Post-Tin-Mining Agricultural Soil Regeneration Using Local Resources, Reduces Drought Stress and Increases Crop Production on Bangka Island, Indonesia

Mining severely affects ecosystems and threatens local food security. Remediation practices, however, are a viable way of reducing the negative impacts on post-mining lands. In this study we aim to improve crop yields and drought resistance on a post-tin-mining site located in Bangka Island, Indonesia, with locally available resources. Plots with five different soil amendments: (1) dolomite; (2) compost; (3) charcoal; combinations of (4) charcoal + compost; and (5) charcoal + sawdust; and a control were established. An intercropping system with cassava and centrosema was employed, and yields were determined. Drought resistance was evaluated by carbon isotope discrimination (∆13C) from crop parts of cassava and centrosema’s shoot. Soil physicochemical properties were determined at harvesting time. Soil amendments significantly improved cassava and centrosema yields. In particular, the compost and combined (charcoal + compost) treatments enhanced centrosema yields (1.18 and 1.99 kg·plot−1, respectively) and were related to higher nutrient availability. Similarly, compost, charcoal, and combined treatments showed positive effects on the cassava yield (0.15–0.16 kg·plant−1) and a higher drought resistance in the charcoal treatment (∆13C= 21.48‰). Increased water-holding capacity (WHC) reduced the water deficiency and boosted yields of cassava and centrosema when the soil was treated with dual amendments (charcoal + compost). Charcoal, compost, and their combination turned out to be the most sustainable amendments in degraded post-mining tropical soils.