Impact of Commercial Soil Additives on Microbial Activity and Carbon Isotopic Characteristics of Recultivated Post Lignite Mine Soils

Abstract

The impact of commercial soil additives (CSA) on post lignite mine soils was assessed after 14 months of field application by evaluating the changes in microbial respiration, the respiratory quotient and the isotopic signature of microbial respired CO₂-C. Soil samples were randomly collected from 0 to 5 cm depths from: (1) tilled plots amended with polyacrylate hydrophilic polymer, mixed with zeolithes and bentonite (a-CSA) at 5,000 kg ha⁻¹ dry mass; (2) tilled plots amended with a near-natural digester compost enriched with mineral additives, bentonite and synthesized humic acids (b-CSA) at 10,000 kg ha⁻¹ dry mass; (3) plots tilled and without amendment (control), and (4) plots without tillage and amendment. All plots were seeded with orchard grass (Dactilus glomerata, L.). Soil microbial basal respiration was low and not significantly affected by the treatments presumably, due to low availability of CSA for microbial metabolism. Soil microbial respiration, respiratory quotients and ¹³C isotopic characteristics of the respired CO₂ followed a similar trend for all treatments throughout the incubation period and was not significantly different between a-CSA and b-CSA amended plots compared to the control and untilled plots. The results indicate that the current soil microbial communities have similar eco-physiology and substrate utilisation patterns, and may have met their metabolic requirements mainly from the inherent and recent organic matter input from the vegetation cover. This may be due to the recalcitrant nature of the CSAs or the recommended application rates being too low to affect any significant short-term biochemical impact on these recultivated soils in early stages of development.

Keywords:

• Soil microbial activity
• Respiratory quotient
• Respired CO₂-C isotopic signature
• Post lignite mine soil amendments
• Soil organic carbon

ACKNOWLEDGMENTS

This study was funded by the German Federal Ministry of Education and Research (BMBF), and partly by the EU-SENSOR (‘Tools for Environmental, Social and Economic Effects of Multifunctional Land Use in European Regions’) program. The manuscript is based on a contribution to the XIX International Symposia on Environmental Biogeochemistry (ISEB) meeting of 2009 held at the University of Hamburg, Germany, under the session: evaluating biogeochemical cycling. The authors acknowledge the kind assistance from the entire laboratory staff of the Chair of Soil Protection and Recultivation, Brandenburg University of Technology, Cottbus, Germany.