Agrogenic changes in the properties of dark chestnut virgin and arable soil with different use and irrigation

Abstract

In the article, it was provided a comparative analysis of the ecosystem significance of soil characteristics transformed as a result of changes in the use conditions. At the three monitoring stationary sites in the Chaplinka district of the Kherson region, we studied the properties of dark chestnut soil (Haplic Kastanozem) on virgin lands (a biosphere reserve "Askania-Nova") and with more than a hundred years of use in agricultural production without irrigation and with a 50-year irrigation with water from the Kakhovsky trunk canal. Changes in the salt regime of the soil and the composition of exchangeable cations were established. In irrigation the total content of water-soluble salts up to 0.14-0.21% (toxic salts ‒ up to 0.06-0.15 %) was increased. The composition of salts was changed, their migration and accumulation in the lower soil layers. Under the influence of fresh water irrigation the process of dealkalinization in the dark chestnut soil took place. The involvement of virgin soil in agricultural use led to a decrease in the total content of humus and the transformation of its group composition. The content of humic acids (HA) was decreased. The content of fulvic acids (FA) was increased. The HA/FA ratio in the 0-10 cm layer changed from 2.6 (in virgin soil) to 1.6 in irrigated soil. The plowing and agricultural use of the dark chestnut soil led to a change in the state of the microbial cenosis. The number of microorganisms assimilating mineral and organic nitrogen, actinomycetes, oligotrophs, and eutrophs were increased. With irrigation the degree of transformation of the microbial cenosis increases. The indicator of biological degradation of irrigated dark chestnut soil was 4 %. This corresponds to a low level of degradation. A set of 10 indicators of the quality of the studied soil was proposed for calculating the level of its provision of ecosystem services (supplying and supporting). The algorithm and calculation results are presented. The soil of all monitoring sites of Markeev station is characterized by a high level of provision of ecosystem services. In virgin soil it was 8.3 points; in arable soil without irrigation it was 7.2, and with irrigation it was 7.5 points.