Chimitdorzhieva E.O., Korsunova Ts.D.-Ts., Tsybikova E.V. ARABLE DRY-STEPPE SOILS OF WESTERN TRANSBAIKALIA: THEIR PROPERTIES, MORPHOLOGY, MICROBIAL BIOMASS, AND HUMIC ACIDS // Arid Ecosystems. 2025. Vol. 31. № 2 (103). P. 69-79. | PDF

The aim of our work was to study the soil properties, C-biomass and the structure of humic acids in arable chestnut soils of Western Transbaikalia. The objects of the study are arable chestnut soils of the southern basins of Western Transbaikalia (Tugnuyskaya Basin, Selenginskaya Basin, Ivolginskaya Basin). To compare arable soils with their virgin analogues, they were studied in pairs. Arable chestnut soils have a low fertility level: low humus content – 0.98±0.07%, low total nitrogen – 0.08±0.01%, arable horizon thickness – 21.33±2.31 cm, and light loamy granulometric composition. During the vegetation periods, the average biomass carbon accumulation in chestnut soils was 35.77±3.09 mg C/100 g of soil. The share of C-biomass in the total stock of soil organic carbon was up to 2.5%. The aliphatic carbon content in arable chestnut soil was lower than in virgin soil. The content of amino group and methoxyl group carbon in virgin soil was 7.9%±0.14, but about twice as low in arable soils. The amount of carboxyl group carbon in arable chestnut soils was 15.5%±0.42, and 12.55%±0.92 in virgin ones. A detailed analysis of the ¹³C-NMR spectra of humic acids can help to draw a conclusion about the structure and chemical composition of organic matter in soils. For arable and virgin chestnut soils of Transbaikalia, such analysis can reveal differences related to land use in local agriculture. Aliphatic carbon in humic acids of arable soil was less expressed, indicating a greater role of aromatic carbon in the macromolecular structure of arable soil. This reveals a pattern: aliphaticity is lower in arable land than in virgin soil. We doscowered that agricultural tillage transformed the molecular structure of humic acids, which was manifested in an increasing share of aromatic carbon in arable land. In the elemental composition of humic acids of arable chestnut soils of Transbaikalia, the carbon content is higher and hydrogen is lower than in virgin soil analogues. High hydrogen content in virgin soil leads to relatively developed side carbon chains in humic acids. In arable chestnut soil, the humic acids macromolecule contains more nitrogen (2.9 at.%) than in virgin soil (2.7 at.%). The value of the atomic ratio H:C on chestnut arable land was 1.0, and 1.1 on virgin soil. In arable variants, the degree of benzenoid was 22.5, and 16.4 on virgin soils. It was revealed that the elemental composition of arable chestnut soils has a more condensed structure, compared to virgin soils.

Keywords: carbon, microbial biomass, humic acids, ¹³C-NMR spectroscopy, elemental composition, chestnut soils, arable land, virgin soil, Transbaikalia.

DOI: 10.24412/1993-3916-2025-2-69-79

EDN: KFGOLT