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Vol 73, No 3 (2018)

Genesis and Geography of Soils

Modern Soil State of Reclaimed Lands (Northern Meshchera Lowlands, Vladimir Oblast) under Agricultural Stagnation Conditions

Avetov N.A., Avetyan S.A., Shishkonakova E.A.

Abstract

Agriculture in the northern Meshchera lowlands is experiencing considerable difficulties due to both natural causes and the socioeconomic situation in Vladimir oblast. Some properties of reclaimed (drained) sod-podzolic soils remain sufficiently stable, including the considerable thickness of the arable horizon and the relatively high humus content. From the mid-1990s, a decrease in soil nutrient content and an increase in soil acidity have been observed. In recent years, state authorities have not allocated financial means for soil liming. The increase in precipitation in Northern Europe may lead to enhanced gleying in soil profiles and the subsequent transformation of sod-podzolic soils into sod-gley-podzolic. The article presents recommendations on land use.

Moscow University Soil Science Bulletin. 2018;73(3):95-99
pages 95-99 views

Influence of Vegetation on the Lability Characteristics of Sandur Areas of the Bryansky Les Nature Reserve

Kazakova A.I., Semikolennykh A.A., Gornov A.V., Gornova M.V., Lukina N.V.

Abstract

We have assessed the influence of vegetation on the labile characteristics (acidity, total carbon and nitrogen content, and available nutrients) of automorphic soils of polydominant coniferous–broadleaf forests and dwarf-shrub–green-moss pine forests of the Bryansky Les Nature Reserve. Despite the comparable gross and grain size compositions of soil-forming rocks, the differences of soils of these forest types are determined by the influence of vegetation, mainly by its ability to form litters of different quality and to regulate the amount of precipitation percolating through the forest canopy and contributing to the nutrient removal. Soils of pine forests have a higher acidity and lower contents of total nitrogen, organic carbon, and available nutrients than do soils of coniferous–broadleaf forests. The stand of pine forests has a low crown density, which leads to more intensive nutrient removal by atmospheric precipitation infiltrating through the soil.

Moscow University Soil Science Bulletin. 2018;73(3):100-106
pages 100-106 views

Effect of Moisture Deficiency and Increased Salt Content on Silicon State of Some Soils of European Part of Russia and Central China

Yuqiao L., Xu B., Bocharnikova E.A., Matichenkov V.V., Khomiakov D.M., Pakhnenko E.P.

Abstract

Soluble forms of silicon affect a number of physical, chemical, and biological soil properties. Optimization of silicon nutrition enhances plant tolerance to biotic and abiotic stresses. Current climate change and anthropogenic impacts can alter the soil silicon state. Model laboratory experiments conducted with upper horizons of sod-podzolic soil, gray forest soil under different plant associations, chernozem, paddy soil, and red subtropical soil showed that insufficient soil moistening led to a reduction in soil monosilicic acid by 15 to 36% and simultaneous increases in polysilicic acid by 9 to 45%. Soil cultivation resulted in a decrease in plant-available soil silicon. An increase in NaCl concentration in the soil caused an increase in both monomers and polymers of silicic acid by 6 to 79%. The mobile equilibrium and lability of the numerical values of the parameters of the silicon state of the soil–plant system are revealed. These factors should be taken into account when implementing the 4R-STRATEGY for optimizing mineral nutrition in agricultural crops.

Moscow University Soil Science Bulletin. 2018;73(3):107-112
pages 107-112 views

Soil Biology

Application of the Succession Approach in Studying the Prokaryotic Community in Soils of East Antarctica

Kudinova A.G., Lysak L.V., Soina V.S., Mergelov N.S., Dolgikh A.V.

Abstract

Prokaryotic communities of soils in oases of East Antarctica were studied at a model experiment with application of the succession approach. The total number of prokaryotes and filtered forms of prokaryotes, as well as the taxonomical diversity of the saprotrophic bacterial complex, were determined in two soil samples differing in organic matter content at temperatures of 5 and 20°C. We fixed the maximum total number of bacteria on the 14th day and the minimum number on the 1st and 160th (the end of the experiment) days in all variants. The amount and percentage of filtered forms of prokaryotes were the highest at the start of the experiment and the smallest on the 14th day. It is assumed that revival of Antarctica soils by humidification and incubation at temperatures above zero favors activation of dormant cells and their transition to viable status. Filtered forms of prokaryotes can be assigned to the pool of cells, which makes it possible to preserve bacteria at extremely low temperatures and without available water and nutrients. The succession approach enables more complete characterization of the taxonomic diversity of the saprotrophic bacterial complex and isolation of a wider genera of gram-negative bacteria than with a single inoculation of soil kept frozen. So it can be recommended for studying the prokaryotic community of Antarctica soils in model experiments.

Moscow University Soil Science Bulletin. 2018;73(3):113-118
pages 113-118 views

Sustainability of Extreme Microbial Ecosystems to the Comprehensive Impact of Physical Factors of the Martian Regolith

Cheptsov V.S., Vorobyova E.A., Polyanskaya L.M., Gorlenko M.V., Pavlov A.K., Lomasov V.N.

Abstract

As the key parameters of the Martian regolith, we have studied the combined effect of gamma radiation (1 and 10 kGy), low temperature (–50°C), and low pressure (1 Torr) on the microbial communities of extreme ecotopes of Earth to estimate the duration of cryopreservation of hypothetical Martian ecosystems in a viable state. The obtained data suggest that cryopreservation of viable microorganisms in the surface layer of the regolith is possible for at least 130000 years; at a depth of 30 cm, for 170000 years; at a depth of 2 m (the depth which the ExoMars 2020 mission must reach), for 330000 years; and at a depth of 5 m, for 2 million years.

Moscow University Soil Science Bulletin. 2018;73(3):119-123
pages 119-123 views

Soil Physics

Hysteresis of the Water Retention Curve: Wetting Branch Simulation Based on the Drying Curve

Shein E.V., Mady A.Y.

Abstract

Hysteresis of the soil water retention curve (SWRC), manifested as a difference between equilibrium curves of soil wetting and drying (hysteresis loop), is a phenomenon specific to soil hydrology, which is of practical importance for calculating irrigation norms. We have attempted to derive a model of the wetting curve from the drying curve. Modeling was based on parameters proposed by van Genuchten [6] and certain soil physical characteristics. SWRC hysteresis characteristics were obtained experimentally using capillarimetric measurements for wetting and drying curves at soil water pressures ranging from 0 to –800 cmH2O. Two models, М-1 and М-2, based on the hypothesis of dissimilarity of parameters α for wetting (αw) and drying (αd) and the constancy of other parameters of the van Genuchten SWRC approximation for both curves of the hysteresis loop, have been developed for wetting curve assessment based on the drying curve. The M-1 error (RMSE = 0.05 cm–1) was less than that of M-2 (RMSE = 0.06 cm–1), which used clay content and soil density as predictors, as well as that of the well-known model proposed by Kool and Parker [11]. This approach to derive the wetting curve from the drying curve for a presumed correlation between the values of one parameter and equal values of the other parameters, can be used to predict an estimate of the SWRC hysteresis for a specific soil.

Moscow University Soil Science Bulletin. 2018;73(3):124-128
pages 124-128 views

Support Vector Machine and Nonlinear Regression Methods for Estimating Saturated Hydraulic Conductivity

Shein E.V., Mady A.Y.

Abstract

Pedotransfer functions (PTFs) are widely used for hydrological calculations based on the known basic properties of soils and sediments. The choice of predictors and the mathematical calculus are of particular importance for the accuracy of calculations. The aim of this study is to compare PTFs with the use of the nonlinear regression (NLR) and support vector machine (SVM) methods, as well as to choose predictor properties for estimating saturated hydraulic conductivity (Ks). Ks was determined in direct laboratory experiments on monoliths of agrosoddy-podzolic soil (Umbric Albeluvisol Abruptic, WRB, 2006) and calculated using PTFs based on the NLR and SVM methods. Six classes of predictor properties were tested for the calculated prognosis: Ks-1 (predictors: the sand, silt, and clay contents); Ks-2 (sand, silt, clay, and soil density); Ks-3 (sand, silt, clay, soil organic matter); Ks-4 (sand, silt, clay, soil density, organic matter); Ks-5 (clay, soil density, organic matter); and Ks-6 (sand, clay, soil density, organic matter). The efficiency of PTFs was determined by comparison with experimental values using the root mean square error (RMSE) and determination coefficient (R2). The results showed that the RMSE for SVM is smaller than the RMSE for NLR in predicting Ks for all classes of PTFs. The SVM method has advantages over the NLR method in terms of simplicity and range of application for predicting Ks using PTFs.

Moscow University Soil Science Bulletin. 2018;73(3):129-133
pages 129-133 views