Научный журнал Российского НИИ проблем мелиорации (Nov 2020)
FACTORS ENHANCING THE ADVERSE EFFECTS OF LONG-TERM IRRIGATION ON THE ORDINARY CHERNOZEM PROPERTIES
Abstract
Purpose: to identify factors enhancing the negative impact of long-term irrigation on soil fertility. Materials and methods. The influence of mineralization and quality of irrigation water on ordinary chernozems (Neklinovsky district), the level of groundwater table on the reclamation state and soil fertility of ordinary chernozems (Bagaevsky district of Rostov region), the structure of crop rotations was studied, and optimal moisture levels for different irrigation modes were established. Results. Long-term use of sulphate-sodium low-mineralized water led to the degradation of ordinary chernozems. They acquired the properties of medium alkaline and medium solonized soils: alkalinity – 1.29 mmol(eq)/100 g, solonetzicity – 7 % of exchangeable sodium from the total soil absorbing complex (SAC), soil bulk density – 1.34 t/m³, humus content decreased by 23 % during its transformation from fulvate-humate to humate-fulvate. The close ground waters table and their mineralization of 5 g/dm³ contributed to secondary salinization. Fertility reproduction is observed only with the introduction of organic fertilizers. The increase in humus content in the alfalfa-corn crop rotation was 0.68 % with the introduction of 60 t/ha of manure after 4 years of corn cultivation in comparison with the humus content after 3 years of alfalfa cultivation, and in the grain feed – 0.55 %. It was found that with an increase of irrigation rate up to 30 %, leaching of exchangeable calcium is observed with a simultaneous increase in the content of exchangeable sodium up to 4 % of the total SAC, which contributes to an increase in bulk density of ordinary chernozem to 1.38 t/m³. In the variant with over-irrigation, the humus content decreased by 0.22 % over 4 years of regular irrigation, and in the variant with the optimal and reduced by 40 and 60 % rates, its amount decreased from 0.04 to 0.07 %, as in dry land. Conclusions. The investigated factors enhance under certain conditions the negative impact of long-term irrigation on the properties of ordinary chernozem.
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