The aim of the work is to evaluate the tendency of soil formation processes of ordinary chernozem irrigated long-term with fresh water. The studies were conducted in Bagaevsky district of Rostov region. The object of research is the long-term irrigated ordinary chernozem (more than 50 years). To solve this problem the research of soil characteristics was carried out on the following parameters: particle-size distribution, bulk density, structural status, water extract composition, content of exchangeable sodium, magnesium and calcium, total humus and its group composition, carbonate and nutrients content. According to these parameters the evaluation of soil-forming processes has been done. It’s been found out that regular and prolonged irrigation by fresh water with irrigation rates from 2500 to 5000 cubic meters per hectare in ordinary chernozems causes the following negative soil processes: overcompaction of soils (ordinary chernozems with bulk density of arable layer equal to 1.23 tonnes per cubic meter refers to the highly compacted soils with a content of 39 % healthy aggregates and only 32 % of water-resistant ones); visually observed water saturation, marked by the presence of excessive moisture in the form of local puddles on separate sites for 2–3 weeks, preventing the spring field work; deep alkalinity and saline process associated with the rise of mineralized ground water above the critical level; low humus content (3.41 % in the layer of 0–40 cm) and its fulvate-humate composition are indicative of the dehumification in these soils; enleaching with fresh water irrigation is confirmed by carbonate occurrence lower 60 cm and low content of nutrients; low content of phosphorus and humus and average content of potassium in the long-term irrigated ordinary chernozems indicate the process of agro-depletion.
Keywords: soil-forming processes, irrigation, soil properties, humus, overcompaction of soil, water saturation, leaching, dehumidification, agrodepletion.
