Studying Soil Organic Matter Composition in Arable land: Can Soil Management Impact Carbon Pools?

Soil organic matter (SOM) is an essential fraction of soil and contributes to its fertility. Land use and cultivation may affect SOM. This study investigates whether SOM concentration and composition differ in soil pools or are changed by soil management (tillage, fertilisations, and crop covers). Soil samples were collected in April 2019 from cropland and nearby grassland. The study sites were part of a long-term experiment in Martonvasar (Hungary), established in 1958 and characterised by Chernozem soils. Total organic carbon (TOC) contents and compounds were studied in three soil pools (bulk soil, fast pool, and slow pool). Both TOC and total N concentrations were high in the slow pool, with higher stored C contents in grassland than in cropland. Tillage effects reduced aggregate stability in cropland, which explains a lower aliphatic content than grassland. Insufficient physical protection due to the tillage practice may enhance OM loss in cropland even under fertiliser inputs. Neither fertiliser nor crop covers affected SOM compositions, while they were different in soil pools. More complex OM in the slow pool than in the fast pool. It indicates that the slow pool is the main protecting path for SOM, possibly referred to older or decayed organic compounds. To understand the bottom-up process, microorganisms’ community role in SOM stabilisation needs to be studied.