Mycological characteristics of the cultural layer of a medieval settlement on soddy calcareous soils

The difference between fungal communities in the cultural layer of a medieval settlement and in the background soddy calcareous soil is shown. In the cultural layer, the portion of spores, especially large spores (d > 6 μm), in the total fungal biomass is increased, whereas the portion of mycelium, especially with a thickness of > 4 μm, is decreased. The species composition of micromycetes in the cultural layer is also transformed; species from the Aspergillus and Fusarium genera predominate. The frequency and diversity of Penicillium representatives decreases, whereas the fungal species from the Phoma, Doratomyces, Geomyces, and Verticillium genera, which are not typical of the background soil horizons, increases. The diversity of the minor fungal species also increases in the cultural layer. An increased content of keratin-decomposing soil fungi is found in the cultural layer. It is argued that the use of the entire set of these characteristics makes it possible to perform mycological indication of the parts of the cultural layer that served different purposes (ancient streets, house floors, backing of the walls, etc.) within the settlement.     

Humus in paleosols of archaeological monuments in the dry steppes of the Volga-Don interfluve

Traditional chemical methods and ¹³C-NMR spectroscopy were used to study the humus in chestnut paleosols buried under kurgans of different ages (the 16th–15th centuries BC; the 1st, 2nd–3rd, and 13th–14th centuries AD) and under the Anna Ioanovna Rampart (1718–1720) and in their recent analogues on virgin plots. It was found that the decrease in the humus content of the paleosols as a result of the diagenetic processes is exponentially related to the age of the soil burial. The loss of humus from the upper 30 cm of the paleosol buried 3500 yrs ago amounted to 76 ± 14%, and this system did not reach a stationary state. The constants of the humus mineralization in the paleosols were determined. A tendency for an increase in the degree of the organic matter humification in the chestnut soils during the past 3500 yrs was found. With an increase in the age of the burial, the portion of aromatic structures in the structure of the humic acids increased and the portion of aliphatic fragments decreased. The cyclic changes in the composition of the humus related to the secular variations in the climatic humidity were identified.     

Humus of soils of the Altai Mountains

Data on the humus composition and specific features of soils in the Altai Mountains obtained in the long-term studies initiated by R.V. Kovalev are discussed. The average statistical values for the content of the main humus components and their ratios in different soil types were obtained by processing the data on 307 soil pits. The comparison of the soils belonging to the same type and occurring in the northwestern, central, and southeastern regions of the Altai Mountains in terms of the C ha/C fa ratio (one of the integral indices of the humus composition) showed that there were no significant differences between them. The overlapping intervals of the average values of this ratio testified to this fact. For instance, the average C ha/C fa ratios in the mountain tundra soils of the regions mentioned amounted to 0.70 ± 0.03; 0.72 ± 0.02; and 0.69 ± 0.03, respectively, and, in the mountain meadow soils, they amounted to 0.67 ± 0.03; 0.69 ± 0.04; and 0.67 ± 0.03, respectively. The mountain brown forest soils that are components of the soil cover only in the northwestern and central regions also differ insignificantly by this parameter (0.88 ± 0.05 and 0.89 ± 0.03, respectively). In the soils of the Altai Mountains, the dependence between the portion of humic acids and the mean annual air temperature (HA (%) = 29.54 + 1.06T(°C), r = 0.71) and the ratio of the portion of fulvic acids to the mean annual precipitation (FA (%) = 9.70 + 0.029W, r = 0.74) was shown to be similar to those in all the soils of mountainous southern Siberia. These facts enabled us to apply regression equations for a quantitative reconstruction of the paleoclimate components according to the humus composition. Original Russian Text ￠ M.I. Dergacheva, E.I. Kovaleva, N.N. Ryabova, 2007, published in Pochvovedenie, 2007, No. 12, pp. 1416–1421.     

Microbiological characterization of soddy soils of the Severnaya Dvina River floodplain

Soils of virgin lands, hayfields, and plowed lands were studied in the Severnaya Dvina River floodplain. The potential possibilities of microbiological processes were shown to increase in the summer in the soils in the following sequence as related to the increasing number of copiotrophs in them: virgin land—hayfield—plowed land. Copiotrophs are microorganisms that use easily available organic substances, including nitrogencontaining ones. The increase in their number enhanced the nitrification, while other microbiological processes became weaker. The number of fungi increased due to the improvement of the water-air regime. As the agricultural use of the soils became more intense, the cellulose decomposition slowed down, the actual nitrification ability was lowered, and the carbon content in the physiologically active microbial biomass decreased because the area of the natural plant cover was reduced from the virgin land to the plowed land.     

Microbial cenoses of alas soils on the Lena-Amga interfluve in Central Yakutia

The specific features of the microbial population in the soils of alases (thermokarst depressions) of Central Yakutia were revealed: a high number of microorganisms of all the groups (1.1 × 10³–3.9 × 10⁸ cell/g), which is compatible with the microbial density in the steppe soils of Transbaikalia; a particular distribution of the microorganisms along their profiles without decreasing of their number with the depth; and insignificant fluctuations of their population density in some soil horizons. The enrichment of these soils with microorganisms depends on the hydrothermal conditions. The microbial number gradually increases from the elevated peripheral parts of the alases to their centers and drastically decreases towards the lower lakeside areas of the alases. At the same time, the composition of the microorganisms changes, and nitrogen-fixing bacteria appear.     

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.     

Humus status of soils of overgrown quarries in Leningrad oblast

The humus status of young different-aged soils developed on tailings of different quarries of Quaternary and pre-Quaternary raw materials in Leningrad oblast was studied. Organic profiles were characterized; the humus accumulation rates, the organic matter reserves, the humus enrichment with nitrogen, the degree of humification of the organic matter, and the contents of separate fractions of humus acid in soils on different tailing rocks were estimated. The composition of humic acids was also studied. It was shown that the lithological features of the tailings determining the chemical processes of the profile differentiation of humic substances and the ecogenetic successions of vegetation also determine the rate and direction of the humus accumulation in the soils during similar periods of biological activity in the southern taiga.     

Solubility and speciation of zinc in calcareous soils

Water, Air, & Soil Pollution - The objective of this study was to evaluate the formation of a probable Zn solid phase in soils. Thermodynamic solubility isotherms revealed that ZnFe2O4, Zn2SiO4...     

The stability of iron chelates in calcareous soils

The stability of Fe-EDTA and Fe-CDTA was investigated in order to evaluate their effectiveness under calcareous soil conditions. To accomplish this evaluation the reaction rate of fixation, K, the adsorption coefficient, K_d, and the retardation factor, S, of the iron chelate were determined through column experiments at pH 7.8 and two ionic strengths, I, of CaCl₂. The results indicated that iron in Fe-EDTA was more fixed than in Fe-CDTA. The fixation increased by increasing the ionic strength. Also it increased linearly with increasing CaCO₃ content of the soil. The values of retardation factor, S, showed that this parameter depended more on the surface area of the soil than on I or CaCO₃ content. The product KS depends on CaCO₃ content, surface area of the soil, ionic strength and chelating agent used. It can be taken as an index for the efficiency of the iron chelate under different conditions. Fe-EDTA was more adsorbed than Fe-CDTA, the adsorption increased with increasing ionic strength and surface area of the soil.     

Complexing of lead by DTPA in calcareous soils

Ten agricultural soils were spiked with 100 μg of Cu, Zn, and Pb g^?1 of soil. The complexation of Pb by 10^?4 M DTPA was determined after 60 days of metal equilibrium. A theoretical stability model of Fe, Mn, Cu, Zn, Ca, and Pb, between pH 1 and 10 was developed. It showed that CuL^3? (55.4 to 63%), CuHL^2? (0.1 to 9.4%), PbL^3? (29.1 to 33.3%), PbHL^2? (0.01 to 2.5%) and MnL^3? (2.8 to 3.2%) as the predominant species between pH 6 and 9. Other species like CaL^3?, CaHL^2?, FeL^2?, FeHL^?, FeL^3?, FeHL^2?, ZnL^3?, ZnHL^2? and MnHL^2? were less than 0.1% between pH 6 and 9. In the experimental soils, DTPA-Pb complexes accounted for 12.3 to 21.2% of metal complexed after 3 days of DTPA equilibriation. DTPA-Cu complexes were the major complexed species in the soils ranging between 72.5 and 82.2% after 3 days equilibriation with 10^?4 M DTPA. The proportion of Zn complexed by DTPA (3.8 to 10.1%) was much greater than predicted by the theoretical model. On the contrary, Mn was not complexed in appreciable amounts by DTPA.     

Humus status of buried soils in loess deposits of the Minusinsk intermontane trough

The study of the humus status of the buried soil sequence in loess deposits of the Minusinsk intermontane trough revealed that the group humus composition and humus properties of the buried soils did not undergo considerable changes and preserved their initial parameters upon the burial under the conditions of low biological activity. Neither the group humans composition nor the humus substance properties fell beyond the limits typical of the humus status of recent soils. The fractional composition of the humus acids might undergo secondary alternations after the burial. The dependence between the humus type and the length of the biological activity period permitted us to make a paleoclimatic reconstruction of the bioclimatic conditions that might have existed during the formation of the loess deposits in the Minusinsk intermontane trough. It was shown that the soil-climatic zones were repeatedly alternating during the Quaternary period due to the global climate change.     

黄土高原石灰性土壤不同形态磷组分分布特征

以黄土高原自北向南采集的12个0～20 cm耕层土壤为供试土样,采用Tiessen和Moir修正的Hedley土壤有机无机磷分级方法研究了黄土高原石灰性土壤中不同形态磷组分的分布特征。结果表明:供试土壤各形态P总体分布特征为:HCl-P>Residual-P>NaHCO3-Po>NaHCO3-Pi>NaOH-Po>NaOH-Pi>H2O-P,以HCl-P和Residual-P为主,分别占土壤全磷的54.00%～88.96%和0～39.11%。黄土高原土壤磷含量总体分布表现为南高北低。在各土壤类型间,NaOH-Po、Residual-P和全磷平均含量表现为干润砂质新成土<黄土正常新成土<简育干润均腐土<土垫旱耕人为土,自北向南依次增加;H2O-P和HCl-P表现为简育干润均腐土<黄土正常新成土<干润砂质新成土<土垫旱耕人为土,自北向南先降后升,且上升幅度较大。黄土高原土壤全氮与全磷及各形态磷含量相关性均达显著水平,其中与NaOH-Pi、NaOH-Po、HCl-P及全磷含量达到极显著水平。C/N、pH及砂粒与全磷及各形态磷含量呈负相关关系,其中pH与NaHCO3-Po呈显著负相关,与H2O-P、NaHCO3-Pi、NaOH-Pi及HCl-P呈极显著负相关;砂粒与NaHCO3-Pi、Residual-P及全磷呈显著负相关。除NaHCO3-Po、NaOH-Po及Residual-P,CaCO3与其他各形态磷含量具有一定程度负相关。除NaOH-Pi和NaOH-Po外黏粒与其他各形态磷及全磷也具有一定程度负相关。土壤各形态磷组分和有效磷的多元回归分析发现,各形态磷中对有效磷贡献最大的是H2O-P,其次为NaOH-Pi和NaHCO3-Po;土壤各形态磷组分和有效磷逐步回归分析结果,进一步说明H2O-P的有效性最高。     

伊朗一些石灰性土壤中锌解吸动态研究

Desorption of zinc (Zn) from soil is an important factor governing Zn concentration in the soil solution and Zn availability to plants. Batch experiments were performed to study the kinetics of Zn desorption by diethylenetriaminepentaacetic acid (DTPA) from 15 calcareous soil samples taken from Golestan Province in northern Iran. Soils were equilibrated with 0.005 mol L-1 DTPA solutions for 0.25 to 192 h. The results showed that the extraction process consisted of rapid extraction in the first 2 h followed by much slower extraction for the remainder of the experiment. Desorption kinetic data was fitted to pseudo-first-order kinetic model. The experimental data were found to deviate from the straight line of the pseudo-first-order plots after 2 h. The model of two first-order reactions was fitted to the kinetic data and allowed to distinguish two pools for Zn: a labile fraction (Q1 ), quickly extracted with a rate constant k1 , and a slowly labile fraction (Q2 ), more slowly extracted with a rate constant k2 . The applicability of pseudo-second-order model in describing the kinetic data of Zn desorption was also evaluated.     

Water dispersible clay in calcareous soils of southwestern Spain

Water dispersible clay (WDC) is a good indicator of the risk of soil erosion by water and the consequent losses of nutrients and contaminants in overland flow. We measured the content and studied the properties of WDC in 26 samples of calcareous Xeralfs, Xerepts and Xererts of southwestern Spain collected from fields under different crop and tillage management; the soils ranged widely in total clay content (60–455 g kg^− 1), calcium carbonate equivalent (CCE) (< 1–559 g kg^− 1) and active calcium carbonate equivalent (ACCE; 2–135 g kg^− 1), and were poor in organic carbon and soluble salts. The WDC content was determined by shaking 10 g of soil in 1 L of simulated rainwater for 4 hours. Non-carbonate WDC contents were found to be strongly correlated with the total clay content of the soils and ranged from 1 to 92 g kg^− 1 soil (mean = 29 g kg^− 1), the non-carbonate WDC/total clay ratio ranging from 0.01 to 0.29 (mean = 0.12). Based on regression analyses, illite was more dispersible than smectite and iron oxides decreased dispersion of clay. Carbonate WDC contents ranged from 1 to 27 g kg^− 1 (mean = 8 g kg^− 1) and were averaged one third the non-carbonate WDC contents; also, they were strongly correlated with the soil ACCE. WDC was rich in phosphorus (P) relative to the bulk soil. The enrichment ratio (ER) for total P (i.e. the ratio of total P in WDC to total P in soil) ranged from 0.2 to 29 (mean = 5) and was inversely related to the total clay content. On average, about one tenth of the soil total P was exported in the WDC and about one fifth of the total P in WDC was in the form of bicarbonate-extractable P (i.e. relatively soluble or ‘labile’ P). Part of the P in WDC seemingly occurred as metal phosphate particles formed by reaction of P fertilizers with soil. In summary, significant amounts of P can be exported via WDC, even though the proportion of total clay that is water dispersible is substantially lower in these soils than in cultivated soils of other semiarid regions.     

Soil properties related to phosphate buffering in calcareous soils

Abstract

In a group of 24 related calcareous soils, derived from Jurassic oolitic limestone, there was marked variability (13‐fold) in phosphate buffering when expressed as the maximum buffer capacity. This variability was most closely related to the iron content and pH of the soils, and these together accounted for 72% of the variance. This percentage was not increased by including CaC0₃ content or organic matter, which were also correlated with the maximum buffer capacity. A high correlation with specific surface area of CaCO₃ was probably an indirect effect due to the high correlation between this variable and the Fe and pH of the soils.

The equilibrium buffer capacity, which is the traditional measure of phosphate buffering, was less variable but quite unrelated to all the soil properties measured except the soil surface area. However the maximum buffer capacity and quantity of adsorbed P together accounted for 63% of the variance in this parameter.     

Micronutrient extraction in calcareous soils treated with humic concentrates

The use of humic concentrates in drip irrigation cultures in Spain has increased recently. Several companies offer different products to the farmers. It is suggested that such products are useful in improving the structure of the substrates, in increasing CEC of soils, in mobilizing micronutrients towards the roots and in acting as biological hormones. In our work, we have studied the effect of 11 different humic concentrates on extraction of iron and other micronutrients in the soil. Two substrates were used, a calcareous soil and a mixed substrate called “soil standard” since it has been made with components similar to those of a soil, but with standard materials. These soils were incubated with 11 different commercial humic concentrates. After the interaction, soils were extracted by the AB‐DTPA method. The results show that, in general, all commercial products increased extraction of micronutrients, but large amounts of humic concentrates were needed to increase them significantly. These quantities were greater than those reached in the bulk soil with the doses proposed by the distributors. However the amounts of humic substances used in this experiment can be reached in microsites near the droppers in a drip irrigation system. Although all humic concentrates increased micronutrients extraction, differences were noted on the efficiency of the different products. Humic rather than fulvic acids were responsible for this increase in extraction.     

Predicting the incidence of iron chlorosis in calcareous soils of southern Spain

Abstract

Iron chlorosis is a serious crop production problem in many calcareous soils of Southern Spain. The objective of this study was to determine which indigenous soil properties (i.e., those which are essentially permanent) were related to Fe chlorosis. Experiments, using two chickpea (Cicer ariethinum L.) cultivars and a sunflower (Helianthus annuuus L.) cultivar, were carried out in a growth chamber with 25 calcareous soils representing widespread Xerofluvents, Xerorthents, Xerochrepts, Haploxeralfs, Rodoxeralfs, Chromoxererts, and Pelloxererts of Southern Spain. The average chlorophyll contents for the three cultivars were significantly correlated with several properties of the carbonate and Fe oxide phases, such as calcium carbonate equivalent (r = 0.69***), “active lime”; (r = 0.58**), acid NH₄‐oxalate extractable Fe (r = 0.68***), Tiron‐extractable Fe (r = 0.61**), and DTPA‐extractable Fe (r = 0.55**). The present and other studies indicate that the soil property most consistently related to Fe chlorosis is acid NH₄‐oxalate extractable Fe (Feo). The Feo critical level separating soils with a high probability from those with a low probability of responding to Fe fertilization was 0.63 g/kg soil, a value similar to those found in other studies. This further supports the use of Feo as a key property to predicting the appearance of Fe chlorosis.     

Humus and nitrogen in soddy-podzolic soils of different agricultural lands in Perm region

Heavy loamy soddy-podzolic soils (Eutric Albic Retisols (Abruptic, Loamic, Cutanic)) under a mixed forest, a grass–herb meadow, a perennial legume crop (fodder galega, Galéga orientalis), and an eightcourse crop rotation (treatment without fertilization) have been characterized by the main fertility parameters. Differences have been revealed in the contents of humus and essential nutrients in the 0- to 20- and 20- to 40-cm layers of soils of the studied agricultural lands. The medium acid reaction and the high content of ash elements and nitrogen in stubble–root residues of legume grasses favor the accumulation of humic acids in the humus of soil under fodder galega; the C_HA/C_FA ratio is 0.95 in the 0- to 20-cm layer and 0.81 in the 20- to 40-cm layer (under forest, 0.61 and 0.41, respectively). The nitrogen pool in the upper horizon of the studied soddy-podzolic soil includes 61–76% nonhydrolyzable nitrogen and 17–25% difficultly hydrolyzable nitrogen. The content of easily hydrolyzable nitrogen varies depending on the type of agricultural land from 6% in the soil under mixed forest to 10% under crop rotation; the content of mineral nitrogen varies from 0.9 to 1.9%, respectively. The long-term use of plowland in crop rotation and the cultivation of perennial legume crop have increased the content of hydrolyzable nitrogen forms but have not changed the proportions of nitrogen fractions characteristic of this soil type.     

石灰性土壤中硫形态组分及其影响因素

对陕西 ,湖南等 7省 (市 ) 22个农田耕层土壤硫形态组分的分析表明 ,供试土壤总硫平均为405.5 111.8mg/kg ,总有机硫占总硫 85.4 % 10.0%。供试土壤中酯键硫 (C -O-S)、碳键硫(C -S)、惰性硫平均含量分别为 130.3 64.6、65.5 29.4、152.5 96.7mg/kg ,分别占总硫的31.4 % 12.9%、18.0 % 10.7%、36.0 %17.8% ;分别占总有机硫的 36.6 % 14.4 %、21.8 13.8%、41.5 % 19.1%。石灰性土壤C -O -S、C -S形态硫与土壤有机碳之间分别呈极显著 (r =0.7334* * )和显著 (r =0.4426*)正相关。石灰性母质发育土壤C -O -S含量显著大于黄土母质发育的土壤。供试土壤无机硫组分中主要是难溶硫 ,其平均含量达 28.4mg/kg ,占总无机硫 50.7%。土壤中难溶硫与总无机硫 (r =0.6040* *)和CaCO3(r =0.6800* *)之间呈极显著正相关 ,而与总有机硫 (r =- 0.5286*)、C-O -S (r =- 0.4417*)和有机碳 (r =-0.4786*)之间呈显著负相关。黄土母质发育土壤难溶硫含量 ,占总硫和占总无机硫的比例显著或极显著高于石灰性母质发育的土壤。为了全面评价石灰性土壤硫素供应潜力 ,有必要开展石灰性土壤难溶硫形成及转化规律和生物有效性的研究。