Soil microcosm experiments to study the effects of waste material application on nitrogen and carbon turnover of lignite mine spoils in Lusatia (Germany)

The lignite and pyrite containing spoil substrates of the Lusatian mining d istrict are marked by very high acidity and salt concentrations due to pyri te oxidation and by a very low content of pedogenic organic matter and nutr ients. The effects of fly ash application to neutralize the produced acid a nd of organic waste material application to improve the ecological soil fun ctions were studied considering the carbon and nitrogen cycling. Nineteen, 38 and 57 t ha(-1) sewage sludge and 22, 44 and 66 t ha(-1) compost were ap plied to ameliorated lignite and pyrite containing substrate. An automated soil microcosm system was used to analyse the solid, gaseous and liquid pha ses. Almost 9% of total N applied with sewage sludge (620, 1240 and 1860 t N ha(-1) applied) were lost over a period of 150 days mainly as NO3-N. The total N losses from compost treatments were three times lower (2.8-3.1% of applied N-t) and occurred in similar quantities as NH4-N and NO3-N. Only se wage sludge treatments showed slightly increased N2O emissions at the begin ning of the experiment. CO2 emissions determined the carbon losses of all t reatments. The C losses amounted to 3.2-4.7% and 1.5-2.7% of C-t applied wi th sewage sludge and with compost, respectively.