Comparison of the effects of compost versus compost and biochar on the recovery of a mine soil by improving the nutrient content

Numerous studies on the recovery of mine soils focused on the problems caused by metal(loid)s, and did not explore in depth the issue of nutrients and vegetation. In this experiment with soil packed in columns, we studied the capacity of biochar to increase the nutrient supply, pH, total carbon, total nitrogen and cation exchange capacity caused by the compost application. We compost alone and in combination with an oak wood-derived biochar. We also attempted to establish a crop of Brassica juncea L. and to verify which treatment produced the best development. The study was carried out at three different depths over the 45-cm length of each cylinder. The treatments applied increased the pH, nutrient, total carbon and total nitrogen values, and the cation exchange capacity. In overall, the most effective treatment consisted of the one using compost + biochar followed by planting B. juncea with only some exceptions towards the end of the experimentation period. The ability of biochar to improve the conditions of the settling pond soil to allow plant cover was demonstrated analysing the biomass of the B. juncea plants, which was higher in the soil treatments combining compost and biochar.