N and C Stocks and d13c of Soil Organic Matter of a Rehabilitated Mined Area.

The process of rehabilitation after mining operations allows restoration of physical, chemical and biological properties of the soil. The aim of the present study was to evaluate soil organic matter fractions (SOM) under methods of rehabilitation of an area mined using various intercropped plants and types of fertiliser. Soil samples were collected from the 0 - 20 cm layer of an area under four different methods of fertilisation: no fertilization (NF), organic (OF), chemical (CF) and organic + chemical (OF + CF), and three types of ground cover in the rows between the coffee: no plants (NP), brachiaria grass (B) and stylosanthes (S). Stocks were evaluated of the total organic carbon and nitrogen (TOC and TN), labile organic carbon and nitrogen (LOC and LN), free light organic matter (C-LOM_L and N-LOM_L), occluded light organic matter (C-LOM_O and N-LOM_O), coarse and fine particulate organic matter (C-POM_c, C-POM_f, N-POM_c and N-POM_f) and mineral-associated organic matter (C-MOM and N-MOM), as well as the isotopic composition of C (δ¹³C) and the carbon management index (CMI). The C-LOM_L and N-LOM_L were the most sensitive to the management systems used in the rehabilitation of the mined area. The δ¹³C of MOP_c, MOP_f and MOM, demonstrated that the original stocks of soil carbon in the pre-mining phase had been preserved, showing these fractions to be indicators of soil quality, sensitive to changes resulting from the adopted management, and which contribute to the resilience of the edaphic environment. Generally, applying fertiliser (OF, CF + CF and OF) contributed to a better development of the plants in the rows between the coffee plants, especially the organic + chemical fertilizer (OF + CF), and mainly when applied to the areas where the coffee was intercropped with brachiaria grass, providing higher stocks of carbon and nitrogen and soil organic matter compartments.