Arsenic mitigation strategy for rice, using water regime management

S.M. Imamul Huq, U.K. Shila and J.C. Joardar

Abstract

The response of two varieties of rice plant (BR-28 and BR-29) to arsenic accumulation added from two sources (AsIII and AsV) under two different water regimes (100 and 75% of field capacity) were examined. Treatments added to soil were 0, 10, 20 and 40 mg As/kg soil. Plant samples were collected after 120 and 140 days from seed sowing, for BR-28 and BR-29 respectively. Delayed seed-ling emergence; reduced plant growth; yellowing and wilting of leaves; brown necrotic spots on old leaves; and, finally, reduced grain yield of the two varieties, confirmed the symptoms of As toxicity. Arsenic accumulation by plants growing with either AsIII or AsV increased with increasing As treat-ment, irrespective of water regimes. However, the accumulation was greater in the arsenite-treated soil than that in the arsenate-treated one, indicating the higher phytoavailability of AsIII. Most of the As taken up by plants was sequestered in the root, followed by straw and grain. In roots of BR-28, the maximum As accumulation from arsenite-treated soil was 17.6 mg/kg dry weight (d.w.) at 100% field capacity (f.c.), whereas at 75% f.c. it was 15.4 mg/kg d.w. and for the roots of BR-29 the values were 31.04 mg/kg d.w and 22.65 mg/kg d.w. at 100 and 75% of f.c. respectively. Arsenic in straw and grain was lower for plants of both varieties at 75% of f.c. However, there have been some varietal differences in the response to AsIII or AsV. The paper discusses the possible management of moisture regimes to reduce the phytoavailability of arsenic, thereby mitigating its toxicity in the rice crop.

Key words: arsenate, arsenic, arsenite, mitigation, rice, water regime

© 2007 EPP Publications Ltd

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Article code 798