CROP ROTATION OF RICE WITH HYPERACCUMULATOR PTERIS VITTATA TO LOWER ARSENIC ACCUMULATION IN RICE GRAINS: PRELIMINARY STUDIES

Arsenic(As) in the environment is associated with various diseases including cardiovascular disorders, diabetes, obesity, and cancer. Arsenic contamination of groundwater and soil in south-east Asia is a major human health concern. Rice is the major food crop grown in this region. The soil rice is grown in, and the groundwater used to irrigate the crop is often contaminated with As. The anaerobic growing conditions of flooded rice paddies and the unique physiology of the rice plants lead to increased levels As in rice grains. The World Health Organization (WHO) has set advisory levels of As in polished (i.e., white) rice grain at 0.2 mg/kg. However, there are no regulations on the concentration of As in the soil. Most strategies for lowering As accumulation in rice so far are experimental, and have limited applicability. We propose a practical crop rotation phytoremediation approach for the mitigation of As in paddy soil. Soil samples used in this study with As concentration 21士4 ppm were collected from agricultural fields in Nadia, West Bengal. A greenhouse column study is in progress under temperatures between 23-26℃, 8-10 hours of daylight. Rice is grown in the columns submerged in 4-6 inches of water. After harvest and a brief fallow period, As hyperaccumulating fern, Pteris vittata was planted in the columns and grown for three months. Control columns were left without Pteris vittata plants for the same three-month period. After three months, the fern plants were harvested, and rotated with rice. All treatments were carried out in triplicates. Arsenic concentration in the soil, plants and seeds were analyzed by ICP-OES after acid digestion. The crop rotation study with alternating rice and fern will be carried out for two years. Preliminary results after the first rotation cycle will be presented. If successful, this method can be implemented in agricultural fields to lower As accumulation in rice grains from contaminated soil and water.