Development of soil physical parameters in agricultural reclamation after brown coal mining within the first four years

In Lusatia, Eastern Germany, the largest German brown coal (lignite) mining area is located. We study agricultural reclamation of open cast brown coal mining areas over the reclamation period of seven years which is in Germany by law the fixed time after which the agricultural areas are resold to farmers and agricultural cooperatives. This paper shows the development of selected soil physical parameters within the first three and four years of reclamation in dependence of organic fertilization, soil tillage and crop rotation.The sandy substrate which is used to reconstruct the post mining landscape is of Saaleian origin, free of recent organic matter and characterized by a homogeneous fabric. During excavation, deposition on stockpiles and levelling, the substrate becomes partly severely compacted due to extensive mechanical stresses. The extent of induced stresses depends on the contact area pressure and on the number of wheel passes of the levelling machinery during these processes.In this context we investigated the effect of different organic soil additives in combination with different crop rotations on the development of soil structure. The experimental area was reconstructed in 2006 and 2007. Directly after site construction, undisturbed soil samples were taken to characterize the initial mechanical and hydraulic properties of the substrate. Three and four years later again undisturbed samples on selected sub plots were taken. In 2010 samples from plots where Alfalfa had been cultivated for three years were collected. The Alfalfa plots were wheeled only twice per year, once for fertilization and once to cut and chaff the biomass. In 2011 samples from plots with annual ploughing and seedbed preparation were taken to show the effects of different crops and tillage intensities in combination with varying soil organic fertilizers on soil structure development. Furthermore, we evaluated the persistence of the loosening effect of subsoiling in dependence on the reclamation practice. First results of our on-going experimental study indicate that initial soil physical properties are very variable on the sub plots. After three and four years, no loosening effect of deep loosening was found anymore. The comparison of the minimum tilled plots (Alfalfa) with the plots of medium tillage intensity showed that with decreasing soil tillage intensity the functionality of the pore system (saturated hydraulic conductivity, air permeability) is improved.

► Development of soil physical parameters (describing capacity and functionality) of an unstructured substrate within 4 years. ► Dependence of pore volume, pore size distribution on crop rotation, organic fertilizer and tillage intensity. ► Dependence of saturated hydraulic conductivity on crop rotation, organic fertilizer and tillage intensity.