The greater part of cultivated lands for crop production is covered by Chernozems and related Kastanozems in Ukraine. Although there were numerous studies regarding soil humus in Ukraine and former USSR, soil organic matter quality evaluated by the humification index and NMR spectroscopy has not been studied in representative Chernozemic zone of Ukraine. In the present study, different Chernozemic soil types under natural grasslands were mainly selected in eastern Ukraine to investigate the properties and characteristics of the soil organic matter dynamics of humic substances in the typical Eurasian Steppe. Under the moist conditions in the north, Typical Chernozems (Chernic-Siltic Chernozems) and Ordinary Chernozems (Chernic-Siltic Chernozems), which could be distinguished by a deep black surface horizon with stronglydeveloped structures and the highly humified Type A humic acids, of which the RF values were remarkably high. Southern Chernozems (Hypocalcic-Siltic Chernozems) and Dark Chestnuts (Calcic-Siltic Chernozems) were the common subtypes under the relatively drier moisture regime, the profiles of which could be characterized by a relatively thin dark-brown or brownish black surface horizon. These soils were also characterized by the Type A humic acids, however, the RF value was less than Typical and Ordinary Chernozems. The aromaticity of humic acids in the surface soils of these Chernozemic soils calculated from ¹³C NMR spectra were extremely high comparable to that of highly-humified Type A humic acids of Japanese Andisols, suggesting that black carbon might contribute to the highly aromatic and recalcitrant SOM and could be recovered in the chemical fraction defined as humic acids in these black soils. We still need to clarify the impacts of anthropogenic activities and intensive agricultural practices on the soil organic matter quality of humic acids in Chernozemic soils.

This study was conducted to determine the relationship between the soil organic carbon (OC) content and selected soil properties such as pH(H₂O), 1 M KCl-extractable aluminum (KCl-Al, exchangeable Al), pyrophosphate-extractable Al and Fe (Al_p and Fe_p, humus complexed Al and Fe), and acid oxalate-extractable Si (Si_o, Si in allophanic minerals) in 293 A horizons from the Tohoku University World Andosol Database. A path analysis was used to examine the direct effects and indirect effects of the soil properties on the OC content. The path analysis showed that a high correlative coefficient between the OC content and Al_p (r = 0.69, P < 0.01) was mainly explained by the direct effect of Al_p (0.52, P < 0.01) on the OC content. Strong correlations between OC and KCl-Al (r = 0.60, P < 0.01) or pH(H₂O) (r = -0.58, P < 0.01) were due not only to the direct effect (0.21 and -0.27, respectively, P < 0.01), but also to the indirect effects of other properties, especially that of Al_p. Thus, it is considered that, in the humus horizons of the Andosols, the Al-humus complexation mainly contributes to the OC accumulation, and the low soil pH values and Al toxicity partly relate to the humus reservation by depressing the microbial activity.

Soil is a vital natural body that acts as a base for terrestrial ecosystems. The Soil Education Board of the Japanese Society of Soil Science and Plant Nutrition has been holding soil-watch meetings in 10 Nature Sanctuary Forests in Japan in order to disseminate soil education. However, the morphological and chemical properties of the soils under these forests have not been characterized. Our objective was to characterize these soils. We found that Nature Sanctuary Forests located on the main Japanese forest soils without podzolic soil, such as Brown Forest soils, Kuroboku soil (Andosols), and Red-Yellow soils.