Elsevier

Science of The Total Environment

Volume 609, 31 December 2017, Pages 311-318
Science of The Total Environment

Effect of irrigation and genotypes towards reduction in arsenic load in rice

https://doi.org/10.1016/j.scitotenv.2017.07.111Get rights and content

Highlights

  • The concentrations of arsenic (As) in rice grains are cultivar dependent.

  • High grain As bioaccumulation was detected in plants in areas of high soil As.

  • AWD irrigation practice reduced 17% to 35% of grain As concentration.

  • 7% to 38% increase in rice grain yield under AWD irrigation practice.

  • Moderate to high level of As contaminated soils some varieties are quite promising.

Abstract

Arsenic (As) bioaccumulation in rice grains has been identified as a major problem in Bangladesh and many other parts of the world. Suitable rice genotypes along with proper water management practice regulating As levels in rice plants must be chosen and implemented. A field study was conducted to investigate the effect of continuous flooding (CF) and alternate wetting and drying (AWD) irrigation on the bioaccumulation of As in ten rice cultivars at three locations having different levels of soil As and irrigation water As. Results showed that As concentration in different parts of rice plants varied significantly (P < 0.0001) with rice genotypes and irrigation practices in the three study locations. Lower levels of As in rice were found in AWD irrigation practice compared to CF irrigation practice. Higher grain As bioaccumulation was detected in plants in areas of high soil As in combination with CF irrigation practice. Our data show that use of AWD irrigation practice with suitable genotypes led to 17 to 35% reduction in grain As level, as well as 7 to 38% increase in grain yield. Overall, this study advances our understanding that, for moderate to high levels of As contamination, the Binadhan-5, Binadhan-6, Binadhan-8, Binadhan-10 and BRRI dhan47 varieties were quite promising to mitigate As induced human health risk.

Introduction

Arsenic is recognized as a toxic and carcinogenic element (Group I) which is widely distributed in the environment. Presence of As in groundwater poses a significant threat to human health. In many regions of the world including Bangladesh, shallow tube-well water in different locations is heavily contaminated with As. Apart from its domestic use about 86% of these water sources are being used for irrigation (Saha and Ali, 2007), particularly in dry seasons crops, especially Boro season rice which contributes about 60% to rice production in Bangladesh. It has been estimated that 900 to 1360 tons of As end up on arable land in south and southwest Bangladesh due to irrigation with As-contaminated groundwater annually (Ali, 2003). It is well documented that compared to the other cereal crops rice accumulates appreciable levels of As since it is grown under flooded conditions which are conducive to high bioaccumulation of As (Talukder et al., 2012, Williams et al., 2007, Xu et al., 2008). Irrigation using As-contaminated groundwater also results in significant loading of As in soil and as a consequence bioaccumulation of As in rice grains for rainy season rice can also occurred (Islam et al., 2007, Meharg and Rahman, 2003). Elevated levels of As have also been shown to lead to substantial yield losses (Khan et al., 2009, Panaullah et al., 2009).

Rice is the staple food crop of half of the world's population and it provides the main nutritional input for many countries. Therefore, rice itself is an important exposure source of As intake for humans, especially for people consuming substantial amounts of rice in their diet. Given the risk that As poses to human health, mitigation strategies are needed to reduce the transfer of As from root to rice grain to minimize the human exposure risks due to rice consumption. Under aerobic conditions the smallest As bioaccumulation was found in rice straw and grain (Li et al., 2009) but anaerobic conditions enhanced As uptake in rice plant (Talukder et al., 2012). Research showed that aerobic soil conditions resulted in a 10–fold smaller amount of As uptake among a set of several hundred global cultivars compared to a flooded field (Norton et al., 2012). Similar results were obtained from a greenhouse experiment, where maintaining soil under aerobic conditions decreased As concentration in rice grain and straw by 10 to 20-fold, and 7 to 63-fold, respectively, compared with continuous flooded rice (Li et al., 2009, Xu et al., 2008). It was also observed that intermittent flooding reduced As uptake (23% in root, 14% in shoot and 20% in leaf) at panicle initiation stage, instead of continuous flooding (Rahaman et al., 2011). In another field study in Bangladesh, a site employing intermittent irrigation showed lower grain-As content than another site under continuous flooded conditions (Stroud et al., 2011). A field study carried out at Stuttgart, Arkansas, showed that grain contained 41% less As in an intermittently flooded paddy field than in continuous flooded one (Somenahally et al., 2011). Talukder et al. (2011) found that the As concentrations in grain and straw decreased by 62% and 86%, respectively.

Water management and rice cultivars dramatically affect the concentration of As in rice grains and therefore, the combination of water management and use of cultivars that are low As accumulators can reduce As in rice grains. Some research has reported that the use of different water management practice may help reduce bioaccumulation of As in rice (Hu et al., 2013, Liao et al., 2016, Newbigging et al., 2015, Zhang et al., 2015). Using a rice cultivar that thrives under low moisture content may also reduce the amount of As in a paddy field from irrigation of As-contaminated groundwater. Few studies have reported the differences in rice genotypes in As bioaccumulation from As-contaminated soils and irrigation water (Hu et al., 2013, Liao et al., 2016, Zhang et al., 2015). Selecting appropriate water management practices and suitable rice genotypes is likely to reduce As uptake and enhance food security by improving greater productivity. A few published articles have reported on the use of different water management practices in combination with rice genotypes; they can reduce the levels of As in rice. Most studies, however, were based on pot experiments under controlled environments or greenhouse conditions. There is a need to investigate As bioaccumulation under field conditions using commonly grown rice genotypes to determine the level of this bioaccumulation. In this study, we investigated water management options and rice genotypes in three different As graded field sites in Bangladesh to determine: (1) the influence of water management on minimizing As bioaccumulation; (2) genotypic performance to reduce As bioaccumulation in rice; and (3) select rice genotypes that accumulate low As with suitable irrigation practices to grow in As affected areas in Bangladesh.

Section snippets

Experimental sites

Three levels of As-contaminated farmers' rice paddy fields were selected for this study; firstly, one in Domrakandi, Faridpur Sadar, Faridpur (23°34′39.9″N 89°48′16.2″E), a district in central Bangladesh; secondly, one in Damkura, Paba, Rajshahi (24°23′11.9″N 88°32′23.4″E), located in north-western Bangladesh; and thirdly, one at the experimental farm of Bangladesh Agricultural University (BAU), Mymensingh (24°43′11.3″N 90°25′35.7″E), a district of central Bangladesh. The study sites have a

Impact of water management and soil as on grain yield

The AWD irrigation option has a positive impact on rice grain yields (Fig. 1). There was a significant (P < 0.05) yield difference among the cultivars for both CF and AWD irrigation practices. Water management yielded a significant effect on rice productivity with the yield potential of all rice genotypes being very different. The grain yield using the continuous flooding option ranged between 3.9 and 6.1 t/ha, whereas under the AWD irrigation option it ranged between 4.8 and 7.5 t/ha. Compared

Conclusions

Applying AWD water management techniques prove to be highly effective in combating the problem of excessive bioaccumulation of As in rice grains. There was a 17% to 35% decline in grain As concentration under AWD irrigation practice compared to CF irrigation among the rice cultivars. The concentrations of As in rice grains are cultivar dependent which means rice genotypes showed significant differences in As bioaccumulation in rice. Selecting appropriate water management practices and rice

Acknowledgement

The first author thanks the University of Newcastle, Australia for the scholarship support. Financial support from CRC CARE (PG080760) is greatly acknowledged to conduct this study. The authors are also grateful to the authority of the University of South Australia for the laboratory support for this study. Technical assistance from Dr. Sadequl Amin in preparing and analyzing samples are greatly acknowledged. Statistical support from Kim Colyvas, Statistical Consulting Unit Manager, Faculty of

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