Magnesian alkalinity of trenching soils of Prichernomorskaya lowland
Authors: Opanasenko N. Ye. , Yevtushenko A. P. , Grishina A. P. 
Published: February 2020

The data of scientists about spreading, genesis, composition and properties of low natrium soils with high content of magnesium in soil sorption complex, and its influence on plants have been considered. The aim was to determine the absorbed ability of soils and the level of saturation by bases; to determine the dependence of density of foundation, quantity of silt from the content of absorbed magnesium from magnesium water soluble salts in them; to determine kation-anion and salt composition of irrigation waters. The trenching low natrium remaining alkolinic south black soils, dark-chestnut, turf-steppe black soils of Prichernomorskaya lowland with content 20–73 % Mg2+ in soil sorption complex and also irrigation waters have been studied. Physical clay, silt, volumetric mass, general porosity, air-volume, water-permeability, micro-aggregate composition, absorbed base, kation-anion composition of easy soluble salts and hypothetic salts have been determined in soils. Kation-anion composition and hypothetic salts have been determined in irrigation waters. The sum of absorbed bases in studied soils corresponded to the content of fraction of physical clay and silt, and also to the provision of soils with organic substances. The humus reserves in trenching layer 0–60 cm of black south soils were 200–240 t/ha, dark-chestnut soils – 150–180 t/ha, turf-steppe light suglinic – soils 80–130 t/ha/ That’s quite normal that south black soils (30 mg-eq./100 gr.) have the best absorbed ability, and the turf-steppe susand soils have the worst absorbed ability (9 mg-eq./100 gr.). Accordance of absorptive ability of soils to the content of fraction of physical clay, silt, humus has been determined. The largest content and variation of absorbed magnesium in soil sorption complex of trenching layers of light suglinic and susand turf-steppe soils of high river terraces and the lowest content in black south soils and dark-chestnut soils have been established. It has been established that for genetically different soils with high content of exchanged magnesium the high density of formation, low general porosity, air-volume, water-irrigation, micro-aggregation and also clods, cracks and dust in dry condition, absence of illuviration are typical. Kation-anion composition of easy soluble salts in soils and in irrigation waters has been analyzed in details. The sum of all toxic water soluble salts in black south soils was 0.31 mg-eq./100 gr., magnesium salts (MgCO3, Mg(HCO3)2, MgCl2, MgSO4) – 0.18 mg-eq./100 gr. or 58 % from the sum of toxic salts. In dark-chestnut soils these indexes were 0.16 and 0.11 mg-eq./100 gr. and 69 %; in turf-steppe light suglinic soils – 0.32 and 0.18 mg-eq./100 gr. and 56 %; and for turf-steppe susand soils they were 0.26 and 0.15 mg-eq./100 gr. and 58 %. In all soils chlorides magnesium prevailed over toxic salts (NaCl+MgCl2+CaCl2). In south black soils and turf-steppe soils in layer 0–60 cm there were both toxic and magnesium salts. Dark-chestnut soils in comparison with above said ones have less toxic salts and less magnesium salts, but their part in the sum of all salts was the highest – 69 %. The less content of toxic salts in dark-chestnut soils in comparison with others is attributed to their location to good drained height in Ochakov region. Probability of irrigation magnesium solonetzation of soils under long watering of orchards and vineyards by water from artesian well, Ingulets canal and from pond has been studied. In fresh and weakly mineral waters among toxic salts the magnesium salts (67-88%) as also in soils, chloride of magnesium are prevailed. Prevailing of magnesium over calcium in irrigated waters reduces quality of water and leads to accumulation of Mg2+ in soil sorption complex and negatively influences on soils. The following conclusions have been done: Genetically different low natrium remaining alkolinic with high content of exchanged magnesium in soil absorption complex trenching soils are characterized by high density, low porosity, air-volume, water-permeability, micro-aggregation and also clods, cracks and dust in dry condition, absence of illuviration. In soils and irrigation waters magnesium salts prevail over toxic easy soluble salts (67–88 % and 56–69 %). There are the probable sources of large accumulation of magnesium in soil absorption complex, magnesium solonetziration and the reason of unfavourable soil conditions.