Biochar Effects on Rice Paddy Cadmium Contaminated Calcareous Clay Soil: A Study on Adsorption Kinetics and Cadmium Uptake

Abstract

This study investigated the effectiveness of sugarcane bagasse biochar (SBB) in reducing the toxicity of heavy metals (HMs) in Cd-contaminated calcareous clay soil and improving the growth of rice (Oryza sativa L.). A pot experiment with a randomized complete block design (RCBD) was used to examine the adsorption kinetics and growth improvement of rice. Three Cd levels (0.0, 30.0, and 60.0 mg kg−1 of soil from CdSO4. 8H2O) and three SBB levels (0.0, 3.0, and 6.0% by weight) were considered. The study found that the biochar's surface contains functional groups that aid in the immobilization of Cd in contaminated soil. The Langmuir model best fit the Cd adsorption data of all studied soils, predicting the highest adsorption capacity with an R 2 value of 0.9902 for the adsorption of Cd onto soil-SBB 6%. Single application of SBB at a 6% level significantly increased rice grain and biomass by 45.41 and 57.82%, respectively, in soils containing 30 and 60 mgkg−1 soil Cd, compared to single soil Cd treatments. Addition of SBB at a 6% level also significantly reduced the amounts of Cd extracted using DTPA by 53.37 and 45.14%, respectively, and absorption of Cd by 67.00 and 52.14% in soils containing 30 and 60 mgkg−1 Cd. The results suggest that incorporating SBB into soil is a suitable remedial method for promoting plant growth in Cd-contaminated soils.