Variation in soil characteristics of ex-coal mining areas in Sawahlunto, West Sumatra

¹ Department of Soil Science and Land Resource, IPB University, Bogor 16680, Indonesia
² Department of Silviculture, IPB University, Bogor 16680, Indonesia
³ PT Allied Indo Coal Jaya, Sawahlunto, West Sumatra, Indonesia
⁴ Department of Soil Science, Bengkulu University, Kandang Limun, Bengkulu, 38371, Indonesia

^* Corresponding author: wellyherman@unib.ac.id

Abstract

Soil characteristics in ex-coal mining areas can be influenced by reclamation methods and the type and age of revegetation plants used. This reclamation can also significantly impact the soil chemistry of ex-mining areas. This research was conducted in ex-coal mining areas located in Parambahan, Batu Tanjung Village, Talawi District, Sawahlunto City, West Sumatra Province. The objective of this study is to analyze variations in the reclamation process and their effects on the chemical properties of soil in these areas. Observations were made in several plots, including land that had not been mined (natural forest), land revegetated with Acacia in the planting years of 1992, 2007, 2010 (without the use of topsoil), 2019, and 2021, and land revegetated with Sengon in 2022. In each plot, soil samples were collected at three depths: 0–5 cm, 5–10 cm, and 10–20 cm, to analyze soil chemical properties. These properties included pH, total nitrogen (N), available phosphorus (P), organic carbon (C), exchangeable base cations (K, Ca, Mg, and Na), cation exchange capacity, and exchangeable aluminum (Al). The results showed that variations in the years of revegetation and reclamation practices, such as the use of topsoil and plant types, significantly influenced soil chemical characteristics. The longer the period of revegetation, the better the improvement in the soil’s chemical properties, as indicated by changes in pH, total N, organic C, exchangeable K, Na, Ca, and Mg, cation exchange capacity, and a reduction in exchangeable Al. However, the availability of P, as indicated by available P, decreased after more than 30 years of revegetation.