A1 Horizon Research Articles

Influencia de la mineralogía de arcillas, textura y contenido de carbono orgánico sobre el índice de friabilidad de suelos cultivados con caña de azúcar

La friabilidad es una propiedad física esencial en el manejo mecánico del suelo y su comportamiento está asociado a la naturaleza de otras propiedades edáficas; que requiere ser estudiada de manera integral con diferentes propiedades mineralógicas, físicas y químicas. Se evaluó el efecto del dominio de los minerales arcillosos tipo 1:1 (caolinitas) y 2:1 (esmectitas y vermiculitas), la textura y el contenido de carbono orgánico (CO), sobre el índice de friabilidad (IF) de suelos cultivados con caña de azúcar. El IF se determinó por el método del coeficiente de variación, a partir del límite inferior del intervalo de confianza (IFi). Se utilizaron 7280 agregados de los horizontes Ap y A1, tomados en 18 fincas localizadas en el Valle Geográfico del Río Cauca, Colombia. Se determinó la mineralogía de la fracción arcilla a partir de difracción de rayos X, la distribución granulométrica por el método de la pipeta y el contenido de CO por el método de Walkley & Black. El análisis estadístico se realizó a partir de un enfoque descriptivo e inferencial, univariante y multivariante. No se encontró efecto significativo de la dominancia de arcillas 1:1 y 2:1 sobre la variable respuesta IFi; sin embargo, de manera descriptiva se observaron valores más altos deI IFi en suelos con dominio de arcillas 1:1. No se encontró efecto significativo atribuible a las fracciones de arcilla y limo total (FaT y FLT) sobre el IFi de los suelos, por el contrario, la fracción arena total (FAT) y el contenido de CO presentaron efecto altamente significativo en el IFi, con valores más altos del IFi en los suelos con mayores contenidos de CO y menores contenidos de la FAT.

Soil with high organic carbon concentration continues to sequester carbon with increasing carbon inputs

Identifying soil with a large potential to accumulate organic carbon (OC) could maximise the mitigation benefits of carbon (C) sequestration and help prioritise resources to achieve increases in soil OC. The purpose of this laboratory incubation experiment was to determine if an upper limit to OC accumulation in soil was approached with increasing C input in basalt- and granite-derived soil. For each parent material, two soil layers were compared to observe OC accumulation in soil with a high OC concentration (0 to 0.10m, A1 horizon) and soil with a low OC concentration (0.40 to 0.50m, B2 horizon). Soil samples were incubated for up to 146days. The experiment consisted of three soil incubation cycles, with four treatments applied at the start of each cycle: soil only (control), soil and nutrients only (nutrients), high organic matter (OM) and nutrients (approximating a field equivalent of 12.4MgDM/ha; HOMN) and very high OM and nutrients (31.1MgDM/ha; VHOMN). At the beginning of cycle one 13C labelled OM was applied. There was no asymptotic behaviour between C inputs and OC accumulation in soil observed in this study. Thus, OC accumulation was not approaching an upper limit for either parent material at OM application rates ranging from field equivalents of 12.4 to 93.3MgDM/ha (equivalent to 5.4 to 40.6MgC/ha). There was no significant increase in OC concentration between cycle 2 and 3 for the VHOMN treatment in the granite-derived 0.40 to 0.50m soil. While this is not conclusive, this may indicate the soil is approaching an upper limit to OC accumulation at a lower OC concentration due to the dominance of 1:1 clays, compared to the 2:1 clay dominated basalt-derived soil. This suggests that mineralogy rather than texture may influence OC accumulation and any potential C saturation behaviour of soil. Despite increasing microbial activity, evidenced by increasing soil respiration (P<0.001) and microbial biomass C (P<0.05), as well as a significant (P<0.05) narrowing of the C:N ratio of soil, there was substantial 13C recovery (mean between 19.8 and 25.9 (1.1 se) % for both parent material) at the end of the soil incubation. This supports the hypothesis that the increases in OC accumulation were at least partly due to the conversion of plant residues into microbial detritus which is a major component of the relatively stable pool of OC in soil.

Thermal properties of typical chernozems in Kursk Oblast

Thermal diffusivity and heat capacity of virgin and plowed heavy loamy typical chernozems of Kursk oblast were studied. Thermal diffusivity was determined in the course of step-by-step drying of the initially capillary-saturated samples to the air-dry state. Specific heat capacity was determined for absolutely dry samples. Volumetric heat capacity was calculated according to the de Vries equation. Thermal diffusivity varied within the ranges of (1.15–3.46) × 10–7 m2/s in the Ap horizon, (1.14–3.35) × 10–7 m2/s in the А1 horizon, (1.49–3.70) × 10–7 m2/s in the АВ horizon, (1.49–3.91) × 10–7 m2/s in the В1 horizon, and (1.60–3.80) × 10–7 m2/s in the Вса horizon. The thermal diffusivity vs. water content dependencies had distinct maximums and were flattened in the range of low water contents. The maximums were most pronounced for the mineral B1 and Bca horizons; for the A1 and Ap horizons, the curves were rather S-shaped. Volumetric heat capacity of the air-dry soils varied from 0.96 J/(cm3 K) in the A1 horizon to 1.31 J/(cm3 K) in the Bca horizon; in the state of capillary saturation, it varied from 2.79 J/(cm3 K) in the А1 horizon to 3.28 J/(cm3 K) in the Вса horizon. Thermal properties of topsoil horizons were higher in the plowed chernozem compared with the virgin chernozem, which is explained by an increase in the bulk density and a decrease in the organic matter content in the plowed soil.

The Alleviation of Nutrient Deficiency Symptoms in Changbai Larch (Larix olgensis) Seedlings by the Application of Exogenous Organic Acids

Exogenous organic acids are beneficial in protecting plants from the stress of heavy metal toxins (e.g., Pb) in soils. This work focuses on the potential role of organic acids in protecting Changbai larch (Larix olgensis) seedlings from the stress of growing in nutrient deficient soil. The seedlings were planted in a nutrient rich or deficient soil (A1 horizon of a Haplic Cambisol without organic acid as the nutrient rich control, or fully-mixed A1 + B horizons in a proportion of 1:2 as deficient) in pots in a greenhouse. In A1 + B horizons the seedlings were treated daily with concentrations of oxalic or citric acid (OA or CA) at a rate approximately equivalent to 0, 0.04, 0.2, 1.0, or 2.0 mmol·kg−1 of soil for 10, 20, and 30 days. Nutrient deficiency stressed the seedlings as indicated by lipid peroxidation and malondialdehyde (MDA) content in leaves significantly increasing, and superoxide dismutase (SOD) activities, proline, photosynthetic pigment contents, and chlorophyll fluorescence (Fv/Fm) decreasing. The stress increased in controls over the application periods. When nutrient deficient plants were exposed to an organic acid (especially 5.0 or 10.0 mmol·L−1 for 20 days), the stress as indicated by the physiological parameters was reversed, and survival rate of seedlings, and biomass of root, stem, and leaf significantly increased; CA was more effective than OA. The results demonstrate that exogenous organic acids alleviate nutrient deficiency-induced oxidative injuries and improve the tolerance of L. olgensis seedlings to nutrient deficiency.

Increases in organic carbon concentration and stock after clay addition to sands: validation of sampling methodology and effects of modification method

Plant growth on sands is often constrained by water repellence, low fertility and low water-holding capacity (WHC). These soils also have low organic carbon (OC) concentration, particularly in a bleached A2 horizon. Addition of subsoil clay to sands (clay modification) can overcome these constraints and increase WHC; however, little is known about the effect on OC concentration. Clay addition is predicted to increase OC storage via increased OC input from improved plant growth and increased stabilisation of OC by binding to clays. The objectives of this study were (i) to validate the number of soil samples required within a 25-m grid for accurate OC and bulk density measurement in clay-modified soils and (ii) to determine OC concentration, bulk density and OC stocks in clay-modified compared with unmodified soil. The study was carried out on two agricultural properties in South Australia, where unmodified controls (sands with 1–3% clay) were compared with three methods of modification using clay (clay spread, delved and spaded). Soil cores to 50cm depth were collected after harvest within a 25-m grid. The study showed that clay modification could increase OC stocks (0–30cm) by up to 14tha–1 in the South East and 22tha–1 in the Eyre Peninsula. However, the magnitude of the OC stock increase was influenced by the modification method and depended on concentration and depth of incorporation of the added clay and organic matter.

A qPCR assay that specifically quantifies Tricholoma matsutake biomass in natural soil.

Tricholoma matsutake is an ectomycorrhizal basidiomycete that produces prized, yet uncultivable, "matsutake" mushrooms along densely developed mycelia, called "shiro," in the rhizosphere of coniferous forests. Pinus densiflora is a major host of this fungus in Japan. Measuring T. matsutake biomass in soil allows us to determine the kinetics of fungal growth before and after fruiting, which is useful for analyzing the conditions of the shiro and its surrounding mycorrhizosphere, predicting fruiting timing, and managing forests to obtain better crop yields. Here, we document a novel method to quantify T. matsutake mycelia in soil by quantifying a single-copy DNA element that is uniquely conserved within T. matsutake but is absent from other fungal species, including close relatives and a wide range of ectomycorrhizal associates of P. densiflora. The targeted DNA region was amplified quantitatively in cultured mycelia that were mixed with other fungal species and soil, as well as in an in vitro co-culture system with P. densiflora seedlings. Using this method, we quantified T. matsutake mycelia not only from shiro in natural environments but also from the surrounding soil in which T. matsutake mycelia could not be observed by visual examination or distinguished by other means. It was demonstrated that the core of the shiro and its underlying area in the B horizon are predominantly composed of fungal mycelia. The fungal mass in the A or A0 horizon was much lower, although many white mycelia were observed at the A horizon. Additionally, the rhizospheric fungal biomass peaked during the fruiting season.

Effect of Biochar on Nutrient Leaching in a Young Apple Orchard.

Nutrient leaching from agricultural soils is a worldwide problem that has been implicated in deleterious impacts on the environment. Application of biochar to soil has been proposed as a means to reduce nutrient leaching and improve fertilizer use efficiency. The potential for biochar to reduce nutrient leaching and increase fertilizer use efficiency was tested by applying 47 Mg ha hardwood biochar before replanting a commercial apple () orchard, in the Huon Valley, Tasmania. Passive wick flux meters were installed at the base of the A1 horizon at a depth of 25 cm to monitor leachate volume and the concentration of nutrients leached below the A1 soil horizon over a 38 mo period. Biochar application significantly increased the concentration of phosphorous in the leachate, while having no significant effect on nitrate or potassium concentration. The volume of leachate collected in the flux meters was significantly higher in the biochar treatment, which resulted in significantly higher amounts of potassium and phosphorous being leaching from the biochar treatment than the control. Biochar application had no significant effect on either the concentration or the flux of nitrate leached from the A1 horizon. Nonetheless, nutrient application was well in excess of tree requirements, such that between 53 to 78% of the applied nitrogen, 5 to 11% of the applied phosphate, and 69 to 112% of the applied potassium were leached below the A1 horizon.

Gas diffusivity in chinampas soils in Mexico City .

In this laboratory experiment we measured soil gas diffusion coefficients (&lt;em&gt;D&lt;/em&gt;) on undisturbed cores of anthropogenic &lt;em&gt;chinampas&lt;/em&gt; soils and tested the validity of some classical gas diffusivity models for predicting the ratio of &lt;em&gt;D&lt;/em&gt; to the gas diffusion coefficient in free air (&lt;em&gt;D&lt;/em&gt;&lt;sub&gt;&lt;em&gt;0&lt;/em&gt;&lt;/sub&gt;) as a function of the soil air-filled porosity (&lt;em&gt;ε&lt;/em&gt;). The A1 horizon (0-7 cm) of &lt;em&gt;chinampas &lt;/em&gt;soils had the highest gas diffusivity and a linear relationship between &lt;em&gt;D/D&lt;/em&gt;&lt;sub&gt;&lt;em&gt;0&lt;/em&gt;&lt;/sub&gt; and &lt;em&gt;ε&lt;/em&gt;, and thus, the Penman model gave an adequate prediction for this sub-horizon. The Millington-Quirk model was similar to the &lt;em&gt;D/D&lt;/em&gt;&lt;sub&gt;&lt;em&gt;0&lt;/em&gt;&lt;/sub&gt; at all values of &lt;em&gt;ε&lt;/em&gt; for the A2 sub-horizon (7-18 cm) and at &lt;em&gt;ε&lt;/em&gt; &amp;lt; 0.5 cm&lt;sup&gt;3&lt;/sup&gt; cm&lt;sup&gt;-3&lt;/sup&gt; for the A3 (18-30 cm) and A4 (30-50 cm) sub-horizons. Gas diffusivities in &lt;em&gt;chinampas&lt;/em&gt; soils were lower than in mineral soils, as predicted by &lt;em&gt;D/D&lt;/em&gt;&lt;sub&gt;&lt;em&gt;0&lt;/em&gt;&lt;/sub&gt;(&lt;em&gt;ε&lt;/em&gt;) models, likely due to the high content of soil organic carbon. The predictive models could be used for the evaluation of greenhouse gases emission from &lt;em&gt;chinampas&lt;/em&gt; soil.

Caracterização e classificação de solos com horizontes subsuperficiais escuros derivados de rochas graníticas no Escudo sul-rio-grandense

Horizontes subsuperficiais escuros com características morfológicas similares aos solos com caráter sômbrico são encontrados nas áreas mais elevadas da porção leste do Escudo sul-rio-grandense, desenvolvidos nos horizontes A2, AB (ou AC) e BA de Argissolos, Luvissolos e Neossolos Regolíticos, respectivamente. Os mecanismos responsáveis pela sua gênese são ainda pouco compreendidos, apesar de a maioria dos autores concordar com a origem iluvial do húmus e de constituir horizonte diagnóstico. Os objetivos deste trabalho foram caracterizar e analisar o enquadramento de nove perfis de solos com horizontes subsuperficiais escuros do Escudo sul-rio-grandense nos critérios do SiBCS, WRB e Soil Taxonomy, sendo sete deles com características morfológicas de sômbrico. A observação de campo (continuidade lateral na paisagem) e a morfologia (ausência de horizonte E, cores mais escuras que os horizontes sobrejacentes e presença de cutans) apóiam o caráter sômbrico para a maioria dos perfis estudados, com a inserção do caráter sômbrico em nível de subgrupo nas classes de Argissolos Bruno-Acinzentados, Amarelos e Vermelho-Amarelos, bem como em Luvissolos e Neossolos Regolíticos, além da inclusão de eutrófico no nível de grande grupo na classe dos Argissolos Bruno-Acinzentados. Os dados sugeriram a revisão da definição de dessaturação na determinação do caráter sômbrico (distrófico) no SiBCS, com a adoção do valor V de 65 %, adequando essa à definição do Soil Taxonomy e WRB, bem como uma investigação mais aprofundada quanto à não associação do húmus com Al; e a consideração da retirada da capacidade de troca de cátions da matéria orgânica no cálculo da atividade da argila, para os horizontes subsuperficiais escuros.

Effect of cryogel on soil properties

Samples from the A1 and A1A2 horizons of sandy loamy gray forest soil containing 3.1% organic matter have been mixed with a 5% solution of polyvinyl alcohol (PVA) at a ratio of 7 : 1 under laboratory conditions. The samples were frozen at −20°C in a refrigerator; after a freezing-thawing cycle, the evaporation of water from their surface, their thermal conductivity coefficient, their elasticity modulus, and other properties were studied. It has been experimentally found that the thermal conductivity coefficient of cryostructured soil is lower than that of common soil by 25%. It has been shown that the cryostructured soil retains water for a longer time and that the water evaporation rate from its surface is significantly lower compared to the control soil. Cryogel has no negative effect on the catalase activity of soil; it changes the physical properties of soils and positively affects the population of indigenous soil microflora and the growth of the sown plants.

Soil Microbial Biomass Carbon, Nitrogen and Sulphur as Affected By Different Land Uses in Seronga, Okavango Delta, Botswana

Aim: The Okavango Delta at Seronga is fragmented into different land uses ranging from grasslands to woodland (Ximenia and mopane), often punctuated w ith cropped and fallow fields.The influence of land uses o n surface (A1 horizon) soil physico -characteristics, nitrogen, sulphur, carbon, microbial population and biomass were studied to understand soil variability in order to devise conservation strategies for the area. Methodology: Total soil nitrogen (N) was analysed using a Leco N analyser, total carbon +

Hydropedology and Preferential Flow in the Tasmanian Texture‐Contrast Soils

The two‐way interaction between soil morphology and the processes governing soil water movement were investigated for a range of texture‐contrast soil profiles. The texture‐contrast soils consisted of a seasonally water‐repellent sandy loam A1 horizon over a bleached silica‐cemented A2e horizon and a mottled vertic clay subsoil. Differences in soil morphology and structure among sites had little influence on the proportion of soil that participated in infiltration or the maximum depth of infiltration; however, differences in subsoil structure influenced the processes by which water infiltrated and was stored within the B2 horizons. The occurrence of preferential flow was largely controlled by the effects of antecedent soil moisture content on water repellence in the A1 horizon, silica bridging in the A2e horizon, and clay shrinkage in the B2 horizons. Under dry soil conditions, infiltration resulted from up to five different forms of preferential flow. When soils were near field capacity, most forms of preferential flow ceased; however, wetting front instability and lateral flow developed in the A1 horizon. Preferential flows are not thought to have contributed to the pedogenesis of the texture‐contrast soils. Development of the contrasting soil texture horizons, sand infills, and bleached A2e horizons developed before and independently of the observed preferential flow processes in which reworked aeolian sands buried previously developed clay columns.

Assessment of the postagrogenic transformation of soddy-podzolic soils: Cartographic and analytic support

The results of experimental studies of the postagrogenic transformation of loamy soddy-podzolic soils on the southern slope of the Klin-Dmitrov Moraine Ridge are discussed. A chronosequence of soils (arable soils (cropland)-soils under fallow with meadow vegetation-soils under secondary forests of different ages-soils under a conventionally initial native forest) was examined, and the stages of the postagrogenic transformation of the automorphic soddy-podzolic soils were identified. The differentiation of the former plow horizon into the A1 and A1A2 horizons (according to the differences in the humus content, texture, and acidity) served as the major criterion of the soil transformation. A stage of textural differentiation with clay depletion from the uppermost layer was identified in the soils of the 20- to 60-year-old fallows. The specificity of the postagrogenic transformation of the soils on the slopes was demonstrated. From the methodological point of view, it was important to differentiate between the chronosequences of automorphic and semihydromorphic soils of the leveled interfluves and the soils of the slopes. For this purpose, a series of maps reflecting the history of the land use and the soil cover pattern was analyzed. The cartographic model included the attribute data of the soil surveys, the cartographic sources (a series of historical maps of the land use, topographic maps, remote sensing data, and a digital elevation model), and two base maps: (a) the integral map of the land use and (b) the map of the soil combinations with the separation of the zonal automorphic, semihydromorphic, and erosional soil combinations. This scheme served as a matrix for the organization and analysis of the already available and new materials.

Desempenho de sementes de soja sob deficiência hídrica: rendimento e qualidade fisiológica da geração F1

O vigor das sementes interfere significativamente na tolerância à deficiência hídrica e no rendimento de sementes. Assim, o objetivo no presente trabalho foi avaliar a influência da deficiência hídrica sobre o rendimento e a qualidade fisiológica das sementes de soja produzidas na geração F1. O trabalho foi desenvolvido utilizando-se sementes de soja da cultivar M-SOY 8008 RR, semeadas em vasos com capacidade de 15 kg de solo, coletado do horizonte A1 de um Planossolo Háplico Eutrófico solódico, em casa de vegetação. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2x2, sendo os fatores sem e com deficiência hídrica do 1° ao 10° dia após a emergência e nível de vigor das sementes (alto e baixo), totalizando quatro tratamentos, com cinco repetições. As variáveis analisadas foram a fitomassa seca da parte aérea e a área foliar aos 10, 20, 30 e 40 dias após a emergência, rendimento e qualidade fisiológica através dos testes de germinação, primeira contagem de germinação, envelhecimento acelerado e massa de mil sementes na geração F1. A utilização de sementes de alto vigor proporciona acréscimos superiores a 15% no rendimento, em relação ao uso das sementes de baixo vigor. A deficiência hídrica do 1° ao 10° dia após a emergência não interfere no rendimento e na qualidade fisiológica de sementes da geração F1, tanto daquelas de alto como de baixo vigor.

Biological activity of modern and buried dry-steppe chestnut soils

A comparative assessment of the biological activity of modern chestnut soils and chestnut soils buried beneath the Caucasian line set by Anna Ioannovna (1718–1720) on the dry steppes of the Volga Upland was carried out based on determination of enzymatic activity and the state of microbial communities. It was found that, in the modern soil, maximal values of microbial parameters and phosphatase activity, but a minimal value of the humification coefficient were observed in the A1 horizon, whereas in paleosoil, these values were found in the B1 horizon. This fact is consistent with the data on more humid and cold climate during the construction of the historical monument.

Soil organic matter content and composition as influenced by soil management in a semi-arid Mediterranean agro-silvo-pastoral system

The aim of this study was to assess the impact of different long term soil managements on soil organic matter (SOM) quantity and quality in a semi-arid Mediterranean dehesa-like agro-forestry system (North-East of Sardinia, Italy). Seven soil managements were compared: cork oak forest, pasture under oak trees, open pasture, hay crop under oak trees, open hay crop, grass-covered vineyard and tilled vineyard. Analyses include chemical and spectroscopic (FT-IR) characterization of the humic substances (fulvic acids, humic acids and humin) of the A horizons. Lower amounts of total organic C and humic substances were found in the more disturbed soils such as those of the tilled vineyard, while the other soil managements showed a rather similar pattern for many indices of SOM quality (e.g., HA-C/FA-C, fulvic H/C and humic and fulvic C/N ratios) and for spectroscopic characteristics. These results indicated that the impact of soil management on the humic composition was relatively low for these sub-acid (pH ranging from 5.1 to 6.4) sandy soils under Mediterranean type of climate. The relatively small differences between the forest and the grassland land uses also suggested that the periodical light tillage applied to the grassland did not strongly affect SOM accumulation in the topsoil of this land use. In the oak forest soils, a sharp decrease (–77%) of the organic C from the thin A1 to the A2 horizon was observed, which could constrain the resilience of these soils towards disturbance factors, while the grasslands soils, where the organic C sequestration occurred in a thick horizon, may be more resilient.The compared soil managements revealed to be quite conservative, demonstrating that the traditional agro-silvo-pastoral management practices are effective in maintaining relatively good soil quality traits under semi-arid Mediterranean conditions.

Analysis of the spatial distribution of geochemical signatures for the identification of prehistoric settlement patterns in ADE and TMA sites in the lower Amazon Basin

The Archeological Dark Earth (ADE) and Terra Mulata (TMA) anthrosols found at Juruti, on the lower Amazon River, extend over a wide area located within the local ferralsol domain. The ADE soils are dark in color and contain large quantities of fragmented ceramics, while the TMA soils are also relatively dark, but lack ceramics. Multi-element chemical analyses of soil samples of ADE and TMA from the A2 horizon (depths of 10–20 cm) indicated that the ADE soils are characterized by higher concentrations of P2O5, CaO, K2O, MgO, Cu, Mn, and Zn, while the TMAs have median levels of these compounds, and the ferralsols have much lower concentrations. These chemical elements make up the geochemical signature of these anthrosols, whereas Al2O3, Fe2O3, TiO2, Cr, Sr, La, Li, Ni, Pb, V, Y, and Zr characterize the geochemical signature of the ferralsols, which was identified partially in the ADEs and TMAs. The isoline maps of these two geochemical associations permitted the delimitation of the different areas and the identification of the ADEs as sites of long-term human occupancy, and the TMA as an area of temporary occupation associated with agricultural activities. Seven villages were delimited within the study area, and were separated by corridors of ferralsols. These settlements were established on the riverbank, with the more temporary cultivated areas behind them, running almost parallel to the river. The identification of functional patterns based on geochemical associations, the abundance of ceramic material, and concentrations of organic matter, indicated that an area of more than 350 ha was occupied.

Effects of Conservation Tillage on Total and Aggregated Soil Organic Carbon in the Andes

Many Andisols of the Andes have been disturbed by traditional potato-based rotation agriculture disrupting soil structure, water retention capacity and organic matter content. This study was undertaken to investigate the contribution of conservation farming technology or reduced tillage in potato-based rotations in the Colombian Andes in order to rehabilitate total and aggregated soil organic C in disturbed organic matter-rich Andisols. Soils were sampled from farms with 7-year of reduced tillage and farms with conventional farming practices. Ultrasound energy was applied to samples to disrupt aggregation and total soil C was determined in order to investigate the amount of carbon held inside the aggregates of different soil size classes. Results indicated that reduced tillage in potato-based crop rotations increased the soil C concentration and average C content in the whole profile (≈117 cm depth) by 50 and 33% (1636 t C ha?1 vs. 1224 t C ha?1), respectively, as compared to conventional farming practices. Carbon content increased 177% in the subsoil (A2 horizon, 78 -117 cm depth, from 215 to 596 t?ha?1), although most of the soil C was in the A1 horizon (between 0 -78 cm average thickness, 1097 t?ha?1). These increases show that reduced tillage enhances C stores in Andisols which are already high in organic matter. In addition, C in aggregates represented more than 80% of the total organic matter and it was positively affected by conservation practices. The C increase was preferential in the smaller macroaggregates (

Phosphatase activity in the surface and buried chestnut soils of the Volga-Don interfluve

The phosphatase activity (PA) was studied in the chestnut paleosols buried in 1718–1720 under the Anna Ivanovna rampart in the southern part of the Privolzhskaya Upland and in the middle of the third millennium BC under the burial mound of the Bronze Age on the Northern Yergeni Upland; the background analogues of these soils were also examined. The PA values in the fresh soil samples varied from 2.5 to 37 mg of P2O5/10 g of soil per h with maximums in the A1 horizon of the surface soils and in the B1 horizon of the paleosols. The PA values depended on the time of storage of the samples: with time, they increased by 2.6–2.9 times in the A1 horizon of the background surface soil and decreased by 20–60% in the other soil samples. The specific distribution patterns of the PA values in the soil profiles remained the same independently of the time of storage of the samples. Relatively small amounts of the soil samples were sufficient for the reliable determination of the PA: 1–2 g for the A1 horizon and 3–5 g for the B1 and B2 horizons. The time of incubation with the substrate had to be increased up to 4 h for the long-stored samples.

Thermal diffusivity of plowed leached meadow-chernozemic soils in the Adygeya Republic

Thermal diffusivity of the upper horizons of leached meadow-chernozemic soils varies in dependence on the soil water content within the following limits: 1.20–4.11 × 10−7 m2/s for the Ap horizon, 1.21–3.85 ×10−7 m2/s for the A1 horizon, and 1.35–3.73 × 10−7 m2/s for the A1B horizon. The relationships between the thermal diffusivity and the soil water content are described by S-shape curves with a long gently inclined segment within the range of water contents of 0.30–0.35 cm3/cm3) water contents. The thermal diffusivity of air-dried soil samples correlates with the physical clay (<0.01 mm) content. The Pearson correlation coefficient for these two variables equals −0.67 and is statistically significant at the significance level of 0.05. Regression equations allowing one to calculate the thermal diffusivity of the investigated soil horizons on the basis of data on the soil water content have been obtained.