Influence of Arsenic on Rice Growth and its Mitigation with Different Water Management Techniques
Rice is the staple food for more than half of the worlds population. Arsenic (As) contaminated irrigation water (groundwater) is a threat to irrigated rice cultivation. A pot study was conducted to mitigate Arsenic (As) problem in rice by two water managements (aerobic and anaerobic) practices. In this study two rates of As (0 and 40 mg kg-1) were applied as; aerobic As0, anaerobic As0, aerobic As40 and anaerobic As40 and other two treatments were kept as aerobic As40a (before flowering anaerobic and after flowering aerobic) and anaerobic As40b (before flowering aerobic and after flowering anaerobic). A rice variety, BRRI dhan28, was grown. Application of 40 mg kg-1 As significantly affected plant growth in anaerobic condition. The higher seedling survibility, filled grain and yield were in aerobic condition. The tissue analysis showed that plant grown in aerobic condition contained less contents of As in root (20%), straw (97%) and grain (61%). Thus, aerobic rice cultivation can be a sustainable technology to mitigate arsenic problem in rice at arsenic contaminated soil.
Received: July 11, 2014;
Accepted: September 15, 2014;
Published: November 13, 2014
Food security is the condition of having enough food to provide adequate nutrition
for a healthy life and nowadays it becomes a critical issue for the developing
world. Nearly half the worlds population depends on rice for their survival.
In Asia as a whole, much of the population consumes rice in every meal. Rice
is also the staple food crop of Bangladesh and farmed in watery conditions.
Farmers are applying imbalanced doses of fertilizer, insecticide and pesticide
to their rice field to harvest maximum yield from their small piece of land
which is creating environmental pollution as well as one of the causes of climate
change. Besides these consequences rice cultivation with arsenic contaminated
irrigation water brought another risk for human health. The higher arsenic contents
have been observed in the top layer of soil (Haq et
al., 2013). The major cause of As contamination in soil is the mining
of coal and oil as well as mining and metallurgy of non-ferrous metals (Lozna
and Biernat, 2008). Furthermore, drinking water is the source of arsenic-rich
rocks through which the water has filtered. The practice of groundwater for
irrigation purpose has increased As concentrations and approximately 80% of
pumped groundwater is being applied for crops. Therefore, it has a possibility
of arsenic accumulation in rice and rice plants from irrigation water (Delowar
et al., 2005). Long term use of arsenic contaminated ground water
for irrigationaccumulating As in the agricultural soil and eventually in rice
plant. The added arsenic gradually accumulates in the topsoil and amounts now
appear to be reaching toxic levels to rice in some soils that had been irrigated
with highly As contaminated water for 10-20 years or more (Brammer,
Rice plant grown in As contaminated soil accumulated arsenic in grain and straw.
In some cases, human As intake from the consumption of rice exceeds that from
drinking water (Williams et al., 2006). So rice
is a major source of dietary intake of inorganic As among the rice feeding population.
Therefore, necessary steps should be taken to mitigate the excessive accumulation
of As in rice plant. Many areas of Bangladesh are already contaminated with
arsenic and in dry season and there is no other option for irrigation except
As contaminated ground water. Some studies showed that rice grown under flooded
conditions accumulated more As than that grown under aerobic condition. Contamination
by As occurs greater in rice plant than other upland crops because of the anaerobic
conditions that lead to arsenic mobilization causing enhanced bioavailability
to rice (Takahashi et al., 2004). Although,
rice plant need trace amount of arsenic for its growth and development, excessive
amount causes physiological disorder that finally reduced crop yield. Study
reports proved that higher amount of As significantly reduced plant height,
effective tiller number, straw weight and grain yield of rice (Wang
et al., 2006; Hu et al., 2013).
Bangladesh is a densely populated agriculture based country and facing intense
pressure to grow more food using existing facilities. There is no other option
for rice production except in arsenic contaminated soil or contaminated irrigation
water. A solution is needed in order to grow rice in this soil and water with
minimum arsenic accumulation in paddy and straw. The main objective of the present
study was to investigate the effect of As on rice growth and its mitigation
by water management techniques.
MATERIALS AND METHODS
Experimental site, soil and treatments: Experiment was conducted in
September, 2013 at a greenhouse of the Soil Science Division (SSD), Bangladesh
Rice Research Institute (BRRI), Gazipur, Bangladesh. Two rates of arsenic (As0
and As40 mg kg¯1) with two different water management
practices (aerobic and anaerobic) were selected. The treatments were: (1) Aerobic
As0, (2) Anaerobic As0, (3) Aerobic As40, (4)
Anaerobic As40, (5) Aerobic As40a (before flowering anaerobic
and after flowering aerobic) and (6) Anaerobic As40b (before flowering
aerobic and after flowering anaerobic). The last two treatments were selected
to evaluate the effect of irrigation after flowering on grain yield of rice
grown in high soil As condition. The experiment was conducted with a completely
randomized design with 4 replications. The pot size was 22.5 cm high×28.5
cm diameter and each filled with 6 kg air dried; sieved (2 mm) soil. Soil of
the experimental field is clay loam in texture. Initial properties of the surface
soil (0-15 cm depth) were as follows: pH 6.04, organic carbon 1.2%, available
phosphorus (P) 8.7 mg kg¯1 (0.5 M NaCO3 extracted)
and exchangeable potassium (K) 0.26 meq/100 g soil (Neutral 1.0 N NH4OAc
extracted). Soil for the pot study was collected from an As contaminated area
in Bangladesh contains 3.21 mg kg¯1 As. Five seedlings of BRRI
dhan46 (Twenty five days old) were uprooted and transplanted in each pot. A
concentration of 40 mg kg¯1 arsenic was prepared by dissolving
AsNaO2 in distilled water and mixed in to the soil before transplanting
the rice seedlings. The greenhouse was kept almost outside temperature, light
Water management and fertilizer application: Water was applied to all
pots for seedling establishment and maintained according to respective. For
aerobic condition, water was maintained at field capacity by drain out excess
water and for anaerobic the pots were maintained flooded throughout the growth.
Fertilizers were given as equivalent (calculated by the soil weight basis) of
115, 20, 60 kg ha¯1 of N, P and K in the form of urea, Triple
Super Phosphate (TSP) and Muriate of Potash (MOP), respectively. The full amount
of TSP and MOP were applied during soil preparation and one third of urea was
applied after 7 days of transplanting. The remaining quantity of urea was applied
at plant tillering and heading stages.
Harvesting: Rice plants were harvested at physiological maturity
stage. The quantitative characters like plant height, tiller number, effective
tiller number, panicle length, number of spikelets and number of filled grain,
sterility percentage, 1000 grain weight and yield were recorded.
Arsenic determination in the rice plant and soil: At harvesting time,
root, straw and grain samples were collected and dried by keeping in oven (80°C)
for three days. Total As content was determined by digesting the soil, root,
paddy and straw samples with tri-acid mixture (HNO3:HClO4:H2SO4,
5:2:1) until it became whitish or clear. Both the initial and post-harvest soil
samples were collected for As analysis following the same procedure.
Sample preparation and digestion: Rice samples were sun-dried and about
1 g samples were taken separately into digestion tube and 10 mL of 69% concentrated
nitric acid and 70% of perchloric acid mixture at the ratio of 5:3 was added.
The samples were left to react overnight in a chemical hood and then heated
in a block digester (M-24 plazas/samples, JP Selecta, Spain) at 120°C until
colourless clear watery fluid appeared. Tubes were gently shaken several times
to facilitate destroying all the carbonaceous material. This digestion converts
all arsenicals to inorganic arsenic for FI-HG-AAS determination. Tubes were
removed from the digestion block, cooled, diluted to 50 mL adding Millipore
water, filtered through filter paper and stored in 50 mL plastic bottles.
Clean and oven-dried rice straw samples were digested as described by Wang
et al. (2006) with modifications. About 0.45-0.50 g rice straw was
weighed after further drying at 60°C to constant weight. It was taken separately
into digestion tube and 7 mL of 69% concentrated nitric acid was added and similar
procedures were followed as before.
Detection of arsenic: The digest was cooled and then filtered and finally
the volume was made up to 50 mL. Concentrations of arsenic in digested samples
were determined using Atomic Absorption Spectrophotometer (AAS), model PG-990
equipped with a computer with Atomic Absorption (AA) Win software (PG Instruments
Ltd., UK) as described by Samanta et al. (1999).
Briefly, samples were spiked with standards at different concentrations. For
constructing standard curve, working standards of 0, 2.5, 5, 10, 15 and 20 ppb
were prepared immediately before use by serial dilution of the stock in 10%
hydrochloric acid. Samples exceeding the standard curve range were diluted again
and analyzed further. The concentration of arsenic in those samples was calculated
by multiplying the appropriate dilution factor. Sample solution concentrations
were determined by direct comparison with the calibration curve and the reading
was automatically transferred to AA Win software. Concentration of arsenic in
the sample was calculated from the following equation:
Statistical analysis: The data was analyzed using SPSS 16.0-a statistical
software and Microsoft Excel 2010. The analysis of variances (ANOVA) for rice
growth and yield parameters of BRRI dhan46 were done for Least Significance
Difference (LSD). Duncans Multiple Range Test (DMRT) was used for mean
comparisons of the treatments at 5% probability level.
RESULTS AND DISCUSSION
Survivability of transplanted seedling and vegetative growth of rice: Transplanted
seedlings were grown in each experimental pot with the selected treatments and
found in various responses. Normal vegetative growth and development was observed
among all the seedlings grown in aerobic and anaerobic conditions at As control
treatment. On the other hand, abnormal growth or even mortality of seedling
was noticed in both water management conditions at 40 mg kg¯1
arsenic (As40) treated soil. Compared with both water management
systems the seedling mortality rate was higher in the anaerobic than aerobic
condition. At 21 Days after Transplanting (DAT) only 3 seedlings were survived
at 40 mg kg¯1 arsenic in anaerobic condition, however at the
same time, more than 4 seedlings were survived in aerobic treatment. With the
time being, the toxic effect of As become more prominent in both the aerobic
and anaerobic condition and at 45 DAT only 2-3 seedlings per pot were alive
(Fig. 1). Moreover, comparatively better growth and survivability
of the rice plant was found in aerobic condition with 40 mg kg¯1
arsenic than that of anaerobic state with the same level of applied arsenic
||Survivability of transplanted seedling with and without As
treated soil at different water management up to 45 DAT
||Effect of arsenic on vegetative growth of rice at different
water management practices
||Effect of different levels of As on different parameters of
|Mean values without common letters are statistically significant
(DMRT, p≤0.05), *Before flowering anaerobic and after flowering aerobic,
**Before flowering aerobic and after flowering anaerobic
Arsenic contamination reduced tiller production in rice plant. Maximum tiller
number (18) was found in the pots treated with As0 in anaerobic state,
on the contrary minimum tillers (5) per pot was observed with anaerobic As40
which was followed by anaerobic before flowering As40b treatment.
It indicated that higher arsenic content significantly decreased tiller number
per pot (Table 1 and Fig. 3). Similar findings
were observed by the Azad et al. (2012) that
the highest values of plant height and straw yield was observed at lower As
concentrations however, the highest tillers number, panicles number, panicle
length and grain yield were found in control treatment.
High soil As had profound effect on the plant height reduction. Similar reports
were observed by Abedin et al. (2002) that As
contaminated irrigation water significantly reduced the plant height. In our
study, the plant height was found to be reduced significantly in 40 mg kg¯1
of As treated soil in both water management practices. More significant reduction
was observed in anaerobic As40 (55 cm) and anaerobic before flowering
As40b (64 cm) treatments than that of aerobic treatments with all
the conditions. However, the tallest plant height was observed in anaerobic
As0 treated pot where the inherent soil arsenic was 3.21 mg kg¯1.
||Effects of different As treatments on spiklets and% sterility
of rice. Bars indicate standard error, n = 4
Yield and yield contributing characters: Arsenic significantly affected
rice yield and yield contributing characters. Rice yield decreased when grown
in As contaminated soils. Similarly, Dilday et al.
(2000) reported more straight head with blank florets and distorted lemma
and palea of rice due to arsenic (6.8 ka ha¯1) contamination.
In general, detrimental effect was more prominent when rice was grown in anaerobic
environment compared to aerobic state (Fig. 4). Application
of As 40 mg kg¯1 in each pot showed a strong negative influence
on the panicle number, filled spikelet, grain and straw yield as compared to
As0 treatment (Table 1). Detrimental effect of
As application on panicle number and grain yield was also reported by Islam
et al. (2004) and Liu and Goa (1987). In
contrast the adverse effect of As contamination on yield was lower in aerobic
condition than anaerobic condition. Even though, the yield in As treatment under
aerobic condition was significantly less than in control treatment, the yield
was higher than that in anaerobic condition. This indicates that, high level
of As had suppressing effect on rice yield, but aerobic condition alleviated
the suppressing effect to some extent. Irrigation after flowering of plant initially
grown in aerobic condition affected the yield. Higher number of spikelets per
pot and less sterility percentage were obtained under aerobic condition compared
to anaerobic condition and this ultimately reflected on higher rice yield (Fig.
Plant uptake and soil arsenic content: Arsenic uptake by plant depends
on its availability in the soil system and As accumulation in different plant
parts increasing with increased the As concentrations (Wang
et al., 2006; Hu et al., 2013).
||Effect of arsenic on reproductive growth of rice at different
water management practices
||Concentration of As in soil at harvest at different treatment
It was reported that flooded paddy soil lead to soil As mobilization and enhanced
bioavailability for plant (Xu et al., 2008; Takahashi
et al., 2004). In the present study, higher As content was found
in rice root than straw followed by the grain irrespective of As addition (initial
soil As was 3.21 mg kg¯1) (Table 2). In anaerobic
condition the accumulation of As in the rice roots and show significantly higher
than that in aerobic condition even without addition of As in soil. Plants grown
in aerobic before flowering also uptake less As (13% in grain, 94% in straw
and 23% in grain) compared to plant subjected to anaerobic condition after flowering
(Table 3). Obviously, the increase of As in different parts
of rice plant was very high in anaerobic condition with aerobic situation which
ultimately influenced rice yield parameters and drastically decreased yield.
It was found that the anaerobic condition in soil released iron oxides that
may also increase inorganic As content.
||Arsenic content in root, straw and grain of BRRI dhan46 with
and without As treated soil
|Values (Mean± SD) without common letters are statistically
significant (DMRT, p≤0.05), *Before flowering anaerobic and after flowering
aerobic, **Before flowering aerobic and after flowering anaerobic
||Plant tissue and grain arsenic content decreased (%) in aerobic
condition compared to anaerobic cultivation method
|*Before flowering anaerobic and after flowering aerobic, **Before
flowering aerobic and after flowering anaerobic
Li et al. (2009) proved a rapid rise in As
concentration as Eh dropped below 200 mv. On the other hand, in the oxidative
condition and also due to rice root respiration, iron plaque form in the rhizosphere
resulting oxidation of ferrous iron to ferric iron and the precipitate iron
oxide on the root surface. It might be due the retention of applied As is generally
important, since most of the As remained in the rooting zone, where it would
have the greatest direct impact on plant processes (Khan
et al., 2009). The Fe oxides have strong adsorptive capacity for
arsenate that reduce the availability for plant uptake (Chen
et al., 2005). Arsenic uptake by rice root can be influenced by the
presence of dominant species in soil solution, root morphology, presence of
Fe, P and Si (Sun et al., 2008; Abedin
et al., 2002).
Higher amount of As was retained in post-harvest soil of aerobic condition
compared to anaerobic condition (Fig. 5). This indicates that
anaerobic condition may increase the soil As availability and create a congenial
situation for higher uptake by the plants resulting in poor plant growth and
It may be concluded that As has a detrimental effect on plant growth and yield
of rice. In high As condition, the growth of rice plant was comparatively better
under aerobic than anaerobic condition because of less As uptake by plant and
higher As retention in soil. Aerobic condition does not create a congenial atmosphere
of bio-available As in rice root rizosphere for plant uptake. Thus, in high
As prone area rice can be cultivated under aerobic condition to minimize As
uptake and obtained better yield compared to under flooded condition.
The authors are grateful to National Agricultural Technology Project Phase-1,
Bangladesh Rice Research Institute (BRRI), Ministry of Education (MOE), Malaysia
for Long-term Research Grant Scheme-LRGS (Food Security) and Universiti Putra
Malaysia technical and financial support.
1: Abedin, M.J., J. Cotter-Howells and A.A. Meharg, 2002. Arsenic uptake and accumulation in rice (Oryza sativa L.) irrigated with contaminated water. Plant Soil, 240: 311-319.
2: Azad, M.A.K., A.H.M.F.K. Mondal, M.I. Hossain and M. Moniruzzaman, 2012. Effect of arsenic amended irrigation water on growth and yield of BR-11 rice (Oryza sativa L.) grown in open field gangetic soil condition in Rajshahi. J. Environ. Sci. Nat. Resour., 5: 55-59.
3: Khan, M.A., M.R. Islam, G.M. Panaullah, J.M. Duxbury, M. Jahiruddin and R.H. Loeppert, 2009. Fate of irrigation-water arsenic in rice soils of Bangladesh. Plant Soil, 322: 263-277.
4: Brammer, H., 2007. Arsenic accumulation in irrigated paddy soils and possible mitigation methods. Proceedings of the Symposium on Geography of a Global Problem, August 30, 2007, University of Cambridge, UK -
5: Chen, Z., Y.G. Zhu, W.J. Liu and A.A. Meharg, 2005. Direct evidence showing the effect of root surface iron plaque on arsenite and arsenate uptake into rice (Oryza sativa) roots. New Phytol., 165: 91-97.
6: Delowar, H.K., I. Yoshida, M. Harada and M. Imtiaz Uddin, 2005. Effect of arsenic-contaminated water on food chain in Bangladesh: Analysis of arsenic in soil, water and plants. Int. J. Food Agric. Environ., 3: 282-286.
7: Dilday, R.H., N.A. Slaton, J.W. Gibbons, K.A. Moldenhauer and W.G. Yan, 2000. Straighthead of rice as influenced by arsenic and nitrogen. Research Series Arkansas Agricultural Experiment Station No. 476, pp: 201-214.
8: Haq, M.R., M.M. Rahman, P. Islam, M.A. Awal, S. Chakma and U.K. Roy, 2013. Detection of arsenic in animal feed chain: Broken rice and water hyacinth. Bangladesh J. Vet. Med., 10: 111-116.
9: Hu, P., J. Huang, Y. Ouyang, L. Wu and J. Song et al., 2013. Water management affects arsenic and cadmium accumulation in different rice cultivars. Environ. Geochem. Health, 35: 767-778.
CrossRef | Direct Link |
10: Islam, M.R., M. Jahiruddin and S. Islam, 2004. Assessment of arsenic in the water-soil-plant systems in gangetic floodplains of Bangladesh. Asian J. Plant Sci., 3: 489-493.
CrossRef | Direct Link |
11: Li, R.Y., J.L. Stroud, J.F. Ma, S.P. McGrath and F.J. Zhao, 2009. Mitigation of arsenic accumulation in rice with water management and silicon fertilization. Environ. Sci. Technol., 43: 3778-3783.
12: Liu, G.L. and S.D. Goa, 1987. The effect of arsenic in red soil on crops. J. Soil Sci., 18: 231-233.
13: Lozna, K. and J. Biernat, 2008. [The occurrence of arsenic in the environment and food]. Roczniki Panstwowego Zakadu Higieny, 59: 19-31, (In Polish).
14: Samanta, G., T.R. Chowdhury, B.K. Mandal, B.K. Biswas and U.K. Chowdhury et al., 1999. Flow injection hydride generation atomic absorption spectrometry for determination of arsenic in water and biological samples from arsenic-affected districts of West Bengal, India and Bangladesh. Microchem. J., 62: 174-191.
15: Sun, G.X., P.N. Williams, A.M. Carey, Y.G. Zhu and C. Deacon et al., 2008. Inorganic arsenic in rice bran and its products are an order of magnitude higher than in bulk grain. Environ. Sci. Technol., 42: 7542-7546.
16: Takahashi, Y., R. Minamikawa, K.H. Hattori, K. Kurishima, N. Kihou and K. Yuita, 2004. Arsenic behavior in paddy fields during the cycle of flooded and non-flooded periods. Environ. Sci. Technol., 38: 1038-1044.
17: Wang, F.M., Z.L. Chen, L. Zhang, Y.L. Gao and Y.X. Sun, 2006. Arsenic uptake and accumulation in rice (Oryza sativa L.) at different growth stages following soil incorporation of roxarsone and arsanilic acid. Plant Soil, 285: 359-367.
18: Williams, P.N., M.R. Islam, E.E. Adomako, A. Raab and S.A. Hossain et al., 2006. Increase in rice grain arsenic for regions of Bangladesh irrigating paddies with elevated arsenic in groundwaters. Environ. Sci. Technol., 40: 4903-4908.
CrossRef | PubMed |
19: Xu, X.Y., S.P. McGrath, A.A. Meharg and F.J. Zhao, 2008. Growing rice aerobically markedly decreases arsenic accumulation. Environ. Sci. Technol., 42: 5574-5579.