Residual effect of biochar from bamboo (Gigantochloa) on the growth of Tithonia diversifolia as a phytoaccumulator of mercury on ex-gold mining soil

¹ Department of Soil Science and Land Resource, Agriculture Faculty, Universitas Andalas, Limau Manis, Padang City, West Sumatra 25164, Indonesia
² Postdoctoral Fellowship of Universitas Andalas, Limau Manis, Padang City, West Sumatra 25164, Indonesia
³ Department of Agroecotechnology, Agriculture Faculty, Universitas Andalas, Pulau Punjung, Dharmasraya, West Sumatra 27573, Indonesia
⁴ Department of Land Management, Agriculture Faculty, University Putra Malaysia, Serdang, Selangor, 43400, Malaysia

^* Corresponding author: herviyanti@agr.unand.ac.id

Abstract

Illegal gold mining harms the environment, notably soil pollution by mercury (Hg), which can be reduced by reclamation with amelioration technology and phytoaccumulator plants. This study examined the residual effect of bamboo biochar (RE-BB) on the growth of Tithonia diversifolia in ex-gold mining soil (ex-GMS) contaminated with Hg, that have been fed for one year and six months and planted with corn plants in the previous growing season. This study used a completely randomized design (CRD) with three replicates and five doses (0-40 tons ha^-1) of RE-BB. The 40 tons ha^-1 RE-BB was significant and still capable of improving the chemical properties of ex-GMS by increasing the pH to 6.37, CEC to 11.07 cmol(+) kg^-1, organic C to 1.27%, total N to 0.19%, available P to 24.24 ppm, and Mg-exch to 0.32 cmol(+) kg^-1, and reducing the soil of Hg to 2.16 mg kg^-1. Additionally, it can increase plant height to 83.67 cm, P to 0.006%, K to 0.13%, and reduce the plant of Hg to 0.04 mg kg^-1. Bamboo biochar till the second planting season has been proven to reduce Hg pollution by enhancing the chemical characteristics of ex-GMS. Tithonia diversifolia shows potential as a renewable phytoaccumulator of Hg.