3.1.1.1. Effect of ET on Drained Water
The drained fraction was evaluated for the volume of each irrigation (
Figure 1) and for the cumulative volume of each treatment (
Figure 2). The findings revealed that the ET of saline water significantly affected the volume of drainage water. Indeed, the volume of ET irrigation water was significantly higher than that of the untreated irrigation water for all five concentrations: C0, C1, C2, C3 and C4. The fraction of the drained water after electro magnetization increased from about 33 to 56% in comparison with non-treated saline water, which showed an increase from 20 to 26%. These results show that the increase in the volume of drainage water was observed over time with the rise in the irrigation frequency. Similar findings were reported in the study conducted by Zlotopolski [
16] who proved that the total volume of water collected in reservoirs under the columns (leachate) was different between the Magnetically-treated water (MTW) and untreated columns. Hamza [
78] also reported an increase of the volume of drainage water by 20%, compared to non-magnetized water (NMW) due to the augmentation in magnetic field in the drainage water. Besides, the magnetization effect was reported to increase at a longer exposure time of water to magnetic field [
79,
80].
Gudigar and Hebbara [
74] stated that the use of magnetically-treated water increased the salt content in drainage water, which was not the case when applying non-magnetized water. This aligns with the findings of Mohamed and Bassem [
81] who observed that the values of EC in drainage water irrigated with magnetized water were higher than in non-magnetized water. Additionally, Raheem [
82] noticed that, by increasing the magnetic intensity, magnetized water can positively affect salt leaching with an augmentation of EC values of the drained water. According to Zlotopolski [
16], the salt content, at a lower depth in a column of soil irrigated with MTW, was higher than that in control. Therefore, the finding in this study aligned with the previous studies in term of the salt accumulation in lower depths of the soil EC contents augmentation in the drainage water.
It was found that the use of EMT irrigation water resulted in significant increase of HCO
3- and Cl
- concentrations, compared with untreated water. Therefore, these results highlight that EMT water played an important role in removing the soluble salts from the soil. In addition, ETW was more efficient in removing salts through drainage water, compared to untreated water, and allowed leaching under the root zone. This ET efficiency was clearly observed at the end of the irrigation cycle. Moreover, Gudigar and Hebbara [
74] reported that dissolved salts, such as carbonates, phosphates, chlorides and sulfates, are slightly soluble in soil under magnetic treatment. Other previous researchers stated that irrigation with MTW boosted the leaching of the excessive amount of soluble salts such as calcium, sodium and bicarbonate [
69].
Compared to the salts provided by saline irrigation water, the quantities of exported salts are significantly higher when the irrigation water was treated electromagnetically (
Figure 4). The salt balance of the water shows that the quantities of exported salts vary from 21 to 31% with non-magnetized water and from 39 to 88% with magnetized water. These values are 88.04, 51.79, 38.73, 50.48 and 58.90% for C0, C1, C2, C3 and C4, respectively, in the case of electro magnetized saline water, while the values recorded under untreated irrigation water are 31.55, 21.77, 20.49, 22.79 and 25.70% for C0, C1, C2, C3 and C4, respectively.
Effect of ET on Soil Water and Salt Contents
The soil moisture contents showed a significant difference (P<0.05) between the ET irrigation water and the untreated irrigation water for five concentrations (
Figure 5). The results demonstrated that irrigation with ETM water, compared to untreated water, increased significantly the soil moisture up to 9.9 % for C0 (1.0 dS.m
-1). However, these findings did not show a remarkable rise for C1 and C2. Accordingly, the use in certain conditions of electro-magnetized water for irrigation is recommended to save irrigation water. The results dealing with the effect of electromagnetic on soil salinity are consistent with those obtained by [
76] where a small reduction in the rate of soil evaporation was observed when electromagnetized water was applied. Zlotopolski [
16] showed that soil irrigated with MTW is wetter than control soil irrigated with the same amount of non-magnetized water. Moreoever, Gabrielli et al. [
84] found also that the formation of aragonite, after the magnetization of water, increases the osmotic pressure of the soil with the decrease in evaporation. It was also concluded that the exposure of water to an electromagnetic field minimizes its surface tension, raises its solubility and, subsequently, increases the wettability of the soil [
68]. Furthermore, Moosa et al. [
34] found that the maximization of the soil moisture may be due to the degradation in the surface tension and water viscosity after exposure to the electromagnetic fields. The high soil moisture obtained under electro-magnetized irrigation water was due to the fact that the water molecules were influenced by hydrogenic bonds and Van der Waals forces and in reaction with the released ions which made water more cohesive [
86]. Thus, the water molecules could be easily attached to the soil particles and water molecules might easily penetrate into the micro-spaces of the soil particles [
86]. Moreover, when water passed through the electro-magnetized field, its structure and some of its physical characteristics changed [
69]. The increase in soil moisture could be attributed to the decomposition of macromolecules of magnetized water into smaller molecules, increasing the mobility of water and then allowing it to enter smaller soil pores, which consequently, improved the retention of water soil macro-porosity [
6,
87].9
The variation of average ECe of soil according to the irrigation water treatment is presented in
Figure 6. The results revealed a significant increase in ECe with the increase in EC of irrigation water. For different treatments, the lowest mean values of soil EC were recorded under irrigation with electromagnetized water, compared with initial conditions. These results are consistent with those reported by Hamza [
77] who revealed that soil leached with magnetically-treated water had lower salinity than soil leached with untreated water due to the significant salt removal using TM, compared to control. Amer [
89] have also affirmed that soil irrigated with magnetically-treated fresh, saline, and highly saline water decreases the soil EC, compared to soil irrigated with non-magnetically treated water. Likewise, Mohamed and Ebead [
90] concluded that magnetic treatment of irrigation water reduces the risk of sandy soil salinization. Such removal plays an important role in improving the regeneration of salt-affected soils [
90,
91,
92].
Data showing the effect of leaching using untreated and electro-magnetized water on the soluble soil cation concentrations are presented in
Table 3.
The latter revealed that salinity in the ET soil significantly decreased, compared with that in the untreated soil. This finding indicated that the soluble soil salts and the electro-magnetized irrigation water improves the solubility of Na+ salts in soil because Na is a paramagnetic element that has a small positive susceptibility to the magnetic fields, while other elements are diamagnetic and slightly repelled by a magnetic field [
35]. It was also observed that the soil irrigated with EMT water significantly increased the available soil Mg and Ca content, compared with the soil irrigated with untreated water [
93,
94].
However, no clear trend for using ETM irrigation water in soluble K concentration was observed, compared with untreated water. This result is in contrast with that obtained by Abd-Elrahman [
35] and Maheshwari and Grewal [
94] who found that the potassium increased using the magnetically treated water. The concentrations of HCO
3-, Cl
-, and SO
42- in soil decreased significantly with soil irrigated by EMT water. These results are in accordance with those of Mostafazadeh-Fard et al. [
69] who indicated that the concentration of sulfate decreases in soil extraction by magnetized irrigation water. Hilal and Hilal [
65] reported that magnetized water dissolves slightly soluble salts such as carbonates and sulfates. Hachicha et al. [
57] have reported that the concentrations of SO4, Mg, Ca and HCO3 decreased when the saline water irrigation is exposed to ET in the soil, which is not the case when untreated water was used. The results of this study are in agreement with those provided by Mohamed and Ebead [
90], who confirmed that irrigation with MTW declined remarkably Cl
-, Na
+ and SO4
– content in the soil, compared to the control. Moreover, Kronenber [
96] confirmed that, in untreated water, a quantity of carbonate is deposited in soil pores and on the plant roots. However, by using magnetic water, the carbonate salts cannot precipitate. Moreover, this water can break down the precipitated salts on the internal surface of irrigation pipes and laterals. Thus, its movement will occur easily than that of untreated water. In addition, the chloride content becomes lower in soils subjected to electromagnetic treatment due to the increase of salt leaching by electro-magnetized water. A similar result was reported by Maheshwari and Grewal [
93] and Hilal et al. [
94].
The variation of the ionic composition was analyzed at the level of the ratio between the cations through the SAR (Sodium Adsorption Ratio). The decrease in the SAR was highly significant for the C0, C3, and C4 concentrations, reflecting a more balanced cationic composition between Na
+ and Ca
2+ Mg
2+ produced from a higher Na
+ drain. These results are in agreement with those obtained by AL-Mosawi [
97] who showed that the high values of the SAR can be provided by adding NaCl salts to drinking water, causing an excessive increase in Na
+. Besides, Papadopoulos et al. [
98] reported a decrease in SAR with the increase of magnetic field (MF) levels.
Soil salt balance can be deduced from the ECe applying the parameters necessary for its mass conversion per pot using the following relationship:
where:
S: Salt stock (g pot-1).
0.64: Conversion factor from ECe (g).
PS: Saturation percent equal to 0.4.
Bd: Bulk Density equal to 1.3 (g cm-3).
The in
Figure 7 confirm that the quantity of residual salts in the soil is less when the saline irrigation water is treated electromagnetically for the five concentrations. The quantities are 2.03, 6.42, 8.45, 10.81 and 13.31 g pot
-1 for C0, C1, C2, C3, and C4, respectively, when the soil is subjected to EMT treatment and 3.49, 7.89, 9.22, 11.71, and 15.44 g pot
-1 for C0, C1, C2, C3 and C4, respectively when the soil is subjected to untreated water.
For the same electrical conductivity of irrigation water (treated water and untreated water), the comparison between the quantities of salts in the soils deduced from the final salinity (ECe) and those estimated from the difference between the salts brought back by the irrigation water and those evacuated by the drainage water shows that these quantities are higher in soils for water of concentration C0 and C1, and lower for the other three concentrations (C2, C3 and C4).