Influence of chestnut soil agricultural exploitation in Transbaikalia on the elemental composition of humic acids

Bioclimatic conditions of soil formation in the cryoarid climate zone of Transbaikalia determine the specific composition of humus and humic acids. Its peculiar that despite the harsh conditions of chenut soil formation (the influence of long-term seasonal permafrost, continental climate), kastanozems cohtain humic acids with a fairly high content of carbon and nitrogen. A distinctive feature of the humic acid macromolecule of arable kashtanozems compared to virgin ones is a less developed peripheral part with a high degree of benzenoidity. An increase in the proportion of aliphatic structures (peripheral part) and a decrease in the proportion of aromatic fragments helps to reveal a simplification of the structure of humic acid macromolecules in the studied soils. However, the structure characteristic of the genetic series of dry-steppe soils is preserved in humic acid macromolecules of kashtanozems. A short growing season, the influence of deflation processes, insufficient moisture in combination with a light granulometric composition significantly reduce the rate of organic matter transformation, which leads to an increase in the proportion of unoxidized aliphatic fragments, formation of humic acids with more developed side chains.