**Abstract**

Soil salinity is a growing threat all over the world due to its toxic effect to reduce soil fertility and water uptake in the crops. An average of 418 million ha soil is saline in nature. Various climatic, geomorphic and rainfall pattern causes which involved in saline soil formation. To reduce the toxic effect proper management of saline soil is required. Irrigation water also a major concern regarding soil salinity management. Saline irrigation water enhances and maintains the severity soil salinity. Crop production aspects root zone salinity provides a strong negative impact on soil fertility. Salinity causes the reduction in nutrient ion, and water uptake has a significant negative effect on crop yields. Soil and water salinity interactions and their influence on crop growth and management of salinity are deliberated in this chapter.

**Keywords:** salinity, management, soil fertility, crop growth

#### **1. Introduction**

All over the world more than hundred countries approximately 418 million hectare of saline soils are present. Asia alone contribute 46% of soils are salt affected the world. Arid and semi-arid regions of the word highly affected by salinisation 6.27 percentage of soil in Asia affected by salinity. In India 10 mha salt affected soil or 5.5 mha saline and 3.8 mha are sodic soils [1, 2]. Saline soil mainly consist soluble salts like chloride and sulphates of calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), bicarbonate (HCO3 − ), carbonate (CO3 2−) and nitrate (NO3 − ) also present. The EC (electrical conductivity) of saline soil is less than 4 dS m−1 (deci Siemens/meter), ESP (exchangeable sodium percentage) is less than 15% and pH is less than 8. Less soluble salts like calcium carbonate and calcium sulphate also present. Saline soil having more ionic salt species like Ca2+ which flocculates the soil when its dominated by Na which disperse the soil. Saline soils are mostly Ca2+ dominated flocculated and well aerated in nature. Dispersion and flocculation also based on clay content of the soil.

#### **2. Process of soil salinisation**

There are two forms of salinisation process are present. They are primary or natural salinisation and secondary or anthropogenic salinisation. Due to various hydropedological, geomorphic and climatic factors involved in primary salinisation. Hydeopedological factors like weathering of basic rocks like basalt, gabbro

and dolerite, etc. Hydrological factors like high annual moisture flux, climatic factors like low precipitation and high temperature cause more evapotranspiration and geomorphic factor like low relief are the cause of primary salinisation [3–5]. Secondary salinisation due to shallow water level, poor quality irrigation water, over irrigation with improper drainage make increase in water table and discharge of salt near soil surface, over use of ground water in coastal regions sea water intrusion takes place. Finally untreated industrial effluents and waste water having high dissolved salts are the reasons for secondary salinisation [6–9].

### **3. Measure of analysing soil salinity**

Electrical conductivity (EC) is a measure of soil salinity and it's measured by EC meter. EC is reciprocal to the resistance of the conductor. Resistance is directly proportional to the distance between the electrode and inversely proportional to the cross sectional area of the conductor. Resistance expressed as ohms cm−1 conductivity expressed m mhos cm−1. Conductivity depends on concentration of the ions in the solution, temperature, valence and length between two electrodes. The conductivity is directly proportional to the, concentration of the solution, solution temperature and valance and inversely proportional to length between two electrodes [10].

Resistance is calculated by ohms law.

$$\mathbf{R} = \mathbf{V}/\mathbf{L}$$

$$\mathbf{G} = \mathbf{1}/\mathbf{R}.$$

where V is the voltage; I, current (ampere); R, resistance of the solution; G, conductance.

Conductance – Reciprocal of electrical resistance of a solution between two electrodes [11].

#### **3.1 Saturation extract (ECe)**

In this method involves saturation and subsequent extraction of soil water under partial pressure in order to quantify the salts in the extracted liquid phase. Crop growth response mainly depends on ECe (saturation paste) conversion of EC to ECe on different structural soil important in plant growth point of view. Sand particles can able to hold or adsorb more ions which leads to concentration of salinity will be more in the sandy than clay soil when the amount of salt ion will be the same [12].

#### **3.2 Ranges of soil salinity**


### **4. Irrigation water salinity**

Irrigation water salinity also a major concern regarding secondary salinisation and crop production (**Table 1**). Saline water highly affects germination,

**111**

*Soil Salinity and Its Management*

**EC (dS m−1)**

**Table 1.**

zone salinity [14].

**5. Salinity effects**

available water [16].

some conditions.

and Cl/NO3 [19].

*5.2.1 Nutrient ratios*

**5.2 Effect on soil fertility**

**5.1 Effect on plant growth**

*Irrigation water-salinity based classification.*

*DOI: http://dx.doi.org/10.5772/intechopen.93329*

chlorophyll content, growth yield characters of the crop. Due to high salinity of water osmotic and ion imbalance reduction in activation of enzyme responsible for the seed germination and also affects the total chlorophyll due to reduction in leaf pigments and membrane stability. Usually saline water highly influence root

<0.7 Fresh water – drinking and irrigation <500 0.7–3.0 Slightly saline – irrigation 500–2000

management

>6.0 Highly saline – not suitable for irrigation 4000 >14 Very saline – secondary drainage water >9000 >45 Brine – sea and industrial water >30,000

3.0–6.0 Medium saline – suitable for high salt tolerant crops with proper

**Status TDS** 

**(mg l−1)**

2000–4000

The deficiency of ions, osmatic stress and oxidative stress to the plants. Under high saline condition for plants are not able to maintain osmotic balance leads to loss of turgidity, dehydration of cell due to higher saline environment movement of water from plant sap to soil in order to reduce the concentration gradient [15]. Due to ion toxicity and osmatic stress nutrient absorbed by mass flow greatly reduced. Due to high ion concentration affects soil osmatic potential which reduces the plant

Soil nutrient availability and uptake affected by higher saline condition. Phosphorus can be affected by fixation of calcium phosphate (Ca-P) due to higher saline condition Ca ion activity is high [17]. N bioavailability and accumulation affected by soil salinity. The 25% of N requirement is fulfilled by N fixation. Soil salinity greatly reduces the N fixing rhizobacterial growth and spread due to lesser photosynthesis cause reduction in photoaccumulates [18]. Also, nitrification reduced by salinity cause increase in NH4 content which facilitates the loss of NH4 by volatilisation. Potassium uptake and assimilation affected by Na/Ca ratio cause reduction in K/Na ratio of the plant [19]. Salinity did not have much negative influence on micronutrient bio availability but solubility of micronutrients is little decreased in

More than concentration of the ions ratio of nutrient ions which greatly influence the bio availability and uptake of nutrient ions ratios like Na/Ca, Na/K, Ca/Mg


**Table 1.**

*Soil Moisture Importance*

and dolerite, etc. Hydrological factors like high annual moisture flux, climatic factors like low precipitation and high temperature cause more evapotranspiration and geomorphic factor like low relief are the cause of primary salinisation [3–5]. Secondary salinisation due to shallow water level, poor quality irrigation water, over irrigation with improper drainage make increase in water table and discharge of salt near soil surface, over use of ground water in coastal regions sea water intrusion takes place. Finally untreated industrial effluents and waste water having high

Electrical conductivity (EC) is a measure of soil salinity and it's measured by EC meter. EC is reciprocal to the resistance of the conductor. Resistance is directly proportional to the distance between the electrode and inversely proportional to the cross sectional area of the conductor. Resistance expressed as ohms cm−1 conductivity expressed m mhos cm−1. Conductivity depends on concentration of the ions in the solution, temperature, valence and length between two electrodes. The conductivity is directly proportional to the, concentration of the solution, solution temperature and valance and inversely proportional to length between two electrodes [10].

R V / I. =

G 1 / R. =

where V is the voltage; I, current (ampere); R, resistance of the solution; G,

Conductance – Reciprocal of electrical resistance of a solution between two

In this method involves saturation and subsequent extraction of soil water under

partial pressure in order to quantify the salts in the extracted liquid phase. Crop growth response mainly depends on ECe (saturation paste) conversion of EC to ECe on different structural soil important in plant growth point of view. Sand particles can able to hold or adsorb more ions which leads to concentration of salinity will be more in the sandy than clay soil when the amount of salt ion will be the same [12].

Irrigation water salinity also a major concern regarding secondary salinisation and crop production (**Table 1**). Saline water highly affects germination,

**Non saline Slightly saline Moderately saline Strongly saline Extremely saline** 0–2 2–4 4–8 8–16 >16

dissolved salts are the reasons for secondary salinisation [6–9].

**3. Measure of analysing soil salinity**

Resistance is calculated by ohms law.

conductance.

electrodes [11].

**3.1 Saturation extract (ECe)**

**3.2 Ranges of soil salinity**

**4. Irrigation water salinity**

*Electrical conductivity (EC) in dS m−1 [13].*

**110**

*Irrigation water-salinity based classification.*

chlorophyll content, growth yield characters of the crop. Due to high salinity of water osmotic and ion imbalance reduction in activation of enzyme responsible for the seed germination and also affects the total chlorophyll due to reduction in leaf pigments and membrane stability. Usually saline water highly influence root zone salinity [14].
