Studies of the water-physical, physical-chemical and biological properties of meadow-chernozem soils were carried out on a rice irrigation system located in the present-day delta of the Kuban River. Rice meadow-chernozem soils have good water and general physical properties of humus layers. An increase in compaction is observed in the lower horizons of these soils. Meadow-chernozem soils are distinguished by low content of organic matter in arable horizons (3,2-3,4 %), neutral reaction of soil solution (рН 6,8-6,9) and high indices of cation exchange capacity (38,7-39,1 mmol/100g). The mycological composition of the studied soils in the autumn-spring periods was identified and identified. The soil was more saturated with representatives of the suppressive group at the beginning of rice vegetation, the opportunistic group was not detected and the antiphytopathogenic potential was 1:2. The spring-fed rice crop rotations soils are prone to soil stresses that are oversaturated with suppressors. In autumn, the ratio of conditionally suppressive to saprotrophic and pathogenic mycota was 1.5:4.5:7. The growth of colonies of the micromycete genus Trichoderma is traced, which confirms the beginning of a long process and the slow recovery of soil degradation processes.
Background: The studies were carried out on the Maryano-Cheburgolsky irrigation array in the Krasnoarmeisky district of the Krasnodar Territory. Aim: This work aims to study the oxidation-reduction processes and activity of iron compounds in meadow-chernozem and meadow-boggy soils of rice agrocenoses of the Kuban region. Methods: Soil samples were taken from paddy fields occupied by rice and perennial grasses, in which the pH value, redox potential (Eh, mV), magnetic susceptibility (χ×10-3 S.I. units), and the content of active iron compounds (FeO and Fe2O3, mg/100 g) were determined. Results and Discussion: The reductive processes created in the soils of rice fields after flooding led to the transformation of poorly soluble Fe2O3 compounds into more active reaction forms of FeO. The maximum content of FeO and the minimum amount of Fe2O3 were recorded during the period of negative Eh values. The maximum reduction of iron in meadow-boggy and meadow-chernozem soils was achieved by the phase of flowering of rice plants at Eh = -127, pH = 7.36 units, rH2 = 10 and Eh = -152...-167 mV, pH = 6.89-7.10 units, rH2 = 9, respectively. Conclusions: In the soil of permanent rice cultivation, the dynamics of Eh and iron compounds are similar to the fields of rice crop rotation. In non-flooded soils of rice fields under perennial grasses, the oxidative regime prevails, and the transformation of iron compounds is not expressed. The minimum values of χ coincide with the maximum content of ferrous iron in soils at negative Eh values, which corresponds to the rice flowering phase. Correlation coefficients of χ with Eh, FeO, and Fe2O3 equal from +0.66 to +0.75, from -0.69 to -0.84, and from +0.74 to +0.77, respectively. The χ value increases in the soil under crops of perennial grasses with a predominance of oxidative processes. The correlation coefficient between χ and Fe2O3 equals from +0.83 to +0.90.
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