils have various sorts that negative effect on agricultural production, for instance, irrigation-induced salinity and 'transient' dry-land salinity have been arranged in detail with different perspectives considered by [10], and illuminate that salinity in the soil is one of the vast abiotic stress that hamper the agricultural production in the world. The estimation has been done that >50% of

the agricultural land would be affected by agricultural till 2050 [11].

Salinity is the issue of almost all the continents and under a wide range of climates. However, the salinity issue is more in arid and semi-arid climate contrasted with the humid climate where yearly precipitation is not as much as evapotranspiration in the world. It is need of great importance to comprehend the mode and sources of salinity with classification, and its role in the plant life cycle. The characteristic critical source of salinity is the primary minerals in exposed layers of the earth crust by weathering process with the assistance of atmospheric

/N+ equilibrium, and cytosolic K+

, transpiration

from older leaves, maintenance of K+

DOI: http://dx.doi.org/10.5772/intechopen.87982

2. Salinity stress and its causes

199

#### Table 1.

Global estimate of secondary salinity in irrigated lands of the world.


Whereas, ECe = electrical conductivity, ESP = exchangeable sodium percentage, SAR = sodium adsorption ratio, and pHs = negative log of H+ ion [12].

#### Table 2.

The USDA classification system of salt affected soils.

also need to produce more food up-to 70% till 2050 to feed the increasing mouths of the world [2].

Many major field crops such as wheat (Triticum aestivum L.), rice (Oryza sative L.), maize (Zea mays L.), sorghum (Sorghum bicolor (L.) Moench), cotton (Gossypium hirsutum), and sugarcane (Saccharum officinarum), etc. show negative response towards salinity. However, plant performance and grain yield may not decrease until a 'threshold'salinity level is reached. Threshold levels of salinity are generally defined as the maximum amount of salt that a plant can tolerate in its root zone without impacting growth (Table 2). Plant physiology is very susceptible to high salinity in its rhizosphere and affects germination rate, growth stages, and ultimately plant yield [1]. Similarly, many other growth hampering effects on plants due salinity are low net CO2 assimilation to plant tissues, leaf area, leaf cell enlargement, dry matter production, and relative growth, poor development of spikelets (rice and wheat), boll (cotton), etc. [4, 5]. There are many reasons for hampering of plant production under salinity. Generally, salinity affects plant growth in three ways, such as osmotic stress, ionic stress or ion imbalance, and oxidative stress [6]. Osmotic stress disturbs the salt water balance, which results in a high concentration of salts and loses of water in plant

#### Salinity Stress in Arid and Semi-Arid Climates: Effects and Management in Field Crops DOI: http://dx.doi.org/10.5772/intechopen.87982

cell sap and tissues. This imbalance causes ion toxicity within plant tissues, and plant shows leaf burn or wilting symptoms due to Na+ and Cl accumulation. Ionic stress also causes nutrients disequilibrium and results in reduce final germination percentage (FG %), decrease vegetative and reproductive growth, decline yield, and yield components of the plant under salinity. Similarly, ionic stress in the plant due to salinity causes reduction of photosynthesis activity, alteration of enzymatic activities, oxidative stress, disrupted the biochemical membrane structure and function, destroy the ultrastructural cellular components, and hormonal imbalance are the primary reason for the reduction of overall plant's growth and development [7, 8].

For better plant performance under salinity stress, natural adaptation responses at physiological, molecular, and cellular levels to tolerate salinity stress is of great concern. These adaptations are an osmotic adjustment, closure of stomata, Na+ exclusion from older leaves, maintenance of K+ /N+ equilibrium, and cytosolic K+ , transpiration efficiency, and increased antioxidant defense system are very important for ideal plant growth under salinity. Besides these, various other management strategies have been embraced on a scientific basis to improve plant growth efficiency under salinity. These strategies are genetic modification, identification, sequencing of gene, microarray analysis, and plant transformation, and agronomic strategies to reduce salinity stress by soils reclamation via water and nutrients management, seed priming, and usage of hormone regulator to create homeostasis in hormonal production under salinity. These management strategies are being useful for stress management, including salinity. In this book chapter, we will review the latest information about the 'Salinity Stress in Arid and Semi-Arid Climates: Effects and Management in Field Crops, which could be a good advantage to the scientific community and farmers for the understanding of salinity issue in the field crops and their solution.
