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More exact information on soil nutrient management is crucial due to environmental protection, nature conservation, decreasing sources for mining, general precaution, etc. Soil magnesium (Mg) analytical methods of potassium chloride (KCl), Mehlich 3 (M3), water (WA) and cobalt hexamine (CoHex) extractions are compared with an elemental analysis and X-ray fluorescence (XRF) analysis. The ratio of the available to the total Mg content was calculated and compared on the whole dataset. The results showed that the linear regressions between all the pairs of Mg content measurement methods were significant. The linear relationship between the KCl and CoHex methods has the highest determination coefficient (R2 = 0.96), followed by WA–M3 (R2 = 0.68), M3–CoHex (R2 = 0.66) and M3–KCl (R2 = 0.60). The M3 solution demonstrated a greater capacity for extracting Mg from the soil. The second part is the analysis of the influence of CaCO3, pH, soil texture and clay content on the measurable magnesium content of soils. It was established that the extraction methods, the soil and the classification method of the soil properties affect the evaluation. These results may help through the nutrient replenishment and the melioration of soils. These results can help the examination of mineral nutrients, especially the Mg uptake. [ABSTRACT FROM AUTHOR]

Water-level fluctuation (WLF) can destroy soil aggregates and induce soil organic carbon (SOC) loss, potentially triggering impacts on the concentration of atmospheric carbon dioxide. However, responses of soil aggregate content and aggregate-associated organic carbon to WLF have not been well studied, especially in the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR). Therefore, samples from different elevations (145 m, 155 m and 165 m) in the WLFZ of the TGR were collected for experiments. The wet sieving method was used to divide soil into silt and clay (<0.053 mm), micro-aggregate (0.053–0.25 mm) and macro-aggregate (>0.25 mm). The K2Cr2O7-H2SO4 oxidation method was used to measure total SOC content in different soil aggregates. A modified Walkley and Black method was used to measure labile carbon in different soil aggregates. Results showed that macro-aggregate content substantially decreased, while micro-aggregate content remained stable and silt and clay fraction accumulated with a decrease in water-level elevations. Moreover, total SOC content and labile carbon in macro-aggregate were obviously higher than those in the micro-aggregate and the silt and clay fraction. Macro-aggregate contributed the most to SOC sequestration, while micro-aggregate contributed the least, and the contribution of macro-aggregate increased with a decrease in water-level elevations. We concluded that the macro-aggregate was the most active participant in the SOC sequestration process, and preferentially increasing the macro-aggregate content of the lowest water-level elevation was conducive to an improvement in soil carbon sequestration potential and would mitigate climate change. [ABSTRACT FROM AUTHOR]

The availability of nitrogen in the soil is influenced by several factors associated with the forms and characteristics of organic nitrogen present in it, as well as by any property that impacts its microbiological and biochemical activity. The objective of the present work was to evaluate the combined effect of manure fertilization, soil type, and incubation time on soil N forms and availability. The experiment was conducted in a factorial scheme (2 soils × with (20 Mg ha−1) or without manure × 4 incubation times (15, 45, 90, and 180 days)). The levels of organic matter and fractions of organic N and mineral N were evaluated. Fertilization increased the organic matter and mineral N content in both soils, but the effect of fertilization on the organic N fractions was different depending on the type of soil. In the clayey soil, there was an accumulation of nitrogen in the unidentified hydrolysable fraction, whereas, in the sandy soil, the greatest increase occurred in the hydrolysable ammonium fraction. The application of manure generated different effects on the dynamics of N forms, depending on the type of soil. It is important to understand the impacts of different soil properties on the forms of nitrogen. [ABSTRACT FROM AUTHOR]

Steel storage tanks are widely used in different fields. Most of these tanks contain hazardous materials, which may lead to disasters and environmental damage for any design errors. There are many reasons which cause the failure of these tanks such as excessive base plate settlement, shear failure of soil, liquid sloshing, and buckling of the tank shell. In this study, five models of above-ground steel storage tanks resting over different types of clay soils (medium-stiff clay, stiff clay, and very stiff clay soils) are analyzed using the finite element program ADINA under the effect of static and dynamic loading. The soil underneath the tank is truly simulated using a 3D solid (porous media) element and the used material model is the Cam-clay soil model. The fluid in the tank is modeled depending on the Navier–Stokes fluid equation. Moreover, the earthquake record used in this analysis is the horizontal component of the Loma Prieta Earthquake. The analyzed tanks are circular steel tanks with the same height (10 m) and different diameters (ranging from 15 m to 40 m). The soil under the tanks has a noticeable effect on the dynamic behavior of the studied tanks. The tanks resting over the medium-stiff clay (the weakest soil) give a lower permanent settlement after the earthquake because of its low elastic modulus which leads to the absorption of the earthquake waves in comparison to the other types of soil. There are 29.6% and 35.6% increases in the peak dynamic stresses under the tanks in the cases of stiff clay and very stiff clay soils, respectively. The maximum values of the dynamic vertical stresses occur at a time around 13.02 s, which is close to the peak ground acceleration of the earthquake. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination in the soil potentially hampers microbial biomass and adversely affects their services such as decomposition and mineralization of organic matter. It can reduce nitrogen (N) metabolism and consequently affect plant growth and physiology. Further, Cd accumulation in plants can pose health risks through vegetable consumption. Here, we investigated consequences of Cd contamination on fertilizer value and associated health risks following the application of biogas residues (BGR) to various soil types. Our results indicate that the application of BGR to all soil types significantly increased dry matter (DM) yield and N uptake. However, the Cd contamination negatively affected DM yield and N recovery from BGR in a dose-dependent manner. Organic N mineralization from BGR also decreased in Cd-contaminated soils. The highest DM yield and N recovery were recorded in sandy soil, whereas the lowest values were observed in clay soil. Cadmium was accumulated in spinach, and health risk index (HRI) associated with its dietary intake revealed that consuming spinach grown in Cd-contaminated soil, with or without BGR, is unsafe. Among the soil types, values of daily intake of metals (DIM) and HRI were lowest in clay soil and highest in sandy soil. However, the application of BGR curtailed HRI across all soil types. Notably, the application of BGR alone resulted in HRI values < 1, which are under the safe limit. We conclude that soil contamination with Cd reduces fertilizer value and entails implications for human health. However, the application of BGR to the soil can decrease Cd effects. [ABSTRACT FROM AUTHOR]

The cementitious jet grout method (CJG) is one of the most preferred methods for the ground reinforcement of building foundations. As a result of the soil improvement made with the CJG, it was observed that there was a decrease in settlement, permeability, and liquefaction potential and an increase in the bearing capacity. In this study, columns with different grouting pressures (400, 450, and 500 bar) and water/cement ratios of 0.75, 1.00, and 1.25 were produced on several soil types (sand, clay, and alluvial soil) that have high liquefaction, settlement potential, and low bearing capacity. CJG columns were kept for 28 days after completion and then removed from the soil, and diameter measurements were made and significant differences were observed according to pressure and w/c ratios. Three samples were taken in CJG columns extracted from the ground. Laboratory tests were conducted to determine the physical (water absorption rate, density, and porosity) and mechanical (UCS and UPV) properties of CJG column samples. The highlighting of this paper is to build full-scale CJG columns in sandy soil, clay soil, and alluvial soil, increase the geotechnical engineering properties, and investigate the strength development, and diameter under different w/c ratios and different injection pressures. The strength of CJG columns in sandy soils was found between 36 and 15 MPa, in clay soils between 15 and 4 MPa and in alluvial soils between 32 and 15 MPa. Moreover, it was observed that there was a significant increase in the diameters with the increase in the injection pressure and a decrease in the compressive strengths. When the CJG column diameters were compared with constant injection pressure and increasing w/c ratios, the maximum increase was found to be 13% for sandy soils, 10% for clayey soils, and 14% for alluvial soils. The column diameters were 37% larger for sandy soils than clayey soils and 26% larger than alluvial soils at the same w/c ratio and constant injection pressure. In conclusion, since the results found in this study were made on a real scale in the field and for three different soil conditions, the results can be used directly in future engineering applications. [ABSTRACT FROM AUTHOR]

Featured Application: We found that in the areas with high seasonal rainfall, to stabilize clay soils, if the amount of Montmorillonite mineral is greater than a certain amount (for example, in this study, 45%), with any amount of chemical additives, they do not maintain their stability and collapse. Conversely, soils containing certain amounts of Illite and Kaolinite minerals with the smallest amount of chemical additives have the best performance. Although the interaction between clay minerals and lime is the most effective factor in lime stabilization techniques, it has not been deeply evaluated. This research study investigated the microstructural characteristics of lime-stabilized Bentonite and Kaolin soils using X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analyses. To consider the variation in clay mineralogy, these soils were mixed at varied ratios, stabilized, and then subjected to a durability process. The microstructural findings showed that the pozzolanic reactions with lime did not occur or occurred at a low level for Bentonite soil. However, they occurred at a very high level for Kaolin soil. The durability test confirmed the microstructural results and showed that the samples in which Bentonite soil had a share of 40 to 100% by dry weight of the soil did not last with any percent of lime. When the Kaolin soil content reached 100% by dry weight of the soil, the specimens lasted in the best possible way, even with 4% of the lime. This study concluded that the determination of optimum lime content based on the amounts and types of soil clay minerals is an important innovation for geotechnical projects and may be very cost-effective. [ABSTRACT FROM AUTHOR]

The best approach to avoid collisions between adjacent structures during earthquakes is to provide sufficient spacing between them. However, the existing formulas for calculating the optimum seismic gap preventing pounding were found to provide inaccurate results upon the consideration of different soil types. The aim of this paper is to propose new equations for the evaluation of the sufficient in-between separation gap for buildings founded on different soil conditions. The double-difference formula has been taken into account in this study. The seismic gap depends on the correlation factor and on the top displacements of adjacent buildings. The correlation factor depends on the ratio of the periods of adjacent buildings (smaller period to larger period). The modification of the correlation factor has been introduced for buildings founded on five different soil types. Five soil types were taken into account in this study, as defined in the ASCE 7-10 code, i.e., hard rock, rock, very dense soil and soft rock, stiff soil, and soft clay soil. The normalized root mean square errors have been calculated for the proposed equations. The results of the study indicate that the error ranges between 2% and 14%, confirming the accuracy of the approach. Therefore, the proposed equations can be effectively used for the determination of the optimum seismic gap preventing earthquake-induced pounding between buildings founded on different soil types. [ABSTRACT FROM AUTHOR]

Soil stabilization is a critical step in numerous engineering projects, preventing soil erosion, increasing soil strength, and reducing the risk of subsidence. Due to its inexpensive cost and potential environmental benefits, waste materials, such as waste marble powder (WMP), have been used as additives for soil stabilization in recent years. This study investigates waste marble powder's effects on unconfined compressive strength (UCS) and clayey soil's ultrasonic pulse velocity (UPV) at different water contents and curing times, and artificial neural networks (ANNs) are also used to predict the UCS and UPV values based on three input variables (percentage of waste marble dust, curing time, and moisture content). Geo-engineering experiments (Atterberg limits, compaction characteristics, specific gravity, UCS, and UPV) and analytical methods (ANNs) are used. The study results indicate that the soil is high-plasticity clay (CH) using the Unified Soil Classification System (USCS), and adding waste marble powder (WMP) can significantly improve the UCS and UPV of clay soils, especially at optimal water content, curing times of 28 days, and 60% WMP. It is found that the ANN models accurately predict the UCS and UPV values with high correlation coefficients approaching 1. In addition, this study shows that the optimum water content and curing time for stabilized clay soils depend on the grade and amount of waste marble powder utilized. Overall, the study demonstrates the potential of waste marble dust as a soil stabilization additive and the usefulness of ANNs in predicting UCS and UPV values. This study's results are relevant to engineers and researchers working on soil stabilization projects, such as foundations and backfills. They can contribute to the development of sustainable and cost-effective soil stabilization solutions. [ABSTRACT FROM AUTHOR]

In Cambodia, rice is predominantly produced in areas with rainfed lowland conditions where photoperiod-sensitive varieties are cultivated. A number of varieties have been released for rainfed lowland areas, and the rice grain yield has reportedly increased by approximately 12% over the past ten years. Moreover, great fluctuations in yield performance have been observed across different soil types of the rainfed ecosystems of Cambodia. Therefore, the present study aimed to analyze the grain yield and stability among ten popular varieties that were released for rainfed lowland ecosystems across the four different soil types in Cambodia in two years. The grain yield varied 566 g m−2 as the highest in clay soil and about 220 g m−2 as the lowest in sandy soil. A combined ANOVA revealed significant differences for the main effect of genotype, environment, and genotype-by-environment interaction (GEI) for all yield-related traits and grain yield per square meter. The principal component test results showed that the heterogeneity of grain yield was mainly attributable to the effect of environment, followed by the effect of genotype. In fertile conditions, a higher percentage of filled grains was supported by higher leaf N until the late stage with a wider flag leaf. In conditions of moderate fertility, larger numbers of panicles were supported by a higher percentage of productive culms with higher leaf N until the late stage. In conditions of poor fertility, a higher percentage of filled grains was supported by higher leaf N until the late stage, which is considered to be important for higher grain yield. The variety Phka Rumduol showed these preferable traits and produced higher yields in fertile to poor natural soil fertility conditions with moderate variation. This variety is considered to be more desirable and ideal due to its stability and higher grain yield. The other varieties, namely, Phka Mealdei, Phka Rumdeng, and CAR4, were identified as above-average yielders. Therefore, those varieties potentially may be recommended for cultivation in rainfed lowland rice ecosystems in Cambodia due to their high yields. CAR4 showed moderate variation at the same level as Phka Rumduol. From the point of stability, Phka Rumduol and CAR4 can be expected to excel. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the stabilization of different soil types using a hydraulic binder. A study was carried out on soils that can be classified into two groups: cohesive and non-cohesive soils. Clay soils of medium and low plasticity according to the USCS classification were used as cohesive materials, while the sandy material containing dust was considered as non-cohesive material. Samples were taken from fifteen locations in Vojvodina province, Serbia. A hydraulic binder was used as a binder based on cement and lime. The amounts of the binder were estimated at 3, 5, 7, and 9%. In order to determine the basic physical and mechanical characteristics of the specimens, the following tests were performed: unconfined compressive strength after 7 and 28 days, indirect tensile strength after 7 and 28 days, as well as the California Bearing Ratio. Based on the obtained results, it can be concluded that increasing the amount of binder results in an increase in the subgrade load-bearing capacity. However, it should be emphasized that the subgrade containing non-cohesive material had a lower growth in the load-bearing capacity than those with the cohesive material. [ABSTRACT FROM AUTHOR]

Featured Application: This model can be valuable in creating micro-zonation mapping for quick assessment of soil characterization, soil selection based on tender documents and liquefaction assessment of fine-grained soils. Soil plasticity characteristics are of great importance to practicing engineers and academics due to their wide range of applications mainly concerning settlement and soil strength assessment and volume change behavior. Therefore, assigning a plasticity value to soils under any discipline concerning soil engineering is critical. This is almost always carried out by determining plasticity index of soils in geotechnical engineering. However, overall plasticity characteristics of soils might not be reflected by using plasticity index alone. This research demonstrates the creation of a single model to define the plasticity potential of soils by using multivariate statistical techniques. Various soil properties including mineralogical features were integrated into the model. Some of these properties explained the soil plasticity positively and some of them negatively. The difference in plasticity characteristics of clayey soils were also identified. The model is created to be applied simply by using only two inputs for worldwide suitability. A single expression and two different scaled charts are proposed along with six ranges of plasticity potential for easy and broader application. This model proved that plasticity index alone needs refinement in practical applications. [ABSTRACT FROM AUTHOR]

The adoption of flowable mixtures of treated soils is suggested as a sustainable solution for repairing the damage caused by burrowing animals in the Po River embankments. Soil from damaged sites is proposed to be mixed with lime or cement, other additives, and water in order to obtain mixtures with an adequate compromise between viscosity—which is crucial for flowing the mixture into the hole with site machines—and shrinkage that might occur over time according to the hole boundary conditions. Injections of soil-treated mixtures must guarantee hydraulic and mechanical continuity with the existing embankment and reduce shrinkage phenomena that frequently occur with cement–bentonite grout, which is commonly used for this purpose. This study presents an interdisciplinary experimental programme in the search for the best formulation among several recipes of mixtures of soils, collected from four embankments of Po River or its tributaries and treated with lime or cement, different percentages of water, and other additives. The mixtures, after soil classification and viscosity determinations, were then used to create samples for which shrinkage and erosion susceptibility were estimated, respectively, through a non-standard volume measurement procedure and crumb tests. An abacus will be then proposed in order to give, as a first estimation, applicative indications on the best recipe among the investigated mixtures. [ABSTRACT FROM AUTHOR]

Although a number of studies have provided information on soil texture, soil classification, and depth to bedrock throughout China, few studies have combined this information, which is the basis for agricultural field management. A total of 81% of China's cultivated lands are distributed among the Middle–Lower Yangtze Plain (18.2%), arid and semiarid North China Plain (18.2%), Northeast Plain (17%), Huang-Huai-Hai Plain (16.1%), and Yunnan–Guizhou Plateau (11.6%). The Huang-Huai-Hai Plain has the highest density of agricultural land (58.5%) and the greatest depth to bedrock of cultivated land (243–402 m). The lowest cultivated depth to bedrock (4–84 m) is concentrated in the Sichuan Basin and its surrounding regions. The main cultivated soil types are Anthrosols, Fluvisols, Cambisols, Phaeozems, Luvisols, Kastanozems, Leptosols, and Acrisols, under the main topsoil texture classes of loam, clay loam, silty clay loam, silt loam, sandy loam, and clay. The Fluvisols had the largest depth to bedrock (156 m) on the Middle–Lower Yangtze Plain and Huang-Huai-Hai Plain, with the highest silt soil distributions but comparable lower sand contents. The Yunnan–Guizhou Plateau had the highest clay soil content. The cultivation under Kastanozems and Leptosols on the Qinghai–Tibet Plateau and in arid and semiarid North China and under Phaeozems on the Northeast Plain should be restricted and managed very cautiously facing erosion risk. The higher percentages of Anthrosols are on the Middle–Lower Yangtze Plain (37%), in Southern China (32%), and on the Yunnan–Guizhou Plateau (26%). The same cultivation aim (i.e., more crop 0production) has produced a similar range of properties over time among the soils developed on agricultural fields, which are classified as Anthrosols. However, various soil types can still be found in agroecosystems because of the variations in climate and topography. Our results highlight that the agriculture-based soil climate and topography shape the interaction of the soil development and not only the pedogenic history of the soil development under variations in the soil depth to bedrock but also the cultivation of distinct pedogenic features. This study provides cultivated soil information on the depth to bedrock, soil classification, and soil texture in China, as well as instructions for field strategies for sustainable agricultural development. [ABSTRACT FROM AUTHOR]

Soils from the superficial layers of the Guabirotuba formation (in Brazil) are problematic due to their expansive and low-bearing capacity. Stabilizing these soils with a calcium-based binder is a technique that must be explored. Therefore, this study aims to determine the mechanical behavior of stabilized sedimentary silts with cement and binder in various conditions. Four types of fine soils were used in deformed conditions. These soils were mixed with cement and compacted to measure their mechanical behavior. The specimens were tested in unconfined compressive and split tensile tests prepared with respect to several molding conditions: the moisture content, the curing period, durability cycles, the dry unit weight, the cement content, the cement type, and the soil type. This study was also carried out to develop a simplified approach to estimating the unconfined compressive strength (qu or UCS) and split tensile strength (qt or STS) of soil-cement or soil-cement–binder mixes. The results further demonstrate the influence of the porosity/volumetric cement index (η/Civ) on the qu- and qt-adjusted two new parameters—bo = 0.174 (dependent on cement) and k = 2.565 (dependent on the type of soil)—proposed herein for all mixtures studied. Using the proposed new parameters, a unique equation was developed to estimate the strength of the compacted blends as a function of the porosity and binder content, with an acceptance of 93% and an error close to 6%. [ABSTRACT FROM AUTHOR]

We explored the concentration patterns of the bioactive metabolite plumericin produced by Himatanthus tarapotensis (Apocynaceae) under different edaphic conditions and variations in rainfall intensity, as well as its potential role in the chemical defense against insect herbivores. Values of plumericin concentration from leaves were obtained by High-Performance Liquid Chromatography, and evaluated as a function of differences in soil types, variation of precipitation, and variation of the abundance of insect herbivores, using first a Repeated Measures Correlation (rmcorr) and then a Generalized Linear Mixed Model (GLMM) analysis. Plumericin concentration is highly variable among plants, but with a significantly higher concentration in plants growing on clay soil compared to that of the white-sand soil habitat (p < 0.001). Plumericin concentration is not affected by precipitation. The caterpillar of Isognathus leachii (Lepidoptera: Sphingidae) is the most conspicuous herbivore of H. tarapotensis, and its presence is continuous but not related to plumericin concentration, probably because of its capacity to elude the chemical defense of this plant. Nevertheless, our multivariate model revealed that plumericin concentration is related to the abundance of Hymenoptera (Formicidae), and this relationship is significantly influenced by the soil parameters of carbon percentage, clay percentage, and phosphorous percentage (p < 0.001). Plumericin is a mediating agent in the interaction between H. tarapotensis and its natural environment. Variation in plumericin concentration would be induced by the abundance of Hymenoptera (Formicidae), probably as a chemical response against these insects, and by differences in soil nutrient availability. [ABSTRACT FROM AUTHOR]

Subgrade conditions significantly affect functionality of the road pavement during its service life. Among the different stabilization techniques for upgrading poorly performing in-situ soil subgrades, an economically attractive example involves the use of waste materials, such as lignin. A deep bibliographic analysis of previous studies is carried out in the first section of this paper. The literature review suggests that use of lignin as a stabilizing agent of road subgrade soils is not completely consolidated. In addition, this study reports an investigation on the strength and performance characteristics of a lignin-treated clayey soil. Several experimental tests were carried out on both the untreated and lignin-treated soils in order to shed some light on different aspects with limited knowledge available, such as the behaviour of the stabilised soil in specific conditions (e.g., the presence of water). Finally, the test results are discussed and compared with those obtained when the same soil is treated with lime, which is more widely used. The most relevant finding is the poor ability of lignin to upgrade the bearing capacity of the soil in wet conditions compared to lime; on the contrary, the presence of lignin helped in controlling the swelling potential of this type of soil. [ABSTRACT FROM AUTHOR]

Soil dilatancy and partial drainage have great influence on the consolidation coefficient assessment of silty soils with clay content of less than 30% in the Yellow River Delta using the CPTu. This paper discussed the effect of soil dilatancy and partial drainage on the pore pressure response and dissipation of piezocone test in shallow silty soil of the Yellow River Delta through variable penetration rate tests in a pressure chamber and a series of supplementary soil element tests. The results show that the pore pressure dissipation curve is affected by soil type and degree of consolidation. The soil dilatancy is the key factor affecting consolidation coefficient inversion of shallow silt and silty clays. The initial pore pressure is negative and the pore pressure increases to umax first, but the umax value is very small in the Yellow River Delta silt. The inversion method used for shear contractile soil cannot be used to invert the mechanical properties of shallow silty soil directly, and a new consolidation curve normalization method is proposed. This paper provides a reference for the consolidation coefficient inversion of CPTu data in the Yellow River Delta area. [ABSTRACT FROM AUTHOR]

In recent years, ocean current turbines have proven to be a reliable device for renewable energy generation. A crucial element of these turbines are the foundations, since they limit the displacement of the turbine, which is key in achieving efficiency in energy conversion, and can account for up to 26% of the total cost of the project. Most design procedures for foundations focus on sandy and clayey soils, but rock soils often predominate in tropical locations where marine currents are suitable for the installation of this type of turbine. This paper presents a design procedure for steel pile anchors (PAs) and concrete dead weight anchors (DWAs) on weak rock soils, using the assumptions of current technical documents and design codes commonly used in the industry for marine structures. Using specific designs for PA and DWA anchors, the procedure was theoretically assessed for a site off Cozumel Island, Mexico. The results show that the dimensions needed for DWAs are substantially larger than those for PAs. Therefore, whenever drilling is economically and operatively possible, piles would be preferable for the foundations of current turbine systems. [ABSTRACT FROM AUTHOR]

Combining biochar with chemical fertilizers or compost not only improves the shortcomings of biochar's lack of fertility, but also extends the benefits of the compost. The application of biochar composite materials will be a future agricultural management strategy. In this study bagasse compost was mixed with wood biochar (w/w) at rates of 0% (B), 25% (BC), 50% (BC3), and 100% (no biochar, C) to produce four types of particle biochar compound materials (pBCM). These materials were applied to two types of soil (sandy soil and clayey soil) for a 180-day incubation to determine the decomposition rate and the nutrient release efficiency of the pBCMs. The results showed that C treatment had the highest decomposition rate in both types of soil. Overall, the materials decomposed faster in the sandy soil than in the clayey soil. Plants were grown over two 30-day crop periods. The plant yields of treatments C and BC3 were the highest in the first period and respectively decreased and increased in the second period. The experiment results revealed that in the biochar–compost compounds, compost increased the use efficiency of nitrogen and phosphorus in the soil, and biochar increased the nutrient use efficiency in the second period. These compound materials had greater capacity for long-term supply of nutrients in soil than did single-component ones. [ABSTRACT FROM AUTHOR]

This study explores whether Thermomagnesium (TM), a by-product of Ni ore mining, is an efficient fertilizer for maize. The effects of TM on soil pH, the supply of Si and Mg to the soil and plants, carbohydrate metabolism, grain filling, and yield were assessed in two simultaneous experiments performed in greenhouse conditions. Five TM doses were applied to two soil textures—clayey (0, 55, 273, 709, and 2018 mg kg−1) and sandy (0, 293, 410, 645, and 1260 mg kg−1). In general, the best results in soil and maize plants occurred at the highest TM dose for both soil textures (clayey 2018 mg kg−1 and sandy 1260 mg kg−1). The results demonstrated that in both soils, the concentrations of Mg and Si in the maize leaves increased with the dose of TM, similarly to that which occurred in the soil. Interestingly, in clayey soil, the soil pH increased linearly, whereas in sandy soil, the pH reached its maximum value between the two largest TM doses. The concentration of reducing sugars increased at the highest TM dose, whereas the concentrations of sucrose and starch decreased. The enhancement of carbohydrate partitioning led to higher maize growth, grain filling, and yield. Overall, the results clearly demonstrate that TM is a sustainable alternative fertilizer for maize and can be used for countless other crops and soil classifications, thus providing a suitable destination for this by-product of Ni ore mining. [ABSTRACT FROM AUTHOR]

Earthworm activity is a key factor in creating soil aggregates, but introduced organic matter and abiotic factors are also equally important. The purpose of this study was to investigate the stability of aggregates made by earthworms in soils with organic additives. Additionally, the two aggregate stability measurement methods were compared: (i) the wet-sieve method and (ii) the laser diffraction method. A six-month container experiment containing sixteen treatments and controls were made. Each treatment included one of four types of soil texture: sand, loam, silty loam and clay, and one of four additives: straw, peat, compost and compost with added microorganisms. To each treatment, six earthworms were added, two each of species commonly occurring in Polish soils: Dendrodrilus rubidus, Aporrectodea caliginosa and A. rosea. This study confirmed that earthworm activity was the factor favoring aggregate formation. In terms of the investigated organic additives, the efficiency of aggregate creation was as follows: compost with active bacteria, compost, peat and straw. Nevertheless, earthworms alone, without the addition of an organic additive, did not form permanent aggregates. The wet sieving and laser diffractometry methods of measuring aggregate stability were comparable for silty, clayey and loamy soils. [ABSTRACT FROM AUTHOR]

Soil moisture plays an important role in rice (Oryza sativa L.) root development and grain quality. However, little is known about the effects of soil type on rice root morphophysiological traits (RMTs) and grain quality under different irrigation modes. A soil-grown experiment was conducted during the 2016–2017 rice growing seasons in Yangzhou city with three soil types, namely, clay soil, loamy soil, and sandy soil, and three irrigation regimes, namely, conventional irrigation (CI, 0 kPa), alternate wetting and moderate drying (AWMD, −15 kPa), and alternate wetting and severe drying (AWSD, −25 kPa). The AWMD regime improved the RMT by 3.05–48.95% when compared with the CI and AWSD regimes, and the RMTs in loamy were 7.38–93.67% higher than those in clay and sandy soil under AWMD across 2016 and 2017. The AWMD regime improved the rice milling quality and appearance quality both in clay and loamy soil by 2.88–10.08% and 15.43–45.77%, respectively. The CI regime improved the processing quality and nutritional quality of rice in sandy soil. Both loamy and clay soils improved the rice RMTs and grain quality under an AWMD regime. The RMTs were very significantly correlated with water use efficiency, rice milling, and cooking quality and were negatively correlated with rice appearance quality. The AWMD regime can affect the rice RMT and can improve the rice grain quality in loamy soil. Our results provide a theoretical basis for the design of water-saving rice irrigation regimes and for an improvement in rice grain quality in the process of rice cultivation. [ABSTRACT FROM AUTHOR]

Crop management and soil properties affect greenhouse gas (GHG) emissions from cropping systems. Irrigation is one of the agronomical management practices that deeply affects soil nitrous oxide (N2O) emissions. Careful management of irrigation, also concerning to soil type, might mitigate the emissions of this powerful GHG from agricultural soils. In the Mediterranean area, despite the relevance of the agricultural sector to the overall economy and sustainable development, the topic of N2O emissions does not have the same importance as N2O fluxes in temperate agricultural areas. Only some research has discussed N2O emissions from Mediterranean cropping systems. Therefore, in this study, N2O emissions from different soil types (sandy-loam and clay soils) were analyzed in relation to the irrigation of a maize crop grown in two contrasting seasons (2009–2010). The irrigation was done using a center pivot irrigation system about twice a week. The N2O emissions were monitored throughout the two-years of maize crop growth. The emissions were measured with the accumulation technique using eight static chambers (four chambers per site). Nitrogen fertilizer was applied in the form of ammonium sulphate and urea with 3,4 dimethylpyrazole phosphate (DMPP) nitrification inhibitors. In 2009, the N2O emissions and crop biomass measured in both soil types were lower than those measured in 2010. This situation was a lower amount of water and nitrogen (N) available to the crop. In 2010, the N2O fluxes were higher in the clay site than those in the sandy-loam site after the first fertilization, whereas an opposite trend was found after the second fertilization. The soil temperature, N content, and soil humidity were the main drivers for N2O emission during 2009, whereas during 2010, only the N content and soil humidity affected the nitrous oxide emissions. The research has demonstrated that crop water management deeply affects soil N2O emissions, acting differently for denitrification and nitrification. The soil properties affect N2O emission by influencing the microclimate conditions in the root zone, conditioning the N2O production. [ABSTRACT FROM AUTHOR]

A liquid culture enrichment-polymerase chain reaction (E-PCR) assay was investigated as a potential tool to overcome inhibition by chemical component, debris, and background biological impurities in soil that were affecting detection assay performance for soil samples containing Bacillus atrophaeus subsp. globigii (a surrogate for B. anthracis). To evaluate this assay, 9 g of matched sets of three different soil types (loamy sand [sand], sandy loam [loam] and clay) was spiked with 0, ~4.5, 45, 225, 675 and 1350 endospores. One matched set was evaluated using a previously published endospore concentration and colony-forming unit spreadplate (CFU-S) assay and the other matched set was evaluated using an E-PCR assay to investigate differences in limits of detection between the two assays. Data illustrated that detection using the CFU-S assay at the 45-endospore spike level started to become sporadic whereas the E-PCR assay produced repeatable detection at the ~4.5-endospore spike concentration. The E-PCR produced an ~2-log increase in sensitivity and required slightly less time to complete than the CFU-S assay. This study also investigated differences in recovery among pure and blended sand and clay soils and found potential activation of B. anthracis in predominately clay-based soils. [ABSTRACT FROM AUTHOR]

A two-year study was conducted to determine how soil texture affects calcium (Ca) absorption and partitioning in potted 'Hass' avocado trees. Trees were planted in 200 L pots in one of four soil types: clay (C), clay loam (CL), sandy loam (SL) or sand (S). Prior to planting, Ca content in each soil was in the normal range of availability, although the Ca concentration was highest in C soil. After two years of tree development, dry weights of shoots and roots were significantly higher in the SL and S soils than in C soil. Trees in the C soil had higher wood dry weight than trees in SL or S soils. The Ca contents (absolute quantities, not concentrations) in the roots, shoots and whole tree were significantly lower in the C soil than in the SL or S soils. The K/Ca ratio of trees in the C soil (K/Ca = 1.5) was significantly higher than that in the other soil types. Stem water potential was significantly lower for trees in the C soil compared to the other soils. These results indicate that Ca absorption and partitioning in young avocado trees varies with soil texture, probably associated with soil effects on root growth and/or plant water status. [ABSTRACT FROM AUTHOR]

The effects of soil and topography on the responses of soil respiration (Rs) to climatic variables must be investigated in the southeastern mountainous areas of China due to the rapid land-use change from forest to agriculture. In this study, we investigated the response of Rs to soil temperature (ST), precipitation over the previous seven days (AP7), and soil water content (SWC) across two hillslopes that had different land uses: a tea garden (TG) and a bamboo forest (BF). Meanwhile, the roles of soil properties including soil clay content and total nitrogen (TN), and topography including elevation, profile curvature (PRC), and slope on the different responses of Rs to these climatic variables were investigated. Results showed that mean Rs on the BF hillslope (2.21 umol C m−2 s−1) was 1.71 times of that on the TG hillslope (1.29 umol C m−2 s−1). Soil clay content, elevation, and PRC had negative correlations (p < 0.05) with spatial variation of Rs, and ST was positively correlated (p < 0.01) with temporal variation of Rs on both hillslopes. Across both hillslopes ST explained 33%–73% and AP7 explained 24%–38% of the temporal variations in Rs. The mean temperature sensitivities (Q10s) of Rs were 2.02 and 3.22, respectively, on the TG and BF hillslopes. The Q10 was positively correlated (p < 0.05) with the temporal mean of SWC and TN, and negatively correlated (p < 0.05) with clay and slope. The mean AP7 sensitivities (a concept similar to Q10) were greatly affected by clay and PRC. When Rs was normalized to that at 10 °C, power or quadratic relationships between Rs and SWC were observed in different sites, and the SWC explained 12%–32% of the temporal variation in Rs. When ST and SWC were integrated and considered, improved explanations (45%–81%) were achieved for the Rs temporal variation. In addition, clay and elevation had vital influences on the responses of Rs to SWC. These results highlight the influences of soil, topographic features, and land use on the spatial variations of the Rs, as well as on the responses of Rs to different climatic variables, which will supplement the understanding of controlling mechanisms of Rs on tea and bamboo land-use types in Southeastern China. [ABSTRACT FROM AUTHOR]