Fractional composition of humus in leached chernozems and gleyed podzolized chernozem-like soils of the northern forest-steppe zone

The composition of humus in leached chernozems differs from that in gleyed podzolized chernozem-like soils in the northern forest-steppe zone of European Russia. Leached chernozems have the fulvate-humate humus. Gleyed podzolized chernozem-like soils have the humate-fulvate humus. A more aggressive composition of humus in the latter soils is caused by their overwetting and the development of gley processes under conditions of a stagnant-percolative soil water regime.     

On some general regularities of the formation and changes in properties of mn‐fe concretions in soils of humid landscapes

An attempt is made to formulate general regularities of changes in the amount and composition of Mn‐Fe conoretions in soils of humid landscapes, confined to various soil‐forming rocks within the Russian platform. It is concluded, that the intensive formation of concretions is highly conditioned by waterlogging degree of soils and their hydrological regime. The content of concretions is always maximum in gley‐like soils (seldom in gley ones), independing on genesis of parent rocks; the fraction distribution of Mn‐Fe concretions proves to be stable in time; Mn amount is declined with increasing the waterloggiing degree of soils, while the content of Fe becomes increased; the highest accumulation of such microelements as Co, Pb, Cd is observed in concretions, which are rich in Mn. The concretions are characterized by a high amount of X‐ray‐amorphous Fe as well as by a low magnetic susceptibility. The chemical composition of concretions is shown to be preferable for quantitative diagnosis of the water‐logging degree in soils.     

水稻土的渗漏性能对土壤环境更新的影响及其意义

1.试验结果表明,水稻的土壤环境宜常予更新,否则由于耕层土壤中氧气的缺少和有害物质的积累,对水稻产生不良的影响.在实践中除了一些人为措施以更新土壤环境外,工壤所具有的渗漏性能,在土壤环境更新中也起一定的作用.2.由于土壤具有渗漏性能,这样就引起了灌溉水向土层中的渗漏,从而带入了氧气和养分,促进了土层中养分的分配和移动,也稀释和排出了耕层土壤中的养分和有害物质,对土壤环境起着更新的作用.在这些作用中可分有利的和不利的两个方面,这两个方面的相对大小和转化,受到渗漏速度的制约.3.渗漏速度过慢和过快都对水稻生长产生不利的影响.渗漏速度过快虽有利于毒害物质的排除、氧气的输入等,但用水不经济,养分流失过多,反而易于引起水稻生长后期的脱肥.反之,渗漏速度过慢虽可减少水分和养分的流失,但由于毒害物质不能得到排除,也抑制了根系的活动,削弱了地上部分的生长.     

THE MEASUREMENT AND PREDICTION OF AVAILABLE WATER CAPACITY OF FERRALLITIC SOILS IN UGANDA

Field capacity was measured directly, and soil moisture characteristics were determined on undisturbed cores, for a wide textural range of ferrallitic soils in Uganda. The initial moisture conditions of the soils were shown to affect results and thus standardized procedures were adopted for field and laboratory determinations. Laboratory estimates of field capacity for undisturbed and disturbed samples were shown to be unreliable, but a correction factor was found which improved them. There was no single moisture tension for undisturbed core samples that corresponded to field capacity. Particle-size composition could be related to field capacity, permanent wilting-point, and available water capacity by multiple regression equations having correlation coefficients of 0.96, 0.98, and 0.88 respectively. The relationships predicting available water capacity were different from those found for soils in England, but those for field capacity and permanent wilting-point were similar. Particle-size analyses were carried out using three methods of dispersion of different efficiencies. Particle-size composition following gentle dispersion by shaking soil with distilled water was poorly correlated with moisture-holding properties. There was little advantage in using vigorous ultrasonic dispersion compared with overnight shaking with sodium hexametaphosphate. Two soils formed on alluvial deposits with kaolinite the only clay mineral, and one soil with montmorillonite the dominant clay mineral, showed markedly different relationships between moisture-holding properties and particle-size composition.     

Ecological-hydrological and genetic features of chernozem-like soils of closed depressions in the northern Tambov Lowland

Specific features of the genesis and water regime of soils in closed depressions were studied in two catenas located on the interfluvial and terrace surfaces. In humid years and in the years with moderate precipitation, the surface flooding up to early May reduced the Eh values up to 60–100 mV in the soils of the interfluvial depressions. The contrasting stagnant-percolate water regime under the surface waterlogging caused podzolization of the soils manifested in the skeletans, iron nodules, humus cutans, and podzolic horizons. The pro-files acquired eluvial-illuvial differentiation, and the water-physical properties of the soils became less favorable. In the soils of the terrace depressions upon bogging due to the shallow ground water and stagnation of water up to mid-July, the Eh values decreased to ?20 to ?80 mV. The reductive conditions were responsible for the appearance of the morphochromatic signs of gley. The ground water of bicarbonate-calcium composition at a depth of 80–120 cm hindered podzolization. The soils with features of gley and podzolization are low-productive.     

Using landscape and depth gradients to decouple the impact of correlated environmental variables on soil microbial community composition

Simultaneously assessing shifts in microbial community composition along landscape and depth gradients allows us to decouple correlations among environmental variables, thus revealing underlying controls on microbial community composition. We examined how soil microbial community composition changed with depth and along a successional gradient of native prairie restoration. We predicted that carbon would be the primary control on both microbial biomass and community composition, and that deeper, low-carbon soils would be more similar to low-carbon agricultural soils than to high carbon remnant prairie soils. Soil microbial community composition was characterized using phospholipid fatty acid (PLFA) analysis, and explicitly linked to environmental data using structural equations modeling (SEM). We found that total microbial biomass declined strongly with depth, and increased with restoration age, and that changes in microbial biomass were largely attributable to changes in soil C and/or N concentrations, together with both direct and indirect impacts of root biomass and magnesium. Community composition also shifted with depth and age: the relative abundance of sulfate-reducing bacteria increased with both depth and restoration age, while gram-negative bacteria declined with depth and age. In contrast to prediction, deeper, low-C soils were more similar to high-C remnant prairie soils than to low-C agricultural soils, suggesting that carbon is not the primary control on soil microbial community composition. Instead, the effects of depth and restoration age on microbial community composition were mediated via changes in available phosphorus, exchangeable calcium, and soil water, together with a large undetermined effect of depth. Only by examining soil microbial community composition shifts across sites and down the soil column simultaneously were we able to tease apart the impact of these correlates environmental variables.     

Effect of Organic matter application on the fate of 15N-labeled ammonium fertilizer in an upland soil

Abstract

The clay mineral composition of two “terra roxa estruturada” (TRE) soils occurring in the tropical rain forest and tropical forest/savannah transition zone, and a reddish brunizem in the savannah/semi-arid transition zone was studied comparatively in the southeast Amazon region.

Kaolin minerals were dominant in these soils, and hematite and goethite were found in the clay fraction. A small amount of 2 : 1-type clay minerals was found in two soils. The mineral composition of the clay fraction in the TRE soils was hardly influenced by the difference of the meteorological factor or their water condition in this region, and this factor should not control the influence of parent materials derived from basic rocks. The TRE soils were developed under the condition of laterite genesis, and were regarded claymineralogically as a kind of the lateritic soils.     

Rekonstruktion des Ausgangszustandes und Bilanzierung von Böden einer Moränenlandschaft

Reconstruction of the original composition and balancing of soils developed on glacial till In this paper a method for the reconstruction of the original composition of soils formed on heterogeneous glacial till is described. As an exampel the original contents of carbonates, iron and clay were calculated in two soils. The soils investigated are “Rostbraunerde” under forest and ?Braunerde”? under meadow. The “Braunerde” has been regularly irrigated with waste water for the last 70 years. The heterogenity of the fine earth of the parent material is caused by the successive deposition of materials with varying particle size distribution as well as in situ cryoclastic weathering of the different rock fragments. The reconstruction was calculated from the relation between the above mentioned weatherable components and less weatherable components in the pleistocenic sediments of Berlin. The sorting grade (So, Muller, 1962), median (Md) of the particle size distribution in the 2–600 γ fraction and the contents of coarse sand, Zr and Ti in the fraction 2-2000 pm were considered as unweatherable. The calculations were performed using multi regression analysis. The influence of the pedogenetic processes of decarbonatisation, acidification, clay formation and clay migration as well as the pedological changes resulting from the waste water irrigation were quantified through the comparison between the calculated original and the measured actual contents of the weatherable components.     

太行山区不同土地利用方式保水防蚀能力研究

从植被和土壤状况两个方面对太行山区常见的不同土地利用方式的保水防蚀能力进行了研究。研究表明,栓皮栎林、刺槐林和矮刺槐林具有较好的层次结构、较大的枯落物积累量及根系数量,保水防蚀能力较强;板栗林因为人为干扰较为强烈,层次结构单一,保水防蚀能力弱于另外3种林地;撂荒地具有较高的植被盖度和数量较多的草本植物根系以及枯落物的积累,其保水防蚀能力优于农田。农田层次结构单一,枯落物的积累和根系数量少,保水防蚀能力最弱。该地区大部分土壤都具有较大的非毛管孔隙度和较好的渗透性,但抗蚀性较差,植被有提高土壤抗蚀性的作用。     

干旱区农田不同类型土壤盐碱化发生规律

为明晰西北干旱区平原农田典型土壤发生盐碱化的规律,2014年在新疆代表性平原农场采集砾砂、粉土/粉砂、粉土/粉细砂、粉土和亚黏土5类主要土壤进行试验,分析其岩性组成、毛细管作用及土壤表层积盐之间的内在关系,寻求3者相互影响机理。结果表明:土壤中粗颗粒含量越大,早期毛细管现象越明显,土壤表面积盐越多。细颗粒含量越多,早期毛细管作不明显,地表积盐量较少但持续时间较长,最终积盐量大于粗颗粒土壤。5类土壤在盐碱化发生早期(12 d左右)毛细现象最为突出,尤其1~4 d内地表的积盐大,速度最快。粗颗粒的砂性土发生盐碱化时,表面容易形成3~4 mm厚盐痂,阻止了地表盐碱化的发展。当土壤中粉粒和黏粒较多时,地表积盐主要以晶体形式出现。土壤的颗粒级配较好、压实度较大时,土壤表面的积盐量就较少。研究成果可为西北地区不同类型的土壤盐碱化治理方法、治理时段的选取等提供参考。     

Water distribution pattern in treated wastewater irrigated soils: hydrophobicity effect

The shortage of fresh water (FW) in Israel and other semiarid regions has forced farmers to significantly expand the use of treated wastewater (TWW). Recently, farmers utilizing reclaimed wastewater (TWW) reported a unique type of water distribution regime in drip-irrigated soils, as follows: (i) limited wetted area on the soil surface; and (ii) small saturated areas around and below the dripper, in TWW irrigated soil as opposed to an even, onion-like wet profile, formed under fresh water (FW) irrigation. Following this observation in the field and after conducting preliminary tests in the laboratory, we hypothesized that TWW irrigation introduces water-repellent organic constituents into the soil. Tests characterizing the water distribution showed the diameter of the saturated area on the soil surface and its water content (at a depth of 0–10 cm) was smaller with TWW than with FW irrigation. The TWW accumulated on the soil surface in small lenses and then flowed rapidly into the ground. The repellency of soils irrigated with FW and TWW was measured with the water drop penetration time test. Soils irrigated with FW were hydrophilic, whereas those irrigated with TWW exhibited hydrophobicity. Fourier transform infra-red spectroscopy (FTIR) and ¹³C-NMR analyses of organic components extracted from the soils with organic solvents indicated differences in composition only at a depth of 0–2 cm. Extracting soils with a methanol + chloroform (1:1, by volume) mixture was found to be very effective in the removal and extraction of hydrophobic aliphatic components from soils irrigated with TWW.     

Physical Properties of Urban Soils in Rostov Agglomeration

Transformation of particle-size composition, structure, and density of soils upon urbopedogenesis is considered for Rostov agglomeration. Various soils are compared by horizons. It is found that the share of sand fractions increases in upper and middle horizons of migration–segregation chernozems (Calcic Chernozem (Hyperhumic, Loamic)), above all, at the expense of particles of 0.05—0.001 mm in size; with the coarse medium sand fraction 1–0.25 mm being diagnostic for urbopedogenesis. The reason is the introduction of sandy particles upon urban construction, arranging water conduits and other utility lines, as well as the use of icing-control sandy mixtures. The Dolgov-Bakhtin schedule appears to be the most appropriate for assessing the structure of urban soils. Dry sieving testified to the decreasing amount of agriculturally valuable aggregates in all compared pairs of horizons in the sequence of urban soils: under forest vegetation → under steppe vegetation → in the buried massif of urbosoils. The water stability of aggregates decreases in the sequence: soils under steppe vegetation → buried horizons of urbosoils → soils under forest vegetation. The following sequence of urbic horizons (UR and RAT) shows a decrease in the share of agriculturally valuable fractions and an increase in their water stability: heavy-textured UR → light-textured UR → RAT. The density of natural soils varies insignificantly within the city territory, with its urbostratified soils (Calcic Chernozem Novic (Technic Loamic) in residential areas often manifesting the maximal density.     

四种不同母质发育的红壤水分状况研究

在相同的地形和气候条件下,研究了我国东南部地区红砂岩、花岗岩、玄武岩和第四纪红粘土发育的4种典型红壤水分状况及其透水性能。结果表明,4种红壤的持水和透水性能存在不同程度差异,其原因是不同成土母质的土壤机械组成、土壤结构的变化造成的。除玄武岩和红砂岩发育红壤的某些层外,其他土壤各层的土壤渗漏量不随时间变化而变化。4种土壤含水量的年动态变化一般可划分为3个时期:土壤湿润期、土壤水分耗竭期和土壤水分恢复期,但不同年份的时间划分也不尽相同。     

Quantitative Mineralbestimmung in der Schlufffraktion von Böden auf der Grundlage der chemischen Analyse und unter Anwendung der Karl-Fischer-Titration. I. Verfahren

Quantitative estimation of the mineralogical composition of silt fractions of soils based on both, chemical analysis and application of Karl-Fischer-titration. I. Method This paper describes a method for calculating the mineralogical composition of the silt fractions of soils. The chemical analysis and the temperature dependence of water release are used for determining micas and feldspars, each in three components in a relatively short procedure. The release of water was measured by Karl-Fischer-titration at controlled temperatures. At temperatures above 550°C the water release of the particle size fractions correlates with their content of micas. The quantity of micas can be obtained from the amount of released water and the results of the chemical analysis. The influence of kaolinite, amphibole and the fluoride content on the calculation is described. By considering the potassium content of the mica fraction results of the chemical analysis are used to quantify feldspars.     

Transferability of continuous‐ and class‐pedotransfer functions to predict water retention properties of semiarid Syrian soils

Hydraulic properties of soils, particularly water retention, are key for appropriate management of semiarid soils. Very few pedotransfer functions (PTF s) have been developed to predict these properties for soils of Mediterranean regions, where data are particularly scarce. We investigated the transferability of PTF s to semiarid soils. The quality of the prediction was compared to that for soils originating from temperate regions for which most PTF s were developed. We used two soil data sets: one from the Paris basin (French data set, n  = 30) and a Syrian data set (n  = 30). Soil samples were collected in winter when the water content was near field capacity. Composition and water content of the samples were determined at seven water potentials. Continuous‐ and class‐PTF s developed using different predictors were tested using the two data sets and their performance compared to those developed using artificial neural networks (ANN ). The best performance and transferability of the PTF s for both data sets used soil water content at field capacity as predictor after stratification by texture. The quality of prediction was similar to that for ANN ‐PTF s. Continuous‐ and class‐PTF s may be transferable to other countries with performances that vary according to their ability to account for variation in soil composition and structure. Taking into account predictors of composition (particle size distribution, texture, organic carbon content) and structure (bulk density, porosity, field capacity) did not lead to a better performance or the best transferability potential.     

灌溉对哈萨克斯坦南部农业富镁土壤的影响

Irrational irrigation practices in the Arys Turkestan Canal command area in the southern part of Kazakhstan have led to the formation of soils with poor physical and chemical properties. To study whether irrigation and leaching practices and/or groundwater rise have contributed to the accumulation of Mg²⁺ on the cation exchange complex of these soils, historical changes in soil and groundwater quality were used as source data and the Visual MINTEQ model was applied to analyze the chemical composition of water and soils in the study area. The imposed irrigation regime and the leaching of light sierosem soils led to the dissolution and subsequent leaching of inherent gypsum and organic matter from the soil profile. Further, the domination of bicarbonate in the irrigation water promoted weathering of the carbonate minerals present as calcite. The higher concentrations of Mg²⁺ in comparison to Ca²⁺ in the irrigation water resulted in the replacement of Na⁺ by Mg²⁺ on the cation exchange complex. In the lower part of the command area, shallow groundwater has contributed to the accumulation of Na⁺ and to a large extent of Mg²⁺ on the cation exchange sites.     

Weathering patterns in representative soils of Guanxi Province, south-east China, as indicated by detailed clay mineralogy

The mineralogy of five soils situated on a south-west to north-east transect of Guanxi Province, south-east China was determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA) and chemical composition. One soil had formed on granite under tropical conditions, the others on sedimentary rocks under subtropical conditions. In all soils, kaolinite dominates the clay fractions, and is accompanied by vermiculite or chloritized vermiculite. In the saprolites of the granite-derived and sandstone-derived soils, the kaolinite has a morphology close to that of hydrated halloysite. The formamide and hydrazine/water tests suggested the presence of both poorly-crystalline (dehydrated halloysite) and well-ordered kaolinite. Gibbsite was identified in the saprolites of the granite-derived and sandstone-derived soils but not in the soils themselves. Gibbsite was also identified in the lowermost horizon of a soil derived from Pleistocene sediments. The upper horizon clay of a Rendzina soil formed on Permian limestone contains much more gibbsite and is much more weathered than the corresponding lower horizon clay. Only in the more humid, southernmost soil can the mineral composition be explained by present-day climatic conditions. In the soils from drier areas, the clay mineral composition reflects weathering that had taken place under moister, paleoclimatic conditions. Some of these paleoclimatic conditions had been conducive to lateritic weathering, as is indicated by the presence of goethite-containing pisolitic nodules in one of the soils and in its parent material. Two of the soils appear to be polymorphic, with one part of the soil having weathered more strongly than the other part.     

钙质结核放射性碳断代的研究

本文运用放射性碳方法对钙质结核进行了断代研究,阐明了钙质结核的化学组成及其与年龄的关系,进而对影响钙质结核形成的地下水、石灰岩碎屑物质和人为活动几个主要因子进行了探讨。     

Role of soil drying in nitrogen mineralization and microbial community function in semi-arid grasslands of north-west Australia

We examined effects of wetting and then progressive drying on nitrogen (N) mineralization rates and microbial community composition, biomass and activity of soils from spinifex (Triodia R. Br.) grasslands of the semi-arid Pilbara region of northern Australia. We compared soils under and between spinifex hummocks and also examined impacts of fire history on soils over a 28 d laboratory incubation. Soil water potentials were initially adjusted to −100 kPa and monitored as soils dried. We estimated N mineralization by measuring changes in amounts of nitrate (NO₃⁻-N) and ammonium (NH₄⁺-N) over time and with change in soil water potential. Microbial activity was assessed by amounts of CO₂ respired. Phospholipid fatty acid (PLFA) analyses were used to characterize shifts in microbial community composition during soil drying. Net N mineralized under hummocks was twice that of open spaces between hummocks and mineralization rates followed first-order kinetics. An initial N mineralization flush following re-wetting accounted for more than 90% of the total amount of N mineralized during the incubation. Initial microbial biomass under hummocks was twice that of open areas between hummocks, but after 28 d microbial biomass was<2 μ g⁻¹ ninhydrin N regardless of position. Respiration of CO₂ from soils under hummocks was more than double that of soils from between hummocks. N mineralization, microbial biomass and microbial activity were negligible once soils had dried to −1000 kPa. Microbial community composition was also significantly different between 0 and 28 d of the incubation but was not influenced by burning treatment or position. Regression analysis showed that soil water potential, microbial biomass N, NO₃⁻-N, % C and δ¹⁵N all explained significant proportions of the variance in microbial community composition when modelled individually. However, sequential multiple regression analysis determined only microbial biomass was significant in explaining variance of microbial community compositions. Nitrogen mineralization rates and microbial biomass did not differ between burned and unburned sites suggesting that any effects of fire are mostly short-lived. We conclude that the highly labile nature of much of soil organic N in these semi-arid grasslands provides a ready substrate for N mineralization. However, process rates are likely to be primarily limited by the amount of substrate available as well as water availability and less so by substrate quality or microbial community composition.