Comparative efficacy of different biochars and traditional manures in the attenuation of cadmium toxicity in rice (Oryza sativa L.)

Cadmium (Cd) toxicity in paddy soil and its accumulation in rice has caused widespread concern due to its negative health effects. Biochar (BC) and traditional manures (farmyard manure and press-mud) are well-known to improve plant growth by decreasing the uptake of toxic heavy metals. However, the impact of various organic amendments on Cd and the accumulation of major mineral nutrients in rice have been less understood. Therefore, in the present study, wheat straw biochar (WSB), sugarcane straw biochar (SSB), press-mud (PRM), and farmyard manure (FYM) at the rate of 1% (w/w) were evaluated for Cd immobilization in soil and to enhance nutrient uptake in rice plants grown in Cd contaminated soil (6.0 mg kg −1 ). Before 18 days of rice nursery transplanting, the amendments were applied to Cd contaminated soil, and rice plants were harvested at maturity after 120 days of transplanting. Results depicted that the use of WSB significantly enhanced the number of grains panicle −1 , straw, and paddy yield by 35, 96, and 76% as compared to the control without any amendment under Cd stress. Cd uptake was reduced by 12, 25, 58, and 44% in rice straw, and paddy yield increased by 38, 45, 76, and 66% with the use of FYM, PRM, WSB, and SSB respectively. The application of WSB and SSB caused an increase of 191 and 158% in N uptake in rice straw compared to control, respectively. Similarly, FYM and PRM improved P uptake in paddy by 118 and 136%, respectively over the control. The maximum Zn uptake in rice grains and straw was noted with the application of WSB which was around 261 and 346% higher than in control. In conclusion, BC proved more effective in soil Cd immobilization and reduction of Cd uptake in straw and paddy compared to traditional manures.