Characterization of the Soil Organic Matter in Agricultural Mine Spoils and Reclaimed Soils Treated with Organic Amendments

Abstract

Recycling organic waste in agricultural soils is a valid solution. We performed short‐term experiments to investigate the fate of urban sludge and composts, in mine spoils, cultivated or uncultivated, and reclaimed soils located in Florence and Milan, Italy. The samples, either treated or untreated, were fractionated by density into light (<1.63 Mg m⁻³) and heavy (>1.63 Mg m⁻³) fractions. The fractions were analyzed for total carbon (C) and nitrogen (N) contents and for δ ¹³C and δ ¹⁵N isotopes, and they were characterized by ¹³C NMR spectroscopy. Treatment increased the heavy fraction. The addition of sludge in the Florence area acts in synergy with the cultivation, increasing the light fraction (LF). In the Milan area, the LF tends to be decomposed and apparently transformed into HF. The addition of amendments or cultivation enhances the decomposition with release of carbon dioxide. For future research, we suggest lengthening the time of the experiments to integrate climatic variations.

Keywords:

• Amendments
• δ ¹³C abundance
• density fractionation
• mine spoils
• δ ¹⁵N abundance
• organic matter
• reclaimed soils
• sludge

Acknowledgments

This research was supported by the funds of MIUR (Ministero Istruzione Università e Ricerca, Italy). We are thankful to Dr. Cappelli and Dr. Fabbricanti for obtaining the samples in the farm near Florence and for providing information about the soils and the crop management. We are also thankful to the University of Milan for obtaining the samples from the Milan area and to Dr. P. Gioacchini for CHN and isotopic analyses.