Soil salinity severely affects soil ecosystem quality and crop production in semi-arid and arid regions. A vast quantity of data on soil salinity has been collected by research organizations of the Commonwealth of Independent States (CIS, formerly USSR) and many other countries over the last 70 years, but using them in the current international network (irrigation and reclamation strategy) is complicated. This is because in the CIS countries salinity was expressed by total soluble salts as a percentage on a dry-weight basis (total soluble salts, TSS, %) and eight salinity types (chemistry) determined by the ratios of the anions and cations (Cl−, SO42−, HCO3−, and Na+, Ca2+, Mg2+) in diluted soil water extract (soil/water = 1:5) without assessing electrical conductivity (EC). Measuring the EC (1:5) is more convenient, yet EC is not only affected by the concentration but also characteristics of the ions and the salinity chemistry. The objective of this study was to examine the relationship between EC and TSS of soils in a diluted extract (1:5) for eight classic salinity types. We analyzed extracts (1:5) of 1100 samples of a clayey soil (0–20 cm) collected from cultivated semi-arid and arid regions for EC, TSS, soluble cations (Na+, Ca2+, Mg2+), and anions (HCO3−, Cl−, SO42−). Results revealed that (i) the variation in the proportional relationships (R2 ≥ 0.91–0.98) between EC (0.12–5.6 dS m−1) and TSS (0.05–2.5%) could be related to salinity type, and (ii) the proportionality coefficient of the relationships (2.2 2–3.16) decreased in the following order of salinity type: SO4 < Cl(SO4)–HCO3 < Cl(HCO3)–SO4 < SO4 (HCO3)–Cl < Cl. The findings suggest that once the salinity type of the soil is established, EC (1:5) values can be safely used for the evaluation of the soil salinity degree in the irrigated land in the context of sustainable soil and crop management.

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The experience shows that when constructing soil fertility models, many researchers prefer single-valued regression analysis. This is primarily due to the fact that regression analyses require simpler statistical calculations, and on the other hand, regression equations enable a physical explanation of the process under study. The research goal is to determine the effect of soil fertility indices and mineral fertilizers on the yields of crops (cereals) grown in the Karabakh Steppe on gray-brown irrigated soils.

The geographical principles are used in grouping of the soils the highest taxonomic standards in the soviet soil scientists works concerning the classification. But the Azerbaijan soil classification is based on genetic profile. Traditionally -topographic, color, climate and so on names are used in this classification, which in the soils genetic types idea is assumed as a basis. The International classification system is identified on the basis of the diagnostic parameters in the field researches and specified as a result of the laboratory analyses. The Azerbaijan soil classification consists of eight taxonomic level and a high taxonomic level is considered-soil class, section, genetic soil type, low soil taxa -soil gender, sort, diversity, row, soil variants. Mainly used central taxon is soil type. An aim of the research is to determine correlative chances of WRB-2015 International soil classification system with the Azerbaijan soil classification. It was detected that a correlation of both soil classifications is possible. The correlation is taken place in different taxon levels. Therefore, the soils were analysed at a type and subtype standard besides high taxas when the soils were correlated. As a result of correlation, it was defined that irrigated meadow-grey soils should be correlated Anthrosols, but meadow-grey soils concerned Calcisols and Gleysols.

The aim of the study. The aim of the research was obtaining new information about the genesis, current status, diagnostic features and properties of the Zheltozem-Gley Soils of the Lankaran region of Azerbaijan and to perform the taxonomic attribution of those soils in accordance with the International Classification of Soils in compliance with the Reference Base for soil resources (IUSS Working Group WRB, 2014). Location and time of the study. Zheltozem-Gley Soils of the Lankaran region of Azerbaijan were the objects of the study. Methodology. Field experiments (relief, vegetation, laying of soil profiles, their description, selection of soil samples and establishment of a preliminary classification name of the soils) and physico-chemical analyzes of soil samples (humus and total nitrogen content, ratio of C:N in soil organic matter, soil pH, cation exchange capacity, grain-size analysis, water extract composition) were carried out by standard methods. Results. It was established that the most characteristic features of the irrigated zheltozem-gley soils were as following: blocky angular-subangular structure of the upper horizon, clayiness of the entire soil profile, the presence of iron-manganese concretions and ferruginous mottles. A gradual decrease in the content of humus (from 2.15-3.28 to 0.18-1.24%), nitrogen (from 0.17-0.24 to 0.05-0.24%), the ratio of C:N (from 6.64-7.18 to 1.89-5.91) was found. The cation exchange capacity increased down the profile (from 33.37-37.13 to 34.31-40.89 cmol (eq)/kg). The reaction of the soil environment was weakly acidic, and varied within 5.8-6.0. Under the influence of irrigation, the removal of the silt fraction from the upper horizons and its accumulation in the middle horizons of the soil were observed (42-96 cm – 42.4%, 48-87 cm – 28.8%). According to the granulometric composition, these soils were medium-light-heavy loamy. The soils were not saline. Conclusion. For the first time, an attempt was made to carry out the taxonomic attribution of Zheltozem-Gley soils (irrigated Zheltozem-Gley merged, ordinary Zheltozem-Gleyic, irrigated Zheltozem-Gley, irrigated residual calcareous Zheltozem-Gley) according to the international classification of soils based on the Reference Base for soil resources (WRB). With the different principal and supplementary qualifiers, all soils were classified as Lixisols.