Retention Capacity Of Soils Research Articles

Experimental Investigation of the Soil-Water Characteristic Curves (SWCC) of Expansive Soil: Effects of Sand Content, Initial Saturation, and Initial Dry Unit Weight

Soil-water characteristic curve (SWCC) is an essential parameter in unsaturated soil mechanics, and it plays a significant role in geotechnical engineering to enhance theoretical analysis and numerical calculations. This study investigated the effects of key factors, such as the percentage of sand, initial degree of saturation, and initial dry unit weight, on the SWCC of expansive soil by measuring the matric suction using a pressure apparatus method. The empirical equation of SWCC was obtained using the Van Genuchten and Fredlung Xing models, and the processing of experimental data checks the fitting of the two empirical models. The findings revealed that the Fredlung Xing model fit the relationship between matric suction and volumetric water content of expansive soil better than the Van Genuchten model, indicating that the pressure apparatus approach’s experimental data are correct and acceptable. The study also found that the matric suction increased with decreasing percentage of added sand at the same volumetric moisture content, and the increase in initial dry unit weight increased the matric suction, with the water retention capacity decreasing significantly after adding 20% sand. Moreover, as the initial degree of saturation increased, the volumetric water content decreased, and the characteristic curves became identical when the initial saturation degree reached 90%. Finally, to minimize the water retention capacity of expansive soils, the study recommended adding a percentage of sand not less than 30% to the expansive clay sample.

Use of solid mining waste to improve water retention capacity of loamy soils

Purpose. The research explores the possibility of increasing the fertile properties of agricultural soils of loamy type by adding burnt-out dump mass from coal enterprises. Methods. Laboratory research on parameters of penetration and retention capacity of sorbed and meniscal water for diffe-rent burnt-out rock fractions. The burnt-out rock was sampled from the mine No. 5/6 waste rock dump in the city of Myrnohrad, Donetsk Oblast, and divided into four fractions from 0.63 to 10 mm. The water penetration coefficient of the soil with the added dump mass is measured by the velocity of water seepage into the test samples. The ability of rock additives to retain film-sorbed and capillary water is assessed by comparing the weight of dry and moistened samples of crushed dump mass. Findings. The velocity parameters of water penetration into samples of loamy mixtures with burnt-out dump mass with fractions ranging from 10 to 0.63 mm in size have been determined. It has been found that an increase in the percentage of burnt-out rock in the mixture leads to an increase in the water penetration velocity from 1.2 ml/cm2·min with a rock content of 30% to 30.66 ml/cm2·min with a rock content of 70%. The highest penetration coefficients are achieved when adding rock with a small fractional composition of 0.63-3 mm, since an increase in grain size leads to a reduction in the coefficient by se-veral times. It has been determined that with an increase in the size of the rock fractions in a loamy mixture, the retention capacity of sorbed and pore water suitable for plant nutrition decreases by approximately 40%. Originality. For the first time, the parameters of penetration coefficients, as well as the accumulation of sorbed and meniscal water for mine waste in the Selidovo-Pokrovskyi district of Donbas, have been determined. Practical implications. The results obtained can be used to improve the physical properties of agricultural soils of loamy type by increasing their water retention capacity.

An experimental study of stress-dependent water retention behaviour of two lateritic clays with different minerals

Lateritic soils are associated with a high content of sesquioxides, which enhance the aggregation of fine particles. The formation of aggregates can induce significant changes in the pore size distribution (PSD) and consequently affect the hydro-mechanical behaviour of lateritic soils. The influence of mineral types on the extent of aggregation and the stress-dependent water retention behaviour of lateritic clays is not well understood. In this study, the stress-dependent water retention curves (SDSWRCs) of a compacted lateritic sandy fat clay with halloysite (i.e., GLH) obtained from Ghana were measured at different net vertical stresses using an improved stress-controlled pressure plate apparatus. The results were then compared with those of another lateritic sandy lean clay with goethite (NLG) obtained from Nigeria. Additionally, scanning electron microscopy (SEM) was employed to examine the microstructure associated with these soils. The experimental results show that GLH has a higher ability to retain water than NLG at any given suction, even though the former has a higher void ratio than the latter prior to the drying-wetting cycle. This is because of the presence of relatively small aggregates and small-size macropores in GLH, as revealed by SEM images. On the other hand, the water retention capacity of both soils reduces with elevated stress levels, except at net vertical stress of 120 kPa for GLH, with a corresponding decrease in the rate of desorption. Furthermore, the overall increase in the total degree of hysteresis measured is almost 2 times higher for NLG (i.e., 116%) than GLH (i.e., 72%) in the stress and suction range considered, contrary to the decreasing trends commonly reported in the literature. It was found that the sizes of aggregates in GLH reduced (‘finer soil’) as stress level increased and caused more water to be retained. Conversely to GLH, the aggregate size remained unchanged for NLG, as revealed by aggregate size analysis. This is mainly because of the differences in the strengths provided by the unique minerals in the two soils (i.e., halloysite for GLH and goethite for NLG) to the aggregates, due to the different parent rocks from which the soils were formed.

Effect of Different Cellulose Fillers on the Properties of Xanthan-Based Composites for Soil Conditioning Applications

The aim of this study was to investigate the effect of different types of natural cellulose-based fillers on the properties of Xanthan gum (XG) in order to develop novel bio-based soil conditioners (SCs) that could be used in forestry and agricultural applications. Rheological measurements highlighted that SCs with cellulose fillers characterized by a high aspect ratio and low oxide ash content exhibited an average increase of 21% in yield stress compared to neat Xanthan gum. The presence of cellulose fillers in the composites resulted in a slower water release than that of neat XG, limiting the volumetric shrinkage during the drying process. Furthermore, an analysis of the water absorption and water retention capacity of soils treated with the different SCs was carried out, demonstrating that the addition of 1.8 wt.% of SC with optimized composition to the soil led to an increase in water absorption capacity from 34% up to 69%. From the soil water retention curves, it was observed that the addition of SCs significantly increased the amount of water effectively available for plants in the area between field capacity and permanent wilting point (100–1000 kPa). From practical experiments on grass growth, it was observed that these SCs improved the water regulation of the soil, thus increasing the probability of plant survival under drought conditions.

Particle arrangement and internal porosity of coarse fragments affect water retention in stony soils

AbstractInformation about water retention in stony soils lags behind due to methodological difficulties. We applied a new strategy to measure the water retention in soils with coarse fragments (CFs) and to get insights into the effect of CFs porosity on water retention. Water retention at zero, 10, and 150 m suction, bulk density, and the mass fraction of six particle size classes were measured in undisturbed blocks from soils with variable CFs contents, originating from three parent materials. The results showed that some soils contain porous CFs (2–250 mm) with a water holding capacity as high as the fine fraction (<2 mm). The water held in the suction range of 1–150 m in a soil with porous CFs was twice as high as in soils with non‐porous CFs. Multilinear regressions revealed that both the water retention capacity at 1 m suction and in the range 1–150 m were more dependent on bulk density than on the fraction of CFs and fine particles. In the soil with porous CFs, there was no correlation between their fraction and soil water retention. These results show that the bulk water retention capacity of soils with CFs is underestimated when not considering the internal porosity of the CFs. A better understanding of the effect of the porosity of CFs on bulk soil porosity and water retention is important to propose suitable pedotransfer functions and refine physically‐based hydraulic functions for stony soils.

Sawdust Amendment in Agricultural and Pasture Soils Can Reduce Iodine Losses

Iodine loss is common in the soil of hilly regions due to higher precipitation rates and steeper slopes. Iodine deficiency in soil reduces iodine’s bioavailability to fruits and vegetables and consequently may contribute to health complications. However, the iodine retention of soils after the addition of selected organic and inorganic amendments has not been studied. Therefore, a study was carried out to investigate iodine loss during surface runoff. For this purpose, a soil amendment (namely, sawdust, charcoal, wood ash, lime or gypsum) was applied separately to pasture and agricultural soils under natural rainfall conditions. The soil was fertigated with iodine in the form of potassium iodide (KI) at the rate of 200 ppm. Surface runoff was related to soil properties. Results showed that iodine content in surface runoff was linearly related with soil pH (R2 = 0.89, p < 0.05) and inversely related with soil organic carbon (R2 = −0.76, p < 0.05). Soils amended with sawdust had significantly reduced iodine content in runoff. A higher amount of iodine was lost via surface runoff from soil after inorganic amendment. Soil amendments were varied for iodine retention in soil in the order of sawdust > charcoal > wood ash > lime > gypsum. The study results indicated that organic amendments, especially sawdust, improved soil properties and increased the iodine retention capacity of soils.

National-scale spatial variations of soil phosphorus retention capacity in Brazil

Phosphorus (P) retention capacity of soils directly affects the management of phosphate fertilization, and has economic and environmental importance. Brazil has expressive agricultural production and high edaphoclimatic variability; still, the detailed spatial distribution of P retention capacity is not known. Thus, machine learning models were created to estimate the P retention capacity of soils at superficial horizons using the variables: clay content, sand content, soil organic matter, pH, base saturation. The four best models were combined to create an ensemble (a combination of models), which was applied in a dataset (5524 samples) that comprises a sample data from the entire Brazilian territory. The ensemble was used to build a map of P retention capacity. Most of the country presented soils with medium P retention (40–60%), and large areas with very high retention capacity were found in the south of Brazil, a subtropical region mostly associated with clayey soils. High P retention was observed for Histosols, probably related to humic-Al(Fe) complexes. Nitisol, Ferralsol, Gleysol and Cambisol classes presented high P retention, especially for clayey soils with qualifiers related to bases/weathering (Dystric) and organic matter (Umbric and Humic). The correlation between Fe oxide minerals and P retention varied with soil color and drainage conditions mainly associated to redoximorphic reactions; the same was not observed for Al oxide minerals. This pioneer study revealed the distribution of P retention capacity across different soil classes in Brazil, which can help to define land use suitability and soil P management strategies that ensure profitable agricultural exploration.

Combined Effect of Biochar and Fertilizers on Andean Highland Soils before and after Cropping

Although a number of works present biochar as a promising material for improving the quality of degraded soils, only a few show the effect of this material in soils from the Andean highlands. The objective of this work was twofold: (a) to study the effect of two types of biochars on two agricultural soils commonly found in the Andean highlands (Andisol and Inceptisol) and the corresponding soil–biochar–fertilizer interactions, and, (b) to assess the response to biochar of two vegetable crops (lettuce and radish) grown in succession in a simulated double-cropping system. Biochar was produced at 400 °C and 500 °C, for 1 h (B400 and B500, respectively), using hardwood residues. Properties of biochar that could potentially affect its interaction with soil and water (e.g., functional groups, surface area, elemental composition) were assessed. Experiments were conducted to test for main and interaction effects of biochar type, soil type, and the addition of NPK fertilizer on the soils’ characteristics. Bulk density and water content at field capacity and permanent wilting point were affected by two-way interactions between biochar and soil type. Biochar impacted bulk density and water retention capacity of soils. Higher available water content was found in soils amended with B400 than with B500, which is a consequence of the higher hydrophilicity of B400 compared to B500. After the lettuce crop was planted and harvested, the soil pH was unaffected by the biochar addition. However, after the second crop, the pH in the Inceptisol slightly decreased, whereas the opposite was detected in the Andisol. The CEC of the Inceptisol decreased (e.g., from 36.62 to 34.04 and from 41.16 to 39.11 in the control and in the Inceptisol amended with B400 only) and the CEC of the Andisol increased (e.g., from 74.25 to 90.41 in the control and from 79.61 to 90.80 in the Andisol amended with B400 only). Inceptisol amended only with biochar showed decrease of radish weight, while a large increase was found in B400 + fertilizer Inceptisol (i.e., from 22.9 g to 40.4 g). In Andisol, the weight of radish after the second crop increased in less proportion (i.e., from 43 g in the control to 59.7 g in the B400 + fertilizer Andisol), showing a visible positive impact of B400. The results suggest that biochar produced at 400 °C performs better than biochar produced at 500 °C because B400 apparently promotes a better environment for bacteria growth in the soils, as a consequence of more OH available groups in B400 and its better interaction with water and the fertilizer.

Anomalous water retention capacity of alpine meadow soil with eolian dust accretion on the Tibetan Plateau

Under high altitude or cold climatic conditions, the characteristics and factors controlling the water retention capacity of alpine meadow soils are poorly known. Here, we focus on alpine meadow soils, with eolian dust accretion, in the Tibetan Plateau and measured basic soil physiochemical properties and soil water retention curves (SWRCs). The results indicate that the competition between eolian processes (dust transport, eolian sorting, and dust accretion) and pedogenesis have led to significant changes of the physicochemical properties and soil water capacity of the alpine meadow soils in both spatial and with depth in the studied area. The most significant features of the alpine meadow soils are the strong accumulation of soil organic matter (SOM), soil acidification, and carbonate leaching. The studied alpine meadow soils have an unusually high saturated water content (SWC), field capacity (FC), and permanent wilting point (PWP). However, the plant available water content (AWC) does not always increase with increasing SOM, because of the rate of increase of the FC does not exceed that of the PWP. We conclude that the negative effects of carbonate leaching on soil aggregate formation and soil structural stability are likely responsible for the observed variations in FC and the resulting AWC. Finally, based on direct measurements of SWRCs and the corresponding alpine meadow soil physicochemical parameters, we developed and validated several pedotransfer functions (PTFs) for these alpine meadow soils which can be used to predict water retention from basic soil data.

Phosphate coprecipitation affects reactivity of iron (oxyhydr)oxides towards dissolved iron and sulfide

Iron (Fe) cycling exerts strong control on the mobility and bioavailability of the key nutrient phosphate (PO4) in soils and sediments. Coprecipitation of PO4 is known to alter the structure of Fe (oxyhydr)oxides (FeOx), however the environmental fate of PO4-bearing FeOx is not well-understood. Here, PO4-bearing FeOx with 9 mol% coprecipitated PO4 were prepared by Fe(III) hydrolysis and Fe(II) oxidation in the presence of dissolved PO4, in addition to pure FeOx synthesized in PO4-free solutions. The pure and PO4-bearing FeOx were subsequently exposed to different concentrations of dissolved Fe(II) and sulfide (2 and 10 mmol L−1). Mineral transformations and the fate of PO4 were tracked over 7–14 days with wet chemical techniques (including sequential Fe and S extraction) and synchrotron-based Fe K-edge X-ray absorption spectroscopy. Coprecipitation of PO4 affected the rate and extent of FeOx transformation differently for Fe(II) and sulfide. Poorly-ordered PO4-bearing FeOx was preserved in the presence of dissolved Fe(II) while pure ferrihydrite was nearly completely transformed into goethite over 7 days. By contrast, coprecipitation of PO4 rendered FeOx more reactive towards sulfide compared to pure FeOx. Reaction with dissolved sulfide resulted in the formation of non-sulfidized Fe(II) or Fe(II) sulfide under high and low Fe/sulfide ratio, respectively. Under low Fe/sulfide ratio, Fh and PO4-bearing, poorly-ordered FeOx were nearly completely sulfidized after 14 days. Sulfidation of FeOx led to efficient release of PO4 into solution, and at low Fe/sulfide ratio more PO4 was released than expected based on the extent of Fe sulfidation. The results suggest feedback mechanisms of environmental relevance: coprecipitation of strongly-sorbing species such as PO4 disrupts FeOx structure, which affects FeOx reactivity and the overall nutrient or contaminant retention capacity of soils or sediments differently depending on the ambient redox conditions. Specifically, the switch from reducing to sulfidic conditions may be associated with the disproportionate release of nutrients and contaminants.

THE SHORT TERM EFFECT OF TILLAGE SYSTEM ON SOIL MOISTURE RETENTION IN BAYELSA STATE, NIGERIA

The objective of the study was to determine the short time effect of tillage system on the water retention capacity of soils in the Niger Delta University Teaching and Research Farm, Bayelsa State. Five treatments (No-till, Digging, Hoeing, Hoeing+Digging once, and Hoeing+Digging twice) were considered. Plant Available Water Content (PAWC) and the Soil Water Holding Capacity (SWHC) were used to determine the soil water retention capacity. The results revealed that the crude tillage methods had a significant (P<0.05) impact on some soil properties. The highest bulk density (1.18g/cm3) was found in the No-till zone, while the lowest (0.89g/cm3) was in the Hoe+Digging twice method. The tillage methods also affected the hydraulic conductivity as the highest value (4.67cm/hr) was found in the hoe+digging zone and the lowest (2.61cm/hr) in the no-till area. Furthermore, the PAWC and SWHC were highest (0.14cm3cm-3 and 2.03cm) at the No-till zone and lowest (0.06 cm3cm-3 and 0.95cm) at the Hoe+Digging twice zone. It is therefore recommended that, for unrestricted flow of water through the soils, compacted soils should be pulverized using tillage implements. Also, for optimal plant water availability, there should be less tillage on coarse-textured soils, as the disturbance promotes rapid leaching.

Changes in soil water retention following biochar amendment

ABSTRACT To mitigate water runoff from arable land, a variety of measures can be applied. One of them is the amendment of highly porous biochar to increase the water retention capacity of soils and store the runoff water. Various types of biochar are made under variable production conditions and amended to soils of different quality in a wide range of quantities. Since reported data show ambiguities due to various feedstock, pyrolysis parameters, soil characteristics, and a highly variable change in water retention capacity (WRC), robust statistical methods were applied to compare the reported data from previous studies. The results revealed that biochar increased WRC by 0.26% t ha−1 of biochar added on average. In terms of WRC, biochar produced at lower pyrolysis temperatures functioned surprisingly better than that produced at higher temperatures, which was confirmed by a decision tree made by J48 algorithm. The increase of WRC was higher with sandy soils, whereas silty and loamy soils did not show a significant increase. Biochar made from easily biodegradable, post-harvest residues such as straw or rice husk showed higher impact than others made from wood that is appreciated for its high porosity. This is a groundbreaking argument for stopping the usage of biochar for energy purposes. The high organic content in soils was the major driver damping the WRC increase. The most effective measure for increasing WRC is the application of 90 t ha−1 biochar, preferably made of an easily biodegradable phytomass that is pyrolyzed at low temperatures. The presented study compares 166 specific combinations of various biochar and soil properties, shows the effectivity of biochar amendments for WTR increment, and reviews the impact of biochar amendment in terms of water retention in agricultural landscapes.

Pyrolysis temperature affects pore characteristics of rice straw and canola stalk biochars and biochar-amended soils

Soil physical properties are potentially affected by the addition of biochar. The effect is largely determined by the pore characteristics of biochar, especially the biochar’s feedstocks and pyrolysis processes. This study examined the pore characteristics of rice straw biochars (RSB) and canola stalk biochars (CSB) produced at pyrolysis temperatures of 250, 350, 450, 550, and 650 °C, and evaluated the effects of biochars on soil pore properties. The pore characteristics of biochars were characterized by nitrogen adsorption isotherm (NAI), mercury intrusion porosimetry (MIP), and scanning electron microscope (SEM). Each biochar was mixed into two soils (Ultisol and Alfisol) at the rate of 1% (w/w), then the soil-biochar mixtures were incubated for 90 days. The specific surface area (SSA) and total pore volume (TPV) measured by NAI technique increased with increasing pyrolysis temperature of biochar. Biochars pyrolyzed at 450 °C had the highest porosity and TPV measured by MIP. The largest pore class for RSB was the macropore (>75 μm), while the main pore classes for CSB were micropore (5–30 μm) and ultramicropore (0.1–5 μm). Incubation experimental results showed that biochar addition altered the pore size distribution of the Alfisol and Ultisol. RSB enhanced the total porosity and microporosity of soils, whereas CSB decreased total porosity, macroporosity, and mesoporosity. The water-holding capacity of soil was increased by increasing the amount of soil storage pores caused by biochar. Heatmap analysis on the correlation among pyrolysis temperature of biochar, pore characteristic and water retention capacity of biochar-amended soils illustrated that the pore properties of the Ultisol amended with CSB and the water properties of the Alfisol with CSB were highly correlated with pyrolysis temperature of biochar. Our results suggested the meso- and micro-pores in biochars played an important role to affect the soil response to biochar addition. Based on pore properties, pyrolysis temperature around 450 °C was found to be the optimal condition for producing porous biochar with larger porosity.

Using Different Approaches of Particle Size Analysis for Estimation of Water Retention Capacity of Soils: Example of Keszthely Mountains (Hungary)

PSD (particle size distribution) is a key factor affecting soil hydro-physical properties (e.g. hydraulic conductivity and water retention), which makes its determination essential. Climate change increases the importance of water retention and permeability as extreme weather events can severely impair the water supply of drought-sensitive vegetation. The amount of water in soils is expected to decrease. The modified Thornthwaite model considers soil properties such as root depth, topsoil layer thickness and particle size distribution (silt and clay fraction) of soil particles combined with the most significant soil properties. At the beginning of the research, we developed a laser diffraction method to replace the standard based “pipette” sedimentation method. The theoretical background of laser diffraction measurements is already known, but their practical application for estimating soil water retention capacity is still poorly understood. The pre-sieving of soil aggregates, the pre-treatment (disaggregation and dispersion) of the samples greatly influence the obtained results. In addition to the sedimentation method, laser diffraction measurements (Malvern Mastersizer 3000) were applied with three variants of pre-treatment. For comparison, the results of a Leptosol, a Cambisol, and a Luvisol were prepared for the first modified Thornthwaite water balance model. Significant differences appeared, especially during drought periods, which could be a basis for studying soil drought sensitivity. The development of our method can estimate the water retention capacity of soil, which could support adaptive forest management plans against climatic and pedological transformations.

Evaluation of Sequential Extraction Procedure (SEP) to Validate Binding Mechanisms in Soils and Soil-Nano-Calcium Silicate (SNCS) Mixtures

The soils in hazardous waste sites contain heavy metals which would leach into groundwater by various biotic and abiotic processes and eventually pose a threat to human health by contaminating the drinking water. In order to understand pattern of heavy metal leachability, the field conditions can be simulated by adopting various types of sequential extraction methods. In this study, an attempt was made to evaluate the effectiveness and selectivity of a sequential extraction process to determine heavy metal binding mechanisms in soils and soil treated with nano-calcium silicate (NCS). A five-step sequential extraction (SE) procedure was adopted on four soils obtained from a sanitary dumpsite, automobile and battery work units from different localities of Bangalore and a steel plant commissioned at Toranagallu, Bellary, India. The soils were mixed with NCS at varying range of 0.5 to 2% by dry weight of the soil. The NCS-amended soils were spiked with cadmium (Cd2+), nickel (Ni2+) and lead (Pb2+) in concentrations to the tune of 3000 mg/kg. It has been observed that there seems to be a gradual increase in binding ability for the targeted heavy metals when soils were amended with NCS compared to untreated soils. This binding phenomenon was attributed to the presence of exchangeable ions, carbonates, oxides of iron and manganese, organic matter and residual fractions. It was noticed that the residual fractions in soils amended with NCS attenuated maximum quantity of metal ions with Pb2+ at 21.46%, followed by 18.8% for Cd2+ and 9.25% for Ni2+ compared to untreated case. Further, this work highlights the role of residual fraction in enhancing the retention capacity of soils by encapsulation of higher concentrations of contaminants. The current study corroborated the fact that the addition of NCS aids in the better encapsulation of selected heavy metal ions.

Correction to: A green biorefinery platform for cost-effective nanocellulose production: investigation of hydrodynamic properties and biodegradability of thin films

Non-degradable plastics are a global crisis that has a detrimental effect on human life and all living systems. Normally, extraction of nanocellulose passes through several tedious processing including a number of steam explosions. This paper is demonstrating an easy method for the extraction of nanocellulose by using a cheaper, effective and modified acid hydrolysis route from sugarcane bagasse. The films were characterised using FT-IR, XRD, FESEM and DLS techniques. The effects of acid, alkali and salt on the thin films and the various hydro-dynamic and tensile properties were also analysed. The degradation of nanocellulose thin films in three types of soils having different moisture-holding capacities using soil burial method (ASTM D 2216) was studied. This study revealed that degradation has a direct correlation to water retention capacity of soils. Also, these thin films could be effectively degradable in soils, salt, acidic and alkaline environments. So, these fall under the category of bio-based, biodegradable and compostable bag class.

Evaluation of soil hydrophysical parameters along a semiurban small river: Soil ecosystem services for enhancing water retention in urban and suburban green areas

Urban green areas are subjected to distinct environmental conditions, and plants are exposed to numerous adverse factors. Urban areas are characterised by extensive hardened surfaces, paved or covered by asphalt, which are practically impermeable to water. Appropriate maintenance of ditches and rivers—an issue that has been neglected in recent times—is key for increasing the water-holding capacity of urban soils. Various human activities also adversely affect rainwater retention in urban soils; the transformation of the landscape by urban development changes hydrographic conditions quite radically. This study investigates the hydrophysical conditions and evaluates the variability in water retention capacity of urban (a designed river park), suburban, and rural soils in and around Kraków, Poland. This evaluation is based on hydrophysical measurements in the topsoil and in soil layers below 100 cm. Based on the distribution of water-retention parameters, we found that during the period of investigation, the soil water content at the urban site was comparable to that at rural farmlands. The factors most decisive for water retention in the soil were the soil bulk density and hydraulic conductivity. Multivariate analysis of variance showed that soil compactness influences water retention in urban soil and also the permanent wilting point (PWP, pF = 4.2). These results can inform the evaluation of periodic water supply shortages in urban water-soil systems. Subsequent studies should focus on effective ways to improve water retention in urban soil. Water storage in soils will be an important ecosystem service in many cities where the water table is lowered due to drought and/or the urban heat island effect.

Slow Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica

This study aims to synthesize slow released fertilizer in the form of Chitosan-Silica micro nutrient composite (CSiMN) by utilizing mining waste as a source of micronutrients whose release can be controlled by the presence of silica ash supporting material in rice chitosan as chelating from agricultural and fishery industrial wastes. The research method includes the synthesis of composite fertilizers in the ratio of chitosan: silica: tailings extract (TE) which is 1:1:2; 1:2:2; 1:3:2; 1:4:2 (v/w/v); swelling capacity test, and water retention capacity test from soil containing CSiMN composite fertilizer. The results showed that the CSiMN composite pellet in formula 1: 2: 2 was stable for 8 days in incubation with 100 mL distilled water. The ability to absorb water (swelling ratio) of chitosan silica composites in all comparisons, increased until the 120th minute and tended to be constant after the 120th minute. Chitosan-silica-ET composite at a ratio of 1: 2: 2, is the composition with the highest swelling power. The water retention capacity of soils containing CSiMN composite fertilizers is higher than soils without composite fertilizers. Increased silica composition in CSiMN composites can improve the retention of water capacity in soil. The release profile Fe2+ is different from Mn2+. After an incubation time of 20 days, the release of Fe2+ has increased while the release of Mn2+ tends to be constant. How to Cite this Article Pubmed Style Mangallo B, Mallongi A, Musaad I, Taberima S. Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. SRP. 2020; 11(9): 494-498. doi:10.31838/srp.2020.9.71 Web Style Mangallo B, Mallongi A, Musaad I, Taberima S. Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. http://www.sysrevpharm.org/?mno=12367 [Access: March 29, 2021]. doi:10.31838/srp.2020.9.71 AMA (American Medical Association) Style Mangallo B, Mallongi A, Musaad I, Taberima S. Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. SRP. 2020; 11(9): 494-498. doi:10.31838/srp.2020.9.71 Vancouver/ICMJE Style Mangallo B, Mallongi A, Musaad I, Taberima S. Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. SRP. (2020), [cited March 29, 2021]; 11(9): 494-498. doi:10.31838/srp.2020.9.71 Harvard Style Mangallo, B., Mallongi, . A., Musaad, . I. & Taberima, . S. (2020) Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. SRP, 11 (9), 494-498. doi:10.31838/srp.2020.9.71 Turabian Style Mangallo, Bertha, Anwar Mallongi, Ishak Musaad, and Sartji Taberima. 2020. Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Reviews in Pharmacy, 11 (9), 494-498. doi:10.31838/srp.2020.9.71 Chicago Style Mangallo, Bertha, Anwar Mallongi, Ishak Musaad, and Sartji Taberima. Slow Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. Systematic Reviews in Pharmacy 11 (2020), 494-498. doi:10.31838/srp.2020.9.71 MLA (The Modern Language Association) Style Mangallo, Bertha, Anwar Mallongi, Ishak Musaad, and Sartji Taberima. Slow Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Chitosan-Silica. Systematic Reviews in Pharmacy 11.9 (2020), 494-498. Print. doi:10.31838/srp.2020.9.71 APA (American Psychological Association) Style Mangallo, B., Mallongi, . A., Musaad, . I. & Taberima, . S. (2020) Released Fertilizer of Fe2+ and Mn2+ from Composite Micronutrient Reviews in Pharmacy, 11 (9), 494-498. doi:10.31838/srp.2020.9.71

A generalized water retention model with soil fabric evolution

This paper introduces a novel soil–water retention curve model that considers two different mechanisms of water retention – namely capillarity and adsorption – and their evolution with soil fabric along a generalized stress path. The model is formulated based on a new developed framework, which is justified against experimental evidence and incorporates the following developments: (i) the characteristics of the capillary and adsorption water retention curves are identified, and an ad-hoc water retention model is developed for each mechanism; (ii) the capillary and adsorption water retention curves are related to the experimentally determinable water retention curve thanks to a newly defined parameter named “contribution factor”, which changes with the evolution of the fabric. The proposed model is an elastoplastic water retention model and it allows to describe satisfactorily the water retention capacity of different soils. All simulation results support the statement that the adsorptive mechanism plays a crucial rule in the high suction range while capillarity is important in the low suction range. Moreover, it is shown that the developed capillary water retention curve allows to easily compute, at any state of the soil, a suitable capillary degree of saturation; the latter, adopted within the generalized effective stress concept, makes it possible to interpret shear strength data under different saturation conditions properly.

Characterizing hydro-mechanical behaviours of compacted subgrade soils considering effects of freeze-thaw cycles

Abstract This paper presents a series of experimental studies for evaluating the effects of closed-system freeze–thaw (FT) cycles on the hydro-mechanical behaviours of two subgrade soils (a low plastic lean clay, SS and a lean clay with higher plasticity, HC). Investigated hydro-mechanical behaviours include the soil–water characteristic curve (SWCC) obtained from the filter paper method, resilient modulus (MR) determined from cyclic triaxial tests, unconfined compression strength (qu) and reloading tangent modulus (E1%) and stress (Su1%) at 1% strain measured from unconfined compression tests, with emphasis on the SWCC and MR. Specimens compacted at the maximum dry density (ρdmax) and optimum moisture content (wopt) were firstly subjected to multiple FT cycles (number of FT cycles NFT = 0, 1, 3, 6 and 10) and then dried or wetted to different moisture contents before determining hydro-mechanical behaviours. Experimental results revealed that (i) FT cycles reduce the magnitude of volumetric strain upon moisture variation for the HC but have little impact on the SS; (ii) FT cycles reduce the water retention capacity of both soils. For each soil, the void ratio (e)-moisture content (w)-suction (s) relationships after different FT cycles are possibly distributed on a unique surface; (iii) Reductions in the mechanical properties (i.e. MR, qu, E1% and Su1%) are more significant at NFT = 1 and vary with the post-FT cycle moisture content. Reductions in the MR are most serious at a threshold w level on the wet side of wopt; (iv) FT cycles reduce the sensitivity of the mechanical properties to moisture content for the HC but exert minor influence on that of the SS; (v) Relationships of the MR to the qu, E1% and Su1% are not influenced by the NFT and moisture content for both soils. They are non-linear and can be well described by quadratic polynomials. Soils with higher plasticity such as the HC is, in general, more vulnerable to effects of closed-system FT cycles at wopt than low plastic soils such as the SS.