EFFECTS OF SOIL pH AND ORGANIC MATTER ON THE ACCUMULATION OF CADMIUM IN THE GRAINS OF SALT TOLERANT RICE GENOTYPES GROWN IN Cd CONTAMINATED SOIL

Abstract

Cadmium (Cd) poses a serious threat to the environment and its concentration in rice grain causes significant dangers to people’s health. However, the effects of soil pH and organic matter (OM) on the accumulation of Cd in salt-tolerant rice genotypes under Cd stress remain unknown. In this study, separate pot experiments were conducted under Cd stressed soil (5 mg kg-1) with variations in soil pH and OM for the growth of rice plants. The study includes three pH (4, 7 and 9) and OM levels (1%, 2% and 3%). Under these conditions, the bioavailability of Cd in soil and its subsequent entry into the grain of rice genotypes were examined. Cd translocation from soil to the grain was compared among non-salt tolerant varieties (BRRI 28 and Heera) and salt-tolerant varieties (BRRI 67 and BRRI 47). The associated health risk assessment was also undertaken. All rice genotypes absorbed more Cd from soil and accumulated it in their grain when grown under low pH soil conditions. With increasing soil pH, grain Cd deposition declined significantly (p ≤0.05) in the order of Heera, BRRI 28, BRRI 67 and BRRI 47. Among the varieties a marked variation was obtained in the Cd absorption by each plant. OM addition in soil at a rate of 2% greatly reduced Cd accumulation in the grain of rice genotypes. A noticeable reduction was found in non-salt tolerant varieties over salt-tolerant genotypes. The hazard quotient (HQ) of Cd for both adults and children revealed the highest values at low soil pH conditions. Significant reductions in HQ values occurred in grain grown with OM only in non-salt-tolerant varieties. The result means that lower soil pH favors the accumulation of Cd in rice. Furthermore, grain Cd in rice genotypes can be reduced thorough the modification in soil bioavailable Cd and OM application in soil.