Effect of water management on cadmium and arsenic accumulation by rice (Oryza sativa L.) with different metal accumulation capacities

Abstract

Purpose Water management affects the bioavailability of cadmium (Cd) and arsenic (As) in the soil and hence their accumulation in rice grains and grain yields. However, Cd and As show opposite responses to soil water content, but information, particularly on irrigation, is missing on a field scale. The purpose of the present study was therefore to find a water management regime that can lower accumulation of both Cd and As in grain without yield loss. Materials and methods Two rice (Oryza sativa L.) cultivars, A16 and A159, with different grain Cd accumulation capacities were employed in field plot experiments with four water management regimes comprising aerobic, intermittent, conventional practice and flooded. The dynamics of Cd and As bioavailability in the soil and Cd and As concentrations in roots, straw and grains were determined at the early tillering, full tillering, panicle initiation, filling and maturity stages of crop growth. Results and discussion The lower water content regimes (aerobic and intermittent) mostly led to higher soil HClextractable Cd than the higher soil water content regimes (conventional and flooded). HCl-extractable As in contrast was favoured by the higher soil water content treatments. Conventional and flooded irrigation accordingly gave higher plant As concentrations but lower Cd compared to aerobic and intermittent irrigation. Cd concentrations in roots and straw of both varieties increased with growth stage, especially in aerobic and intermittent regimes, while As concentrations in plants showed little change or a slight decrease. As the water irrigation volume increased from aerobic to flooded, brown rice Cd decreased from 1.15 to 0.02 mgkg −1 in cultivar A16 and from 1.60 to 0.05 mgkgin cultivar A159, whereas brown rice As increased. Aerobic and flooded treatments produced approximately 10-20 % lower grain yields than intermittent and conventional treatments. Cultivars with low Cd accumulation capacity show higher brown rice grain As than those with high Cd uptake capacity.Conclusions Of the four water management regimes, the conventional irrigation method (flooding maintained until full tillering followed by intermittent irrigation) ensured high yield with low Cd and As in the brown rice and so remains the recommended irrigation regime.

Effects of water management on arsenic and cadmium speciation and accumulation in an upland rice cultivar

“…Comparatively, intermittent and intermittent-aerobic conditions in pot conditions and the conventional regime (e.g., flooding-intermittent) were suitable for acceptable yields of this cultivar. Furthermore, the responses of As and Cd accumulation in this upland rice cultivar to water management in this study are similar to those of lowland rice cultivars used in previous studies (Hu et al, 2013a(Hu et al, , 2013b. Therefore, it can be speculated that the accumulation of As and Cd in the grains is mainly dependent on elemental availability in the soil as influenced by water management no matter what rice cultivar is grown.…”

“…However, Cd concentrations in straw, husk and brown rice decreased markedly in higher irrigation regimes (flooding and conventional) compared to aerobic and intermittent treatments under field conditions. Thus, irrigation regime merits special attention in the mitigation of metal(loid) accumulation in rice grains when crops are grown in soils with combined pollution by As and Cd (Hu et al, 2013a(Hu et al, , 2013b.…”

“…Selection and breeding of rice cultivars with low As and Cd accumulation have been practiced to reduce As and Cd in the rice grains (Zhang and Duan, 2008;Li et al, 2012;Ye et al, 2012). Water management is another promising method that affects Cd and As bioavailability in soils and their subsequent uptake by rice (Arao et al, 2009;Rahaman et al, 2011;Hu et al, 2013b). When a paddy field is flooded and the soil has a low redox potential, any Cd present in the soil combines with sulfur (S) to form CdS which has low solubility in water (Bingham et al, 1976).…”

Solubility of trace metals in two contaminated paddy soils exposed to alternating flooding and drainage

“…Flooding conditions prevail during almost the entire cropping period, because lowland rice is extremely sensitive to water shortage (Kögel-Knabner et al, 2010). Flooded paddy soils undergo one or two drainage periods: one at the filling stage to enable faster rice ripening and easier harvesting and sometimes at the tillering stage to control ineffective tillering (Hu et al, 2013). During flooding of paddy soils, the redox potential (Eh) will decrease after the depletion of O 2 and subsequently the following reduction reactions will either sequentially or simultaneously take place: denitrification and transformation of Mn(III/IV) to Mn(II), of Fe(III) to Fe(II), and of SO 4 2 − to HS − (Murase and Kimura, 1997;Yu et al, 2007).…”

Effects of soil drying and wetting-drying cycles on the availability of heavy metals and their relationship to dissolved organic matter

“…Some of these properties can change with variation in soil moisture content and thus change soil metal availability (Cornu et al 2007). Studies have shown that water management can change soil metal mobility and availability and thus manipulate metal accumulation in rice plants (Yang et al 2009;Hu et al 2013;Xu et al 2013). However, the effects of soil drying during wetting-drying cycles on metal availability have received little consideration in these studies.…”