Effects of Biochar on Soil Cadmium Forms and Cadmium Accumulation in Peanut Kernels

Heavy metal pollution has become one of the major problems in the world and cadmium(Cd) is the common heavy metal existing in the farmland soil. The biochar can play an important role in crop growth and soil remediation in the polluted farmland by the heavy metal. By means of pot experiment of peanut(Arachis hypogaea L.), this paper made a study of the effects on different dosages of cadmium and biochar to the forms and contents of soil cadmium and the cadmium content in peanut kernels, with biochar being used as cadmium pollution soil conditioner. The cadmium concentrations(by pure cadmium) were 0, 1, 10 mg·kg-1, denoted as Cd0, Cd1, Cd10 and the biochar concentrations were 0, 3.3, 6.6 and 10 g·kg-1, denoted as C0, C50, C100, and C150 respectively, including twelve treatments in total. The forms and contents of soil cadmium were dealed with the methods of Tessier sequential extraction and atomic absorption spectrophotometer in peanut seedling stage, flowering stage and podding stage, then the cadmium content of grain was measured in mature period. The results showed that the contents of available cadmium and water-soluble cadmium in soil significantly decreased(P0.05) with the increase of the dosage of biochar, while the cadmium contents of other various forms increased. Soil available cadmium concentration of Cd1 decreased 8.24%~20.24% in seedling, 5.95%~38.46% in flowering stage and 6.23%~26.03% in podding stage with the increase of biochar application amount. Soil available cadmium content decreased by 12.56%, 18.44% and 15.52% respectively in the same growth period under Cd10 concentration, which reached the minimum at C150. Soil p H value showed a trend of slight decrease followed by an increase at the same treatments in different growing stages. The cadmium content in peanut kernels increased with the increase of applied cadmium content. The cadmium content of peanut kernels decreased with the increase of biochar when cadmium concentration was 1, 10 mg·kg-1 and soil remediation effect is the optimum as a result of the lowest cadmium content in peanut, applying 10 g·kg-1 of biochar application amount.