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Isotopic exchange of 43K, 24Na, 86Rb, and 45Ca was used to measure the equilibria between some arable soils and mixed chloride solutions of the ion pairs, K–Ca, K–Rb, and K–Na; the results were interpreted by a thermodynamic treatment of the exchange isotherm (Gaines and Thomas, 1953). The cation exchange capacities of the soils were not constant for the three ion pairs and decreased appreciably with K-saturation in the K–Ca systems because Ca ions were trapped inside the interlayer spaces. That soils preferred K to Na in the K–Na systems and Rb to K in the K–Rb systems, was explained in terms of the standard free-energy changes of the exchange reactions. The activity coefficients of the adsorbed ions, f, changed with K-saturation differently for the three ion pairs: fNa and fCa decreased continuously with increasing K-saturation whereas fRb remained almost constant. However, with increasing K-saturation, fK increased in the K–Na systems, remained unchanged in the K–Rb systems, and first increased and then decreased in the K–Ca systems. These changes are interpreted in terms of the effect of the various ions on the interlayer space of 2 : 1 type clay minerals and the possible distribution of adsorbed ions between the Gouy and Stern layers. 相似文献
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Gustavo Pereira Valani Aline Fachin Martíni Laura Fernanda Simes da Silva Renata Cristina Bovi Miguel Cooper 《Soil Use and Management》2021,37(1):22-36
Integrated crop–livestock–forest is a promising strategy to improve soil quality. It comprises four different integrated farming systems: crop–livestock, crop–forest, forest–livestock and crop–livestock–forest. This work systematically reviewed studies about integrated crop–livestock–forest systems and soil quality. A total of 92 papers were retrieved from the Web of Science—Clarivate Analytics platform, and the following information was analysed: publication year, institution, region of the studied site, type of integrated system, soil type, tillage system, maximum soil depth and the soil quality indicators assessed. Most studies were published in the second half of the 2010s. Brazil is a prominent focus of research about soil quality and integrated crop–livestock–forest systems, with significant contribution from its central and southern regions. The Embrapa was the main publishing institution, present in over one‐third of the studies. Crop–livestock was the most common integrated system, Ferralsols was the most common soil group, and most of the studied soils were clayey. No tillage was the main tillage system. Most studies focused on the topsoil, assessing physical and/or chemical soil quality indicators. More emphasis on biological indicators of soil quality is required, as well as assessments integrating biological, physical and chemical indicators of soil quality. Future works should compare different integrated systems, including assessments deeper in the soil profile, especially in systems with the forest component, and also in sandy and silty soils. Soil quality indicators that have been rarely used should be further tested. Novel indicators should be added to better understand the promotion of soil quality by integrated crop–livestock–forest systems. 相似文献
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《Land Degradation \u0026amp; Development》2017,28(5):1528-1537
An attempt was made to employ the reliability (Rel)–resilience (Res)–vulnerability (Vul) conceptual framework to develop a typical indicator system for quantitative assessment of watershed health. The study aimed to conceptualize and customize the RelResVul framework to watershed health assessment for the Shazand Watershed in Markazi Province, Iran, for the period of 1977–2014. To this end, four easily, reliable, available and accessible criteria viz. standardized precipitation index (SPI), low and high flow discharges (LFD and HFD), and suspended sediment concentration (SSC) were selected, and corresponding indices for reliability–resilience–vulnerability (RelResVul) framework were accordingly conceptualized and calculated. The thresholds of 0.1, 0.16 m3 s−1, 12.63 m3 s−1 and 25 mg l−1 day−1 were thus selected for SPI, LFD, HFD and SSC, respectively. The results showed a decreasing trend in Rel and Res, and an increasing trend in Vul for SPI and LFD in the Shazand Watershed. The results further showed an increasing trend in Rel, and a decreasing trend in Vul for HFD and SSC. A decreasing trend was ultimately recognized in watershed health index for all criteria except SSC. Additionally, the integrated hydrological watershed health index of 0.16 ± 0.11 obtained from the geometric mean of the RelResVul framework indices also showed a decreasing trend for the Shazand Watershed health during the study period. The results of the present initiative study can be considered as a baseline by decision makers and managers to effectively adjust watershed management strategies to handle land degradation issues in the area. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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《植物养料与土壤学杂志》2017,180(2):231-240
Selenium (Se) is an essential micronutrient for humans, animals, and certain lower plants, but at higher concentrations Se becomes toxic to organisms. The boundary between the Se beneficial effect and its toxicity is narrow and depends on its chemical form, applied concentration, and other environmentally regulating factors. Due to the potential risk of toxicity in higher concentration, the aim of this study was to estimate the impact of increased concentrations of different forms of Se on the response of the wheat–soil–earthworm system. Soil, earthworms, and wheat grains were exposed to the Se in form of selenite and selenate in concentrations of 0.01, 0.1, and 1 mg kg−1. As an indicator of oxidative stress in wheat, lipid peroxidation levels (LPO) and total H2O2 content were determined, while antioxidative response was determined by catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) activities. The biomarker responses in earthworms were determined by acetylcholinesterase (AChE), carboxylesterase (CES), and antioxidative enzymes (CAT and glutathione S‐transferase) activities. Selenite and selenate increased Se content in the wheat and earthworms, while selenate application was more efficient, indicating higher bioaccumulation of this Se form. Both Se forms did not cause significant changes in the LPO level and H2O2 content, while GPX activities were elevated in all treatments, suggesting that oxidative stress was not induced in wheat. In earthworms, Se significantly reduced activities of AChE and CAT at some concentrations, while CES activity was increased at all concentrations applied. This study showed significant impact of Se on measured biochemical responses in wheat and earthworms, indicating the disruption of homeostasis. Obtained results can serve as basis for further studies on Se effects and will help in including different aspects necessary for understanding of Se impact on different components of soil ecosystems. 相似文献
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R. P. C. Morgan 《CATENA》2001,44(4)
A revised version of the Morgan–Morgan–Finney model for prediction of annual soil loss by water is presented. Changes have been made to the way soil particle detachment by raindrop impact is simulated, which now takes account of plant canopy height and leaf drainage, and a component has been added for soil particle detachment by flow. When tested against the same data set used to validate the original version at the erosion plot scale, predictions made with the revised model gave slopes of a reduced major-axis regression line closer to 1.0 when compared with measured values. The coefficient of efficiency, for sites with measured runoff and soil loss, increased from 0.54 to 0.65. When applied to a new data set for erosion plots in Denmark, Spain, Greece and Nepal, very high coefficients of efficiency of 0.94 for runoff and 0.84 for soil loss were obtained. The revised version was applied to two small catchments by dividing them into land elements and routing annual runoff and sediment production over the land surface from one element to another. The results indicate that, when used in this way, the model provides useful information on the source areas of sediment, sediment delivery to streams and annual sediment yield. 相似文献
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Variables needed to characterize solute transport in soils are soil water pressure (SWP) and solute concentration, which are typically obtained from tensiometers and suction solution samplers, respectively. In this paper we describe a combined tension–solution sampling probe that measures SWP, and allows extraction of soil solution during or between SWP measurements. A separate porous ceramic cup and ring to be used for the tensiometer and suction solution sampler were built into a single unit. Laboratory soil column experiments were carried out to evaluate the performance of the combined tension–solution probe, and the data obtained were compared with those from using separate tensiometer and suction solution samplers. Differences in tensiometric measurements were attributed to differences in size between the tensiometers. An apparent increase in pore water solution concentration as soil water potential is decreased could be explained by anion exclusion. 相似文献
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T. Mimmo D. Del Buono R. Terzano N. Tomasi G. Vigani C. Crecchio R. Pinton G. Zocchi S. Cesco 《European Journal of Soil Science》2014,65(5):629-642
Poor iron (Fe) availability in soil represents one of the most important limiting factors of agricultural production and is closely linked to physical, chemical and biological processes within the rhizosphere as a result of soil–microorganism–plant interactions. Iron shortage induces several mechanisms in soil organisms, resulting in an enhanced release of inorganic (such as protons) and organic (organic acids, carbohydrates, amino acids, phytosiderophores, siderophores, phenolics and enzymes) compounds to increase the solubility of poorly available Fe pools. However, rhizospheric organic compounds (ROCs) have short half‐lives because of the large microbial activity at the soil–root interface, which might limit their effects on Fe mobility and acquisition. In addition, ROCs also have a selective effect on the microbial community present in the rhizosphere. This review aims therefore to unravel these complex dynamics with the objective of providing an overview of the rhizosphere processes involved in Fe acquisition by soil organisms (plants and microorganisms). In particular, the review provides information on (i) Fe availability in soils, including mineral weathering and Fe mobilization from soil minerals, ligand and element competition and plant‐microbe competition; (ii) microbe–plant interactions, focusing on beneficial microbial communities and their association with plants, which in turn influences plant mineral nutrition; (iii) plant–soil interactions involving the metabolic changes triggered by Fe deficiency and the processes involved in exudate release from roots; and (iv) the influence of agrochemicals commonly used in agricultural production systems on rhizosphere processes related to Fe availability and acquisition by crops. 相似文献
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Soils are the central organizer of the terrestrial ecosystem. Their colloidal and particulate constituents, be they minerals, organic matter, and microorganisms, are not separate entities; rather, they are constantly interacting with each other. Interactions of these components control biogeochemical reactions, namely, the formation of short-range-ordered metal oxides, catalysis of humic substance formation, enzymatic stability and activity, mineral transformation, aggregate turnover, biogeochemical cycling of C, N, P, and S, and the fate and transformation of organic and inorganic pollutants. Furthermore, the impacts of mineral–organic matter–microorganism interactions and associated biogeochemical reactions and processes on biodiversity, species composition, and sustainability of the terrestrial ecosystem deserve close attention for years to come. This paper integrates the frontiers of knowledge on this subject matter, which is essential to uncovering the dynamics and mechanisms of terrestrial ecosystem processes and to developing innovative management strategies to sustain ecosystem health on the global scale. 相似文献
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Sampling seepage water with suction cups – a literature study The article presents a literature study concerning the sampling of seepage water with suction cups. It gives a general view about construction and materials of different types of suction cups as well as proposals for the installation and arrangement of sampling equipments. Furthermore the article deals with questions related to the release or the sorption of substances by the cup material. Other problems like the influence of the applied suction on the concentration of the solutants in the seepage water sample and the potential field around the suction cup are discussed. 相似文献
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Elizabeth H. Denis Peter D. Ilhardt Abigail E. Tucker Nicholas L. Huggett Joshua J. Rosnow James J. Moran 《植物养料与土壤学杂志》2019,182(3):401-410
The intimate relationships between plant roots, rhizosphere, and soil are fostered by the release of organic compounds from the plant into soil through various forms of rhizodeposition and the simultaneous harvesting of nutrients from the soil to the plant. Here we present a method to spatially track and map the migration of plant‐derived carbon (C) through roots into the rhizosphere and surrounding soil using laser ablation‐isotope ratio mass spectrometry (LA‐IRMS). We used switchgrass microcosms containing soil from field plots at the Kellogg Biological Station (Hickory Corners, Michigan, USA) which have been cropped with switchgrass since 2008. We used a 13CO2 tracer to isotopically label switchgrass plants for two diel cycles and tracked subsequent movement of labeled C using the spatially specific (< 100 µm resolution) δ13C analysis enabled by LA‐IRMS. This approach permitted assessment of variable C flow through different roots and enabled mapping of spatial variability of C allocation to the rhizosphere. Highly 13C‐enriched C (consistent with production during the 13CO2 application period) extended ≈ 0.5–1 mm from the root into the soil, suggesting that the majority of recent plant‐derived C was within this distance of the root after 48 h. Tracking the physical extent of root exudation into the rhizosphere can help evaluate the localization of plant‐microbe interactions in highly variable subsurface environments, and the use of the isotopic label can differentiate freshly fixed C (presumably from root exudates) from other types of subsurface C (e.g., plant necromass and microbial turnover). The LA‐IRMS technique may also serve as a valuable screening technique to identify areas of high activity for additional microbial or geochemical assays. 相似文献
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Trace elements in pedosequences II. Two Pararendzina-Pseudogley-sequences on loess Total amounts and fractions of Cu, Zn, Pb, Cd, Co and Ni extractable in boiling oxalate (replacing dithionite for analytical reasons), oxalate at room temperature and EDTA were determined in two hydro-pedosequences on loess ranging between Pararendzina-Braunerde-Parabraunerde-Pseudogley. The pedogenic influence on the depth functions of these trace elements was much weaker in the loess soils than in those on slates of part I of this study. With a few exceptions external additions seem to be masked by soil cultivation. Clay movement (Alfisols) produced maxima of Fe and Cu in the Bt horizon. Carbonates of the parent loess contain trace elements which are released into the soil during solum formation. As long as they exist in carbonates they are hardly extractable with oxalate but with EDTA. In contrast, after pedogenic decomposition of the carbonates in the B horizon their trace elements are now oxalate but no longer EDTA extractable. In the A horizon, where organic matter is involved the trace elements are again EDTA extractable. As in the soils from slate (part I) Cd behaves more similarly to Pb than to Zn. The total element balance indicates a slight gain of Pb and loss of Zn whereas the total amount of the other elements was essentially unchanged. Generally, the more mobile fractions increased during soil formation. 相似文献