Report by Mamadou Welle
In the frame of the module EM39 Soil & Land Resources an excursion on open cast lignite mining sites was organized on Tuesday 28th Jun 2016. Under the guidance of Prof. Kalbitz and Prof. Michael Haubold-Rosar, participants got the chance to learn more about the challenges of soil management. Besides discovering the impressive landscapes in such areas, we had deep insights in the principles and practices of soil reclamation and rehabilitation regarding water capacity or quality, nutrients status and ecological aspects.
It was reminded that soil formation takes time as shown by the geological map of the visited area, where the mining began at the end of the 19th century. The mining process was then explained, from mining preparation and water management to overburden removal and dumping. For instance, it is essential that the deposit is kept free from water in opencast mining. These operations are resources consuming but they are necessary to protect the soil and limit damages in the environment and people`s people health. Even some beneficial effects might derive from such investments as it is the case of recreation areas provided by man-made lakes emerging out of mining activities. The process of lands reclamation was documented with the visit of a former mining area where agriculture and forestry are now back.
For agriculture purposes, the reclaiming measures depend on the types of soil. Plants are selected in a rotation so as to fit to soil fertility. However it is difficult to reach the initial level of soil fertility. For example, it is needed 10 to 20% more seeds in reclaimed lands than in natural sites. Machines damages are also higher there.
The last stage of the excursion was to walk around a forest developing on a former dump site. In the context of forestry the time frame for reclamation is rather longer. A monitoring system has to be set up progressively about the behavior of plants response to this unusual situation. It was indicated that weathering, and stabilization effect of fly ash can have a positive impact on the growth of trees. Hot spots of nutrients occur and a typical humus layer formation may be found in this forest.