Arable Horizon Research Articles

Influence of degree of cultivation of sod-podzolic soil on dynamics of content of soil organic carbon

In 1999–2001 on the fields of the Falenky Breeding Station (Kirov region), the dynamics of the content of soil organic carbon (Corg) and its labile part (Clab) in sod-podzolic arable soil of varying degrees of cultivation were studied. The arable layer of weakly cultivated variant of the soil was characterized by high acidity (pHKCl – 3.88) and low organic carbon content (Corg – 0.91 %). The well cultivated variant had an acidity close to neutral in the arable horizon (pHKCl – 6.14) and a total carbon content at the average level for sod-podzolic loamy soils of the region (Corg – 1.10 %). Soil samples were taken during the growing season once a month in a sixfold repetition from the arable horizon and in a threefold repetition for horizons A2B and B. It was revealed that during all years of observation in the arable horizon of the soil of the cultivated variant, the Corg content was significantly higher (by 16–76 %). In the underlying horizons of soils of both variants, the carbon content was sharply reduced to 0.2–0.6 %. The content of labile part of organic carbon did not differ by variants and varied from 0.05 to 0.19 % depending on the horizon and observation period. However, in the arable horizon of weakly cultivated soil, the proportion of labile carbon in the composition of total organic carbon was significantly higher, which indicated less stability of the soil organic matter system. The content of both forms of soil organic matter varied significantly over the years and during the growing season. Maximum values of Corg content were noted at the beginning and at the end of the observation season. Minimum values were noted in July. Content of Clab was decreasing from the beginning to the end of the season.

The influence of degradation processes on enzymatic activity and the content of forms of mineral nitrogen in agricultural soils

The purpose of the work was to study the concentration of various forms of mineral nitrogen and nitrogen cycle enzymes in farmland soils. The objectives of the research included studying the content of ammonium and nitrate forms of nitrogen, as well as the activity of urease and nitrate reductase in soils of farmland on the territory of the Donetsk People's Republic (DPR). To study the soils of agricultural lands, model sites located in the southern part of the Shakhtersky district of the DPR were selected and represented by moderately washed-out chernozems with low, low and medium humus. The control was an area with steppe vegetation (ordinary chernozem, thick, with medium humus content). The results of the researches allow us to draw conclusions about the development of degradation processes in a number of model sites and their impact on the content of ammonium and nitrate nitrogen in agricultural soils. Growing crops removing substantial amount of mineral nutrients, the slope of the sites surface, and the duration of cultivation of grain crops in the same sites lead to a significant decrease in the concentration of ammonium and nitrate nitrogen. Thus, the most significant decrease in the concentration of nitrogen of ammonium compounds (by 77–82%) was recorded in model slope areas under maize and sunflower. Analysis of the data showed that exchange ammonium is confined to the underlying genetic horizons. The minimum concentration of nitrates in the arable horizon was recorded under the joint influence of such unfavorable factors as: unreasonable layout of fields along the relief elements; violation of crop rotation conditions; use of precursor crops with a significant level of removal of nutrients (wheat, maize). When studying the activity of urease, it was found that a low number of soil microorganisms associated with the cultivation of maize and sunflower, as well as with the development of degradation processes of various genesis, led to the suppression of the functioning of the urease of soils in model areas. The maximum urease activity was observed in areas under winter wheat and amounted to 68–72% in relation to the control indicators. As a result of studies of nitrate reductase activity, a decrease in its values was also found in areas used to grow crops that form a large phytomass (maize and sunflower).

Restoration of the structure and soil protection role of no-till in chernozems and chestnuts soils of the Stavropol Territory

The results of research on the example of southern chernozem and chestnut soil are presented. Long-term use of plowing with rotation of the soil layer and the use of fallows leads to a critical state of the soil in terms of the content of aggregates measuring >10 mm and >1 mm. The introduction of notill on old arable soils leads to a general increase in the mean weighted diameter of aggregates (MWD). The intensity of restoration of the structural state of the soil during no-till in southern chernozem occurs more intensively than in chestnut soil, and the main changes are recorded in the fractions of agronomically valuable aggregates. In southern chernozem there is an increase in diameter from 6.0 mm to 9.5 mm, while in chestnut soil the MWD increases only to 7 mm. The content of erosion-susceptible aggregates <1 mm and their change depending on the intensity of agricultural cultivation in southern chernozem and chestnut soil indicates a tendency to restore the structure in the no-till variant. In southern chernozem, the content of particles of 1–0.5 mm size decreased by 1.2%, and in chestnut soil – by 6.2%. Refusal of mechanical tillage showed that, in contrast to dry aggregates, the influence of no-till on the water stability of the structure of the arable horizon is more significant and is presented in the form of fractions rearrangement. The use of no-till technology results in a reduction in the content of erosion-susceptible aggregates and increases the water stability of the structure of the arable horizon, which, together with the influence of crop residues on the soil surface, provides an anti-erosion effect. The restoration of the structural state of the soil during notill in southern chernozem proceeds more intensively than in chestnut soil. The main changes in the form of rearrangement occur in fractions of agronomically valuable aggregates.

Productivity of Biocenosis Plants and Humus Accumulation Processes in Eroded Meadow-Chernozem Soils

In long-term experiments, the content of humus in natural and agroecosystems on meadow-chernozem soils depended on the species diversity of plants, the state of the vegetation cover, the cultivation of the arable horizon and its erosion. During the 10-year observation period, the humus content in arable soil decreased by 4.5% relative to the initial state, while under meadow grasses, on the contrary, it increased by 22%. Then, during the 20-year accounting period, the processes of humus accumulation in the cultivated soil changed little. Among natural ecosystems, humus accumulation processes were most active in the humus-accumulative (A) and transitional horizons (AB) under the aspen forest. The reserves of humus and nutrients in eroded soils decreased dramatically, causing a decrease in the productivity of meadow grasses. It has been established that for a significant accumulation of humus (up to 8%) in the non-eroded soil of the 100-year period of ecosystem functioning, it is necessary to combine incoming carbon in the form of forest litter and roots with the biomass of perennial meadow grasses.

Количественная оценка потерь почвы вследствие водной эрозии на сильновыпаханных почвах бассейна верхней Оки с использованием географических информационных систем

The paper presents some results of studying soil losses appearing due to water erosion in an agricultural field with highly degraded plowed soils. The research was carried out on the arable slope of the southern exposure in an experimental area located in the Oryol district of the Oryol Region (upper Oka basin). A set of methods was used: morphometric analysis of the topography relief, radiocaesium method, soil-morphological method, method for determining easily decomposable organic matter (labile organic matter) designed according to Ganzhara and Borisov, agrochemical methods. The study was based upon the authors’ in-situ data of 2016–2023. Maps are compiled to show the caesium-137, humus and labile organic matter spatial distribution, and of the soil degradation degree (in points on the Ganzhara and Borisov scale) in the arable horizon of 0–25 cm. Analysis of the caesium-137 radioactivity spatial distribution made it possible to identify two sectors in an area of highly degraded plowed soil, which differ in surface slope values and in nature of the caesium-137 radioactivity interdependences with catchment area and sign of profile curvature. Developed semi-empirical computational dependences for the delineated sectors allow to compile a gridded map of the soil runoff intensity (in t/ha/year). The intensity of soil runoff in the area with highly degraded plowed soils is ranged from 5 to more than 20 t/ha/year. The algorithm for the intensity of soil delivery outside of the studied area was developed on the basis of layer-by-layer soil sampling data collected in the mouth of the ravine, removing soil from the highly degraded plowed soil area. The algorithm showed that 4.7–6.5 tons of soil per year are removed from 1 hectare of the catchment area basin. The rest of the outwashed soil material is deposited in accumulation areas within the catchment area basin. The authors recommend verifying the findings in other areas of the agricultural field. The proposed methodology for soil loss estimation, developed for highly degraded plowed soil areas in an agricultural field, requires clarification by enlarging the scale of the study.

DNA-metabarcoding of cyanobacteria and microalgae in chernozem soils of temperate continental climate of the forest-steppe zone of Eurasia under different degrees of agrotechnology intensification.

Chernozem soil is a valuable resource and contains a great diversity of microorganisms that play a global role in the process of soil formation, the species diversity of which has changed over the last five years under the influence of different agrotechnologies. For the first time, under the conditions of the Central Chernozem region, grain and fallow crop rotation, studies using the DNA-metabarcoding method were carried out to study the taxonomic structure of bacteria, fungi, cyanobacteria, and microalgae communities in the arable horizon of typical medium loamy chernozem under winter wheat cultivation. A comparative analysis of the composition of the genotypes showed significant differences in the presented level of mineral nutrition of the soil NPK (60) and NPK (100) compared with the control variant. After processing the 16S and 18S rRNA datasets, a similar trend of decreasing numbers of pro- and eukaryotic species was found from 6296 (control without MF) to 5310 with NPK (60) and to 4643 with NPK (100), respectively. The Chao1 index indicated that the expected diversity within the prokaryotic group was higher in the control without MF at 211, but decreased to 182 and 193 with NPK (60) and NPK (100) fertilizers, respectively. Analysis of the eukaryotic group revealed a 2.6- and 2.9-fold decrease in diversity by class and genus, respectively, depending on the nutritional levels in agrotechnologies, owing to the use of MF. In the prokaryotic community, Alphaproteobacteria microorganisms predominated at an amount of 14.20-14.46%, with Cyanophyceae accounting for 5.2-9.9%. The diversity of eukaryotes was smaller than the number of classes of prokaryotes; the main dominant were Zygnematophyceae 19.5-41%, Chlorophyceae occupied 10.4-15.8%. On the other hand, the doses of fertilizers used contributed to the emergence of dominant species adapted to high doses of mineral nutrients for plants.

Опыт изучения трансформации подзолистых почв в условиях городской среды Севера

The results of soil studies of one of the medium-sized cities of the Russian European Northeast – Syktyvkar (Russia, Komi Republic, middle taiga subzone) are presented in the article. The series from a podzolic soil with a microprofile of podzol (Albic Retisol (Loamic, Protospodic)) typical for the region to various variants of its human transformation in urban conditions – cultivated agrodernovo-podzolic soil (Eutric Albic Retisol (Loamic, Aric, Humic)), represented on the site of the Botanical Garden, to urbodernovo-podzolic soil (Eutric Albic Retisol (Loamic, Humic, Transporti-Novic, Thaptoaric)) and urbostratozem (Urbic Technosol (Loamic, Eutric, Humic Transport)) described in the central part of the city, included in the urban development in the first half of the XX century is considered. In urbo-soil and urbanostratozem the thickness of urbogenic horizons is approximately 40 and 70 cm. It is shown the first stages of the development of the territory of Syktyvkar city are associated with the agricultural impact. Subsequently, the arable horizons overlap with the horizons of the urban cultural layer. In the considered series of soils, weak alkalinization, an increase in the absorbed bases and the total mineralization of the soil solution were found. A noticeable increase in the concentration of organic carbon in modern arable and urban horizons, as well as the thickness of horizons with the organic carbon content of more than 0.6% was revealed. An indirect evidences of changes in the composition of iron and manganese minerals (due to an increase in the pH) with partial preservation of zonal soil formation trends has been found. The revealed direction of soil evolution is consistent with the one previously described in the cities of the European part of Russia.

Aggregate structure of agro-gray soils of Vladimir Opolye: composition and strength of aggregates

A complex of soils characteristic of the Vladimir Opole region was studied: agro-gray typical deep-arable soil, tongue-shaped agrozem and agro-gray gleyic soil. The high contrast of soil properties, which is due to the genesis of field landscapes, can be traced in the differences in the arable and subarable horizons of agro-gray soils at the aggregate and microaggregate levels. The soils have an excellent structural condition, high water resistance and mechanical strength of aggregates. In the aggregate structure of arable horizons, dependences on the position in the relief were found: down the slope the content of agronomically valuable aggregates decreases, the weighted average diameter of aggregates increases, the water resistance of aggregates and the mechanical strength of aggregates at capillary saturation decreases. However, the distribution and size of microaggregates, as well as the strength of aggregates in an air-dry state, reflects the complex genesis of the landscape and retains the influence of paleorelief with depressions and elevations. The weighted average diameter of microaggregates of arable horizons of the soils of the Vladimir Opole region is close to the chernozems of the Kursk region. The granulometric composition of the studied soils is typical of Vladimir Opolye soils and close to each other. In accordance with the classification of N.A. Kachinsky arable horizons are medium loamy, coarse silt, BT horizons are heavy loamy, coarse silt. The most structural is the arable horizon of agro-gray typical deep-arable soil, it has large microaggregates, it also has high water resistance and the highest content of agronomically valuable aggregates. The most homogeneous in terms of aggregate composition is tongue-shaped agrozem; the average diameter of aggregates and microaggregates in the arable and subarable horizons are equal and similar in the content of microaggregates and agronomically valuable aggregates. This soil is also highly water resistant. Agro-gray gleyic soil contains fewer agronomically valuable aggregates and its water stability is unsatisfactory.

Decomposition of green manure and nutrients release in Subarctic, Kola Peninsula, Russia

In the field experiment, the intensity of decomposition and release of nutrients was studied for six types of plant residues – leaves, panicles and straw of oats (Avena sativa), as well as whole plants of lupine (Lupinus angustifolius), phacelia (Phacelia tanacetifolia) and vetch (Vicia sativa) in the arable horizon of Anthrosols on the Kola Peninsula. Samples in mesh nylon bags were sampled after 8, 12 and 24 months of exposure in soil. The loss of weight, the content of Corg and Norg, as well as ash elements – Si, Al, Fe, K, Ca, Mg, P, S and Mn were determined in all plant residue samples. As the results showed, despite the low temperatures, the decomposition of green manure in soil occurred with a high intensity, comparable to the southern chernozem zone: after a year of exposure in the soil, plant residues lost from 47% (oat straw) to 75% (lupine) of their initial ash-free weight. After 2 years, weight loss reached 68% in oat straw and 90% in lupine. The distribution of losses of Corg, Norg, and P between the types of plant residues and decomposition periods correlated significantly (at p≤0.01) with the distribution of weight losses. Changes in the content of other ash elements did not depend on weight loss: depending on the type of material and the stage of decomposition, the samples could not only lose them (K – by all plant residues; Mn – by lupine; S, Ca and Mg – by all plant residues, except straw and oat panicles), but also accumulate them in quantities exceeding the initial ones (Fe – by all species, Mn – by all species except lupine; Ca and Mg – by straw and oat panicles) at certain periods. The accumulation of elements above initial level means that the transformed plant residues can accumulate additional amounts of elements from the soil solution, while the irregular alternation of increases and decreases in Ca, Mg, S, Fe and Mn indicates the reversible nature of the process. Due to the significant differences between the types of green manure in terms of chemical composition, rate and dynamics of decomposition and release of nutrients, their use provides great opportunities for managing soil fertility and the intensity of elements cycling in agrocenoses through the species selection.

Soil Microbiome of Abandoned Plaggic Podzol of Different-Aged Fallow Lands and Native Podzol in South Taiga (Leningrad Region)

The soil microbiome is composed of various communities that play an important role in the existence of ecosystem services and the sustainable functioning of ecosystems under high anthropogenic loads. The transition of soils to a fallow state and their subsequent transformation lead to a notable alteration in the taxonomic composition of the soil microbiome, impacting the biochemical processes within the soil and its fertility levels. The object of this study comprised different-aged fallow soils of the southern taiga in the vicinity of Ban’kovo village, Leningrad region. The method comprising the high-throughput sequencing of 16S rRNA gene fragments using an Illumina MiSEQ sequencer was used to analyze the microbial community. The general processing of sequences was carried out with the dada2 (v1.14.1) package. It was found that the morphological organization of fallow soils has significant differences from the native podzol. In fallow soils, there are signs of leaching expressed in the accumulation of leached mineral particles, which indicates the degradation of the fallow–arable horizon. At the same time, there is a decrease in the content of P2O5 and K2O and an increase in the content of N-NH4 and N-NO3 in fallow soil. The analysis of alpha diversity index values showed that the highest level of alpha diversity in the microbial community is characteristic of 40-year-old soil, the alpha diversity index decreased with the increasing time of the fallow state, and the lowest alpha diversity index was observed in the native podzol. According to the values of the beta diversity index, a high correlation between the soil microbiome and the physicochemical characteristics of the soil was revealed, which indicates the formation of functional specialization in the studied microbial communities. As a result of the study of the taxonomic composition of microbial communities in fallow soils, it was found that the most represented microbial communities in fallow soils belong to Nitrosomonadaceae (Pseudomonadota), Mycobacterium (Actinobacteria), Nitrospira (Nitrospirota), and Luteolibacter (Verrucomicrobiota). The duration of post-agrogenic transformation is the leading factor influencing the changes in microbial communities; so, with an increase in the time that soils were in a fallow state, an increase in the oligotrophic microbial community was observed.

Study in a long-term laboratory experiment of the potential susceptibility to mineralization of organic matter in post-agrogenic light gray soils

Relevance. Since 2021, work has begun in Russia to assess the fertility of unused arable land and its involvement in agricultural circulation. Changes in the farming system of post-agrogenic soils can lead to uncontrolled mineralization of newly formed soil organic matter (SOM) under fallow vegetation and significant CO2 emissions into the atmosphere. Studies of the nature of SOM accumulation under fallow vegetation and assessment of its potential susceptibility to mineralization are relevant, since they can become the basis for the development of agrotechnical methods for returning unused lands to arable circulation with the maximum preservation of their fertility.Methods. In a long-term laboratory incubation experiment, we studied the dynamics of changes in the intensity of basal (BR) and substrate-induced respiration (SIR) in postagrogenic soils to assess the potential susceptibility to SOM mineralization with a change in land use. Layered samples (0–10 and 10–20 cm) were used from the old arable horizons of two fallow plots with different humus conditions. The results of the incubation experiment were compared with the results of assessing the quantitative content and qualitative composition of SOM.Results. In the 0–10 cm layer, the respiration rates are higher than in the 10–20 cm layer. The results of the assessment of the respiration intensity are consistent with the assessment of the qualitative composition of SOM. The accumulation of SOM occurs mainly in the upper part of postagrogenic soils due to mobile easily oxidized organic compounds of a fulvic nature. When developing agrotechnical methods for returning fallow lands to arable circulation, it is necessary to focus primarily on basic processing technologies that ensure maximum preservation of potentially easily mineralized material accumulated in the upper layer.

Agroecological assessment of spatial variability of carbon content in the conditions of disturbed sod-podzolic soils

Soil carbon is one of the main carbon pools of terrestrial ecosystems. The carbon of arable soils is the most labile. In this regard, rapid and accurate methods for determining soil carbon in different forms are of great interest to researchers. Therefore, in this paper we decided to conduct a comparative analysis of the results of organic carbon determination using the Walkley-Black method (colorimetric method), the Dumas dry combustion method (using the CN Vario El Cube analyzer)) and the remote method using the Valeeva approach (Valeeva, Aleksandrova, Koposov, 2016) according to the values of the red channel of the spectrum, on the images obtained using an RGB camera mounted on a DJI Phantom 4 drone. For laboratory analysis, 100 soil samples of the arable horizon were collected at regular grid points, georeferenced using RTK. The correlation between the Dumas dry combustion method and potassium dichromate oxidation was 0.24 (for n = 100, significant p=0.195), allowing comparison at the trend level. The highest correlation (R = 0.39 was observed between the data obtained using the Dumas method and the Valeeva-Alexandrova approach, indicating that it can be used to estimate soil carbon dynamics from RGB images. Correlation analysis showed relationships (R = 0.63) between total carbon and microrelief, which is reflected by the drone-derived digital elevation model.

ПИЛОТНЫЙ КАРБОНОВЫЙ ПОЛИГОН: АНАЛИЗ ЗАПАСОВ УГЛЕРОДА В ПОЧВАХ СЕЛЬХОЗУГОДИЙ

The carbon cycle in agroecosystems is determined by the balance between the absorption of carbon dioxide by terrestrial vegetation of agricultural crops to create organic matter and its release during soil respiration. The soil cover is a powerful source of carbon dioxide and serves as a reservoir accumulating soil organic carbon. Organic carbon accumulating in the humus of soils serves as a drain of carbon dioxide, methane into the atmosphere for hundreds of years. The research was carried out in order to analyze the reserves of organic carbon in the soils of agroecosystems and assess the emission of CO2 and CH4 gases. The work was carried out in 2022-2023 at the site of a pilot carbon landfill (arable land) in the Republic of Bashkortostan. In field and laboratory experiments, technologies for controlling carbon dioxide emissions on agricultural lands were developed and tested. In the field, full-profile soil sections and digs were laid in accordance with GOST R58595-2019 with the determination of morphological properties and the selection of soil samples for laboratory analysis. Agrochemical analysis of the soil for the content of organic matter, the density of addition, the content of mobile phosphorus and potassium, the pH value allowed us to estimate the carbon stock of the soil of the carbon landfill according to the methodology of the Ministry of Natural Resources of the Russian Federation. The total reserves of organic carbon of the arable horizon at the carbon-new landfill amount to 503.8 t/ha, which vary and depend on the employment of the field and the characteristics of the agricultural crop. Measurement of the destructive part of the carbon cycle using a portable LI-COR 7810 camera showed that the fields occupied by crops differ in the intensity of the release of soil carbon dioxide ‒ in the field under pure steam, CO2 emissions were 2.18 times lower than under perennial grasses. The availability of data on the spatial distribution of organic soil carbon makes it possible to introduce carbon-dependent crop rotations with a set of crops that contribute to the maximum absorption of atmospheric CO2 and other greenhouse gases into the practice of agriculture.

Effect of ammonium and potassium nitrate on winter hardiness and yield of winter rye (<i>Secale cereale</i> L.)

The results of research for 3 years (2019–2021) on winter rye (Secale cereale L.) crops in the North-West region of the Russian Federation (Leningrad region) are presented. The effect of different doses and timing of ammonium and potassium nitrate application on winter hardiness and productivity of winter rye plants on the example of Volkhova and Eureka varieties was studied. The soil in the experimental fields was sod-podzolic loamy with the depth of the arable horizon of 20–25 cm. Humus content – 2.0–2.3%, pH of the salt extract – 5.2–5.5. Fertilizers were applied in dry form in the autumn one week after the emergence of the seedlings, and in the spring – at the resumption of vegetation. The studied fertilizer doses in terms of active substance for nitrogen were 0 (control), 30, 60 and 90 kg/ha. It is shown that winter hardiness of both varieties practically did not depend on the doses and timing of the application, as well as on the type of fertilizers. The maximum grain yield was shown by the Volkhova variety at a dose of nitrogen of 60 kg/ha, the Eureka variety – 90 kg/ha, with the maximum yield of the Eureka variety for all the years exceeding that of the Volkhova variety by 24.5%. Within the specified doses of nitrogen for both varieties, the best option was a single spring application of a mixture of ammonium and potassium nitrate, the worst - a single spring application of ammonium nitrate alone. On average for both varieties, potassium nitrate application in spring increased the grain yield by 16% compared to the variants where potassium nitrate was not used.

Effect of mineral fertilizers on sorghum crop yields in the southern forest-steppe of Western Siberia

The results of studying the productivity of sorghum crops under different conditions of mineral nutrition on meadow-chernozem soil of the southern forest-steppe of Western Siberia are presented. The study was conducted in 2019–2022 in the Omsk region as part of a long-term stationary field experiment. The soil of the experimental plot is meadow-chernozem moderately deep heavy loamy soil. The arable horizon is characterized by neutral reaction of the soil solution (pH 7.0–7.2). The scheme of the experiment is two-factor, includes application of nitrogen (N0, 30, 60) and phosphorus (P0, 60) mineral fertilizers before sowing sorghum crops. The dynamics of moisture content in the meter soil profile is closely related to the hydrothermal conditions of vegetation periods. In the most wetted year of 2019, the soil profile had a more stable and uniform moisture content, especially in the second half meter. In subsequent years, the atmospheric moisture deficit was clearly manifested in the content of total moisture both along the soil profile and in time. Drying out of the meter profile even in the initial growing season was observed in 2022, which can be considered as a result of low residual moisture in the preceding, also dry, season. In the control, mineral nutrition was limited by the low content of mobile phosphorus. The studies have shown that in conditions of insufficient and unstable moisture, typical for the south of Western Siberia, it is advisable to cultivate sorghum crops with high responsiveness to the use of mineral fertilizers in field fodder production. In the average of two years, the maximum yield of green mass of sugar sorghum on intensive background was 21.07 t/ha, sorghum-sudangrass hybrid – 16.62 t/ha, which is higher than the control by 47.2 and 62.7%, respectively. The most effective was the complex application of mineral fertilizers, which provided an increase in dry matter content of sugar sorghum from 3.97 to 6.08 t/ha (53.0%), sorghum-sudangrasas hybrid – from 2.81 to 4.73 t/ha (68.3%).

Physic-Chemical Characteristics of Organo-Clay Complexes of Agrochernozems of Different Localization on the Slope

Organo-clay complexes of agrochernozems of different localization on the slope were studied, including by the method of dynamic light scattering (DLS). A decrease in the concentration of organic carbon (Corg) of silty fractions in the arable horizons of washed-out agrochernozems was revealed, which was a consequence of the constant exposure of the soil mass of the underlying horizon, provoking the decomposition of organic matter(s). This was accompanied by changes in the content of non-silicate iron (Fed) as a result of oxidative degradation of organo-iron complexes, which contributed to the desorption of Fed. Different intensity of erosion processes influenced the tendency to change the dynamics of Fed: a lower slope steepness (4°) contributed to an increase in the load of Corg on iron oxides, resulting in an increase in iron desorption, whereas in conditions of greater steepness (6°), a decrease in iron desorption was observed. Regardless of the position on the slope, the highest values of the average diameter of organo-clay complexes (D) were observed in the upper horizons of the studied agrochernozems, which decreased down the profile. As a result of erosion processes, the size of organo-clay complexes in arable horizons decreased in comparison with that in non-eroded agrochernozems (by 1.1 times). It was revealed that the size of organo-clay complexes in the studied agrochernozems was determined by the values of the content of Corg and Fed, although the degree of their significance differed in the upper humus (Aarable, A1, AB) and lower (B, C) horizons. In the upper horizons, the value of D was determined by the content of Corg, whereas in the lower horizons, the main role in the formation of the size of organo-clay complexes belonged to Fed. The obtained data allowed us to assume a more significant role of organic matter (OM) in the aggregation of cley particles compared to that of Fed. The hypothesis of a multiple linear regression dependence of the value of D on the values of the concentration of carbon (Corg and Ccarbonates) and Fed in them turned out to be statistically significant both for the entire set of genetic horizons and for humus horizons The coefficient of determination of the model (R2) increased in a row: 0.578 (Apl + A1) 0.678 (Apl + A1 + AB + B + BC + C) 0.724 (Apl + A1 + AB) 0.983 (AB).

Soils and Carbon Pools on Shungite Rocks of South Karelia under Different Types of Land Use

Azonal organo-accumulative soils (Umbrisols) on shungite rocks and the influence of type of land use on their properties and ecosystem carbon stocks were investigated. Сhanges in soil profile structure, basic agrochemical and microbiological indicators of upper horizons, Corg and Cmik stocks in a meter layer of soils and sites carbon pool structure were analyzed. Pine forest as a control, arable land, hayfield, as well as young alder and middle-aged mixed forest were studied. Land use change does not lead to a significant transformation of the properties of shungite soils in contrast to zonal soils. The removal of stones has the greatest influence, leading to the formation of developed arable horizons. The soils are characterized by a high stony, a weak-divided thin profile, low density values, and a pH close to neutral. The wide range of Corg content values from 1.6% to 11.7% is due to the heterogeneous composition of parent rocks. Agricultural development contributes to the accumulation of exchangeable bases, available potassium and phosphorus, the content of which are initially increased in schungite soils. All sites are characterized by a high rate of organic matter mineralization (C/N ratio not higher than 17). A small content of Cmic (84–245 mg C/kg) was noted in the soils, which may be due to the low availability of substrate because of lithogenic origin of carbon and the increased concentrations of heavy metals and lanthanides in schungite rocks. The structure of Corg and Сmic stocks depends on carbon content, keep of stones and presence of dense bedrock. Soil organic carbon stocks range from 17–251 t C/ha, while Cmic stocks range from 6–43 g C/m2. The total ecosystem carbon stocks are maximum in hayfield (259 t C/ha) and minimum in young forest (74 t C/ha). The stocks of carbon in the sites of arable land, middle-aged and control forests are within 169–211 t C/ha.

Soils and Carbon Pools on the Shungite Rocks of South Karelia under Different Types of Land Use

The azonal organo-accumulative soils (Umbrisols) on shungite rocks and the effect of land use on their properties and ecosystem carbon stock have been studied. The changes in soil profile morphology, main agrochemical and microbiological characteristics of the upper horizons, Corg and Cmic stocks in the 100-cm soil layer, and the structure of carbon pools are analyzed. Pine forest (control), arable land, hayfield, young alder stand, and middle-aged mixed forest are examined. In contrast to zonal soils, a change in land use does not considerably transform the properties of shungite soils. The removal of stones has the greatest effect, leading to the formation of developed arable horizons. The soils are characterized by highly skeletal shallow weakly differentiated profile, low bulk density, and pH close to neutral. A wide range of the Corg content (1.6 to 11.7%) results from a heterogeneous composition of the parent rock. Agricultural development contributes to the accumulation of exchangeable bases and available potassium and phosphorus, the contents of which are initially elevated in shungite soils. Characteristic of all examined sites is a high rate of organic matter mineralization (C/N ratio ≤17). A low Cmic content (84–245 mg C/kg) is recorded in the soils, which is explainable with a low availability of the substrate determined by a lithogenic nature of carbon and increased concentrations of heavy metals and lanthanides in shungite rocks. Soil Corg stock varies in the range of 17–251 t C/ha and Cmic stock, of 6–43 g C/m2. The total ecosystem carbon stock is the highest in hayfield (259 t C/ha) and lowest in young forest (74 t C/ha). The total carbon stock in the arable sites, middle-aged forest stand, and control forest is within 169–211 t C/ha.

Improving the quality of processing the soil environment by determining the rational structural and technological parameters for the rolling working bodies

The object of this study is the process of soil compaction with ring-spur and ring-tooth rollers. Based on the zonal optimization of the agrophysical parameters of the arable horizon, the influence of the rolling working bodies on the soil environment in terms of creating a uniform set layer density during pre-sowing tillage was investigated. It was established that soil density should be evaluated in a zonal section together with its aggregate composition, humus content, moisture, etc. Smooth-water-filled, ring-tooth, and ring-spur rollers were studied. The use of a smooth water-filled roller in previous studies contributed to the high unevenness of the compaction of the upper and lower layers of the arable horizon, which indicated the impracticality of further experiments. The research of ring-tooth and ring-spur rollers was carried out by the method of a multifactorial experiment under defined soil and climatic conditions (soil type, sod-podzolic; layer-by-layer soil moisture, 26...28 %; layer-by-layer soil density, 0.96...1.25 g/cm3). Regression models were built of the influence of the specific load, the frequency of passes, and the working speed of the unit on the density of the soil in layers: 0–5; 5–10; 10–15; 15–20; 20–25; 25–30 cm. To assess the heterogeneity of soil density in layers 0–5 and 5–10 cm, a data array was constructed. It was established that the ring-spur roller, even at a speed of up to 6 km/h, is not a tool suitable for regulating the equilibrium density of the seed layer. The best for pre-sowing soil cultivation is a ring-tooth roller (specific soil load, 350 kg/m; unit speed up to 6 km/h). The derived regression equations make it possible to select such a specific load on the ring-tooth roller that could provide a rational value of the layer density of the soil. This is economically and environmentally expedient.

Influence of the biochar application on the thermal properties of soddy-podzolic soil and on the energy balance fluxes of spring wheat in the Leningrad region under various soil moisture conditions

The article presents the results of a field experiment to assess the effect of pre-sowing application of the biochar on the thermal properties of the arable horizon of soddy-podzolic sandy loam soil, on the energy balance components, on the crop surface temperature and on the leaves temperature of spring wheat (variety “Daria”) under various conditions of soil moisture in 2022. The experiment took place at the Menkovo Experimental Station of the Agrophysical Research Institute, located in the Gatchinsky District of the Leningrad Region. The experiment included the plot with the biochar application at the dose of 21.9 t ha-1 and the control plot. The soil thermal properties were measured by the heat pulse method. The components of the energy balance were determined using agrometeorological measurements, radiation balance measurements, crop surface temperature, and phenological measurements. The crop surface temperature was measured by a non-contact method using pyrometers. The soil moisture conditions and available water for wheat were characterized by volumetric soil moisture and evapotranspiration. The volumetric soil moisture was measured using a capacitive soil moisture sensor. The evapotranspiration was determined using the residual term of the energy balance equation through the latent heat flux. According to the results of field experiments, a significant effect (p < 0.05) of the biochar application on the soil thermal properties was found, however, under different moisture conditions, the effect was multidirectional. At zero soil moisture, the biochar application reduced thermal conductivity by 29.7%, reduced volumetric heat capacity by 18.5%, reduced diffusivity by 13.7%, and reduced thermal inertia by 24.3%. Under the conditions of field capacity, the biochar application increased thermal conductivity by 9.4%, reduced volumetric heat capacity by 2.6%, increased diffusivity by 12.3%, and increased thermal inertia by 3.2%. The biochar application significantly (p < 0.05) increased the turbulent heat flux – by 35.5%, which is due to an increase in the crop surface temperature (by 6.4%). Resulting from the decrease in soil evaporation, the biochar application reduced the latent heat flux by 17.0%, and the evapotranspiration by 13.9%. Leaf temperature is related to transpiration. Transpiration can increase when biochar is applied on light-textured soils due to an increase in soil water capacity. The biochar application did not result in significant changes of leaf temperature. The study results are confirmed by numerous articles of both foreign and Russian researchers.