Изменение противоэрозионной стойкости орошаемых серо-коричневых почв сухой субтропической зоны Азербайджана в зависимости от давности их орошения

The dry subtropical zone of Azerbaijan is located in an erosion-hazardous zone, and irrigation erosion manifests itself on an area of more than 255 thousand hectares. The damage caused by irrigation erosion to the agriculture of the republic is manifested not only in the destruction of the soil structure, but also in the removal of nutrients from the soil. At the same time, the patterns of change in the anti-erosion resistance of grey Cinnomanic soils /Luvic Calcisols /Luvic-Calcic Kastanozems (according to the classification of the USSR), grey Cinnamonic soils (according to the classification of Azerbaijan), (on WRB (2014)-Haplic Kastanozems / Haplic Calcisols) in the dry subtropical zone of Azerbaijan, depending on the age of irrigation, are diverse and not fully studied. Therefore, conducting research in this direction and assessing the antierosion resistance of grey Cinnamonic soils is relevant for Azerbaijan. The aim of this research is to study the changing of the anti-erosion resistance of irrigated grey Cinnomanic soils in the foothill and plain areas of the dry subtropical zone of the republic, depending on the age of irrigation. Based on the results obtained, the place of grey Cinnomanic soils in the international classification system WRB (2014) was determined. The research was carried out on grey Cinnomanic soils of heavy loamy and light clayey granulometric composition of the foothills and plains of the dry subtropical zone of different irrigation periods, in the territories: Grey Cinnomanic (virgin soils) – Beylagan (39°46'02.2''N, 47°36'13.3''E) and Yevlakh region (40°60'67.75''N, 47°17'02.71''E); Newly Irrigated Grey Cinnamonic (20-25 years old) – Agdash region (40°63'24.62''N, 47°49'11.92''E) and Geokchay region (40°37'10.5''N, 47°44'29.5''E); Irrigated Grey Cinnamonic (about 100 years old) – Bilasuvar (39°48'36.49''N, 48°43'35.24''E), Yevlakh (40°44I 34.18''N, 46°96'51.13''E), kshu (40°55'39.53''N, 48°35'04.18''E), and Aghstafa region (41°06'11.17''N, 45°28'07.32''E); For a Long Time-Irrigated Grey Cinnamonic (about 300 years old) – Bilasuvar (39°44'25.56''N, 48°42'52.72''E) and Beylagan region (39°76'45.13''N, 47°59'13.50''E). The research methods are comparative-geographical (geographical patterns of distribution of these soils according to the granulometric competition and humus content of the arable horizon) and comparative-analytical. On the plots, soil sections were laid, a morphological description was carried out, soil samples were taken from the genetic horizons (Field guide of soils in Russia (2008), FAO. Guidelines for soil description (2006), IUSS Working Group WRB. World Reference Base of Soil Resources 2014, update 2015, Kallas and Tanzybayev (2001)). The anti-erosion resistance of soils was determined by the bottom erosion flow rate-according to Kuznetsov MS. (1981), the water resistance of the aggregates – by methods of dry and “wet” aggregate analysis according to Savvinov, the specific gravity of the solid phase – by the pycnometric method, the granulometric compotition – by the pipette method, soil density – with a drill according to the generally accepted method (Arinushkina, 1970; Vadyunina and Korchagina, 1986]. The value of the protrusions of soil roughness was determined by the ratio ∆ = 0.7 dw, where dw is the weighted average diameter of the water-resistant aggregates. The value dw was calculated based on the results of the structural analysis of the soil by the Savvinov method at the initial moisture content W (Grigoryev and Makkaveev, 1979), the content of total humus – according to Tyurin, modified bu Nikitin, cellulolytic activity – by application method for the decomposition of cotton canvases (Kazeev, Kolesnikov and Valkov, 2003). Depending on the age of irrigation, we revealed changes in the morphological profile of soil and qualitative indicators of physical-chemical properties of grey Cinnamonic soils during cultivation. İn newly irrigated grey Cinnamonic soils, the cultivated layer (25-30 cm thick) is not fully formed, new arable (A1-22-27 cm) and subsurface horizons (A2-15-16 cm) have been formed and are somewhat compacted, the structure is deteriorated, the level of carbonate and gypsum horizons is lowered. The profile of irrigated soils differs sharply from virgin and newly irrigated soils, has a clear colour differentation; a cultivated layer is formed (thickness - 52-56 cm), the arable horizon is A1-25-28 cm, subsoil - A2-24-26 cm, the illuvial-carbonate horizon is poorly expressed, down to 96-101 cm. Long time-irrigated (irrigation-accumulative) soils under the influence of long-term irrigation with turbid waters and constant cultivation have lost the signs of zonal primary soils and acquired a special type of soil profile – a monotonous grayish-brownish colour, uniformity of profile and composition, a fully formed cultivated layer with a thickness of 65-70 cm; burried horizons are found at a depth of 61-83 cm. A distinctive feature of the irrigated and irrigation-accumulative (long-irrigated) variants of grey Cinnamonic soils – an increase in the microaggregates content, a high content of physical clay (60.8-64.3%), which, when compared with the non-flush type of water regime (virgin), causes not very high humus content of the upper (0-25 and 25-50 cm of soil) horizons (2.29 and 1.78% humus), their weak resistance to the destructive action of water (See Tables 2 and 3). The content of waterresisant aggregates >0.25 mm in layers (0.25 cm) of the soil in comparison with virgin (54.08%) decreases to 35.83% in newly irrigated, in irrigated - to 38.23 % and in irrigation-accumulative (long-irrigated) - up to 40.40% (See Table 4); the highest values of the coefficient of variation of density (CV = 13.54), with a standard deviation (SD = 0.161) are observed in newly irrigated soils (See Table 5). A high bottom erosive flow rate was noted in virgin soils is 0.070-0.072 m/s, somewhat less - in irrigated (0.050–0.063 m/s), in long-irrigated (irrigation-accumulative) (0.048–0.050 m/s) and in newly irrigated soils - 0.048-0.049 m/s (See Table 6). The highest value of porosity, with a solid phase density of 2.65-2.67 g/cm3 , is noted on non-irrigated (virgin) soils (49-55%), in long-irrigated (irrigation-accumulative) soils, it decreases to 47-49%, and on irrigated at a solid phase density of 2.66-2.77 g/cm3 corresponded within the permissible values (51-52%) (See Table 6). The values of the weighted average diameter of water-resistant aggregates decreased from virgin to newly irrigated and to long-irrigated (irrigation-accumulative) soils (from 0.67- 0.74 mm to 0.27-0.31 mm) (See Fig. 1). The highest value of the ratio of anti-erosion resistance to erosion flow velocity was observed for virgin grey Cinnamonic soils (0,0710±0,102 m/s). The maximum average height of roughness protrusions was noted in long-irrigated (irrigation-accumulative) soils (0.27 mm), then irrigated (0.25 mm), and the smallest - in newly irrigated (0.19 mm) soils (See Table 7). We revealed that depending on the age of their irrigation, the anti-erosion resistance of grey Cinnamonic soils, as the bottom erosion flow rate and anti-erosion resistance decrease, can be arranged in the following row: virgin soils → irrigated → longirrigated → newly irrigated. Based on the results obtained, we determined the place of grey Cinnamonic soils in the international classification system WRB (2014): Virgin soils - Saturated gley calcareous heavy loamy - Duric Gleyic Calcic Kastanozems (Loamic); Newly irrigated Grey Cinnamonic (20-25 years old) - Powerful new irrigated calcareous heavy loamy Grey Cinnamonic - Someric Calcic Kastanozems (Loamic); Irrigated Grey Cinnamonic (about 100 years old) - Powerful cultivated irrigated calcareous heavy loamy - Someric Kastanozems (Anthric, Loamic); For a long time-irrigated Grey Cinnamonic (over 300 years old) - Powerful gley cultivated for a long time irrigated calcareous heavy loamy Grey Cinnamonic - Gleyic Petrocalcic Kastanozems (Anthric, Loamic). The paper contains 1 Figures, 7 Tables, and 46 References.