The aim of this study was to investigate the effects of magnetized water treatment (MWT) on some vegetation growth indices in arid areas of northeast Iran. For this purpose, the impacts of MWT were examined in terms of leaf area, special leaf area, and some of the physiographic indicators such as relative water capacity and foliar chlorophyll content in three species endemic to arid environments, namely Nitraria, Haloxylon, and Atriplex. In addition to the factors mentioned, acidity (pH) and electrical conductivity (EC) were also measured. This research was conducted in a completely randomized block design with three replications. Data analysis was carried out via the analysis of variance using MSTAT software. The results showed that species irrigated with magnetized water had better performance on measured growth indices. On average, the amount of increase for morphology and physiology parameters in the three species irrigated by MW (comparing with those irrigated by normal water) were: leaf development by 121.74 (19.59%), leaf area index (LAI) by 108.97 (17.5%) mm2, special leaf area (SAL) by 8.68%, relative water content (RWC) by 9.81%, and special product analysis division (SPAD) by 14.77%. The water magnetization process also reduced pH by 0.5 and EC by 0.3 μmhos.cm−1.
Desertification and land degradation that are the outcomes of climate fluctuation and human activities (Millennium Ecosystem Assessment 2005) are one the most complex threats to the environment, with considerable effects on socio-economic indicators. Therefore, it is difficult to fully comprehend the spatio-temporal characteristics of this process (Akbari et al. 2016). Studies confirm that 10–20% of the world's arid lands (Rubio & Bochet 1998) and approximately 8–10% of Europe suffer from land degradation (Joint Research Center 2008). Propagation of desertification and limited access to water, especially in arid areas, has made it necessary to search for water-efficiency-improving technologies.
Irrigation in arid areas increases salinity and the limitation of land capability for different uses. Therefore, attempts must be made in order to raise irrigation efficiency in line with the objectives of soil and water conservation programs. There is a growing body of literature on water utilization and irrigation improvement techniques. During recent years, the implications of magnetized water treatment (MWT) have been one of the cases that has been paid much attention. Magnetized water is water passed through a magnetic field, based on certain calculations, which makes considerable improvements in the chemical and physical characteristics of water (Castro Palacio et al. 2007; Maheshwari & Grewal 2009). This technology was first tested in Russia, followed by the USA, Japan, and England, and now it has become a commonplace technology (Nikbakht 2012). It converts marginal and brine water sources into a new freshwater source to be further used in land rehabilitation and vegetation establishment endeavors.
Maheshwari & Grewal (2009) studied the relationship between the application of MWT and vegetable crop yield and also water productivity in Australia, and found up to 23% increase in crop yield and up to 24% increase in water productivity. In addition, they concluded that this technology is capable of reducing water salinity and pH and increasing plant water-use efficacy. Hozayn et al. (2016) evaluated the effects of magnetized water on plant growth indices in Egyptian agricultural organization and concluded that this technology increased growth indices of the plants and also increased water-use efficiency. Pang & Deng (2008) evaluated the variation of water properties when passing through a magnetic field in China, and stated that the properties of water are changed under magnetization, and the rate of changes depends on the intensity of magnetization as well as the water temperature. Lin & Yotvat (1990) evaluated the effects of magnetized water on agricultural production in Israel and concluded that MWT increases crop production, and also the quality and quantity of the crops. Coey & Cass (2000) studied the changes of water molecules under magnetization in Ireland and concluded that this technology decreases water hardness, and changes calcite to aragonite. Yadollahpour et al. (2014), El-Sayed & El-Sayed (2014) and Hozayn et al. (2013) studied the applications of MWT technology in farming and agricultural development, and mentioned the effects of magnetized water on improvements of irrigation water quality and quantity, crop yields and quality, soil improvement, scale prevention/elimination in water-use systems and water saving, germination of seeds, plant growth and development, and the ripening and yield of field crops.
Hasaani et al. (2015) studied the interaction between magnetic fields and the characteristics of flowing water, and reported that magnetic fields change some properties of the flowing water. They concluded that the pH was increased by 12% and total dissolved solids (TDS) and electrical conductivity (EC) were both decreased by 33% and 36% respectively. Also the mechanical parameters like viscosity and surface tension were decreased by 23% and 18%, respectively. In addition, thermal conductivity was decreased by 16%. Musa & Hamoshi (2012) evaluated the effects of magnetic field on the solubility of NaCl and CaCl2.2H2O at different temperature and pH values. They concluded that the MWT increases mineral solution rate compared with non-magnetized water, and they found a relationship between the number of magnetic treatments and the electrical conductivities of NaCl and CaCl2.2H2O solutions at the same concentration and pH values. Teixeira da Silva & Dobránszki (2014) studied the impacts of magnetized water (MW) on plant growth. They reported that irrigation with MW can improve the growth and development of plants both quantitatively and qualitatively. It can improve the germination of seeds as well as early vegetative development of seedlings and can also alter the mineral content of seeds or fruits. They concluded that the effect of MW, which depends on the quality and ion-content of the water and on the type of magnetization, is strongly species and genotype dependent. Wang et al. (2018) studied the effects of magnetic ﬁeld (MF) on the physical properties of water. Tap water (TW) and four types of MWT were measured in the same condition. It was found that the properties of TW were changed following the MF treatment, shown as an increase in evaporation amount and decrease of boiling point after magnetization. Pang & Zhu (2013) evaluated the effects of magnetized water in the concrete industry. They studied the influence of magnetized water on different mechanical and optical properties of concrete. The results indicated that the mass density, tensile strength, compressive strength, deformation modulus, and Poisson's ratio of concrete increase, but its cohesive force internal friction angle decreases, as well as some new peaks in the concrete occurring under the influence of MW compared with those of tap water.
Despite a considerable amount of literature in the fields of agriculture, industry and basic sciences, the application of MWT has not been considered in natural resources management projects. Therefore, in the present research, a case study pilot project was implemented in Fadisheh village, in the northeast of Iran, the area that suffers from inclement weather conditions and intensified desertification. Establishment of adaptable vegetation cover and utilization of marginal water sources could facilitate rehabilitation of these areas. This study is unique in terms of the application of magnetized water, as a modern technology, for the rehabilitation of degraded lands, establishment of vegetation and improvement of water-use efficiency. This study, under the title of ‘The impacts of magnetized water treatment on different morphological and physiological factors of plant species in arid regions’, strives to provide a new strategy to increase water-use efficiency under drought crisis, the utilization of unconventional water sources, and the developing and improving of vegetation cover in line with land rehabilitation and desertification-combating principles.
MATERIALS AND METHODS
The study area, Fadisheh village, is in the southern part of Neishabour County (with 58° 42′ 31″ to 58° 21′ 41″ east longitude and 36° 07′ 34″ to 35° 41′ 47″ north latitude), in the northeast of Iran and about 15 km distance from Neishabour town (Figure 1). The area is characterized by an arid climate according to the De Martonne classification (De Martonne (1926) defined the aridity index for different biomes as follows: AI is the aridity index, defined as AI = P/(T + 10), where P is the mean annual precipitation in mm and T is the mean annual temperature in °C. The De Martonne aridity index divides different climates into Arid, Semi-arid, Mediterranean, Semi-humid, Humid and Very Humid). Based on the ombrothermic diagram, the dry period of the area occurs from May to November. Given the inclement weather and climate conditions of Fadisheh village and the propagation of desertification, there is a real necessity for the rehabilitation of the area using tolerant species by making use of marginal quality water sources (Natural Resources and Watershed Management Service of Khorasan Razavi Province 2011).
This research was completed in different stages, presented as a diagram in Figure 2.
Selection of tolerant species
Based on the objectives of this study concerning the influences of MWT on growth indices (morphological and physiological indices) of the plant species of arid and semi-arid areas, three species were selected, namely Haloxylon, Atriplex, and Nitraria. These species are very useful and compatible with the arid and desert regions of Iran, and are used by the Natural Resources Departments of Khorasan Razavi Province as suitable species for desertification and vegetation rehabilitation projects. Also, these plant species are very similar in terms of water requirement, irrigation intervals and the degree of resistance to environmental stresses (Natural Resources and Watershed Department of Khorasan Razavi Province, Iran 2009). Therefore, these species were selected based on their equal water requirements, irrigation frequencies, growth period, resistance to environmental stressors, and their widespread application in land rehabilitation projects.
To prevent direct rainfall to the plants and also intense direct sunshine, which can be sources of error, a roofed place, but open on four sides, was used to conduct the experiments. A number of 162 seedlings, 3 months old, were purchased from a local nursery and arranged in three replicates each containing 54 seedlings. Two tanks of 10,000-litre volumes were prepared for storing irrigation water. The output of one of the tanks was connected to the inlet pipe of the magnetizer device. The output magnetized water was transferred via a pipe for irrigation. A similar procedure was considered for the irrigation of the control plots, but of course without passing water from the magnetizer device.
Field and laboratory measurements of the morphological–physiological indices
There are many different indices to study the morphological and physiological characteristics of plants, such as leaf area, leaf area index (LAI), special leaf area (SLA), root to branches length ratio, relative water content (RWC), and special product analysis division (SPAD). In this regard, all species in arid and desert areas are morphologically and physiologically different from species in other climatic zones due to their adaptation to severe environmental conditions. Therefore, when using them as suitable species for the regeneration of degraded and desert areas, morphological and physiological indices that can rapidly change these conditions are very important. Also, these indicators can help researchers to evaluate the design of scientific ones (Tabatabaee et al. 2014; Ahani et al. 2015). Therefore, in this research some suitable indicators that have been cited in other scientific sources have been used. These are leaf area index, special leaf area, special product analysis division, and relative water content. A brief definition of these indicators is presented in the following.
It should be noted that the number of leaves of each plant was counted at the beginning of the research period and which was then repeated at the final stage of the experiment. Due to the lack of discernible leaves for Haloxylon, the number of inter-nodes were counted for this plant.
Leaf area index (LAI): To measure this index, the first five leaves of the tallest branch were considered and measured using a leaf area meter device (Ahani et al. 2015).
Special product analysis division (SPAD): This parameter was measured using a standard chlorophyll meter at the Faculty of Agriculture of the Ferdowsi University of Mashhad, Iran.
In this research, the statistical analysis of the measured data was carried out in a randomized complete block design with the factorial method. After examination of data normality, data analysis was performed using one-way analysis of variance (ANOVA) in a completely randomized design with three replicates. Two irrigation schemes were considered, namely regular (normal) and magnetized irrigation water. Group means were subjected to means test (Duncan method) at the 5% significance level using MSTAT-C, and the graphs were generated in Microsoft Excel.
RESULTS AND DISCUSSION
Effects of water on leaf area index and the special leaf area index
Figure 3 illustrates the effects of irrigation water on the leaf area index as well as special leaf area index for the selected plant species.
There were no significant differences between the two classes of water in terms of leaf area index (p < 0.01), as 260.171 mm2 was obtained for the plants of the MWT compared with 157.201 mm2 for the plants in the control plots. However, there was a significant difference between the two groups in terms of special leaf area index (p < 0.01). In comparison with the control plot with 3,997 mm/gr, the MWT plants produced a special leaf area index of 7,801 mm/gr.
Comparing the results, it can be seen that the plants irrigated with the MWT had an improved LAI, suggesting the application of the MWT as a growth stimulant, to produce higher leaf area values. A similar result was also obtained for SLA. It appears that MWT may increase the special leaf area and produce higher yields. Likewise, the values obtained for this index were higher in the treated group, which is consistent with the results of Yadollahpour et al. (2014) and also Teixeira da Silva & Dobránszki (2014). Generally stated, the substitution of regular water irrigation with MWT could escalate leaf development due to higher water and nutrient availability, higher photosynthetic pigments, and accelerated plant vegetative growth.
Effects of irrigation water on leaf development as well as the SPAD index
Figure 4 illustrates the effects of irrigation water on the leaf development index for the selected plant species.
As can be seen in Figure 4, the treated group was significantly more successful in terms of leaf development with 221.99, in comparison with the control group with 100.25 (p < 0.01) for the leaf development index.
When compared with the control group, the group with MWT produced significantly higher levels of SPAD index: 35.79 for the treatment and 19.99 for the control group. Plants irrigated with MWT generated relatively higher SPAD values. The application of MWT may increase nutrient uptake and photosynthetic pigments, especially chlorophylls. These results support previous research findings conducted by Hozayn et al. (2016).
Effects of irrigation water on RWC
Figure 5 illustrates the effects of irrigation water on the RWC index for the selected plant species.
The plants subjected to MWT were significantly different from the control group plants in terms of the RWC index. As can be seen, the treated group produced on average an RWC index of 72.29, compared with that of the control group which was 62.48. Therefore, similar to the results of Hozayn et al. (2016), the RWC index in the group of plants irrigated with MWT is different from the control group. Higher water and nutrient uptake and hence higher turgidity were experienced in the plants subjected to MWT.
Statistical analysis of the pH and EC values
As mentioned earlier, during a time period of 300 min (5 hours) of the study, the pH of the magnetized water was regularly measured (at 30 min intervals). The results of the measurements are provided in Table 1 and Figure 6. Along with the pH, EC was also measured at each water passage, which is also shown in Table 1 and Figure 6.
|Number of times water passed through the magnetizer device .||Generated pH values .||Generated EC values .|
|Number of times water passed through the magnetizer device .||Generated pH values .||Generated EC values .|
As illustrated in Figure 6, pH gradually decreased in response to the increase of the number of passages. The results showed a relatively sharp fall in pH values at the fifth passage. Water magnetization resulted in lower water pH in this experiment. Decreased water pH due to water magnetization has also been reported by other researchers, such as Ebrahimi & Honarjouei (2015). Compared with other experiments, reduction in pH was experienced even for one-time passage of water through the magnetizer device. Likewise, higher numbers of water passages produced lower EC values. Mehrabi & Kouchak Zadeh (2013) and Hasaani et al. (2015) in their similar studies came to the same conclusion. Similar to pH, water EC reduction had a relatively sharp fall at the fifth passage.
Many studies have been carried out on the effects of magnetized water on the amount of electrical conductivity and soil acidity, such as Bogatin (1999), Kney & Parsons (2005), Saliha (2005), Abou El-Yazied et al. (2012), and Mohamed 2013). In all of these studies there has been emphasis on reduction of the amount of soil salinity and increasing plant tolerance. The results obtained in this research also confirm this finding. However, if the salinity exceeds 2,000 ppm, more time is needed to reduce the effects of salinity.
Utilization of MWT may improve the morphological and physiological characteristics of the plant species. The application of MWT could improve plant leaf area index and special leaf area index by respectively 108.97 mm2 and 3,803.74 mm2.gr. Leaf development was also improved by 121.71 leaves. The RWC and SPAD indices were also increased by 9.81% and 15.79% respectively. Reductions were also encountered in terms of water pH by 0.5 and EC by 0.3 μmhos.cm−1, with a more pronounced decrease at the fifth passage of water from the magnetizer device. Various studies in the world and Iran have shown that the use of magnetized water technology is economically important and essential in the management of water resources in arid regions. This technology will increase water use efficiency and lead to water and soil rehabilitation, consequently increasing crop yield and growth of plants in arid and desert regions (Coey & Cass 2000; Maheshwari & Grewal 2009; Hozayn et al. 2013; Tabatabaee et al. 2014). It must be mentioned that in some desert regions like the area of this research, shortage of freshwater is serious and almost any device or project that is able to increase the quality of marginal waters or to raise the efficiency of the limited existing water in these areas is valuable and economically justifiable. Generally, water magnetization devices are made up of the wired network around a tube. The water magnetization device designed in this study has the following differences from other existing devices:
Uses a permanent magnet (neodymium magnet) instead of an electric coil, which makes the magnetic field stronger.
Creates a magnetic field inside a container made of steel to protect the field.
Uses a copper tube to prevent any reaction of the pipe to the magnetic field.
Instead of installing a device on an irrigation tube, the water passes directly from the inside of the device, inside the magnetic field.
Uses steel frames to protect the pipe.
The appearance of the machine is very simple and it is easy to carry it during irrigation.
This device is designed for the first time in this research and its registration process is currently being carried out within the country's record-keeping and intellectual property.
Intensification of the process of desertification in recent decades and limitation of water resources, especially in arid and desert areas, has increased the importance of employing up-to-date and useful techniques such as ‘magnetized water treatment’ for optimum water use. According to the outcomes obtained from this study, in all growth indices of morphology and physiology in three species of Haloxylon, Atriplex and Nitraria (with the same water volume for irrigation), plants irrigated with magnetized water perform better than those irrigated with normal water (P-value < 0.01). In other words, magnetized water has caused more growth of plants in terms of morphology and physiology. Our findings showed that in order to improve the performance of planting seedlings to restore degraded lands in shorter time-periods by Haloxylon, Atriplex, and Nitraria with MWT, the priority is with the two species of Atriplex and Nitraria, and Haloxylon is the third priority in this regard. The study of morphological growth indices showed that the two species of Atriplex and Nitraria were very close in terms of growth performance. Also, in relation to the physiological growth indices, MW increased the RWC and SPAD indices in the three plants. In order to improve the performance of the SPAD and RWC indices, among the three species studied in this research, the priority is with the species Nitraria, Atriplex, and Haloxylon, respectively. Considering that the same water volume was used for irrigation of all the plants, the irrigation with magnetized water led to considerably higher rates of growth indices.
In most of the dryland environments around the world, water shortage is the main limitation for agricultural and natural resource development and generally it is not possible to increase water quantity due to climatic conditions. In such cases, magnetization of available water, especially poorer quality water, can increase the efficiency of water and support agricultural and natural resource development.