Application of Torreya grandis peel biochar in cadmium contaminated soil remediation and pakchoi growth enhancement.

Abstract

This study aims to elucidate the effect of Torreya grandis peel biochar application on cadmium-contaminated soil and pakchoi (Brassica chinensis L.) growth. A pot experiment was designed involving four distinct biochar/soil ratio treatments: 0 (Control, CK), 1% (T1), 2.5% (T2), and 5% (T3). The results demonstrated that the incorporation of 5% effectively modulated the pH of acidic soil, substantially elevating soil organic matter, and available N, P, K content. Moreover, it augmented the activities of catalase, urease, and acid phosphatase in the soil, concurrently diminishing the Cd content. This treatment reduced the exchangeable and carbonate-bound Cd fractions by 45% while enhancing the iron-manganese oxide-bound, organic matter-bound, and residual Cd fractions by 26%, 29%, and 96%, respectively. Regarding the growth of pakchoi, the 5% biochar application significantly decreased the Cd content in the edible portion by 51%. It significantly enhanced the fresh weight per plant, soluble solids, soluble sugar, soluble protein, and vitamin C content of pakchoi. In conclusion, the application of T. grandis peel biochar is a viable approach for improving the properties of Cd-contaminated soil, passivating Cd fractions, and enhancing the yield and quality of pakchoi. A biochar pyrolysis temperature of 500 °C and a biochar/soil ratio of 5% is recommended.