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Magnetic treatment of irrigation water: Its effects on vegetable crop yield and
water productivity
Basant L. Maheshwari *, Harsharn Singh Grewal
1
School of Natural Science, CRC for Irrigation Futures, Building H3 – Hawkesbury Campus, University of Western Sydney, Locked Bag 1797, Penrith South DC NSW 1797, Australia
1. Introduction
Long spell of drought and competing water demands in most
parts of Australia have put enormous pressure on water
resources. Steps need to be taken to conserve both the quantity
and quality of water and appropriate strategies will have to be
developed to avoid risk to future water supplies. The main
efficiency gains must come from the dominant user, irrigation,
accounting for over 70% of the total water use in Australia
(ANRA, 2008).
One of the ways by which we can reduce the total water used for
irrigation is to employ practices that improve crop yield per unit
volume of water used (i.e., water productivity). There have been
some claims made that the magnetic treatment of irrigation water
can improve water productivity (Duarte Diaz et al., 1997). If those
claims are valid, there is scope for magnetic treatment of water to
save water supplies and assist in coping with the future water
scarcity.
There is hardly any study reported, with valid scientific
experiments, on the effects of magnetic treatment of water on
crop yield and water productivity. However, some closely related
studies have reported on some beneficial effects of magnetic field
in a number of other farming situations. For example, Lin and
Agricultural Water Management 96 (2009) 1229–1236
ARTICLE INFO
Article history:
Received 20 August 2008
Accepted 22 March 2009
Keywords:
Magnetic treatment
Water productivity
Recycled water
Salinity
Snow pea
Celery
Pea plants
ABSTRACT
This study examines whether there are any beneficial effects of magnetic treatment of different
irrigation water types on water productivity and yield of snow pea, celery and pea plants. Replicated pot
experiments involving magnetically treated and non-magnetically treated potable water (tap water),
recycled water and saline water (500 ppm and 1000 ppm NaCl for snow peas; 1500 ppm and 3000 ppm
for celery and peas) were conducted in glasshouse under controlled environmental conditions during
April 2007 to December 2008 period at University of Western Sydney, Richmond Campus (Australia). A
magnetic treatment device with its magnetic field in the range of 3.5–136 mT was used for the magnetic
treatment of irrigation water. The analysis of the data collected during the study suggests that the effects
of magnetic treatment varied with plant type and the type of irrigation water used, and there were
statistically significant increases in plant yield and water productivity (kg of fresh or dry produce per kL
of water used). In particular, the magnetic treatment of recycled water and 3000 ppm saline water
respectively increased celery yield by 12% and 23% and water productivity by 12% and 24%. For snow
peas, there were 7.8%, 5.9% and 6.0% increases in pod yield with magnetically treated potable water,
recycled water and 1000 ppm saline water, respectively. The water productivity of snow peas increased
by 12%, 7.5% and 13% respectively for magnetically treated potable water, recycled water and 1000 ppm
saline water. On the other hand, there was no beneficial effect of magneti cally treated irrigation water on
the yield and water productivity of peas. There was also non-significant effect of magnetic treatment of
water on the total water used by any of the three types of vegetable plants tested in this study. As to soil
properties after plant harvest, the use of magnetically treated irrigation water reduced soil pH but
increased soil EC and available P in celery and snow pea. Overall, the results indicate some beneficial
effect of magnetically treated irrigation water, particularly for saline water and recycled water, on the
yield and water productivity of celery and snow pea plants under controlled environmental conditions.
While the findings of this glasshouse study are interesting, the potential of the magnetic treatment of
irrigation water for crop production needs to be further tested under field conditions to demonstrate
clearly its beneficial effects on the yield and water productivity.
Crown Copyright ß2009 Published by Elsevier B.V. All rights reserved.
* Corresponding author. Tel.: +61 2 4570 1235/0410 550 911 (mobile);
fax: +61 2 4570 1787.
E-mail addresses: b.maheshwari@uws.edu.au (B.L. Maheshwari),
h.grewal@uws.edu.au (H.S. Grewal).
1
Tel.: +61 2 4570 1118; fax: +61 2 4570 1787.
Contents lists available at ScienceDirect
Agricultural Water Management
journal homepage: www.elsevier.com/locate/agwat
0378-3774/$ – see front matter . Crown Copyright ß2009 Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.agwat.2009.03.016
Yotvat (1990) reported an increase in water productivity in both
crop and livestock production with magnetically treated water.
Some studies have shown that there is an increase in number of
flowers, earliness and total fruit yield of strawberry and tomatoes
by the application of magnetic fields (Esitken and Turan, 2004;
Danilov et al., 1994). An increase in nutrient uptake by magnetic
treatment was also observed in tomatoes by Duarte Diaz et al.
(1997).Amaya et al. (1996) and Podleoeny et al. (2004) have shown
that an optimal external electromagnetic field accelerates the plant
growth, especially seed germination percentage and speed of
emergence.
Podleoeny et al. (2004) studied the effects of magnetic
treatment by exposing the broad bean seeds to variable magnetic
strengths before sowing and observed marked beneficial effects on
seed germination, emergence rate and seed yield. Plant emergence
was more regular after the use of the magnetic treatment and the
emergence occurred 2–3 days earlier in comparison with the
control treatment. They attributed the higher number of pods per
plant and the fewer plant losses per unit area for broad bean during
the growing season and consequently the yield increase to the pre-
sowing treatment of seeds with magnetic field.
Magnetic fields can also influence the root growth of various
plant species (Belyavskaya, 2001, 2004; Muraji et al., 1992,
1998; Turker et al., 2007). Muraji et al. (1992) demonstrated an
enhancement in root growth of maize (Zea mays)byexposing
the maize seedling to 5 mT magnetic fields at alternating
frequencies of 40–160 Hz. However, there was a reduction in
primary root growth of maize plants grown in a magnetic field
alternating at 240–320 Hz. Highest growth rate of maize roots
was achieved in a magnetic field of 5 mT at 10 Hz (Muraji et al.,
1998). Turker et al. (2007) reported an inhibitory effect of static
magnetic field on root dry weight of maize plants, but there was
a beneficial effect of magnetic field on root dry weight of
sunflower plants.
Belyavskaya (2004) and Turker et al. (2007) reported that weak
magnetic field had inhibitory effect on growth of primary roots
during early growth. The proliferative activity and cell reproduc-
tion in meristem in plant roots are reduced in weak magnetic field
(Belyavskaya, 2004). Cell reproductive cycle slows down due to the
expansion of G1 phase in many plant species and G2 phase in flax
and lentil roots. There was a decrease in the functional activity of
genome at early pre-replicate period in plant cells exposed to weak
magnetic field. In general, these studies conclude that weak
magnetic field caused intensification of protein synthesis and
disintegration in plant roots. Mitochondria were also found to be
very sensitive to magnetic field. The size and relative volume of
mitochondria in cells increased due to a very weak magnetic field
(Belyavskaya, 2001, 2004). Cells of plant roots exposed to weak
magnetic field showed calcium over-saturation in all the
organelles in cytoplasm (Belyavskaya, 2004). Belyavskaya (2001)
reported disruptions in different metabolic systems including Ca
2+
homeostasis in root cells due to low magnetic field.
Impact of heat stress at 40 8C, 42 8C and 45 8C for 40 min in cress
seedlings (Lepidium sativum) was reduced by exposing plants to
extremely low-frequency magnetic field (50 Hz, 100
m
T) (Ruzic
and Jerman, 2002). Magnetic field probably acts on the same
cellular metabolic pathways as temperature stress, and as such, the
study suggested that magnetic field act as a protective factor
against heat stress.
In general, the literature review reveals that there are possibly
some beneficial effects of magnetic field or treatment on plant
growth and other related parameters. However, there is no clarity
as to the extent of these effects and mechanisms operating behind
these effects. Furthermore, there is not much research carried out
on the effects of magnetic treatment of irrigation water on plant
growth and crop and water productivity.
In this study, therefore, we investigate the effects of magne-
tically treated potable water, recycled water and saline water on
plant yield and water productivity under controlled environmental
conditions in glasshouse. The main objectives of the study are:
-
To examine the performance of magnetically treated potable
water, recycled water and saline water on plant growth, yield and
produce nutrient composition of selected plant types,
-
to quantify water productivity and water saving potential of
magnetically treated irrigation water, and
-
to determine the changes in soil properties due to irrigation with
magnetically treated water from different sources.
2. Materials and methods
2.1. Location, plant material and growing conditions
The project involved glasshouse experiments and laboratory
analysis of soil and plant properties. The glasshouse experiments
were conducted to examine the effects of magnetic treatment of
potable water, recycled water and saline water on plant yield, the
total water use, water productivity, soil properties and nutrient
compositionof snow peas, celery and peas. The study was conducted
under controlled environmental conditions with day and night
temperature of 20 8Cand158C respectively in the glasshouse.
Glasshouse experiments were conducted with celery, snow pea
and pea plants. There were two factors in the study: type of
irrigation water and magnetic treatment of water. The following
three types of irrigation waters were selected for the study:
-
Potable water,
-
recycled water, and
-
saline water.
The potable water used was the normal drinking water supplied
by the Sydney Water Corporation in the area, while the recycled
water was the treated effluent sourced from the Richmond Sewage
Treatment Plant. The saline water used in the study was prepared
by adding measured amounts of NaCl salt to potable water to
achieve required salinity levels.
To understand the impact of salinity levels on magnetically
treated water, two salinity levels were used for each plant type.
The salinity levels were 500 ppm and 1000 ppm for snow peas and
1500 ppm and 3000 ppm for celery and peas. The salinity levels of
irrigation water selected for snow peas were lower due to a higher
sensitivity of snow pea plants to salts when compared to celery and
pea plants. By having two salinity levels in the study for each plant
type, in effect, we had a total of four irrigation water types, i.e.,
potable water, recycled water and two variants of saline water.
Snow pea, pea and celery seeds were initially sown in seeding
mixture on 16th April 2007, 16th April 2007 and 2nd July 2007
respectively, and normal potable water was used for establishing
the seedlings. Once seedlings achieved required growth, healthy
seedlings were selected for planting in the study. Pea, celery and
snow pea seedlings were transplanted on 4th May 2007, 9th May
2007 and 17th July 2007, respectively. Two uniform size plants per
pot were transplanted in celery and pea pots, while four plants per
pot were transplanted in snow pea pots. The experiments for snow
pea, pea and celery were conducted in separate areas within the
glasshouse, and there were 48 pots for each plant type studied. The
pea, celery and snow pea plants were harvested on 26th June 2007,
24th October 2007 and 22nd November 2007, respectively.
For achieving statistically valid and unbiased estimates of
treatment means, treatment differences and experimental error,
we used statistical principle of local control, replication and
B.L. Maheshwari, H.S. Grewal / Agricultural Water Management 96 (2009) 1229–1236
1230
randomisation in these experiments. Completely randomised
design was used in the study and each treatment had four
replications.
2.2. Magnetic treatment
The irrigation water of different types was treated with a
magnetic device before applying to the plants. The mean values of
pH, EC, N, P and K values of different irrigation water types before
and after magnetic treatment are presented in Table 1. Magnetic
treatment of water tends to reduce slightly the water pH, while
there is no apparent trend for EC values. The values of N, P and K
content of different water types were not affected by magnetic
treatment of water. Recycled water had greater N, P and K content
compared with tap water and saline water (Table 1).
Magnetic treatment device, supplied by Omni Environment
Group Pty Ltd. (a Sydney based Australian company), with its
magnetic fieldin the range of 3.5–136 mT was used for the magnetic
treatment of irrigation water. The device comprised of a 100 mm
pipe section with its internal diameter 22 mm. The device contains
two magnets, and the arrangement of their north and south poles
and the direction of magnetic field generatedare shown in Fig. 1.For
the magnetic treatment of irrigation water, it was passed twice
through the magnetic treatment device at the flow rate of 10 ml/s,
providing the water magnetic field exposure of about 3 s.
The intensity of magnetic field generated by the two magnets
was measured along the longitudinal and cross-sectional direc-
tions of the pipe by Sypris Model 5070 Gauss/Tesla Meter
TM
. The
values of the magnetic field varied from 3.5 mT to 93 mT along the
axis of the pipe (centre line). In this case, there was a trend of
increasing values at the beginning of the pipe length, reaching peak
values at the middle section of the pipe (between 30 mm and
70 mm distance from the beginning of the pipe length) and the
trend of decreasing values towards the end of the pipe length.
Depending upon the distance along the pipe length, the values
of the magnetic field also varied across the pipe diameter, varying
from 3.3 to 136 mT, 3.2 to 94 mT, 3.2 to 97 mT and 1.8 to 118 mT at
5 mm, 10 mm, 15 mm and 20 mm distances from the one end of
the pipe wall to the other. The peak values of the magnetic field in
this case were observed for the pipe section between 30 mm and
70 mm distances from the beginning of the pipe length.
2.3. Soil properties and planting of seedlings
Soil for the study was obtained from a local garden supplier and
was sieved to remove any pebbles or non-soil material. The soil for
peas and celery was loamy sand in texture and had the value of
pH
1:5(soil:water)
6.3, EC
1:5(soil:water)
655
m
S/cm, available P (Olson-P)
22.2 mg/kg, NO
3
–N 1.52 mg/kg and extractable K (0.05 M HCL)
780 mg/kg. The soil used for snow peas was also loamy sand in
texture but had the value of pH
1:5(soil:water)
6.4, EC
1:5(soil:water)
220
m
S/cm, available P (Olson-P) 19 mg/kg, NO
3
–N 0.85 mg/kg and
extractable K (0.05 M HCL) 530 mg/kg. Results indicate that the
soils had low available N, moderate available P and adequate K.
Before planting the seedlings, each pot was filled with air dried
soil to a constant weight of 14 kg. For celery and peas, two uniform
seedlings of similar size and vigour were transplanted in each pot,
while for snow peas four seedlings were transplanted in each pot.
2.4. Irrigation scheduling
The main irrigation scheduling strategy used in the study was to
apply enough water to bring the soil back to field capacity at the
end of each irrigation. The plants were irrigated alternate days and
the volume of irrigation water applied was determined by knowing
the change in pot weight due to evapotranspiration since the last
irrigation. The volume of water applied varied with treatments and
the stage of crop growth and was recorded for each application.
In celery and peas, initially normal potable water (no magnetic
treatment) was applied to pots for the first 10 days, irrespective of
the experimental treatments, to avoid any salt injury effects on
young seedlings. Thereafter, irrigation water of different types as
described earlier was used for the control and treatments involving
celery, snow pea and pea plants. Over the total growing period,
magnetically treated water was used for 42 days in peas,158 days in
celery, and 143 days in snow peas. Pea plants matured relatively
quickly, and for this reasonthe duration of water application for peas
was shorter when compared with those for celery and snow peas.
2.5. Data collection and analysis
The volumes of water applied at each irrigation were recorded
to determine the total water used in the three types of plants.
Water productivity was calculated, based on both fresh and dry
weights of produce in celery (kg of celery shoots per kL of water
used) and snow peas and peas (kg of pods per kL of water used).
Celery was harvested at physiological maturity and the whole
mass of produce was considered as yield. Both fresh weight and
Fig. 1. Schematic of magnetic fields and direction of water flow during the magnetic
treatment.
Table 1
Effects of magnetic treatment on mean values of pH, EC and N, P and K concentrations in different types of irrigation waters.
Irrigation water type pH EC (mS/m at 25 8C) N (mg/l) P (mg/l) K (mg/l)
Control Magnetic
treatment
Control Magnetic
treatment
Control Magnetic
treatment
Control Magnetic
treatment
Control Magnetic
treatment
Potable water 8.15 8.13 0.254 0.255 0.254 0.257 0.044 0.045 2.28 2.19
Recycled water 9.08 9.09 0.943 0.940 1.475 1.465 0.062 0.062 19.32 19.32
500 ppm saline water 8.38 8.35 1.241 1.230 0.276 0.280 0.047 0.046 2.34 2.40
1000 ppm saline water 8.42 8.37 2.187 2.192 0.275 0.277 0.047 0.048 2.43 2.43
1500 ppm saline water 8.40 8.36 3.07 3.10 0.284 0.286 0.049 0.049 2.49 2.49
3000 ppm saline water 8.41 8.36 5.83 5.80 0.303 0.300 0.050 0.050 2.79 2.79
B.L. Maheshwari, H.S. Grewal / Agricultural Water Management 96 (2009) 1229–1236
1231
oven dry weight of celery were measured and are reported in
Section 3. Pea and snow pea pods were harvested at physiological
maturity every week to determine the influence of different
treatments on plant yield. These pods were oven dried at 65 8Cto
determine the dry weight of pods under different treatments.
Whole shoots of the plants were harvested at maturity and were
also oven dried at 65 8C to determine the dry weight of shoots.
Oven dried samples ofsnow pea pods as well asshoots and roots
of both snow peas and celery were analysed by ICP (inductively
coupled plasma), a method described by Zarcinas et al. (1987) to
determine the Ca, Mg, Na, P and K concentrations in the harvest of
both snow pea and celery plants. Soil samples after the harvest of
snow pea and celery plants were also collected and analysed to
determine the impact of magnetic treatments and different sources
of water on soil pH
1:5(soil:water)
,EC
1:5
, available N (NO
3
–N) and
available P (Olson-P) and extractable K (0.05 M HCl). It should be
noted that, in Section 3, we have presented the results only for the
elements that were significantly affected by magnetic treatment.
It should also be noted that the initial statistical analysis of
glasshouse data for pea plants indicated that there is no significant
effect of magnetic treatment of irrigation water on plant yield, total
water used and water productivity. For this reason, further plant
and soil analysis for pea experiments was not carried out to save
time and resources.
The data relating to plant yield, dry matter weight, water use,
plant nutrient composition and soil properties were tabulated and
statistically analysed to understand the treatment effects on plant
yield, water productivity and soil properties. All data were
subjected to the analysis of variance (ANOVA), including separa-
tion of main effects of irrigation water types and magnetic
treatment and their interaction effects. The least significant
difference (LSD at P= 0.05) was used to assess the differences
among pairs of treatment means and the Fvalues of the ANOVA
indicated the significance.
The effects of magnetic treatment in relation to different plant
and irrigation water types are presented in tabular form. Hereafter,
a change in parameter value indicated to be significant means the
value is statistically significant at 95% confidence level when
compared with the control treatment. In addition, we have referred
the treatment effect differential when the interaction between
magnetic treatment and irrigation water type was significant for
some experimental treatments and not for others. For example, the
treatment effect is referred to differential when there was a non-
significant effect of magnetic treatment of a particular water type
(e.g., potable water) and a significant effect for another water type
(e.g., saline water).
3. Results and discussion
3.1. Plant yield
3.1.1. Celery
There were differential effects of magnetic treatments of
different irrigation water types on yield based on both celery
fresh weight and shoot dry weight (Table 2). The interaction effects
between magnetic treatment and different irrigation water types
indicate significant increase in yield due to the magnetic treatment
of recycled water and 3000 ppm saline water. Irrigation with
magnetically treated 3000 ppm saline water and recycled water
respectively resulted in 23% and 12% increase in plant yield on
fresh weight basis. Similarly, magnetically treated 3000 ppm saline
water and recycled water treatment respectively resulted in 26%
and 12% increase in shoot dry weight. However, there was no
statistically significant increase in the yield or shoot dry weight by
irrigating celery with magnetically treated potable water and
1500 ppm saline water.
It is interesting to note that, the irrigation with recycled and
3000 ppm saline waters (no magnetic treatment) resulted in 8%
and 74% reduction in celery yield when compared to irrigation
with potable water. However, the magnetic treatment of these
waters completely eliminated the yield reduction in recycled
water and changed the yield reduction from 74% to 68% in
3000 ppm saline water.
3.1.2. Snow peas
Similar to celery plants, the magnetic treatment of different
irrigation water types had differential effect on snow pea yield
based on fresh and dry weights of pods (Table 2). Effects of
magnetic treatment of potable water, recycled water and
1000 ppm saline water were significant and respectively resulted
in 7.8%, 5.9% and 6.0% increase in snow pea yield when compared
with control treatments. Similarly, magnetically treated potable
water, recycled water and 1000 ppm saline water respectively
resulted in 8.5%, 7.0% and 8.2% increase in dry weight of pods.
However, there was no significant effect of magnetically treated
irrigation water on snow pea yield for 500 ppm saline water.
The magnetic treatment of irrigation water resulted in significant
increase (6.1%) in number of snow pea pods per pot. The magnetic
treatment also resulted in increasing trend for the number of pods
for individual irrigation water types, but it was not significant.
Unlike celery, the magnetic treatment had no significant effect on
shoot dry weight forsnow peas. The increase in number of snow pea
pods per pot also contributed to the significant increase in the fresh
and dry weights of pods in snow pea plants. This finding in the
current study is similar to the ones of Esitken and Turan (2004) and
Danilov et al. (1994)who reported increased fruit yieldof strawberry
and tomatoes by magnetic fields.
3.2. Water productivity
3.2.1. Celery
Similar to plant yield, there was differential impact of magnetic
treatment of different irrigation water types on water productivity
(kg of fresh or dry weight produced per kL of water used) based on
both fresh and dry weights of celery (Table 2). In particular, there
was significant increase in water productivity based on fresh
weight by applying magnetically treated 3000 ppm saline water
(24%), 1500 ppm saline water (11%) and recycled water (12%)
when compared with the controls. Similar trends were also
observed for the water productivity based on dry weight, but the
increase for 1500 ppm saline water was not significant.
3.2.2. Snow peas
The magnetic treatment of different water types also had
differential impact on the water productivity based on both fresh
and dry weights of snow pea pods (Table 2). For water productivity
based on fresh weight basis, the effects of the magnetic treatment
were significant for potable water, recycled water and 1000 ppm
saline water but non-significant for 500 ppm saline water. There was
12%, 7.5% and 13% increase in water productivity based on fresh pod
weight by respectivelyapplying magnetically treatedpotable water,
recycled waterand 1000 ppm saline water when comparedwith the
control treatments. Similar trends were also observed for water
productivity based on dry weight basis, but the effect of magnetic
treatment was non-significant for recycled water.
3.3. Total plant water use
The total water used by celery, snow pea and pea plants during
the growing period varied considerably with the type of irrigation
water used. However, the magnetic treatment of the water did not
have significant effect on the total water used by the three plant
B.L. Maheshwari, H.S. Grewal / Agricultural Water Management 96 (2009) 1229–1236
1232
types during the growing period for any of the irrigation water types
(Table 2). It is an important finding from this study, particularly
indicating that the magnetic treatment has no direct effect on
evaporation from soil surface and transpiration from plants.
3.4. Dry weight of roots
Except 3000 ppm saline water in case of celery, the magnetic
treatment did not have significant effect on the root dry weight
(Table 2) of celery and snow peas. Irrigating celery with
magnetically treated 3000 ppm saline water had a significant
increase (15%) in celery root dry weight when compared with the
control.
3.5. Nutrient and elemental composition of produce
Overall, irrigating celery with magnetically treated water
significantly increased the Ca and P concentrations of celery
Table 2
Effects of magnetic treatment of irrigation waters on mean values of plant yield parameters, water use and water productivity (based on fresh weight) of (a) celery, (b) snow
peas and (c) peas.
(a) Celery
Water source Yield – fresh
weight (g)
Yield – dry
weight (g)
Shoot dry
weight (g)
Root dry
weight (g)
Water
use (ml)
Water
productivity
(kg/kL water)
Control
Potable water 414.3 54.9 54.9 123.5 37,933 10.94
Recycled water 377.3 51.0 51.0 121.8 35,596 10.60
1500 ppm saline water 181.0 28.0 28.0 49.4 23,945 7.56
3000 ppm saline water 108.5 16.0 16.0 23.8 20,568 5.28
Magnetic treatment
Potable water 414.5 53.8 53.8 119.5 36,307 11.42
Recycled water 424.0 57.1 57.1 125.3 35,822 11.84
1500 ppm saline water 198.3 29.2 29.2 49.2 23,597 8.40
3000 ppm saline water 133.3 20.3 20.3 27.3 20,405 6.53
LSD
0.05
LSD
0.05
water 13.4 2.9 2.9 2.8 907 0.45
LSD
0.05
magnetic 9.5 2.1 2.1 NS NS 0.32
LSD
0.05
water magnetic 18.9 3.8 3.8 4.0 NS 0.64
(b) Snow peas
Water source Mean
yield – fresh
weight (g)
Mean
yield – dry
weight (g)
Mean
shoot dry
weight (g)
Mean
root dry
weight (g)
Water
use (ml)
Water
productivity
(kg/kL water)
Control
Potable water 216 30.93 46.0 4.35 19,279 11.22
Recycled water 198 28.66 44.5 3.84 18,154 10.95
500 ppm saline water 186 27.95 44.6 3.36 17,084 10.88
1000 ppm saline water 164 24.68 34.5 2.89 16,159 10.14
Magnetic treatment
Potable water 233 33.56 46.2 4.19 18,546 12.58
Recycled water 210 30.65 44.7 3.72 17,901 11.77
500 ppm saline water 188 28.44 44.4 3.50 17,032 10.87
1000 ppm saline water 174 26.71 35.4 3.14 15,214 11.42
LSD
0.05
LSD
0.05
water 6.8 2.51 1.95 0.16 691 0.40
LSD
0.05
magnetic 4.8 1.77 NS NS NS 0.29
LSD
0.05
water magnetic 9.6 NS NS 0.23 NS 0.57
(c) Peas
Water source Mean
yield – fresh
weight (g)
Mean
yield – dry
weight (g)
Water
use (ml)
Water
productivity
(kg/kL water)
Control
Potable water 1.60 1.24 4263 0.38
Recycled water 1.23 0.93 4160 0.30
1500 ppm saline water 1.05 1.04 3788 0.28
3000 ppm saline water 0.88 1.05 3695 0.24
Magnetic treatment
Potable water 1.62 1.24 4058 0.40
Recycled water 1.33 1.02 4166 0.32
1500 ppm saline water 1.03 1.02 3704 0.28
3000 ppm saline water 0.93 1.10 3617 0.25
LSD
0.05
LSD
0.05
water 0.12 0.13 208 0.03
LSD
0.05
magnetic NS NS NS NS
LSD
0.05
water magnetic NS NS NS NS
B.L. Maheshwari, H.S. Grewal / Agricultural Water Management 96 (2009) 1229–1236
1233
shoots (Table 3). However, the interaction effects between
magnetic treatment and irrigation water types were not significant
for any of the elements measured in celery shoots.
For snow peas, overall, the magnetically treated water had
significant effects on Ca, Mg and Na concentrations in pods
(Table 4). As to the individual water sources, there was a significant
increase in Ca and Mg concentration in snow pea pods when the
plants were irrigated with magnetically treated recycled water and
1000 ppm saline water. However, there was a decrease in Mg
concentration of pods when the plants were irrigated with
magnetically treated potable water and 500 ppm saline water.
Irrigating snow pea plants with magnetically treated 1000 ppm
saline water resulted in significantly reduced Na concentration in
pods.
3.6. Soil properties after plant harvest
3.6.1. Soil EC
1:5
Except for 3000 ppm saline water, the magnetic treatment of
irrigation water had no significant effect on EC
1:5
values after the
harvest of celery plants (Tables 5 and 6). On the other hand, overall,
the magnetic treatment resulted in significant effects on EC
1:5
value after harvest for snow pea plants when compared with the
control treatment. In particular, the magnetically treated potable
water, recycled water and 1000 ppm saline water resulted in
significant increase in soil EC
1:5
values after the harvest of snow
pea plants.
3.6.2. Soil pH
1:5
For both celery and snow pea plants, the magnetic treatment of
irrigation water types varied significantly and affected soil pH after
the harvest (Tables 5 and 6). Irrigating the two plant types with
magnetically treated potable water and recycled water signifi-
cantly decreased soil pH
1:5
after the harvest when compared with
the control treatments. For snow peas, irrigation with magnetically
treated 1000 ppm saline water also decreased the soil pH.
3.6.3. Available soil P and extractable soil K
For celery, the magnetic treatment of recycled water and
1500 ppm and 3000 ppm saline water significantly increased the
available soil P and extractable soil K when compared with the
controls (Tables 5 and 6). However, the magnetic treatment of
potable water had non-significant effect on the values for the two
elements. On the other hand, for snow pea plants, the significant
Table 3
Effects of magnetic treatment of irrigation water types on mean values of Ca and P concentrations of celery shoots.
Water source Ca concentration (mg/kg dry matter) P concentration (mg/kg dry matter)
Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean
Potable water 10,500 10,500 10,500 2867 2933 2900
Recycled water 10,900 11,767 11,333 2733 2967 2850
1500 ppm saline water 10,167 12,867 11,517 2203 2500 2352
3000 ppm saline water 11,500 13,400 12,450 2373 2667 2520
Mean 10,767 12,133 11,450 2544 2767 2655
LSD
0.05
water 1517 295
LSD
0.05
magnetic 1072 209
LSD
0.05
water magnetic NS NS
Table 4
Effects of magnetic treatment of irrigation water types on mean values of Ca, Mg and Na concentrations of snow pea pods.
Water source Ca concentration (mg/kg dry matter) Mg concentration (mg/kg dry matter) Na concentration (mg/kg dry matter)
Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean
Potable water 3733 3633 3683 2200 2100 2150 25 35 30.0
Recycled water 3700 4100 3900 2100 2200 2150 45 44 44.5
500 ppm saline water 4233 4167 4200 1983 1930 1956 147 166 156.5
1000 ppm saline water 4200 5000 4600 1817 1933 1875 866 517 691.5
Mean 3967 4225 4096 2025 2041 2033 271 190 230.5
LSD
0.05
water 102.74 15.28 14
LSD
0.05
magnetic 72.65 10.80 10
LSD
0.05
water magnetic 145.30 21.60 19
Table 5
Effects of magnetic treatment of irrigation water types on mean value of soil EC
1:5
,pH
1:5
and available P after snow pea harvest.
Water source EC
1:5
(
m
S/cm at 25 8C) pH
1:5
Available P (Olson-P)
Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean
Potable water 178 191 185 6.23 6.20 6.22 17.10 19.05 18.08
Recycled water 240 269 255 6.26 6.22 6.24 18.55 19.12 18.84
500 ppm saline water 375 382 379 6.11 6.13 6.12 18.25 18.34 18.30
1000 ppm saline water 523 563 543 6.15 6.10 6.13 17.71 17.74 17.73
Mean 329 351 340 6.19 6.16 6.18 17.90 18.56 18.23
LSD
0.05
water 7.39 0.02 0.52
LSD
0.05
magnetic 5.23 0.02 0.37
LSD
0.05
water magnetic 10.45 0.03 0.74
B.L. Maheshwari, H.S. Grewal / Agricultural Water Management 96 (2009) 1229–1236
1234
effect of the magnetic treatment was limited to the available soil P
only, and this effect was observed through irrigation with potable
water.
3.7. Influence of magnetic treatment on soil properties,
and other attributes
In the current study, an increase in soil available P and
extractable K, particularly under magnetically treated recycled
water and saline water irrigation, appears to have played some role
in improving yield and water productivity of celery plants.
Magnetic treatment of water may be influencing desorption of P
and K from soil adsorbed P on colloidal complex, and thus
increasing its availability to plants, and thus resulting in an
improved plant growth and productivity. Noran et al. (1996)
observed (under drip irrigation system) differences in the
concentrations of K, N, P, Na and Ca + Mg in soils irrigated with
magnetically treated water when compared those with normal
water. They argued that magnetic treatment of water slows down
the movement of minerals, probably due to the effect of
acceleration of the crystallisations and precipitation processes of
the solute minerals.
In the current study, we also observed a decrease in soil pH after
harvest of celery and snow peas under magnetically treated water
treatment. It is speculated that there may be a relatively greater
soil acidification due to the release of greater organic acids with in
the rhizosphere by celery and snow pea plants irrigated with
magnetically treated water compared with plants irrigated with
water without magnetic treatment. Organic acids released in
rhizosphere may be responsible for desorption of P and K, and thus
making these nutrients more available to plants.
Increased Ca and P concentrations in celery shoots and Ca and
Mg concentration in snow pea pods under magnetically treated
water in current study also suggest an improved availability,
uptake, assimilation and mobilization of these nutrients within
plant system and may have contributed in improving the
productivity of celery and snow pea plants with magnetic
treatment of water. Duarte Diaz et al. (1997) reported an increase
in nutrient uptake by magnetic treatment in tomatoes. A marked
increase in P content of citrus leaves by magnetically treated water
was also reported by Hilal et al. (2002).
Our results of reduced Na concentration in snow pea pods
irrigated with magnetically treated saline water (1000 ppm
NaCl) suggest restricted Na loading into snow pea pods.
Magnetic treatment may be assisting to reduce the Na toxicity
at cell level by detoxification of Na, either by restricting the entry
of Na at membrane level or by reduced absorption of Na by plant
roots. Alternatively, the reduction of Na concentration in snow
pea pods may be associated with dilution effect of increased
yield when snow peas were irrigated with magnetically treated
saline water.
Although Na is required in some plants, particularly halophytes
(Glenn et al., 1999), high Na concentration is a limiting factor for
plant growth in most crops (Franc¸ois et al., 1994; Munns, 2002;
Muranaka et al., 2002). Excessive Na has detrimental effects on
electron transport and photosynthesis, and it also affects through
stomatal closure (Muranaka et al., 2002) which reduces assimilates
supply. Excessive Na may also disrupt the cell wall and increase the
permeability of the cell membrane, leading to increased solute
leakage from leaves at high salt concentration. It is also interesting
to note that the apparently reduced accumulation of Na in plants
with magnetically treated saline water in the current study may
have helped the plants to continue their growth with less
detrimental effects on plant yield.
The beneficial effects of magnetic treatment of some water
types in the current study may be due to some alterations within
plant system at biochemical level and their possible effects at cell
level. External electric and magnetic fields have been reported to
influence both the activation of ions and polarisation of dipoles in
living cells (Moon and Chung, 2000). Electromagnetic fields
(EMFs) can alter the plasma membrane structure and function
(Paradisi et al., 1993; Blank, 1995). Goodman et al. (1983)
reported an alteration of the level of some mRNA after exposure to
EMFs. Increased concentration of gibberellic acid-equivalents
(GAs), indole-3-acetic acid (IAA) and trans zeatin were reported in
sunflower plants under field up application of magnetic field,
whereas concentrations of these hormones decreased in magnetic
field of the opposite direction (Turker et al., 2007). The above
statements further suggest that the magnetic treatment of water
probably alters something in water, makes the water more
functional within plant system and therefore probably influences
the plant growth at cell level. Magnetic treatment of water may
also affect phyto-hormone production leading to improved cell
activity and plant growth.
3.8. Practical implications and future research needs
Results of the glasshouse experiments reveal differential
beneficial effects of magnetically treated potable water, recycled
water and saline water irrigation on the yield and water
productivity of celery, snow pea and pea plants. The effects of
magnetic treatment of recycled water and 3000 ppm saline water
were significant on plant yield and water productivity (kg of fresh
or dry produce per kL of water used) of celery, but the effects of
magnetic treatment of potable water and 1500 ppm saline water
were non-significant. In snow peas, there were significant effects of
magnetic treatment of potable water, recycled water and
1000 ppm saline water, but there was non-significant effect of
500 ppm saline water. On the other hand, in pea plants, the effects
of magnetic treatments were non-significant for all the water
types. In pea plants, their short growing period to harvest and salt
injury effects probably confounded the treatment effects, leading
Table 6
Effects of magnetic treatment of irrigation water types on mean values of soil EC
1:5
,pH
1:5
, available P and extractable K after celery harvest.
Water source Soil EC
1:5
(
m
S/cm at 25 8C) Soil pH
1:5
Available P (mg/kg soil) Extractable soil K
Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean Control Magnetic
treatment
Mean
Potable water 482 468 475 6.14 5.98 6.06 19.43 19.29 19.36 697.4 695.9 696.7
Recycled water 619 686 653 6.15 5.98 6.07 20.7 22.35 21.53 725.3 740.2 732.7
1500 ppm saline water 1556 1541 1549 5.91 5.97 5.94 20.17 24.55 22.36 723.9 735.5 729.7
3000 ppm saline water 2163 2297 2230 5.94 5.94 5.94 22.03 26.44 24.24 724.5 753.6 739.0
Mean 1205 1248 1227 6.04 5.97 6.00 20.58 23.16 21.87 717.8 731.3 724.5
LSD
0.05
water 66 0.08 0.68 7.24
LSD
0.05
magnetic NS 0.06 0.48 5.12
LSD
0.05
water magnetic 93 0.11 0.96 10.24
B.L. Maheshwari, H.S. Grewal / Agricultural Water Management 96 (2009) 1229–1236
1235
to very little effect of magnetic treatment of water. These results
raise some interesting but critical questions that need further
explanation, research and experimentation. For example, one key
question is that why magnetic treatment failed to have any effect
on yield under potable water and 1500 ppm saline water
treatment in celery plants and 500 ppm saline water treatment
in snow pea plants.
Improved water productivity with magnetic treatment of water
in the current study could help in the sustainability of water
resources, particularly in the use of recycled and saline waters for
irrigation. As water productivity is based on the amount of yield
and water required to produce this yield, the increased yield of
both celery and snow peas under magnetically treated water
irrigation mainly contributed to the increase in the water
productivity of the two plant types in the current study.
The results of the current study demonstrate some significant
effects of magnetically treated irrigation water on water productiv-
ity, yield and nutrient composition of snow pea and celery plants
under some conditions. However, the study has raised some
important questions that must be answered before any unequivocal
conclusion could be reached as to the usefulness of the magnetic
treatmentin improving crop yield andwater productivity at farmer’s
field. In particular, the questions are: (a) why did the magnetic
treatment improve the plant yield and water productivity in some
instances and not in others? (b) how does the magnetic treatment
affect water, soil and plant? and (c) will the magnetic treatment of
irrigation water have significant benefits under field conditions?
4. Conclusions
The magnetic treatment of irrigation water resulted in statis-
tically significant increases in the yield and water productivity
for celery and snow pea plants in some instances. However, it had
no significant effect on the yield and water productivity for pea
plant. This means, before this technology can be recommended
to farmers, it will be critical to clearly understand the
mechanisms and processes that affect plant yield and water
productivity through the magnetic treatment, the conditions
under which it will work and the extent of its effectiveness under
field situations.
The effect of magnetic treatment of irrigation water on the total
water used for any of the plant types included was not significant
in this study.
Under some circumstances, when compared with the control
treatment, the magnetic treatment of irrigation water tends to
change soil pH, EC, available P and extractable K measured at the
crop harvest.
Overall, the data collected in this preliminary study under
controlled conditions in glasshouse situation suggest that there
are possibly some beneficial effects of the magnetic treatment of
irrigation water for the plant yield and water productivity. As
such, the results need to be further tested under field conditions
to assess the usefulness of magnetic treatment of irrigation water
in crop production.
Acknowledgement
The authors wish to thank Omni Environmental Group Australia
Ltd. for providing funds to undertake this work. Also, thanks to Mr
B. Simmons from University of Western Sydney for his valuable
input during the study.
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