by soil pH due to the change in surface charge (Bhargava et al. 2012). Electrical
conductivity of soil increases more due to wastewater irrigation than groundwater
irrigation. Ashraf et al. (2013) reported that electrical conductivity of wastewater
reduced the yield of tomato by enhancing the salinity of soil.
6.4.1.2 Soil Organic Matter
Organic matter is the major component to maintain the productivity of soil. The
organic matter content in soil increases due to wastewater irrigation that enhanced
the fertility of soil. Organic matter in soil is mainly in the form of humic substances
or humus and non-humic substances. Major components of humus are humic acids
and fulvic acids. At lower pH, high molecular weight organic acid, i.e., humic acids
are not soluble in the soil solution and removed via precipitation. In case of fulvic
acids, a low molecular weight organic acid is easily soluble at all pH and has more
active sites than humic acid (Gupta et al. 2019a).
6.4.1.3 Soil Temperature and Redox Potential
Temperatures of soil play an important role in the mobility and availability of metals
in the soil and also affect the soil microbial health which helps in regulation of soil
fertility. Soil temperature may be elevated through wastewater irrigation due to
decomposition of soil organic matter which increases the availability of metals in
soil. Cornu et al. (2016) reported that transfer of Cd and Zn from soil to plant
increases at high soil temperature. Several metals are present in soil solution in
oxidized forms or reduced forms and their mobility depends on its redox state, i.e.,
acceptance or removal of electrons from soil solution determined by its redox
potential (Sheoran et al. 2016; Khalid et al. 2018).
6.4.1.4 Some Other Characteristics
Soil bulk density is determined by the mass of undisturbed soil per unit volume and
is represented as g cm
À3 . Soil bulk density is always lower than the particle density
due to occurrence of pore space. If, the bulk density of soil increases its porosity
always decreases. Long-term wastewater irrigation changes the soil bulk density and
porosity which depends on the quality of wastewater, i.e., concentrations of
dissolved and particulate constituents in the wastewater. Shariot-Ullah (2019) studied that the effluents from the North Bengal Sugar Mill in Bangladesh affected
agriculture soil properties, e.g., bulk density reduced from 1.44 to 1.42 g/cm
3 and
porosity of soil increased approximately 2.17%.
The hydraulic conductivity and infiltration rate of soil is altered by wastewater
irrigation. The factors such as types of soil, clay content, CaCO 3 amount, soil
humidity, and types of wastewater are responsible for the alteration of hydraulic
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129
conductivity of soil increases more due to wastewater irrigation than groundwater
irrigation. Ashraf et al. (2013) reported that electrical conductivity of wastewater
reduced the yield of tomato by enhancing the salinity of soil.
6.4.1.2 Soil Organic Matter
Organic matter is the major component to maintain the productivity of soil. The
organic matter content in soil increases due to wastewater irrigation that enhanced
the fertility of soil. Organic matter in soil is mainly in the form of humic substances
or humus and non-humic substances. Major components of humus are humic acids
and fulvic acids. At lower pH, high molecular weight organic acid, i.e., humic acids
are not soluble in the soil solution and removed via precipitation. In case of fulvic
acids, a low molecular weight organic acid is easily soluble at all pH and has more
active sites than humic acid (Gupta et al. 2019a).
6.4.1.3 Soil Temperature and Redox Potential
Temperatures of soil play an important role in the mobility and availability of metals
in the soil and also affect the soil microbial health which helps in regulation of soil
fertility. Soil temperature may be elevated through wastewater irrigation due to
decomposition of soil organic matter which increases the availability of metals in
soil. Cornu et al. (2016) reported that transfer of Cd and Zn from soil to plant
increases at high soil temperature. Several metals are present in soil solution in
oxidized forms or reduced forms and their mobility depends on its redox state, i.e.,
acceptance or removal of electrons from soil solution determined by its redox
potential (Sheoran et al. 2016; Khalid et al. 2018).
6.4.1.4 Some Other Characteristics
Soil bulk density is determined by the mass of undisturbed soil per unit volume and
is represented as g cm
À3 . Soil bulk density is always lower than the particle density
due to occurrence of pore space. If, the bulk density of soil increases its porosity
always decreases. Long-term wastewater irrigation changes the soil bulk density and
porosity which depends on the quality of wastewater, i.e., concentrations of
dissolved and particulate constituents in the wastewater. Shariot-Ullah (2019) studied that the effluents from the North Bengal Sugar Mill in Bangladesh affected
agriculture soil properties, e.g., bulk density reduced from 1.44 to 1.42 g/cm
3 and
porosity of soil increased approximately 2.17%.
The hydraulic conductivity and infiltration rate of soil is altered by wastewater
irrigation. The factors such as types of soil, clay content, CaCO 3 amount, soil
humidity, and types of wastewater are responsible for the alteration of hydraulic
6 Wastewater Reuse in Peri-Urban Agriculture Ecosystem: Current Scenario,. . .
129