Glossic Retisol Research Articles

Investigation of Uncertainty in Organic Carbon Stock Estimates on a Field Scale

The uncertainty sources in the assessment of organic carbon stocks were studied in a layer of 0–30 cm within the sampling site (100 × 100 m) set on soddy-podzolic cultivated soil (Albic Glossic Retisol (Aric, Loamic, Ochric)). In the experiment, two sampling methods were used – the classic sampling in pits, by 10-cm layers, and sampling with an auger to a depth of 0–30 cm. The soil bulk density was determined by the Kachinsky method and the carbon content was analyzed by the Tyurin method. Some samples were additionally analyzed at the Bryansk State Agrarian University. The uncertainties associated with natural variation, sample preparation and the analytical process proper were estimated. The analytical uncertainty of bulk density measurement did not depend on the sampling depth under the experimental conditions and amounted to about 6%. The analytical error of Tyurin’s method did not differ in two laboratories. Its contribution reached 5–9% of the total variation in soil organic carbon content at the test plot. The uncertainty of sample preparation ranged from 11 to 26%, natural variation—from 49 to 68% to the total variance, respectively. Determination of carbon content in the samples taken with an auger from the depth of 0–30 cm is preferable than layer-by-layer sampling as the number of intermediate operations is fewer, and the obtained results are comparable.

An Investigation of the Organic Carbon Stocks Estimates Uncertainty on a Fields Scale

A study of the uncertainty sources in the assessment of organic carbon stocks in a layer of 0–30 cm at the scale of the sampling area (100 × 100 m) laid on soddy-podzolic cultivated soil (Albic Glossic Retisol (Aric, Loamic, Ochric)) was carried out. In the experiment, two sampling methods were used – the classic 10-cm layers from profiles and with an auger to the depth of 0–30 cm. The soil bulk density was determined by the Kachinsky method, the carbon content was determined by the Tyurin method. Some of the samples were additionally analyzed at the Bryansk State Agrarian University. The uncertainties associated with natural variation, sample preparation and the proper analytical process are estimated. The analytical uncertainty of the bulk density under the conditions of the experiment did not depend on the sampling depth and amounted to about 6%. The analytical uncertainty of Tyurin’s method did not differ in two laboratories. Its contribution was 5–9% of the total variation of the soil organic carbon content in the area. The uncertainty of sample preparation determined from 11 to 26%, natural variation – from 49 to 68% of the total variance, respectively. Determination of the carbon content in the samples taken by the auger, when the sample is taken immediately at 0–30 cm, wins in reducing intermediate operations and gives comparable results compared to layer-by-layer sampling. The uncertainty of sample preparation determined from 11 to 26%, natural variation – from 49 to 68% of the total variance, respectively. Determination of carbon content in samples taken by auger, when the sample is taken immediately at 0–30 cm, wins in reducing intermediate operations and gives comparable results compared to layer-by-layer soil sampling.

Structure of the soil pore space in the seedling bed before the seedling stage: studies using the microtomography method

In this paper we present a sequential observation of the barley seed root system germination at early development stages. A target of research was a two-layer seedbed model. The model is constituted by the topsoil material from soddy-podzolic soils (Albic Glossic Retisols (Lomic, Cutanic)). The material contains two differently structured layers of seedbed: the over-seed layer (loose; 40% of the total pore volume-pore diameter 0.5–1.5 mm) and the subseed layer (compacted; fine-pored layer is dominated by soil pore diameter of 0.01–0.2 mm). Control of the root system development was sequentially conducted with the benefit of nondestructive testing (computed tomography), which bring an opportunity to receive detailed images of roots development with an accuracy up to 16 µm. The study found that during 7 days after planting the seed emerging root system doesn’t depend on soil pore space structure surrounding the seed. The fact of a significant excess of the root diameter is noted in comparison with the diameters of soil pores, which indicates the ability of roots to push soil particles apart. It leads to an active pore space (pores-channels) formation.

Biological Indicators of Soil Quality under Different Tillage Systems in Retisol

Soil microorganism diversity has a close relation with soil function, and the changes in the composition of the soil microbial population can directly affect it. The aim of this study was to identify the bacterial community composition and determine the main soil chemical and physical properties formed by the different tillage systems. In the experiment, we analyzed the combination of three tillage systems and four organic fertilizers. Soil samples were taken from the two layers of the soil profile: the upper 0–10 cm and the lower 10–20 cm. The composition and diversity of soil bacterial communities were assessed by the sequencing of 16S rRNA genes. Results revealed that the highest biodiversity was found in the soil with shallow ploughless tillage and enriched with farmyard manure. Actinobacteria and Proteobacteria were the dominant bacterial species across all treatments. Their total abundance varied between 26% and 36% in the different analyzed agroecosystems. For the Dystric Bathygleyic Glossic Retisol, shallow ploughless tillage is the most suitable tillage system, as it creates favorable conditions for the accumulation of organic carbon in the soil under the Western Lithuania climate conditions.

Mobilization of Soil Organic Matter by Ultrafresh Water: Modeling and Assessment of the Impact on the Mobility of Heavy Metals

The experiments on mobilization of soil organic matter during soil washing with ultrafresh water against the background of salinity pulsing were designed and performed. Unpolluted soil and the soil artificially polluted with copper(II) were used in experiments, namely, clay loamy typical chernozem (Haplic Chernozem) of the Alekhin Central Chernozemic Nature Reserve (Kursk oblast, Russia; 51°34.207 N, 36°05.444 E) and sandy loamy soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) from the Domodedovo district of Moscow oblast, Russia (55°17.683 N, 37°50.045 E). Soil samples were taken from the upper humus-accumulative (A1) horizon (5–15 cm). A drastic change in the composition of washing solution from fresh water to 0.1 M NaCl solution and back led to destruction of soil aggregates under the impact of osmotic pressure. Soddy-podzolic soil proved to be more resistant to destruction as compared with typical chernozem. Copper(II) was leached off from artificially contaminated samples of soddy-podzolic soil with the flow of dissolved organic matter, whereas copper leaching from typical chernozem was associated with the destruction of aggregates and release of intraaggregate organic matter. It is argued that copper (II) migration models should take into account the amount of dissolved organic matter for soddy-podzolic soil and the content of aromatic fragments in the organic matter for typical chernozem. A conceptual model of the Cu(II) leaching from contaminated soddy-podzolic soil and typical chernozem in the course of soil washing with fresh water against the background of salinity pulsing and the destruction of soil structure is constructed.

Agrocenosis Stability during Long-Term Application of Fertilizers on Soddy-Podzolic Soil

In a long-term field experiment in the western part of the nonchernozemic zone of Russia (Smolensk oblast) on sandy loamy soddy-podzolic soil (Albic Glossic Retisol (Loamic)), the comparison of the effect of various rates and combinations of organic and mineral fertilizers revealed their efficiency in all the studied variants, except for the separate application of phosphorus fertilizers. It was found that the organomineral system—N90P90K90 + manure 9 t/ha—provided a deficit-free humus balance in the soil and stable productivity of crops (average for 30 years) at the level of 3.79 tons of forage units per hectare, or 37% higher than the control (without fertilizers). The mineral fertilizer system—N90P90K90—by the end of the fourth crop rotation was not inferior in the productivity to the organomineral system, but it led to a decrease in the soil humus content and pHKCl. The organic system with an annual manure rate of 9 t/ha occupied an intermediate position with respect to the crop rotation productivity (3.41 t/ha of forage units), as well as with respect to the soil fertility reproduction. A reliable increase in crop yield in the aftereffect was only recorded in the variants of organic and organomineral fertilizer systems, i.e., when soils were saturated with organic matter from manure. The soil in these variants was characterized by the high total number of microorganisms.

Microbiological Indicators of Heavy Metals and Carbon-Containing Preparations Applied to Agrosoddy-Podzolic Soils Differing in Humus Content

The response of the microbial community (microbial biomass carbon (Cmic), basal respiration (BR), and functional diversity (FD)) of agrosoddy-podzolic soil (Albic Glossic Retisols (Loamic, Aric Cutanic, Ochric)) to pollution by heavy metals (HMs: Cu 660, Zn 1100, Pb 650 mg/kg) and carbon-containing preparations (5% of biochar and 0.25% of lignohumate) was studied in model experiment (30 days). Soils with different organic carbon contents (Corg 3.86 and 1.30%) were sampled at two sites (Chashnikovo, Moscow oblast). We determined Cmic by the substrate-induced respiration method and FD by multisubstrate testing (47 substrates). It was found that HMs application reduced Cmic on average by 49–57%, BR by 23–52%, and FD by 45%, but, on the contrary, increased the microbial metabolic quotient (qCO2 = BR/Cmic) by 9–46%. The changes of these properties were most significant in the soil with low Corg content (1.30%). Carbon-containing preparations did not contribute to variations in Cmic, BR, and qCO2 in both soils with HMs, but increased their FD. It is concluded that the studied microbiological parameters may be used as indicators for optimal assessment of soil quality: FD and Cmic are the more sensitive to HMs than BR and qCO2.

Changes in the Agrochemical Properties of Soddy-Podzolic Soil under the Impact of Long-Term Application of Fertilizers

The influence of long-term application of organic and mineral fertilizers on the changes of soddy-podzolic soil (Glossic Retisol (Loamic, Aric)) properties was studied. These were: organic carbon content, available nitrogen and phosphorus, and soil exchange complex. The studies were carried out in one-meter soil layer in a long-lasting stationary experiment established in the Perm region in 1976. It was determined that mineral fertilizer use during five rotation cycles of the seven-course crop rotation increased significantly the contents of hydrolyzed nitrogen and available phosphorus; the 1.2–2.6 times increase in comparison with control was found for the whole profile. hydrolyzed nitrogen pool increased in the plow layer from 0.3 to 0.4 t/ha, in one meter-thick layer – from 1.3 to 1.6 t/ha, that of available phosphorus – from 0.3 to 0.8 t/ha and 3.1 to 4.8 t/ha, respectively. The increase of organic matter content was found only for 20–40 cm layer. The systematic application of mineral fertilizers promoted a significant decrease of actual and total acidity throughout the whole profile. Cattle manure application (5.7 t/ha) resulted in the improvement of soil exchange complex parameters: an increase in base saturation to a depth of 60 cm. Hydrolyzable and mineral nitrogen contents increased as well as phosphate mobility in the upper soil layer (0–20 cm), the organic carbon content increased insignificantly. Only the combined application of cattle manure and mineral fertilizers increased significantly the content of organic matter in the soil by 1.2–1.6 times in the upper and underlying layers, and provided the recovery of its initial content. Organic carbon pool increased from 28.3 to 32.2 t/ha in the 0–20 cm layer and from 71.5 to 81.8 t/ha in one-meter layer. Cattle manure application reduced the negative effect of mineral fertilizers on soil acidity.

Рентгеновская компьютерная томография структуры корней и динамика почвенной биоты на ранних стадиях роста ячменя (Hordeum vulgare L.)

The architecture of the seed bed, a certain alternation of compacted and loose sections of the arable horizon, largely determines the development of the root system of plants. The morphology and growth of the root system of the germinating seed in the created seed bed is also determined by the composition of the surrounding soil biota. Dynamic studies of the development of the root system and composition of the surrounding soil biota is an essential methodological and practical problem in soil cultivation, agrophysics, and soil biology. This task is especially important in the first few days when the root system is laid and the plant rhizosphere is formed. Modern tomography makes it possible to carry out such studies that do not violate the soil-root biological system, in particular, in model mesoscale experimental physical models. The aim of this research was to use x-ray computed tomography to study the structure of the roots of barley seedlings in the early stages of development, while simultaneously studying changes in the number and dominant groups of microorganisms in the basal biota. Barley seeds (variety Mikhailovsky) in a model physical experiment with a twolayer soil bed density (soil density range from 0.7 to 1.2 g / cm3) Albic Glossic Retisols (Lomic, Cutanic), WRB, 2014 were laid for germination at the layer boundary in a special cylindrical box with a volume of about 3 cm3 at optimal humidity. The position of the seed in the soil of the seedbed model is shown in the tomographic image (See Fig. 1). During the period from planting to 7 days, the dynamics of the root system was studied using a Bruker X-ray microtomography “SkyScan 1172G” (Bruker, Belgium) while studying the composition of soil biota, which was reconstructed by microbial markers (fatty acids and their derivatives). Markers were determined by molecular gas chromatography - mass spectrometry. Computer tomography allowed to record the volume distribution of roots at different periods of germination in the aggregated and compacted layers of agro-sod-podzolic soil. In this case, the roots successfully mastered the entire soil space, regardless of the plowing architecture of soil density created at the initial stage of germination. The total number of bacteria also increased by the 5th day with the constant dominance of 3 phyla: Actinobacteria, Proteobacteria and Firmicutes in the biota; the other two, Bacteroidetes and Cyanobacteria, were represented in relatively small numbers. In the phylum Actinobacteria, aerobic hydrolytics of complex carbohydrates Rhodococcus equi were presented in the largest amount on the 5th day, in the Firmicutes phylum it is anaerobic hydrolytic Ruminococcus sp. and the anaerobic nitrogen fixator Clostridium pasteurianum, in the phylum Proteobacteria-the aerobic nitrifier Nitrobacter sp. with a subsequent decrease in the number on the 7th day. The increase in these species indicates the initial destruction of the cellulose shell of the grain and the processes of fixation and conversion of nitrogen in the microbiota of the germinating seed, necessary for the formation of the C/N ratio. During the germination of the seed, pores are formed that are filled with water, gas, or organic matter. The structure of the microbial community changes in response to the ongoing processes, while the accumulation of metabolic products of aerobic and anaerobic species of microorganisms occurs. The quantitative study of the complex of microorganisms by the molecular method allows us to display the reaction of the microbiome to structural changes in the soil, since certain conditions stimulate an increase in the share of species with appropriate ecological functions in the community. The combination with the computer visualization obtained as a result of the application of the X-ray tomography method makes it possible to more clearly characterize the processes occurring in the rhizosphere.

Characterizing macropore structure of agrosoddy-podzolic soil using computed tomography

Abstract The agrosoddy-podzolic soil (Eutric Albic Glossic Retisol (Abruptic, Loamic, Aric, Cutanic)) is typical for Moscow Oblast and is used for agricultural purposes, resulting in use of various agrochemicals and pesticides. The presence of macropores and cracks in such soils leads to preferential water and substance transfer and nonequilibrium conditions. Therefore, it is important to study the numerical characteristics of the pore space of soils to adjust mathematical models of substance transfer. Undisturbed soil monoliths 10 cm in diameter taken from Ap (from 0 to 30 cm) and E, BE horizons (from 30 to 50 cm) were investigated under the field moisture conditions and after saturation using the tomographic core analyzer RKT-180 with the resolution of 200 μm/pixel. Using the X-ray computer tomography, it has been established that the plough layer of the agrosoddy-podzolic soil contains over 7% of macropores larger than 1 mm, while the subsurface layer has a porosity of about 3%. After saturation, some of the inter-aggregate pores overlap, which leads to a decrease in the total porosity to 4% in the upper and 2% in lower horizons, as well as increase in the average pore diameter. The number of macropores determined by tomographic analysis is one third higher than the values calculated using pedotransfer functions for this soil. The data obtained in this paper are recommended for use in national scenarios of migration of substances (pesticides, agrochemicals, salts) in soils.

Evaluate the Impact of Porous Media Structure on Soil Thermal Parameters Using X-Ray Computed Tomography

Soil thermal parameters are affected by soil texture, soil moisture, and porous media structure. X-ray computed tomography (X-CT) is used for description of soil porosity. The aim of this study was to observe the changes in porous media structure and soil thermal parameters with changes in soil moisture. Moreover, the effect of soil porous media structure, including connectivity and size of pores, on soil thermal parameters was estimated. Soil thermal diffusivity was measured at three different values of soil moisture, whereas soil thermal conductivity and volumetric heat capacity were calculated. Furthermore, the percentages of open, closed, and total porosities, as well as mesopores content were calculated at the same soil moisture using X-CT software programs. The results show that soil thermal parameters decreased along with decreasing soil moisture. In addition to decreasing soil moisture, soil thermal parameters decreased with increasing percentage of total porosity and the content of mesopores. However, the negative correlation between the soil thermal diffusivity and the content of mesopores is weak (r = –0.24). At the same time, a more significant negative correlation coefficient was found between soil thermal diffusivity and tomographic total porosity (r = –0.64) for silty loamy Albic Glossic Retisols. The influence of total porosity on the values of soil thermal diffusivity and other soil thermal parameters is larger than the pore size distribution (mesopores content). Soil heat transfer proceeds through soil particles (solid phase) and is not directly related to pore size distribution. The variations of soil thermal parameters values were in harmony with a quantitative description of soil porous media with the use of X-CT.

Physical and microbiological aspects of the soil seed bed in the early formation of the barley root system (Hordeum vulgare L.): tomographic studies

Barley seeds (Mikhailovsky sort) in a model physical experiment with a two-layer density soil bed (the range of soil density from 0.7 to 1.2 g/cm3) of silty loam arable soil (Albic Glossic Retisols (Lomic, Cutanic), Moscow Region) were placed for germination at the boundary of different-density layers at optimum moisture content. During the period from planting to 7-10 days. the dynamics of the root system development was studied using an x-ray microtomograph “Bruker SkyScan 1172G” (Belgium) while simultaneously studying the composition of soil biota, which was reconstructed from microbial markers (fatty acids and their derivatives).The roots of the germinating seed mastered the entire pore space of the soil, regardless of the density zones studied in experiments. The number of bacteria increases by the fifth day with a noticeable dominance of actinobacteria (aerobacteria Actinobacteria spp., Rhodococcus equi) and Firmicutes (anaerobes Ruminococcus sp.) due to the destruction of the seed coat with its subsequent decrease on the seventh day.

Possibilities of using rheological parameters as physical indicators of soil structural changes

The rheological parameters of structured soddy-podzolic soils (Albic Glossic Retisols (Lomic, Cutanic)) and chernozems (Haplic Chernozems (Loamic, Pachic)) in their natural state and involved in agricultural use were studied by the oscillation amplitude sweep test. Shear resistance parameters of the studied soils (shear stress at the end of the linear viscoelasticity range – LVE-range t L , shear stress t F at the Crossover point and maximum shear stress t max ) were more informative and indicated pronounced differences between soil genetic horizons in contrast to viscoelasticity parameters (deformation γ L at the end of the LVE-range and the integral zone Z) when comparing natural and arable soils. The agricultural land use resulted in decreased organic carbon content and, as a consequence, reduced viscoelasticity and shear resistance of the soils. At the same time, the higher bulk density of arable horizons and the redistribution of fine soil particles (physical clay) could explain maximal values of the rheological parameters in the upper arable horizons and their slight differentiation with depth. Further development in the application of the proposed and studied rheological parameters can give insight into the nature and strength evaluation of interparticle bonds, the soil processes under the impact of agricultural machinery, and can also be integrated into the system of physical indicators of soil structural changes.

Formation of Vesicular Pores in Aggregates from the Eluvial Horizon of Albic Glossic Retisol during Freeze-Thaw Cycles

In this article, we discuss the contribution of capillary wetting and multiple freezing and thawing to the formation and evolution of vesicular micro– and mesoporosity in an aggregate of 3 mm in diameter from the eluvial horizon of soddy–podzolic soil (Albic Glossic Retisol (Loamic, Cutanic)). The main visible changes occur during capillary wetting and the first four cycles of freezing and thawing. Capillary wetting of the air-dry aggregate initiates the formation of vesicular micropores in the soil mass. The first freezing fixates the newly formed vesicles and contributes to the development of microschlieren in the aggregate. The first thawing causes the isolation and growth of individual vesicular pores. In the subsequent three freeze–thaw cycles, freezing fixates the vesicular pore space pattern, whereas thawing promotes the coalescence of small vesicular pores into larger vesicular pores. During the fifth and next cycles, many large vesicular pores leave the deformed aggregates aggregate, so that horizontally oriented cryogenic microschlieren tend to predominate in the frozen aggregate after 10–20 freeze–thaw cycles.

Dynamics, Structure, and Functional Activity of Microbial Biomass in Soils of Restoring Felled Areas in Fir Forests of the Yenisei Ridge

The dynamics, structure, and functional activity of microbial biomass have been studied in soils of felling areas in southern taiga fir forests (the Yenisei Ridge, Krasnoyarsk krai), which are at different stages of natural regenerative successions. The top organomineral horizons of soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) of the after-felling regeneration succession (with the stage of secondary birch forests) is characterized by an increase in the content of carbon of microbial biomass (Cmic) and in the intensity of basal respiration from new felling to the stage of dense young forest. In the soil of the dense young-wood stage, the total reserves of Cmic (170 g C/m3) and microbial CO2 production (528 mg СО2–С/m3 per hour) are the highest and exceed the control by 80–85%. In the humus-accumulative soil horizon of the studied succession series, there is a tendency for a decrease in the portion of fungal substrate-induced respiration and in the fungi to bacteria ratio in comparison with the control. In the middle-aged deciduous forests with dark-coniferous undergrowth, all the considered parameters of microbial complexes decrease but remain higher than the control. A trend for a decrease in Cmic and basal respiration is revealed in the profile of soddy-podzolic soil of the regeneration series without species change over an eight-year period. At the stage of fir dense young forest, all ecological-functional parameters of the microbial complex become closer to the control small-grass–true-moss fir forest.

The effect of over 50 years of liming on soil aluminium forms in a Retisol

AbstractThe aim of the current study was to evaluate the effect of long-term (56 years) liming on changes in soil pH and aluminium (Al) forms in the soil profile compared with an unlimed soil in a sandy moraine loam of a Dystric Glossic Retisol. Long-term liming had a significant influence on soil acidity of the whole profile, causing increased pH values in the following horizons to 120 cm depth: the ploughing horizon (Ahp), where humus accumulates; the eluvial horizon (E), from which clay particles are leached; a horizon having retic properties and predominantly coarser-textured albic material (E/B); and a horizon with retic properties and predominantly finer-textured argic material (B/E). In the solid phase, non-crystalline Al in limed soil decreased in the Ahp horizon; meanwhile a decrease in total organically bound Al (Alp) and organo–Al complexes of low to medium stability was detected in the deeper El and ElBt horizons. High-stability Al complexes with organic matter were the predominant form of Alp in the unlimed and limed whole soil profile. The concentration of total water-soluble Al ranged from 0.61 to 0.80 mg/l in the limed soil profile but 0.62–1.15 mg/l in the unlimed soil. The highest concentration of exchangeable Al was determined in the upper horizons of the unlimed soil profile and the concentration decreased significantly in the same horizons of the limed soil profile. Long-term liming promoted changes in Al compounds throughout the soil profile.

Rheological Properties and Tomographically Determined Pore Space of Undisturbed Samples of Typical Chernozems and Soddy-Podzolic Soils

Coupled studies of pore space and rheological behavior of undisturbed samples from soddypodzolic soils (Albic Glossic Retisols (Loamic, Aric, Cutanic)) of Moscow oblast under forest and under cropland and from typical chernozems (Haplic Chernozems (Loamic, Aric, Pachic)) of Kursk oblast under oak forest, shelterbelt, and cropland were conducted. Soil pore space was investigated using a Bruker SkyScan 1172 G (Belgium) microtomograph, and 3D models of pore space were constructed. The total pore space (in percent of the volume of analyzed samples) and the volumes of open and closed pores were determined from these models. The nondestructive tomographic method made it possible to analyze the rheological properties of soils for the same samples using the amplitude sweep method on an MCR-302 (Anton Paar, Austria) rheometer. The following parameters of the rheological behavior were determined: storage modulus in the range of linear viscoelastic behavior, the range of linear viscoelastic behavior, and the range of plastic behavior. A joint analysis of the rheological properties and morphometric characteristics of the undisturbed samples of soddy-podzolic soils and chernozems demonstrated the dependence of the rheological behavior of these soils on their physicochemical properties and pore space structure reflecting the differences in the genesis and physical and chemical properties of soil horizons. The correlation analysis attested to direct (positive) relationships between the values of the total and open tomographic porosities, the range of linear viscoelastic behavior, and the deformation upon the destruction of soil structure. Negative relationships were found between the values of open and total porosity and the structural strength of the soil monoliths. A hypothesis about an increase in the range of plastic behavior of soils and a decrease in the strength of soil structure with an increase in porosity was suggested.

Changes in the Content, Composition, and Properties of Humic Substances in Particle-Size Fractions of Soddy-Podzolic Soils under the Impact of Long-Term Drainage

Specific features of the transformation of humic substances in particle-size fractions of drained soddy-podzolic soils were studied on a field (12 ha) of the Experimental and Educational Center of Lomonosov Moscow State University in Moscow oblast. The field had a clearly pronounced microtopography. Surface-gleyed soddy-podzolic soils (Albic Stagnic Glossic Retisols (Loamic, Aric, Ochric)) of microdepressions with excessive surface moistening and nongleyed soddy-podzolic soils (Albic Glossic Retisols (Loamic, Aric, Ochric)) of elevated positions were examined. These soils were studied before the field drainage and during 25 years after drainage works in the periods differing in conditions of humification and with due account for not only drainage works but also other factors, such as topography and agrotechnology and their joint action. The specificity of transformation of humic substances in the soils and their particle-size fractions was analyzed in the basis of data on the organic carbon content, group and fractional composition of humus, the intensity of individual stages of humification (the neoformation of humic acids and the formation of humates), and the optical density of the fractions of humic acids. The results of the study of these properties in the fine soil fractions (<50 μm) made it possible to assess the response of the clay (<1 μm) and silt (1–5, 5–10, 10–50 μm) fractions to changes in the ecological situation and the role of separate particle-size fractions in the degradation of humus under adverse impacts. Overall, a clear tendency toward worsening of the humus quality was observed in both soils during the 25-year-long period, which is related to the long-term (20 years) agricultural use of the reclaimed field without application of agrochemicals. The features of humus degradation were mainly manifested in the finest (<10 μm) fractions with a general decrease in the humus content, slowing down of the formation of humic acids and humates, and considerable loss of humic acids, including their agronomically valuable fractions HA1 and HA2. The degradation of humus quality in the clay fraction was largely due to the impact of the reclamation (drainage) factor; the degradation of humus quality in the fine and medium silt fractions was mainly due to the negative changes in the agricultural background. Among negative consequences of the worsening humus quality, the lowering of soil fertility, ecological sustainability, and productivity of agrocenoses should be noted.

Changes in the weed communities as affected by different primary soil tillage and deep loosening

ABSTRACTLong-term soil cultivation at the same depth affects soil characteristics and crop productivity. The aim of the study was to investigate the impact of a long-term different intensity soil tillage methods and deep loosening on weed number, weed agrobiological group and soil seed bank changes in till Bathygleyic Dystric Glossic Retisol soil under the climatic conditions of the Western Lithuania (geographical coordinates 55°43′38″N, 21°27′43″E). The study included different soil tillage methods (conventional ploughing, shallow ploughing and shallow ploughless tillage) and deep loosening. During investigational years, the greatest weed number in crops and the greatest weed seed number in the seed bank were determined in the soil reduced tillage (shallow ploughing and shallow ploughless tillage). The weed number in crops of conventional ploughing soil was 35.8% lover compared to reduced tillage soil. The weed seed number in the seed bank of conventional ploughing was 49.6% lover compared to reduced tillage Decreasing soil tillage intensity resulted in weed seeds concentration in the upper topsoil. A one-time deep loosening had a significant effect during the crop rotation: the weed number in crops and weed seed number in the seed bank were determined to have increased by 26.6% and 51.6% in conventional ploughing soil and by 11.9% and 23.2% shallow ploughless soil respectively. However, after deep loosening, the number of Poa annua in crops decreased 2.9 times in plots of conventional ploughing and 1.7 times – in plots of shallow ploughing soil.

Postagrogenic development of Retisols in the middle taiga subzone of European Russia (Komi Republic)

AbstractReforestation on abandoned agricultural lands is widespread in the belt of boreal forests. We analyzed the morphological and physicochemical properties of a Plaggic Glossic Retisol (Siltic, Cutanic) site that had been abandoned either 7, 19, or 85 years ago, as well as a Glossic Stagnic Retisol (Siltic, Cutanic) as a control. Involvement of forest soils in agricultural use results in the degradation of organic horizons, which are not restored until many decades after the termination of active agricultural use. Arable soil horizons were preserved and were clearly identified 85 years after the land had been abandoned. The morphological features of the eluvial and subeluvial horizons were determined at all sites. Soils at sites that had been abandoned for 7 and 19 years showed lower acidity and higher base saturation compared to the background soil. Total carbon stocks were lower at the abandoned sites. The slow increase of carbon stocks after the soil had been abandoned is caused by C increase as in the organic as in the topsoil mineral horizons. Soils that had been abandoned for 7 and 19 years contained less water‐extractable forms of C and N than the control and 85‐year forest soils. Agricultural use leads to a reduction in C stocks of forest soils. The postagrogenic soil C sequestration rate was estimated to be 30–40 g·m−2·yr−1.