Changes in Molecular Structure of Humic Substances in Cambisols under Agricultural Use

Soil organic matter stability and transformation affected by agriculture is a global problem of great concern. This study aimed to reveal structural changes in humic molecules under conventional soil tillage Cambisols the Transbaikal area. Humic acids were isolated from humus horizons native arable variants Eutric Cambisol Cryic (gleyic, humic, loamic) forest steppe, Haplic (arenic, protocalcic) steppe zone. The substances’ quality evaluated means an elemental analysis 13C nuclear magnetic resonance spectroscopy. results indicate that different agronomic management composition molecular structure acids. induced increase carbon content, proportion aromatic compounds carboxyl groups depletion nitrogen. As measured NMR spectroscopy, intensity these was determined properties hydrothermal regime. Organic suggested as providing significant environmental resistance agricultural impact due optimization water regime loamy texture. Prolonged ploughing sandy arid conditions promoted deep chemical structure.