The content and profile distribution of carbon and nitrogen fractions susceptible to acid hydrolysis in Haplic Chernozems and Mollic Fluvisols of western Slovakia

The studies on the content and profile distribution of carbon and nitrogen fractions of varied susceptibility to acid hydrolysis were performed in arable Haplic Chernozems and Mollic Fluvisols at four locations near Krakovany, Slovakia. The soils were sampled every 10 cm and analyzed, including the content of total organic carbon (TOC) and nitrogen (TN) and fractions of these elements after sequential extraction in 0.25 mol dm-3 KCl, 0.25 mol dm-3 H2SO4 and 2.5 mol dm-3 H 2SO4. Based on extractions, the content of easy hydrolyzable (EHC), hardly hydrolyzable (HHC) and nonhydrolyzable carbon (NHC) and the content of ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), dissolved organic nitrogen (DON), easy hydrolyzable nitrogen (EHN), hardly hydrolyzable nitrogen (HHN) and nonhydrolyzable nitrogen (NHN) was calculated. Mollic Fluvisols were more abundant in TOC and TN as compared to Haplic Chernozems. The content of carbon and nitrogen fractions varied among the soils, showing correlations with the total content of these elements. A low contribution of EHC and HHC in TOC and NO3-N, EHN, HHN in TN and a large share of nonhydrolyzable fractions of these elements were characteristic features of the studied soils. In general, trends in HHC (as % of TOC) and NO3-N, NH4-N, EHN (as % of TN), increasing with depth with a simultaneous decrease of NHN were observed. A-horizons of Haplic Chernozems were characterized by a higher contribution of EHN, NH4-N and NO3-N in TN, but a lower share of NHN as compared to Mollic Fluvisols.