Cadmium evaluation of rice in relation to phosphorus fertilizer application

This study was conducted to determine the uptake of Cadmium (Cd) in rice at different growth stages of the roots, stems, leaves and grain. It also determine the pH and Cd concentration in soil and correlated the Cd uptake of rice with phosphate applications. Three rice varieties were used in this study, namely; IR 64, PSBRc 72 H and Hinamog. Soil and plant parts were collected at each growth stage. Cd concentration was measured using atomic absorption spectrophotometer. Four fertilizer treatments were used: 0.00g single super phosphate (SSP)(P1); 0.226g (P2); 0.726g SSP (P3) and 1.226g SSP (P4). Cd uptake of the three rice varieties was significantly different from each other in their stages of growth. The maximum Cd uptake of IR 64 was noted at the panicle initiation stage, maturity stage for Hinamog, and booting stage for PSBRc 72 H. Of the three rice varieties, PSBRc 72 H was found to be a good Cd absorber. The interactions of the plants parts with stages of their growth were also found to be significantly different at 0.05 level of significance. The leaves of IR 64 at the milk stage were found to contain the maximum Cd concentration while Hinamog and PSBRc 72 H were at the milk or dough stage in the same part of the plants. The parts of the three rice varieties and the stages of their growth had no significant relationship with increasing phosphate concentration. The parts of all rice varieties exhibited the same absorbing capacity for Cd in all stages of growth. Even with increasing phosphate concentration, the plants were found to absorb only a maximum amount of Cd. However, the parts of the three rice varieties showed different behavior in terms of Cd absorption. The leaves of IR 64 and PSBRc 7211 were found to contain the highest Cd concentration at maturity stage. A positive significant correlation was like was noted in soil pH and Cd concentration in soil at different growth stages. Cd concentration in soil was directly proportions to pH. No significant correlation was established between Cd concentration in soil and phosphate concentration. The order of Cd concentration in the rice parts at maturity stage was leaves stem roots grain. These results show that rice parts can absorb this heavy metal at high phosphate concentration.