Effects of magnetized water application on soil and maize growth indices under different amounts of salt in the water

Application of low quality water for irrigation is compulsive in facing water scarcity. Use of a magnetic field is an approach to overcome this challenge. This study examined the impact of magnetic field technology on improving germination under water of different salinity levels. An experiment was conducted to determine the effects of saline water levels, i.e. (S 1 ):0.5, (S 2 ):2, (S 3 ):4 and (S 4 ):6 dS/m combined with magnetized technology (with or without) on maize growth. Thus, magnetic treatment was applied by passing the irrigation water through a 1,500 mT magnetic field at 3 litres per minute (lpm) flow rate. Some emergence indices, such as emergence index, emergence rate index (ERI) and mean emergence time, were used to evaluate the germination of maize seed. As for soil properties after plant harvest, the use of magnetically treated irrigation water reduced soil pH but increased soil electrical conductivity and available N and P. ERI increased from 7.6 to 10.2, 9.1 to 11.1, 10.3 to 13.3, and 11.8 to 13.3 when applying the magnetized field for S 1 , S 2 , S 3 and S 4 , respectively. Overall, the growth parameters of maize were improved by using magnetic technology with saline water, while the opposite trend was shown for increasing salinity without magnetic treatment.


INTRODUCTION
Agriculture is the main consumer of water resources. However, because of the increase in demand from other sectors, water has become scarce and limited. In Iran, agriculture uses more than 85% of the available water resources. In addition, the processes of urbanization and industrialization and the development of irrigated agriculture to support population growth have raised the demand for water, but at the same time have reduced the supply.
Salinity of soil and water resources is a serious threat in many parts of the country. The main difficulty in this regard is the temporal variations of salinity during the growing season, due to the effects of irrigation water which add or leach the salts. Salinity of the ground waters is more serious than that of the surface waters in Iran. This has been increasing in recent years due to the overdraft and intrusion of the surrounding saline bodies of water. Considering the fact that nearly half of the water used in Iran's agriculture comes from the groundwater, the threat of salinity effects on the sustainability of crop production in the country has become evident. Magnetic water treatment works on the principle that as water passes through a magnetic water softener, a Lorentz force is exerted on each ion which is in the opposite direction to each other. The redirection of the particles increases the frequency of collisions between ions of opposite sides, combining to form a mineral precipitate or insoluble compound. Magnetic treatment of saline irrigation water can be used as an effective method for soil desalinization. The application of a magnetic field on water decreases the hydration of salt ions and colloids, having a positive effect on salt solubility, accelerated coagulation and salt crystallization (Hillal & Hillal a). Field experiments conducted in Egypt showed that sandy loam soil pots irrigated with normal highly saline water of an electrical conductivity (EC) value of 8.2 dS/m retained salts compared to pots irrigated with magnetized saline water (Hillal & Hillal b). Subsequently, it was concluded that magnetized water increased leaching of excess soluble salts, lowered soil alkalinity and dissolved slightly soluble salts.
Plants have increasingly become an attractive model system for studying the biological effects of magnetic fields lished that the magnetic field pretreatment had a positive effect on cucumber seedlings, such as stimulating seedling growth and development. Tai et al. () observed that subjecting water to a magnetic field leads to a modification of its properties, as it becomes more energetic and able to flow, which can be considered as the birth of a new science called magneto biology. They also pointed out that magnetized water prevents uptake by the roots of harmful metals, such as lead and nickel, and hence prevents these from reaching the fruits. However, it increases the percentage of nutrient elements like phosphorus, potassium and zinc in plants. Grewal & Maheshwari () investigated the effects of magnetic treatment of irrigation water on snow pea and Kabuli chickpea seed emergence, early growth and nutrient contents under glasshouse conditions.
Hozayn & Qados () studied the application of magnetic water for wheat crop production and found improvements in quantity and quality of wheat. Therefore, using magnetic water treatment could be a promising technique for agricultural improvements, but extensive research is required on different crops. Maheshwari & Grewal () demonstrated some effects of magnetic water treatment on water productivity and yield of snow pea, celery, and pea plants.
Their results pointed out beneficial effects of magnetic treatment, particularly for saline water and recycled water, on the yield and nutrient composition of celery and snow pea plants under irrigation with saline water. Therefore, an attempt was made to understand the applicability of using magnetized saline irrigation water in the evaluation of growth and emergence of maize seeds.

MATERIALS AND METHODS
A pot experiment was carried out in Kashmar Higher Education Institute, Iran, during the summer season of 2015, to study the effects of different irrigation water saline levels and tap water with or without magnetic field on germination rate, dry weight, plant height and some emergence indices.
The experiment was laid in randomized complete block design comprising tap water, i.e. control: S 1 ; irrigation with saline water (2 dS/m): S 2 ; 4 dS/m: S 3 ; and 6 dS/m (S 4 ) as main plots and irrigation water with or without magnetic field (M 1 and M 2 ), respectively, as subplots. The pots were filled with 15 kg of uniform soil. Some physical and chemical properties of the soil are presented in Table 1.
Germination tests were performed under greenhouse conditions with natural light and the average temperature of 36 ± 2 W C to study the effect of magnetized water on maize seed germination and emergence. Saline water of 1,500 ppm was prepared in the laboratory by adding NaCl. Before applying to the plants, for the magnetized treatments, irrigation water was treated with a 1,500 mT magnetic field with 5 circulations.
The water flow rate was 3 litres per minute (lpm). The magnetic field was produced just before the flow outlet using four pairs of neodymium block magnets, fixed to a wooden frame, with 25 mm distance between pairs. Each magnet measured 45 mm long, 5 mm high and 35 mm wide and a 60 cm pipe length was in contact with the magnets. A schematic design of the magnetic device is shown in Figure 1.
where DAP is days after planting.

Mean emergence time
MET is presented in Equation (2) according to Ellis & Roberts ().
where D ¼ number of days counted from the beginning of emergence, n ¼ number of seeds emerged on day D.

Emergence index
Speed of germination index was calculated using Equation (3) as described by association of official seed analysis (AOSA) (): where N es is the number of emerged seeds and D is days.

Emergence rate index
Emerged seeds were counted daily and used to calculate ERI using Equation (4).
where %n ¼ percent of plants emerged on day n; %(nÀ1) ¼ percent of plants emerged on day n-1; n ¼ number of days after planting; f ¼ first day any plants emerged, l ¼ last counting day (emergence complete).

Soil properties at the end of the experiment
The results showed that the magnetic treatment of all types of water led to no significant difference on the soil EC values, but the magnetic treatment of all irrigation water varied significantly and affected soil pH at the end of the experiment (Table 3). Also, soil pH decreased with magnetically treated different saline irrigation water. Furthermore, available soil N and P significantly increased with magnetic treatment when compared with the control (non-magnetized). However, the magnetic treatment of the control (S 1 : tap water) had no significant effect on the values for available soil N and P (Table 3)

Seedling height and weight
The average height of the maize seedlings measured after 15 days is presented in Figure 3. With the application of magnetized water, the maize seedling grew taller and heavier as compared to non-magnetized treatments. The results of Table 4 show increases of 13.95, 10.61, 9.76 and 9.33% in seedling weight with magnetized tap water (S 1 ), S 2 , S 3 and S 4 , in comparison to the non-magnetized water.
This increase in seedling height and weight may be due to earlier emergence of maize seedlings irrigated with magnetized water in contrast to the control (S 1 ) and, as a result, seedlings had two to three more days for growth compared with the control treatment. Seedling emergence indices were examined including EI, FEP, ERI and MET.   Table 5 shows that the magnetized waters have potential for MET reduction and rapid emergence for maize seeds ( Irrigation with magnetically treated water may be responsible for activation of enzymes and hormones involved in the germination process and mobilization of nutrients. As a result, there is probably an enhancement in the mobilization and transportation of nutrients to the embryonic axis and a resultant increase in speed of emergence and germination rate of maize seedlings.

CONCLUSIONS
Results of the experiment revealed some beneficial effects of magnetically treated water for maize seed germination. Irrigation with magnetically treated water increased the vegetative growth of maize seeds in all treatments. Application of magnetized saline water for maize seed emergence reduced the MET as compared with non-magnetized water. Although magnetic water treatment is an environmentally friendly technique and easy to handle, further research is required to understand the ambiguous mechanism of the magnetic field in order to turn it into a technology for sustainable farming.