**1. Introduction**

In the Arid and semi-arid areas salt affected soil poses immense threats to the agriculture industry worldwide [1]. Researchers have reported that about 1128 million ha of land is affected by salinity and sodicity globally [2]. Soil salinization at global level has caused food insecurity in several countries during last decade. In Pakistan approximately 6.8 million hectares of land is affected by salinity [3]. Saline soil is characterized by the presence of high level of sodium and its chlorides and sulphates [4]. Soil having 4 dS m−1 or more electrical conductivity of the saturation soil paste is considered as salt affected soil [5–7]. Due to high concentrations of Na+ and Cl− in the plant, Sodium chloride can reduce crop productivity by making the roots water uptake more difficult that can cause plant toxicity [8]. Research studies proved that approximately 20% of the world's cultivated land is affected by salinity [9].

Due to inappropriate management of irrigation and drainage, soil salinity is gradually increasing in irrigated lands [10]. Global warming as an environmental issue has greatly affected arid regions of the world that are at highest risk of soil salinization. Salt redistribution in the soil profile is due to climatic factor such as precipitation. Agricultural productivity is affected when salt is added by wind to coastal agricultural lands [11]. Soil Biodiversity and microbial activity is affected by the high salt concentration [12].

Under saline soil plant growth is negatively affected by osmotic effects and hormonal imbalance. It also causes nutritional disorder and specific ion toxicity [13]. The adverse effects of saline soil on plants include: (1) Osmotic potential is decreases due to excessive soluble salts in the soil solutions. It also causes physiological drought by decreasing plants ability to absorb water (2) toxicity due to salt ions inside the plant cells. The Growth inhibition is caused by sodium and chloride ions as sodium ions are retained in the roots and stems and only chloride ions become concentrated in the shoot in some plants which is causing negative affects to the plants [14, 15]. (3) Secondary stresses which is mainly caused by osmotic and ionic pressure. It includes high concentration of toxic compounds such as ROS and nutrient imbalance in plants. Sodium ions compete with potassium ions under saline condition and causing reproductive disorders by calcium ions in the cell membrane [16, 17]. The maize (*Zea mays* L). is a major food crop in the world food. The productivity of maize crop is declined as it moderately salt-sensitive plant [18].

In this scenario, it is the need of time that agronomists and environmentalists should develop eco-friendly, cost effective and sustainable methods to reclaim saline soils [19]. Currently, various physico-chemical processes are in practice for the reclamation of saline soils. To some extent these methods are unsustainable and inefficient at high salt concentration [20]. The traditional breeding and biotechnological methods for the production of salinity-tolerant crops is a time-consuming process. By using chemical neutralizers and sustainable approaches sustainable crop yield in saline soils must be secured. It can also be secured by using salt-tolerant varieties or amelioration methods.

For plant growth and development, microorganisms play an important role under different environmental conditions [21, 22]. For enhancing crop productivity in saline soil, the application of plant growth-promoting rhizobacteria has become sustainable approach [23, 24]. Inoculation with PGPR leads towards abiotic stress regulation which can cause systemic tolerance directly or indirectly [25]. Many PGPR have been applied for their positive role in improving plant-water relations and for ion homeostasis. It is also used for photosynthetic efficiency in plants under salt stress. Plants can effectively protect from many stresses by PGPR that produce IAA and ACC deaminase. IAA accumulation increase transcription of ACC synthase genes. It is resulted an increases ACC concentration that can lead to the production of ethylene. Excess ACC are broken by PGPR that produce ACC deaminase. It also decreases plant ethylene levels under harsh environmental conditions. It permits IAA to encourage the growth of the plants [26].

Bacteria secrete exopolysaccharides which can bind soil particles into aggregates. These are helpful in regulating soil structures. It also increases water holding as well as cation exchange capacity of soil [27]. An enclosed matrix of microcolonies is formed by EPS which provide protection against environmental changings. It also leads towards water as well as nutrient retention and epiphytic colonization [28]. The exopolysaccharide secretion by PGPR binds sodium ions and reduces its uptake in plants which is determined by researches studies [29].

In saline soil a diversity of salt-tolerant PGPR such as *Azospirillum, Burkholderia, Rhizobium*, *Pseudomonas*, *Acetobacter* and *Bacillus* have been applied. These are also tested for promoting plant growth under salt stress [30, 31]. Thus, it has been demonstrating by different researches that use of PGPR is a beneficial approach to increase plant performance in saline soil [32, 33]. The physiological drought is

**119**

*Interactive Effect of Organic and Inorganic Amendments along with Plant Growth Promoting…*

caused by salt in soil environment which reduces the ability of plants to remove water. Many biotic and physical stresses on plants can be reduced by application of Si fertilizer which can change the negative effects of saline soil [34, 35]. By improving sodium ions and potassium ions homeostasis, silicon may increase salinity tolerance in plants. It also improves nutritional status and photosynthetic efficiency of plants under stress conditions [36–38]. Many laboratory and greenhouse experiments have determined that under saline conditions, Si reduced the uptake of sodium ions and chloride ions [39, 40]. The use of organic matter increases the physico-chemical and biological properties of salt-affected soils [41]. Organic matter also plays an important role by improving roots to grow more uniformly. The soil CO2 concentration is increased by decaying organic matter. It also releases H+

enhances CaCO3 dissolution. It can release more calcium for sodium exchange [42] Application of press mud is very effective in reclaiming saline sodic soils [43, 44].

Saline soil affects plant growth, development and process of photosynthesis. It also affects protein synthesis and lipid metabolism [45]. Osmotic stress reduces photosynthetic efficiency which is resulted in partial closure of stomata [46]. The nutrient imbalance and membrane destabilization are caused by soil salinity [47]. The cell growth and development are decreased in plants in responses to osmotic

The nutritional imbalances are also caused by decrease in the uptake of calcium ions and potassium ions in leaves and an increase in the uptake of sodium ions. In some cases, there is a requirement of low sodium ions and high potassium ions or calcium ions are required for optimum function, but increased sodium ions resulted in metabolic disturbances. Cell swelling in plants is caused by accumulation of sodium and chloride which can affect plant enzymes. It can also result in physiological changes and reduced energy production [49]. The photosynthetic function is disturbed by nitrate reductase activity due to chloride ions [50]. There are competitive interactions with nutrient ions for binding sites. It can also affect transfer of protein in root cells under excessive sodium and chloride ions in rhizosphere. It also affects processes like movement of material, deposition, and partitioning within plants [51]. Salts can increase in intercellular spaces resulted in cell dehydration [52]. Oxidative stress increases due to the accumulation of reactive oxygen species which has negative impact on cell membranes, proteins, enzymes, and nucleic acids [53] Both antioxidant enzymes and non-enzymatic antioxidants are produced by

**2.1 Impact of soil salinity on plant growth and development**

stress. It resulted in decreased leaf area and chlorophyll content [48].

plants to protect against oxidative stress [54].

**2.2 Impacts of soil salinity on rhizosphere microbial diversity**

Microbial biomass is an important parameter as it functions as an agent transformation and plays its role as the recycling of the organic matter by providing soil nutrients. In the first few centimeters of the soil surface, there are microbial biomass and organic matter. Microbiological activity is affected by the salinization process [55]. Microbial diversity, functions, and compositions are negatively affected by salinity [56]. Total bacteria and actinobacteria are reduced by a 5% increase in salinity. The attachment of *Azospirillum brasilense* to maize roots was observed to reduce due to salinity [57]. Due to increase salinity in the rhizosphere, the plant root secretion and organic matter decomposition by microorganisms are adversely affected [58].

and

*DOI: http://dx.doi.org/10.5772/intechopen.99063*

**2. Impacts of soil salinity**

*Interactive Effect of Organic and Inorganic Amendments along with Plant Growth Promoting… DOI: http://dx.doi.org/10.5772/intechopen.99063*

caused by salt in soil environment which reduces the ability of plants to remove water. Many biotic and physical stresses on plants can be reduced by application of Si fertilizer which can change the negative effects of saline soil [34, 35]. By improving sodium ions and potassium ions homeostasis, silicon may increase salinity tolerance in plants. It also improves nutritional status and photosynthetic efficiency of plants under stress conditions [36–38]. Many laboratory and greenhouse experiments have determined that under saline conditions, Si reduced the uptake of sodium ions and chloride ions [39, 40]. The use of organic matter increases the physico-chemical and biological properties of salt-affected soils [41]. Organic matter also plays an important role by improving roots to grow more uniformly. The soil CO2 concentration is increased by decaying organic matter. It also releases H+ and enhances CaCO3 dissolution. It can release more calcium for sodium exchange [42] Application of press mud is very effective in reclaiming saline sodic soils [43, 44].

## **2. Impacts of soil salinity**

*Landraces - Traditional Variety and Natural Breed*

the high salt concentration [12].

varieties or amelioration methods.

It permits IAA to encourage the growth of the plants [26].

in plants which is determined by researches studies [29].

issue has greatly affected arid regions of the world that are at highest risk of soil salinization. Salt redistribution in the soil profile is due to climatic factor such as precipitation. Agricultural productivity is affected when salt is added by wind to coastal agricultural lands [11]. Soil Biodiversity and microbial activity is affected by

Under saline soil plant growth is negatively affected by osmotic effects and hormonal imbalance. It also causes nutritional disorder and specific ion toxicity [13]. The adverse effects of saline soil on plants include: (1) Osmotic potential is decreases due to excessive soluble salts in the soil solutions. It also causes physiological drought by decreasing plants ability to absorb water (2) toxicity due to salt ions inside the plant cells. The Growth inhibition is caused by sodium and chloride ions as sodium ions are retained in the roots and stems and only chloride ions become concentrated in the shoot in some plants which is causing negative affects to the plants [14, 15]. (3) Secondary stresses which is mainly caused by osmotic and ionic pressure. It includes high concentration of toxic compounds such as ROS and nutrient imbalance in plants. Sodium ions compete with potassium ions under saline condition and causing reproductive disorders by calcium ions in the cell membrane [16, 17]. The maize (*Zea mays* L). is a major food crop in the world food. The productivity of maize crop is declined as it moderately salt-sensitive plant [18]. In this scenario, it is the need of time that agronomists and environmentalists should develop eco-friendly, cost effective and sustainable methods to reclaim saline soils [19]. Currently, various physico-chemical processes are in practice for the reclamation of saline soils. To some extent these methods are unsustainable and inefficient at high salt concentration [20]. The traditional breeding and biotechnological methods for the production of salinity-tolerant crops is a time-consuming process. By using chemical neutralizers and sustainable approaches sustainable crop yield in saline soils must be secured. It can also be secured by using salt-tolerant

For plant growth and development, microorganisms play an important role under different environmental conditions [21, 22]. For enhancing crop productivity in saline soil, the application of plant growth-promoting rhizobacteria has become sustainable approach [23, 24]. Inoculation with PGPR leads towards abiotic stress regulation which can cause systemic tolerance directly or indirectly [25]. Many PGPR have been applied for their positive role in improving plant-water relations and for ion homeostasis. It is also used for photosynthetic efficiency in plants under salt stress. Plants can effectively protect from many stresses by PGPR that produce IAA and ACC deaminase. IAA accumulation increase transcription of ACC synthase genes. It is resulted an increases ACC concentration that can lead to the production of ethylene. Excess ACC are broken by PGPR that produce ACC deaminase. It also decreases plant ethylene levels under harsh environmental conditions.

Bacteria secrete exopolysaccharides which can bind soil particles into aggregates.

In saline soil a diversity of salt-tolerant PGPR such as *Azospirillum, Burkholderia,* 

These are helpful in regulating soil structures. It also increases water holding as well as cation exchange capacity of soil [27]. An enclosed matrix of microcolonies is formed by EPS which provide protection against environmental changings. It also leads towards water as well as nutrient retention and epiphytic colonization [28]. The exopolysaccharide secretion by PGPR binds sodium ions and reduces its uptake

*Rhizobium*, *Pseudomonas*, *Acetobacter* and *Bacillus* have been applied. These are also tested for promoting plant growth under salt stress [30, 31]. Thus, it has been demonstrating by different researches that use of PGPR is a beneficial approach to increase plant performance in saline soil [32, 33]. The physiological drought is

**118**

#### **2.1 Impact of soil salinity on plant growth and development**

Saline soil affects plant growth, development and process of photosynthesis. It also affects protein synthesis and lipid metabolism [45]. Osmotic stress reduces photosynthetic efficiency which is resulted in partial closure of stomata [46]. The nutrient imbalance and membrane destabilization are caused by soil salinity [47]. The cell growth and development are decreased in plants in responses to osmotic stress. It resulted in decreased leaf area and chlorophyll content [48].

The nutritional imbalances are also caused by decrease in the uptake of calcium ions and potassium ions in leaves and an increase in the uptake of sodium ions. In some cases, there is a requirement of low sodium ions and high potassium ions or calcium ions are required for optimum function, but increased sodium ions resulted in metabolic disturbances. Cell swelling in plants is caused by accumulation of sodium and chloride which can affect plant enzymes. It can also result in physiological changes and reduced energy production [49]. The photosynthetic function is disturbed by nitrate reductase activity due to chloride ions [50]. There are competitive interactions with nutrient ions for binding sites. It can also affect transfer of protein in root cells under excessive sodium and chloride ions in rhizosphere. It also affects processes like movement of material, deposition, and partitioning within plants [51]. Salts can increase in intercellular spaces resulted in cell dehydration [52]. Oxidative stress increases due to the accumulation of reactive oxygen species which has negative impact on cell membranes, proteins, enzymes, and nucleic acids [53] Both antioxidant enzymes and non-enzymatic antioxidants are produced by plants to protect against oxidative stress [54].

#### **2.2 Impacts of soil salinity on rhizosphere microbial diversity**

Microbial biomass is an important parameter as it functions as an agent transformation and plays its role as the recycling of the organic matter by providing soil nutrients. In the first few centimeters of the soil surface, there are microbial biomass and organic matter. Microbiological activity is affected by the salinization process [55]. Microbial diversity, functions, and compositions are negatively affected by salinity [56]. Total bacteria and actinobacteria are reduced by a 5% increase in salinity. The attachment of *Azospirillum brasilense* to maize roots was observed to reduce due to salinity [57]. Due to increase salinity in the rhizosphere, the plant root secretion and organic matter decomposition by microorganisms are adversely affected [58].
