Agrogray Soils Research Articles

Statistical parameters of the properties of agro-gray soils in the Northern part of the forest-steppe

The paper analyzes the regional statistical characteristics of analytical and morphometric properties of agro-gray soils formed in one-factor conditions of the Privyatskaya band of the Pre-Kama region of the Republic of Tatarstan. The sampling of analytical data was carried out in accordance with the systematic group and non-eroded soil analogues. The upper part of the soil profile of the studied soil has a low humus content, medium acid reaction, the profile distribution of the sum of absorbed bases is almost uniform and is in the range of 22.6 to 26.8 mmol /100 g of soil. Generalization of the accumulated analytical and morphological information is a zero cycle of monitoring of arable soils and can serve as a reference for comparison to identify changes in the properties and morphological structure of arable soils in the region. In conditions of intensive agriculture, statistical parameters make it possible to purposefully manage soil fertility in the studied region.

Magnesium in soils and plants of a sloping agrolandscape in the south-east of West Siberia

The aim of the study. To carry out a comparative assessment of the magnesium status in soils, situated on the various hypsometric levels of sloped agrolandscape and with different soil organic matter content by measuring total, mobile (exchangeable) and water-soluble magnesium in soils and to compare different analytical methods for determining magnesium in soils and plants. Location and time of the study. The study site was located in the Cis-Salair drained plain in the south-east of West Siberia (55˚02΄20˝N; 83˚50΄00˝E), administratively being within the boundaries of the Toguchin district of the Novosibirsk region, Russia. Altitude increments were marked on the slope positions of the investigated plot of 225 hectares in area and 4 km in length: the upper part of the slope BCI (280-310 m a.s.l. ), the midslope BCII (260-280 m) and BCIII (220-260 m), and the lower slope BCIV (190-220 m) (see figure 1). Soil and plant samples were collected in July 2013. Materials and methods. Prevailing soils were podzolized and leached chernozems, dark-gray and gray-forest soils according to the classification of soils of the USSR (1977), which correspond to clayey-illuvial eluvialed and dark-tongue agrochernozems, agro-dark gray soils and agro-gray soils to according of the Russian soil classification (2004, 2008), or Luvic Greyzemic Chernozems, Haplic Chernozems, Luvic Greyzemic Phaeozems, Luvic Retic Greyzemic Phaeozems by WRB Soil Classification (2014) (see table 1, figure 1). Individual soil samples (n=55) were taken with a drill from 0-30 cm layer (ploughed horizon) according to an irregular grid. The aboveground phytomass stock of oat-pea mixture (n=38) was collected using the hay cutting method on the ​​0.25 m2 area. The geographical coordinates of the soil and plant sampling sites were determined using the geopositioning system (GPS, Garmin eTrex Vista). The soil samples were analyzed for organic carbon content by dichromate digestion. Overall the studied soils were grouped according to soil organic matter (SOM) content into high-SOM (5-8%) and medium-SOM soils (3-5%). Total magnesium (Mgtot) was measured in dry powdered samples by atomic emission spectrometry; mobile (exchangeable) magnesium was measured by atomic absorption spectrometry using 1 M KCl, 1 M CH3COONH4, 0.1 M C4H4O5(NH4)2 and 0.5 M CH3COOH as extracting solutions. The same extracts were used to measure water-soluble magnesium atomic absorption spectrometry and capillary electrophoresis. The content of total magnesium in plants was determined by atomic absorption spectrometry using two methods of sample digestion, namely wet ashing in a mixture of sulfuric and perchloric acids and dry ashing followed by quantitative transfer of the digest with 1 M HCl. Magnesium content in soils and plants was presented per element and calculated on the air-dry mass basis. Statistical analyses (descriptive statistics, correlation analysis, calculation of student criterion and Mann-Whitney U-test) were performed using Microsoft Office Excel 2007 and Statistica v.6.1. Results. The average content of total magnesium in the slope soils varied from 0.79 to 0.88%. The proportion of mobile magnesium in its total content in soils averaged 3.3-6.0%, whereas that of water-soluble magnesium was 0.06-0.13%. In medium-SOM soils down along the slope the total magnesium content gradually decreased: agrochernozems → agro-dark gray soils → agro-gray soils (see table 2, figure 2). The similar pattern was revealed an earlier for the content of total phosphorus and total potassium in the slope soils. The average content of mobile magnesium in the high-SOM soils on the upper part of the slope (BCI) varied from 3.2 to 4.0 cmol(+)∙kg-1, depending on the extractant used. The medium-SOM soils (BCII-IV) contained 2.2 to 3.2 cmol(+)∙kg-1 of mobile magnesium. Atomic absorption spectrometry and capillary electrophoresis produced very close values water-soluble magnesium content in soils: on average, 0.06-0.08 and 0.04-0.09 cmol(+)∙kg-1, respectively. However, capillary electrophoresis proved to be more sensitive to the decreased content of water-soluble magnesium in the midslope medium-SOM soils. Magnesium content in aboveground phytomass of an oat-pea mixture, collected in the tillering phase of its cereal component, determined by dry ashing, averaged 0.21-0.26%, which corresponded to the optimal level of the element; estimated by wet ashing it was 1.3-1.6 times lower (see table 2). Conclusions. Under the conditions of the sloping agrolandscape of the Cis-Salair in the south-eastern part of West Siberia, high-SOM soils in the upper part of the slope are characterized by higher content of mobile magnesium as compared with the medium-SOM soils mid- and downslope. We believe that for assessing magnesium status of soils it is more expedient to use 1 M KCl or 1 M CH3COONH4 to determine mobile (exchangeable) magnesium. Moreover, these extractants can be used for simultaneous determination of other soil properties, i.e. exchangeable calcium and potassium content, pHsalt, etc.

Magnesium in soils and plants of a sloping agrolandscape in the south-east of West Siberia

The aim of the study. To carry out a comparative assessment of the magnesium status in soils, situated on the various hypsometric levels of sloped agrolandscape and with different soil organic matter content by measuring total, mobile (exchangeable) and water-soluble magnesium in soils and to compare different analytical methods for determining magnesium in soils and plants. 
 Location and time of the study. The study site was located in the Cis-Salair drained plain in the south-east of West Siberia (55°02΄20˝N; 83°50΄00˝E), administratively being within the boundaries of the Toguchin district of the Novosibirsk region, Russia. Altitude increments were marked on the slope positions of the investigated plot of 225 hectares in area and 4 km in length: the upper part of the slope BCI (280-310 m a.s.l. ), the midslope BCII (260-280 m) and BCIII (220-260 m), and the lower slope BCIV (190-220 m) (see figure 1). Soil and plant samples were collected in July 2013. 
 Materials and methods. Prevailing soils were podzolized and leached chernozems, dark-gray and gray-forest soils according to the classification of soils of the USSR (1977), which correspond to clayey-illuvial eluvialed and dark-tongue agrochernozems, agro-dark gray soils and agro-gray soils to according of the Russian soil classification (2004, 2008), or Luvic Greyzemic Chernozems, Haplic Chernozems, Luvic Greyzemic Phaeozems, Luvic Retic Greyzemic Phaeozems by WRB Soil Classification (2014) (see table 1, figure 1). Individual soil samples (n=55) were taken with a drill from 0-30 cm layer (ploughed horizon) according to an irregular grid. The aboveground phytomass stock of oat-pea mixture (n=38) was collected using the hay cutting method on the 0.25 m2 area. The geographical coordinates of the soil and plant sampling sites were determined using the geopositioning system (GPS, Garmin eTrex Vista). 
 The soil samples were analyzed for organic carbon content by dichromate digestion. Overall the studied soils were grouped according to soil organic matter (SOM) content into high-SOM (5-8%) and medium-SOM soils (3-5%). Total magnesium (Mgtot) was measured in dry powdered samples by atomic emission spectrometry; mobile (exchangeable) magnesium was measured by atomic absorption spectrometry using 1 M KCl, 1 M CH3COONH4, 0.1 M C4H4O5(NH4)2 and 0.5 M CH3COOH as extracting solutions. The same extracts were used to measure water-soluble magnesium atomic absorption spectrometry and capillary electrophoresis. The content of total magnesium in plants was determined by atomic absorption spectrometry using two methods of sample digestion, namely wet ashing in a mixture of sulfuric and perchloric acids and dry ashing followed by quantitative transfer of the digest with 1 M HCl. Magnesium content in soils and plants was presented per element and calculated on the air-dry mass basis. Statistical analyses (descriptive statistics, correlation analysis, calculation of student criterion and Mann-Whitney U-test) were performed using Microsoft Office Excel 2007 and Statistica v.6.1. 
 Results. The average content of total magnesium in the slope soils varied from 0.79 to 0.88%. The proportion of mobile magnesium in its total content in soils averaged 3.3-6.0%, whereas that of water-soluble magnesium was 0.06-0.13%. In medium-SOM soils down along the slope the total magnesium content gradually decreased: agrochernozems → agro-dark gray soils → agro-gray soils (see table 2, figure 2). The similar pattern was revealed an earlier for the content of total phosphorus and total potassium in the slope soils. The average content of mobile magnesium in the high-SOM soils on the upper part of the slope (BCI) varied from 3.2 to 4.0 cmol(+)ꞏkg-1, depending on the extractant used. The medium-SOM soils (BCII-IV) contained 2.2 to 3.2 cmol(+)ꞏkg-1 of mobile magnesium. Atomic absorption spectrometry and capillary electrophoresis produced very close values water-soluble magnesium content in soils: on average, 0.06-0.08 and 0.04-0.09 cmol(+)ꞏkg-1, respectively. However, capillary electrophoresis proved to be more sensitive to the decreased content of water-soluble magnesium in the midslope medium-SOM soils. Magnesium content in aboveground phytomass of an oat-pea mixture, collected in the tillering phase of its cereal component, determined by dry ashing, averaged 0.21-0.26%, which corresponded to the optimal level of the element; estimated by wet ashing it was 1.3-1.6 times lower (see table 2). 
 Conclusions. Under the conditions of the sloping agrolandscape of the Cis-Salair in the south-eastern part of West Siberia, high-SOM soils in the upper part of the slope are characterized by higher content of mobile magnesium as compared with the medium-SOM soils mid- and downslope. We believe that for assessing magnesium status of soils it is more expedient to use 1 M KCl or 1 M CH3COONH4 to determine mobile (exchangeable) magnesium. Moreover, these extractants can be used for simultaneous determination of other soil properties, i.e. exchangeable calcium and potassium content, pHsalt, etc.

Changes in some properties of agro-gray soil fertility under the influence of biofertilizer

In the field experiment with the agro-gray soil of the Krasnoyarsk forest-steppe, the improvement of the agro-physical properties was established with the use of organic fertilizers, regardless of their type and application rate. Under the influence of bio-fertilizer and chicken manure introduced into the agro-gray soil, there is a tendency to increase the amount of humus and nitrate nitrogen, mobile phosphorus and the yield of wheat grain. The correlation between the yield of wheat grain and mobile forms of humus is estimated at the average level. Using the method of multiple regression, a model of wheat yield was calculated, according to which it depends on the content of mobile humus substances.

Sustainability of Agro-Gray Soil to Pollution and Acidification, and its Biodiagnostics

The aim of investigations is to study the resistance of agro-gray heavy loamy soil to heavy metal pollution and acidification on the basis of determining corresponding parameters of buffering, as well as microbiological activity, as a biological diagnosis of fertility potential under stress conditions.The object of investigations is the agro-gray soil of different cultivation degrees: fertile and infertile. In fertile soil, the humus content in barren soil was 2.2-2.5 % and that in fertile soil was 5.4 %.A model of soil resistance to heavy metals and acidification has been developed. The low level of stability of the agro-gray soil appears when the maximum Langmuir adsorption value is less than 91 mM / kg for zinc, less than 104 mM / kg for copper, less than 93 mM / kg for lead, and less than 61 mM / kg for cadmium. The average level of stability is provided for zinc, copper and lead in the range from 91 to 143 mM / kg, 104 - 130 mM / kg and 61 - 132 mM / kg, respectively. A high level of soil stability is guaranteed if the maximum adsorption value exceeds 93 - 143 mM / kg. Bio diagnostics included a series of experiments with imitation of pollution and acidification. Soil pollution was modeled by adding 200 and 600 mg / kg of copper to it (experiment 1). In experiment 2, soil was polluted by cadmium at the rate of 10, 30 and 100 MAC. The exposition was 1, 10, 35 and 57 days.Acidification of the soil was simulated by adding dilute sulfuric acid at a rate of 0.018, 0.044, and 0.120 mM / l (experiment 3).In experiment 4, the effect of zinc on the activity of azotobacter in barren and fertile soil was studied. The dose of zinc was 50 and 100 mg / kg.It was established that when the content of humus is not less than 5 %, the average decrease in activity for all groups of microorganisms was not more than 20 % as compared with clean samples. When the humus content was below 3 %, the microbiological activity decreased by more than 30 %.

Specific Features of Profile Distribution and Crystallochemistry of Phyllosilicates in Soils of the Cisbaikal Forest-Steppe

The mineralogical composition of agrogray, dark gray, and agro-dark gray soils (Luvic Greyzemic Retic Phaeozems); agro-dark gray residual-calcareous soils (Calcaric Cambic Phaeozems); clay-illuvial agrochernozems (Luvic Chernic Phaeozems); and agrochernozems with migrational–mycelial carbonates (Haplic Chernozems) developed in the forest-steppe of Central Siberia within the Irkutsk Depression has been studied. The clay (<1 μm) fraction separated from these soils consists of mixed-layer minerals with alternating layers of hydromica, smectite, vermiculite, and chlorite; the proportions between them change within the soil profiles. The clay fraction also contains hydromicas, kaolinite, chlorite, and some admixture of the fine-dispersed quartz. Each type of the soils is characterized by its own distribution pattern of clay material with specific alternation of layers in the mixed-layer formations. Mixed-layer minerals of the chlorite–vermiculite type predominate in the upper horizons of texture-differentiated soils. Down the soil profile, the content of mixed-layer mica–smectitic minerals increases. In the clay fraction of arable dark gray-humus soils with residual carbonates, the distribution of the clay fraction and major mineral phases in the soil profile is relatively even. An increased content of well-crystallized kaolinite is typical of these soils. The parent material of agrochernozems has a layered character: the upper horizons are generally depleted of clay, and the middle-profile and lower horizons are characterized by the considerable kaolinite content. In general, the clay material of soils of the Tulun–Irkutsk forest-steppe differs considerably from the clay material of foreststeppe soils developed from loesslike and mantle loams in the European part of Russia. In particular, this difference is seen in the proportions between major mineral phases and between biotitic and muscovitic components, as well as in the degree of crystallinity and behavior of kaolinite and chlorite.

Effect of rainfall intensity and slope steepness on the development of soil erosion in the Southern Cis-Ural region (A model experiment)

The effect of rainfall intensity on the erosion of residual calcareous agrogray soils and clay-illuvial agrochernozems in the Southern Cis-Ural region on slopes of different inclination and vegetation type has been studied by simulating with a small-size sprinkler. It has been shown that soil loss linearly depends on rainfall intensity (2, 4, and 6 mm/min) and slope inclination (3° and 7°). When the rainfall intensity and duration, and the slope inclination increase, soil loss by erosion from agrogray soils increases higher than from agrochernozems. On the plowland with a slope of 3°, runoff begins 12, 10, and 5 min, on the average, after the beginning of rains at these intensities. When the slope increases to 7°, runoff begins earlier by 7, 6, and 4 min, respectively. After the beginning of runoff and with its increase by 1 mm, the soil loss from slopes of 3° and 7° reaches 4.2 and 25.7 t/ha on agrogray soils and 1.4 and 4.7 t/ha on agrochernozems, respectively. Fallow soils have higher erosion resistance, and the soil loss little depends on the slope gradient: it gradually increases to 0.3–1.0 t/ha per 1 mm of runoff with increasing rainfall intensity and duration. The content of physical clay in eroded material is higher than in the original soils. Fine fractions prevail in this material, which increases their humus content. The increase in rainfall intensity and duration to 4 and 6 mm/min results in the entrapment of coarse silt and sand by runoff.

Use of empirical Bayesian kriging for revealing heterogeneities in the distribution of organic carbon on agricultural lands

Empirical Bayesian kriging (EBK) is a modern mapping method, which accounts for the uncertainty of parameter estimates in functions describing the changes in property variance with increasing the survey area (variograms). Cartograms plotted using ordinary kriging and EBK have been compared for the data on the content of organic carbon in an isolated land with agrogray soils (Greyzemic Phaeozems (Loamic, Aric)) located in the Bryansk Opol’e region. It is shown that the cartograms of EBK errors reveal the structure of the spatial variability of the property, which cannot be revealed by other methods. Thus, the EBK method can be recommended for revealing heterogeneities in disputable cases.

The methods of geomorphometry and digital soil mapping for assessing spatial variability in the properties of agrogray soils on a slope

The relationships between the morphometric parameters (MPs) of topography calculated on the basis of digital elevation model (АSTER GDEM, 30 m) and the properties of the plow layer of agrogray soils on a slope were analyzed. The contribution of MPs to the spatial variability of the soil moisture reached 42%; to the content of physical clay (<0.01 mm particles), 59%; to the humus content, 46%; to the total nitrogen content, 31%; to the content of nitrate nitrogen, 28%; to the content of mobile phosphorus, 40%; to the content of exchangeable potassium, 45%; to the content of exchangeable calcium, 67%; to the content of exchangeable magnesium, 40%; and to the soil pH, 42%. A comparative analysis of the plow layer within the eluvial and transitional parts of the slope was performed with the use of geomorphometric methods and digital soil mapping. The regression analysis showed statistically significant correlations between the properties of the plow layer and the MPs describing surface runoff, geometric forms of surface, and the soil temperature regime.

Effect of soil type and overgrowth time on agrochemical parameters of fallow lands located along the accumulation trend of material–energy flow

It has been shown that changes in agrochemical parameters of fallow lands depend on the type of soil and the time of overgrowth. A gradual acidification of the postagrogenic layer, its differentiation into two sublayers by the contents of humus and total exchangeable bases, and a decrease in the content of mineral nutrients are observed in overgrown agrosoddy-podzolic soils. In agrogray soils, these processes are less intense.

Агрогенная и постагрогенная трансформация почв Льговского района Курской области

In this work we consider the processes of degradation and changes of properties of gray forest soils and migration-mycellar chernozems as a result of agrogenesis and erosion. We also consider progradation processes, which lead to forming of anthropogenic deeply transformed soils, and post-agrogenic processes, which are characterized by reclamation of the natural parameters of soils. The most dramatic changes occur in the composition of profiles, and also in morphological, physical and agrochemical properties. The results of investigations allowed us to determine four trends of the development: agrogenically-degradational and also agrogenically progradational, which is familiar for large areas of arable lands, and also postagrogenic nature-like, which is typical for laylands. The most of the soils, involved in agricultural activivities, are affected by degradation as a result of agrogenesis. This is manifested in the developments of processes of surface and linear erosion, in the decrease of humus content and the thickness of humus layer of the soil mass. There are also observed such processes as forming of compaction under the arable layer, the changes in structure and the decrease of water resistance of aggregates. In the agro-gray soils of agrogenically-degradational trend we observe the significant decrease of the thickness arable layer and humus content, and as contrary, the increase of silt and physical clay content, and also the increase of solidity values in comparison to the gray soils. In the same agrogray soils of agrogenically-erosional trend, we observed the increased density and solidity, the increase of non-agregated material content, the decrease of humus content, the decrease of melkozem content and the decrease of fine fraction content, which are valuable for plants. The results obtained are the additional information base for the convertion of Uniformed State Register of the soil resources of Russia on a regional and local level.

Modern climate fluctuations and their correlation with CO2 emission in agroecosystems on agrogray soil in the forest steppe of the Cis-Baikal region

The correlation between climatic factors and CO2 emission into the atmosphere in particular seasons has been studied during the long-term (1997–2012) monitoring of agroecosystems on agrogray soil in the forest steppe of the Cis-Baikal region. It is revealed that CO2 emission depend to a greater rate on the water and temperature characteristics in spring and autumn than in summer. The part of summer CO2 flow from the fallow and crop land was 67 and 72%, respectively. The long-term annual average CO2 emission into the atmosphere from the fallow land and croplands under spring wheat evaluated within a 16-year-long observation period is 173 and 229 g of C per m2, respectively.

Assessing the stability of soil organic matter by fractionation and 13C isotope techniques

Carbon pools of different stabilities have been separated from the soil organic matter of agrochernozem and agrogray soil samples. The work has been based on the studies of the natural abundance of the carbon isotope composition by C3-C4 transition using the biokinetic, size-density, and chemical fractionation (6 M HCl hydrolysis) methods. The most stable pools with the minimum content of new carbon have been identified by particle-size and chemical fractionation. The content of carbon in the fine fractions has been found to be close to that in the nonhydrolyzable residue. This pool makes up 65 and 48% of Corg in the agrochernozems and agrogray soils, respectively. The combination of the biokinetic approach with particle-size fractionation or 6 M HCl hydrolysis has allowed assessing the size of the medium-stable organic carbon pool with a turnover time of several years to several decades. The organic matter pool with this turnover rate is usually identified from the variation in the 13C abundance by C3-C4 transition. In the agrochernozems and agrogray soils, the medium-stable carbon pool makes up 35 and 46% of Corg, respectively. The isotope indication may be replaced by a nonisotope method to significantly expand the study of the inert and mediumstable organic matter pools in the geographical aspect, but this requires a comparative analysis of particle-size and chemical fractionation data for all Russian soils.

Transformation of the organic matter in an agrogray soil and an agrochernozem in the course of the humification of corn biomass

The transformation of the organic matter in the course of corn residues humification in an agrogray soil and an agrochernozem was studied in long-term experiments using the method of solid-phase 13C-nuclear magnetic resonance spectroscopy. The humification of the plant residues was found to be accompanied by a decrease in the content of the O-alkyl fragments comprising polysaccharides and polypeptides, an increase in the unsubstituted alkyds content, and by the relative accumulation of aromatic fragments and carboxyl groups. The most strongly transformed pool of the organic matter, as compared to the initial plant residues, was the humic acids with their maximal content of aromatic and carboxyl functional groups and the minimal content of O-alkyls. The chemically stable aromatic fragments were concentrated not only in the pool of humic acids; their content was 64–89% of the pool of the aromatic fragments identified in the soil organic matter. Therefore, to assess the stable pool, the distribution of the functional groups is necessary to be analyzed not only in the humic acids but also in the whole soil organic matter.

Effect of errors in positioning the sampling points on the assessment of the relationships between the remote sensing data and the soil properties

The stochastic modeling of the shift in coordinates of the sampling points was performed for a typical land plot in Bryansk opolie with the purpose to assess the influence of the accuracy of the sampling point positioning on the predicted properties of the plow horizon. It was proved that, for agro-gray soils, an occasional shift of the sampling points by 2–6 m regarding the coordinates on satellite photographs of superhigh resolution may significantly change the correlation between the soil properties and the brightness in the infrared channel. Based on the modeling data, the 95% confidence interval was estimated for the possible correlation coefficients of such properties of the arable agro-gray soil as the density, moisture, specific surface, carbon, and mobile nitrogen content. The use of the brightness in the infrared channel as a covariate for building charts may noticeably improve the map’s quality; however, it may unjustifiably complicate the mapping units delineation.

Physical properties of soils and the simulation of the hydrothermal regime for the complex soil cover of the Vladimir Opol’e region

A methodological approach to the physically sound mathematical simulation of the hydrothermal regime for a complex soil cover on an agricultural field scale was proposed. To realize the approach, it is necessary (1) to restore the hydrothermal regime of two contrasting soils using a physically sound mathematical model on the basis of the experimental thermophysical and hydrophysical characteristics, (2) to adapt and optimize the model using the available experimental regime data, (3) to determine the hydrophysical and thermophysical properties for the entire plot under study using pedotransfer functions, and (4) to restore the hydrothermal regime of the entire soil plot using a mathematical model and the meteorological data for a specific time period. The proposed procedure allows simulating the hydrothermal regime of an agrogray soil complex in the Vladimir Opol’e region with a normalized standard error of about 8%. The analysis of the hydrothermal regime for the soil cover of the studied plot calculated from the meteorological data for the period from May to August of 2009 showed that the lower temperature values were confined to the areas of the agrogray soils with the second humus horizon: their average temperature was lower than the temperature of the agrogray soils by 0.44, 0.93, and 1.32°C at depths of 20, 40, and 70 cm, respectively, and the differences between their sums of the active temperatures for the considered period of 2009 reached 89 and 74°C at depths of 20 and 40 cm, respectively.

Identification of labile and stable pools of organic matter in an agrogray soil

The intensity of decomposition of the organic matter in the particle-size fractions from a agrogray soil sampled in a 5-year-long field experiment on the decomposition of corn residues was determined in the course of incubation for a year. The corn residues were placed into the soil in amounts equivalent to the amounts of plant litter in the agrocenosis and in the meadow ecosystem. A combination of three methods—the particle-size fractionation, the method of 13C natural abundance by C3–C4 transition, and the method of incubation—made it possible to subdivide the soil organic matter into the labile and stable pools. The labile pool reached 32% in the soil of the agrocenosis and 42% in the meadow soil. Owing to the negative priming effect, the addition of C4 (young) carbon favored the stabilization of the C3 (old) carbon in the soil. When the young carbon was absent, destabilization or intense decomposition of the old organic matter was observed. This process was found even in the most stable fine silt and clay fractions.

Organophosphates in agrogray soils with periodic water logging according to the data of 31P NMR spectroscopy

The composition of organic phosphorus compounds was studied using the 31P NMR spectroscopy method in agrogray soils with periodic water logging. The phosphorus content was determined by the specific difference between the hydrological and the redox regimes of these soils. The phosphorus of the organic compounds in the agrogray soils with contrasting water regimes is composed mostly of phosphoric monoesters and diesters, including nucleic and teichoic acids. The relative distribution of the monoesters and inorganic orthophosphates is shown depending on the climate and the soil’s position in the relief. The area of the monoester peaks increases by two times and that of the mineral orthophosphate decreases by six times in the agro-gray soils of Bryansk opolie with an optimal regime of moistening and evaporation in comparison with the agro-gray gleyed soils of Kolomna opolie. As the degree of the soil hydromorphism in the sequence of deeply gleyed soils and gleyic soils increased, the portion of monoesters decreased. Favorable conditions for the microbial activity are formed in soils with a contrasting redox regime, and this is expressed in the accumulation of labile diesters. Inverse relationships were found between the distributions of the mono- and diesters in iron-manganic nodules and in the soils enclosing them; this was caused by the different mechanisms of the stabilization of the stable and labile phosphorus containing compounds. A high percentage of mineral orthophosphate in the nodules allows assuming the presence of chemisorbed orthophosphate ions in organomineral phosphate-metal-humus complexes. The transformation of iron-manganic nodules under the influence of drying demonstrates the more direct participation of microorganisms in the nodules’ formation than the contribution of the physicochemical processes.

Carbon dioxide emissions from agrogray soils under climate changes

The effect of droughts and drying-wetting cycles on the respiration activity of agrogray soils was studied in field and laboratory experiments. The alternation of drought periods and rains during the vegetation season did not increase the annual emission of CO2 from the soils under a sown meadow and an agrocenosis. In laboratory experiments, the wetting of dried soil released 1–1.5% of Corg with a high decomposition constant n × 10−1 day−1 and a very short renewal time (2.1–2.4 days); therefore, an abrupt change in the wetting conditions did not intensify the loss of soil carbon under field conditions.

Spatial variability in the distribution of particle-size fractions in agrogray soils and agrogray soils with the second humus horizon

The degree of spatial variability in the distribution of particle-size fractions has been determined for agrogray soils of an experimental field of Bryansk Agricultural Academy. The degree of spatial variability is close to the analytical error; for comparing different plots, particle-size distribution analysis has to be performed in two-three replicates. If the particular sets of data (e.g., data sets on the content of clay in the upper and lower parts of the plow horizon) are used, the statistical probability of differences increases. Cluster analysis can be used for the initial grouping of particle-size distribution data.