Effect of bentonite on arsenic uptake by beet leaf cultivar Pusa Bharti grown on contaminated soil

Abstract

Greenhouse experiments were conducted to assess the effect of bentonite amendment on arsenic uptake by beet leaf (Beta vulgaris L. bar. bengalensis Roxb.) cultivar Pusa Bharti. Application of bentonite to the contaminated soil increased biomass yield from 0.24 (control) to 0.44 g pot-1 @ 0.25% bentonite amended soil (T3) at first harvest and 0.65 g pot-1 @ 0.5% bentonite amended soil (T4) after second harvest over the two years. The bio-accumulation factor (%) of arsenic varied from 13.60 in control (T1) to 3.77 (T3) in soil amended with 0.25% bentonite at first harvest and reduced by 62.4% in the second harvest. The hazard quotient was significantly reduced below 0.50 because of 0.25 and 0.50% bentonite application after first and second harvest. The arsenic concentration in plants was reduced to 0.49 from 1.77 mg kg-1 in first harvest, while the values were 0.50 and 1.39 mg kg-1 in 0.5% amended and control soil, respectively after second harvest. Importantly, clay amendments effectively reduced the labile arsenic content up to 54.8 and 58.5% in soil during first and second harvest, respectively. Soil pH was raised significantly only in 0.5% clay amended soil (7.89) as compared to control (6.70) after complete crop harvest. The effect of bentonite application @ 0.25 and 0.5% was statistically at par in most of the parameters. Hence, it may be recommended that application of bentonite @ 0.25% may be useful to reduce the arsenic uptake by beet leaf as well as its immobilization in polluted soil.