Transformation of Chernozem by increasing land use intensity in suburban Hajdúság, Eastern Hungary

Chernozem under different agricultural land use were compared in a suburban area: three on cropland with different land use histories; one in an area of complex cultivation; one fallow; and one under grassland, considered to be in close to natural state, as a control. Soil profiles at each site were described and classified, and chemical characteristics analyzed in detail. Topsoil (0-40 cm) bulk density (BD), total organic carbon (TOC), total nitrogen (TN), ammonium lactate-extractable P, K, Ca and Mg were measured, and microbiological communities were characterized by phospholipid-fatty acid (PLFA) markers. We found significantly increased BD but decreased TOC and TN in the cultivated sites compared to the control. Values of ammonium lactate-extractable P (P-AL) were higher at the natural site, but Ca-AL, Mg-AL and K-AL content of the cultivated and mineral-fertilized agricultural sites were higher than or equal to the grassland site. Total microbiological activity correlates significantly positively with TOC and TN and negatively with the BD. Sites with perennial vegetation cover and higher biodiversity showed greater microbiological activity and, in case of the arbuscular mycorrhizal fungi, actinobacteria and anaerobe bacteria, the differences are significant. Despite the nutrient depletion and lesser microbiological activity, cropland sites preserved their taxonomic status as Chernozem. Sites that have undergone more extreme human impacts before the recent land use had lost their diagnostic features (aggregation, color, secondary carbonate accumulation) and now key out as Kastanozem, Phaeozem or Regosol.