Dry Soil Research Articles

Optimization of anaerobic soil disinfestation against Verticillium wilt in strawberry cultivation using local agrowastes as amendments.

The study explores anaerobic soil disinfection as an alternative to soil fumigants for controlling Verticillium wilt in strawberry crops. For this purpose, two agrowastes close to the strawberry-growing areas of Huelva province were tested as potential amendments for the control of Verticillium wilt: rice bran and residual strawberry extrudate. Furthermore, two application rates were evaluated: 13.50 and 20.00 t/ha for the rice bran and 16.89 and 25.02 t/ha for residual strawberry extrudate. Amended and anaerobically disinfested soils were compared with a non-amended soil under anaerobic conditions, a soil treated with the chemical fungicide metam sodium and an untreated soil. One week before the start of disinfection treatment, these soils were artificially inoculated with 250 microsclerotia/g dry soil of Verticillium dahliae. After disinfestation treatments, pathogens were quantified, and strawberry plants were cropped in a growth chamber to further evaluate Verticillium wilt severity, which was measured with a symptom scale in the same potting soils. Measurements of the anaerobic condition, pH and microbial population densities were performed, and the results showed significant differences between the different amendments. In addition, the treatment with rice bran at 20 t/ha recorded the lowest population density of V. dahliae. Likewise, it was possible to achieve a reduction in foliar disease severity in all amended treatments in similar percentage to those obtained by chemical treatment. These results suggest potential application of this technique for the control of Verticillium wilt in the strawberry-growing area of Huelva, reducing the use of chemical fumigants.

Effects of poly‐γ‐glutamic acid addition on the transformation and distribution of soil nitrogen under different water conditions

AbstractThe impact of external poly‐γ‐glutamic acid (γ‐PGA) on soil nitrogen (N) transformation and distribution remains unclear, despite its contrasting effects on N use efficiency. Therefore, soil culture and soil column experiments were conducted using three different γ‐PGA addition rates (0%, 4% and 8% of dry soil weight, w/w) under different soil water contents (40%, 60% and 80% of field water capacity) and dry–wet cycles (0, 2, 4 and 8 times cycles; a single dry–wet cycle involved reducing soil water content from 80% to 40% of field water capacity) in sandy loam soil. The results of soil culture experiment showed that the γ‐PGA significantly increased soil –N and –N contents, as well as nitrification and transformation rates. However, these effects were observed to be influenced by both the culture time and soil water content. In addition, the results of soil column experiment showed that γ‐PGA not only significantly enhanced the soil inorganic nitrogen content within the 0–20 cm soil layer, but also improved water retention capacity. However, the differences between the γ‐PGA treatments gradually diminished with an increase in dry–wet cycle times. These results indicate that γ‐PGA addition enhanced soil inorganic N content and soil water retention by influencing soil N transformation and water distribution. However, the impact of γ‐PGA addition on soil improvement was regulated by soil water content, which should be taken into full consideration in agricultural practices.

IoT Based Irrigation and Fertigation System for Smart Smallholder Farming Application

Integrating Internet of Things (IoT) technology with irrigation and fertigation systems has transformed traditional farming methods by enabling reliable monitoring and control of critical environmental parameters. This project aims to design an automated irrigation and fertigation system as a prototype to reduce water wastage and monitor the pH level in the soil, temperature, soil dryness and detection of intruders. Sensors strategically placed throughout the system monitor and control these elements. This system has several important features, including the ability to automatically control water pumps to maintain proper hydration levels, detect intruders within a range of one to six meters of the plant by using the Blynk app, and monitor pH levels through the same app to ensure appropriate neutral levels. Automation and control features are also assessed to confirm that sensors, pumps, and other components precisely respond in line with predetermined requirements. This evaluation helps to determine the overall health of the farmed plants as well as the effectiveness of the system. Finally, the irrigation and fertilizing system for the targeted smallholder farming area has been developed. The resulting smart irrigation and fertigation system is not only a practical solution but also an effective alternative to modern agricultural methods.

استخدام المجهر الألكتروني الماسح في تشخيص المعادن الطينية في بعض ترب الرز العراقية

The Middle Euphrates region, represented by the governorates of Diwaniyah and Al-Najaf, was chosen to conduct the current study. As the two governorates are famous for cultivating various varieties of rice crop. Two methods using to irrigated these soils during the growing season, and called locally wet and dry methods. The morphological features of clay minerals were studied using scanning electron microscope (SEM), to describe the changes that occurred to the mineralogical features of these minerals due to the influence of the irrigation patterns used during irrigation of these soils. The scanning electron microscope (SEM) results show that were many changes in morphological features occurs such as in size and shape of clay minerals, in particular to smectite minerals. The scanning electron microscope (SEM) figure of clays in Al-Najaf(dry) soil showed some of particles appeared as well-formed imperfect hexagonal shape, which revealed that these particles belong to the chlorite mineral. While the mica minerals were appeared in lath-shaped, and rounded flakes in clays of all studied soils. Whereas the montmorillonite particles appear as a thin, webby crust, and have a flat, perming morphology. The variation in the size of the montmorillonite particles was adopted as a basis for the occurrence of the Mg-hydroxide layer within the interlayers of montmorillonite.

Перспективы переработки угля с низкой степенью метаморфизма

Introduction. The relevance and significance of this work is due to the fact that the soils of Kazakhstan are about 48% salt marshes. The reasons for their occurrence are different: harsh climatic conditions, the drying Aral Sea, the Baikonur cosmodrome, numerous test sites, etc. With an increased content of water-soluble salts in the root layer of soils, most cultivated plants develop poorly and yield a reduced yield. To solve the above problem, the technology of processing brown coal from the Kiyakty deposit and its substandard part for the production of drugs-growth stimulants for agricultural plants, high-calorie fuel briquettes and coal-alkali reagents is proposed. Materials and methods. Development of technology for the production of a humic preparation from brown coal deposits in Kazakhstan. It is known that these coals are amorphous polymers containing bitumen, humic acids, residual organic substances and moisture. Laboratory experiments were carried out by the method of biotesting according to B.P. Strogonov in glasses with a capacity of 0.5 liters in accordance with the requirements of GOST (GOST 10250–80, GOST 12038–84). The methodology for conducting research on the manufacture of briquettes, carbon-alkali reagents based on the humic acid hypothesis and various local binding materials with the involvement of certified CeLSIM laboratories is substantiated. The most optimal binder is a liquid bardic concentrate. Results. As a result of the application of new methods of pre-sowing treatment of rice seeds with a 2.5 % aqueous solution of the preparation from coal, its yield increased by 9.5–12.1 quintals per 1 ha, or by 33.8–41 % compared with the control. Discussion. The works of a number of foreign and domestic researchers on this topic have proved the possibility of using humic substances from brown coals to obtain organo-mineral fertilizers, and a comparative study of the chemical composition has been conducted. However, according to our technology, it is clear that we do not get fertilizer, but plant growth stimulants. It should be noted that the technology developed by the authors makes it possible to obtain a humic preparation, the use of which on low-yielding soils of Kazakhstan ensures a stable increase in the yield of cereals and legumes. Conclusion. The developed technology for the production of humic preparations for various purposes can be used to increase crop yields on degraded soils, for the bio recultivation of man-made formations, the manufacture of a substrate for greenhouse farms, the production of fuel briquettes and coal-alkali reagents, as well as during the operation of other brown coal deposits of the Republic of Kazakhstan with a high content of humic acids in their composition. Suggestions for practical applications and directions for future research. The territory of Kazakhstan is considered to be arid zones of dry steppe soils without rains. In these conditions, agricultural technicians resort to plants of halophyte varieties, therefore, the prospects for using this technology are very large, for example, to suppress dust formation on the surface of tailings ponds with the cultivation of green mass of wild plant varieties. Preparations from brown coals can be used to purify water and wines, leach precious metals, etc.

LABORATORY DETERMINATION OF THE MAXIMUM DENSITY AND OPTIMAL HUMIDITY OF LARGE-BLOCK SOILS

he purpose of our field research was to develop and select a method of work on laying and compacting the material of large-block soils, ensuring the receipt and determination of maximum density and optimal soil moisture. On the basis of these studies, technical conditions for the construction of thrust prisms are further drawn up. This article presents the results of the work performed with a brief methodology of field and laboratory research. The article provides data characterizing the material intended for installation in the body of the dam. The currently existing methods for determining the control parameters of laying large-block soils are contradictory and require experimental work. A number of parameters are taken into account: grain composition, humidity, density. Therefore, the article considers a laboratory method for determining the maximum density and optimal humidity of stone material when laying in the body of the dam. The results of the research carried out on the development of our quarry area, the thickness of the uncompacted layer was determined, the choice of a sealing mechanism, the number of passes along one track, the determination of the density of dry soil in experimental field sites intended for use in filling the body of the dam, graphs of the required densities for full-scale grain composition are presented. The strength properties of the stone material were determined experimentally for the average grain composition and for the upper curve of the accepted “fish”

Alternate wetting and drying: a water-saving technology for sustainable rice production in Burkina Faso?

With emerging water scarcity and rising fertilizer prices, optimising future water use while maintaining yield and nutrient efficiency in irrigated rice is crucial. Alternate wetting and moderate soil drying irrigation (i.e., re-irrigation when the water level reaches 15 cm below the soil surface) has proven to be an efficient water-saving technology in semi-arid zones of West Africa, reducing water inputs without yield penalty. Alternate wetting and severe soil drying (AWD30), by re-irrigating fields only when the water table reaches 30 cm below the soil surface, may further reduce water inputs compared to farmers’ irrigation practices (FP). However, acute soil drying may impair fertilizer use efficiency and reduce the bio-availability of some key nutrients. This study assessed the potentials and risks associated with AWD30 for smallholder rice farmers in the semi-arid zones of West Africa. We conducted 30 on-farm field trials over three seasons (wet and dry seasons of 2019, and dry season of 2020), in Kou Valley, Burkina Faso. We assessed yield, water productivity, nutrient uptake, and use efficiency under AWD30 and FP. In FP, farmers maintained their fields submerged as frequently as possible according to the scheme-dependent water provision schedule. With AWD30, irrigation frequency was reduced by 30%, however, soils were seldom completely dried due to a shallow groundwater table. Compared to FP, AWD30 reduced irrigation water input by 37% with no significant effects on grain yields (average of 4.5 Mg ha−1), thus increasing average water productivity by 39%. Both irrigation management practices provided comparable crop uptake of N, P, and K, and use efficiencies of applied N and P. However, the N content in straw and the P concentration in grain generally increased with total water input (rain + irrigation). We conclude that at locations with a shallow groundwater table, AWD30 can effectively save irrigation water without significantly reducing the grain yield and the use efficiency of applied mineral nutrients.

Combined effects of salinity and soil drying on growth, water, status, and photosynthesis in Medicago ciliaris and Medicago polymorpha

Combined effects of salinity and soil drying on growth, water, status, and photosynthesis in Medicago ciliaris and Medicago polymorpha

<span><strong>Enhanced thiamethoxam degradation in water  and soil by </strong><em>Phanerochaete </em><strong>sp. Th1 and </strong><em>Ensifer </em><strong>sp. Th2</strong></span>

Thiamethoxam is widely applied to control pest insects, but it causes serious environmental contamination. In this study, the degradation processes of the compound in soil and water collected from a rice field by native microorganisms, by mixed culture of Phanerochaete sp. Th1 and Ensifer sp. Th2, and by both the mixed pure culture and native microorganisms were conducted. The result showed that the mixed culture inoculation increased thiamethoxam in all media. In liquid media, the degradation percentage of the substrate in collected water was 21.8±4.4%, collected water + inoculation was 44.2±5.0%, and mineral medium + inoculation was 98.0±0.4%. Degradation determination in media with 70% collected water and 30% dry soil showed that the main degradation occurred in the liquid phase. The degradation rates in the media with 50% collected water and 50% dry soil were higher in the surface layer, and lower in the bottom. Indigenous microorganisms also played an important role in the degradation process. This study provided valuable information on the thiamethoxam degradation in simulated media of a rice field and the role of Phanerochaete sp. Th1 and Ensifer sp. Th2 to enhance the degradation.

Traffic induced compaction and physical quality of grassland soil under different soil moisture deficits

Soil compaction is widely recognised as one of the key contributors to soil degradation in Europe. Information is needed for farmers and land managers to guide management decisions and prevent traffic-induced soil compaction. Predicted soil moisture deficit (SMD) from the hybrid SMD model may provide information on when soil conditions are suitable for machinery trafficking. The objective of this study was to investigate the relationship between soil water content and traffic induced soil compaction and if a predicted SMD threshold level could be identified, above which soils can be trafficked without significant soil compaction occurring. The study also evaluated the capacity of selected soil physical indicators such as soil bulk density and water stable aggregates to indicate soil physical degradation across a range of soil water contents. The experiment was carried out on grassland with moderately drained soil, located in Wexford, Ireland. Machinery trafficking of the soil with a tractor equipped with a fully loaded slurry tanker, was assessed in the field across the four seasons of the year. Traffic was imposed at target predicted SMD + 10 mm (relatively dry soil), 0 mm (relatively moist soil), and −10 mm (relatively wet soil). After each traffic event, samples were taken in the middle of the wheel track at three depths (0–10, 10–20 and 20–30 cm) to assess soil bulk density. Water aggregate stability was evaluated at the same three depths following the fourth traffic event. Results showed that when planning field machinery operations, especially repeated trafficking events, soil becomes prone to physical degradation when predicted SMD ≤ 0 mm. Traffic on soil at predicted SMD 0 mm (close to field capacity) lead to compaction after two traffic events. However, when predicted SMD was −10 mm, soil bulk density indicated no significant difference from the non-trafficked soil. When water-stable aggregates were measured on the predicted SMD 0 mm and −10 mm trafficked soils, it indicated physical degradation of soil. Hence, bulk density alone did not give an accurate indication of soil structural quality when soils where trafficked under relatively wet or saturated conditions (SMD −10 mm). These results indicate that avoiding machinery trafficking of grassland soils at predicted SMD ≤ 0 mm will help protect soil physical structure. On soils where multiple machinery operations are likely to occur over the year, trafficking when the predicted SMD > 0 mm is recommended to minimise loss of soil physical quality.

The Effects of Dust Storms on People Living in Beijing: A Qualitative Study.

Dust storms, which are common aversive occurrences in northern China, result from high winds, dry soil or dust, and soil surface disturbance. Exposure to dust storms, regardless of duration, can induce varying mental and physical distress levels. Recognizing the urgency of comprehending the impact of dust storms on residents and the scarcity of information on their effects on the indigenous civilians there, this study aims to address this gap by qualitatively sampling 29 participants from Beijing, a typical city in northern China. The current study seeks to gain insights into residents' dust storm experiences and explore their perspectives on effective coping mechanisms. The findings align with existing knowledge regarding the mental and physical repercussions of dust storms while identifying some emerging patterns of coping mechanisms already employed by residents in Beijing. Concerns regarding mental well-being, either directly influenced by the environmental conditions or indirectly stemming from disruptions to life routines on a broader scale, persistently dominate people's perceptions of dust storms. New themes emerged following the step-by-step exploration of feelings and coping mechanisms. This study aims to enlighten the public about the ramifications of the dust storms in Beijing and advocate for essential policy support.

Severity of topsoil compaction controls the impact of skid trails on soil ecological processes

Abstract Skid trails are a major management‐induced disturbance in temperate forest ecosystems with considerable impact on soil ecological processes that are so far poorly understood. In German forests, skid trails comprise 10%–20% of the forest area that is potentially affected by soil compaction through heavy machinery. We systematically investigated the influence of skid trails on physical, chemical and microbiological soil parameters at 84 paired plots across four Central European forest types. In low mountain forests with steeper topography, skid trails had more drastic effects than in lowland forests. Skid trails in low mountain areas showed a decrease in the C to N ratio of microbial biomass (MBC/MBN), as well as increased microbial (MBC/SOC) and enzyme activities leading to faster carbon turnover (lower C/N, EOC/EN) and increased CO2 losses (CO2/SOC) from the soil. The overall effects of the skid trails in lowland forests were small. On base‐poor soils, we found an increase in the MBC/MBN ratio, while skid trails in base‐rich lowland soils showed a reduction in CO2/SOC, suggesting a proportional increase in soil carbon storage. Regardless of region‐specific effects, the relative increase in the bulk density of the fine soil was identified as a ‘golden trait’ that determined the effects of skid trails on many soil parameters, as shown by negative correlations with SOC, N, MBC, MBN, MBP, MBC/SOC and CO2/SOC and positive ones with the activities of certain hydrolytic enzymes. Synthesis and applications: Our data clearly showed that carbon conversion processes and soil respiration leading to significant carbon and nutrient losses increased significantly on skid trails in low mountain regions with relatively steep slopes, which was in sharp contrast to lowland sites. The strong context dependence of our findings suggests that the mapping of soil conditions in terms of slope, substrate and moisture with high spatial resolution is mandatory to assess the vulnerability of sites to soil compaction by heavy machinery. Based on such vulnerability analysis, negative impacts can be minimised through the designation of permanently fixed skid trails, technical adaptation of vehicles (e.g. wide base tyres) as well as careful planning and timing of management operations that should be restricted to dry weather and soil moisture conditions or periods of frost.

Cyclobutrifluram (TYMIRIUM® technology): Low risks of a soil applied nematicide and fungicide to non-target soil invertebrates and bees

Cyclobutrifluram (TYMIRIUM® technology) is a seed- and soil-applied nematicide and fungicide which protects the plant root mass. Cyclobutrifluram acts by inhibiting mitochondrial complex II electron transport and succinate dehydrogenase inhibition (SDHI). Concerns over the potential adverse effects on non-target species were addressed by assessing whether recommended field application rates of cyclobutrifluram would result in adverse impacts on soil invertebrates or honeybees. Studies conducted under laboratory conditions with the active ingredient and two formulations provided No Observed Effect Concentrations for earthworm (Eisenia andreii) reproduction of 71–171 mg a.i./kg dry soil with no effects on soil mite (Hypoaspis aculifier) reproduction. There were no effects on honeybee (Apis mellifera) adults or larvae following chronic exposure to doses up to 400 and 160 mg/kg diet respectively. Using Brazil as a target market (soybean seed treatment and in-furrow application in fruiting vegetables), our laboratory studies indicate that the risk to two species of soil invertebrates and honeybees of the use of cyclobutrifluram either in-furrow or as a seed treatment was orders of magnitude below any levels of concern.

Enhancing biodegradation of aged hydrocarbon-contaminated soils through toluene addition: assessing effects on solid and slurry phase treatments.

The main challenge in treating aged soils highly contaminated with total petroleum hydrocarbons (TPH) is to enhance their bioavailability for microbial degradation. Hydrocarbons in soils undergo chemical changes that make them more resistant to biodegradation. This study investigates toluene's efficacy in enhancing the biodegradation of aged hydrocarbon-contaminated soil containing 292,000mg TPH kg-1 dry soil. Toluene's effect was compared between solid phase (SOP) and slurry phase (SLP) treatments using a microbial consortium isolated from Cyperus laxus rhizosphere. TPH biodegradation and microbial respiration were measured, the latter to estimate the respiratory quotient (RQ, the ratio between moles of carbon dioxide released and moles of oxygen absorbed during respiration). Toluene significantly accelerated TPH biodegradation in both treatments, achieving ~ 30% higher removal than in a non-solvent control, possibly through improved bioavailability of aromatic compounds and other low molecular weight compounds. According to the RQ analysis, toluene enhanced microbial respiratory processes and hydrocarbon catabolism with higher hydrocarbon mineralization (RQ = ~ 0.5) in both SOP and SLP assays. Our results reveal toluene's potential to increase hydrocarbon availability and microbial degradation efficiency in aged contaminated soils; its use in various bioremediation techniques could be of broad applicability across diverse soil types and pollutants.

Time domain reflectometry coil probes for measuring thin surface layer soil moisture: Field tests over 21 years (2002–2022) under highly variable climate conditions in Mongolia

A coil probe (CP) for time-domain reflectometry (TDR) with a sensor length of 40 mm (CP40) was developed for long-term field soil moisture measurements in a thin surface soil layer (0–3 cm depth). In laboratory, soil moisture measurements of CP40 were nearly identical to those of a traditional two-rod type TDR (2RTDR) probe (rod length: 15 cm, diameter: 0.3 cm, spacing: 3 cm). The CP40 measurement accuracy was between 0.01 m3/m3 and 0.03 m3/m3. For long-term field soil moisture measurements, five CP40 units were installed in the highly wetted soil at the Sanzai site (SS), which is in the permafrost area of the Taiga, and dry soil at the Mandalgobi site (MGS) in the semi-arid area of Mongolia. Four units accurately measured soil moisture at both sites over six years (2002–2007and 2008–2009). Three units succeeded in conducting precisely continuous soil moisture measurements between 2008 and 2022 at the MGS. Two units successfully measured soil moisture over 21 years at both the sites. The representativeness of the CP40 soil moisture measurements in highly wetted soils was low because of heavy rainfall and soil heterogeneity. The accuracy of CP40 soil moisture measurements in highly wetted soils was slightly lower than that of the traditional 2RTDR probe. However, the accuracy of the CP40 soil-moisture measurements in the dry soil was comparable to that of the traditional 2RTDR probe. CP40 units are durable and their field soil moisture measurements demonstrate stable and precise performance (bias, RMSE), even under severe environmental conditions.

DEM analysis of constrained modulus nonlinearity and damping factor of dry granular soils

The seismic site response analysis requires the dynamic soil properties (i.e., the modulus and damping). While it is well understood that the shear modulus and damping ratio are nonlinearly shear-strain dependent, the knowledge on the constrained modulus and damping ratio of compressional waves is still very limited due to lack of laboratory testing equipment. This study aims to simulate cyclic tests of constrained compression for granular specimens by discrete element method (DEM) to understand the dynamic soil properties of compressional waves, i.e., the nonlinearity in constrained modulus and damping ratio with the compression strain. The evolution in microstructure of granular specimens is revealed to provide micromechanical interpretations for the compressional soil nonlinearity. The results show that the dependency of constrained modulus on compression strain is different in compression and extension stages, and the modulus reduction is only observed in the extension path. The damping ratio of samples under cyclic constrained compression is smaller than that of cyclic shear. The nonlinear soil behavior is more obvious at lower confining pressure and for dense sample. The nonlinearity of constrained modulus depends on the coordination number, contact normal force and fabric anisotropy, while the associated damping ratio is only related to fabric anisotropy.

Effect of Soil Texture on Soil Nutrient Status and Rice Nutrient Absorption in Paddy Soils

Soil texture affects rice nutrient uptake and yield formation by influencing soil structure, microbial activity, and soil nutrient supply capacity. Analyzing the relationship between soil texture, nutrient content, and rice agronomic traits is of great significance for precise and efficient fertilizer application. The tillage layer (0–20 cm) of 31 paddy fields in China’s main rice-producing areas was collected to perform rice pot experiments, and soil texture characteristics, physicochemical properties, microbial-related indicators, and rice agronomic traits were measured and analyzed. The results showed that these soils could be classified into four types of soil texture: loamy sandy soil, sandy loam soil, silty loam soil, and silty soil. Analysis of variance showed that the available nitrogen (AN), available potassium (AK), and available phosphorus (AP) contents were the highest in silty loam, silty, and sandy loam soils, respectively, and silt loamy soil had the highest CEC. Principal component analysis (PCA) also showed that soil physicochemical properties can be distinguished to a certain extent according to soil texture types. For the relationship of soil texture parameters and soil physicochemical properties, soil organic matter (OM), total nitrogen (TN), AN, ammonium nitrogen (NH4+-N), and microbial carbon (MBC) contents were positively correlated with soil clay content, AK was positively correlated with silt content, and soil phosphorus status was significantly related to pH. Mantel’s test revealed significant correlations between rice N, P, and K nutrient status, dry matter accumulation, and yield, and soil available nutrient content, MBC, pH, and soil texture parameters. Structural equation modeling (SEM) indicated that sand affected soil available nutrients by regulating pH, while clay can positively influence soil available nutrients by affecting soil organic matter mineralization and microbial activity, thus influencing nutrient absorption and yield formation in rice. Overall, in rice production, the silty and silty loam paddy soil with fine texture and higher clay content facilitates the mineralization of soil organic matter and the activity of soil microbes, resulting in more available soil nutrients, which benefits the rice absorption and accumulation of nutrients. Furthermore, a higher content of clay also promotes the distribution of dry matter to the panicle, thereby promoting rice yield formation.

Seismic response of braced excavation wall supporting deep sand layer using dynamic centrifuge tests

This paper presents the dynamic centrifuge model tests to investigate the seismic performance of a 24.8 m deep braced diaphragm wall supporting dry sand backfill soil at 40 g level acceleration. The model tests aim to determine the acceleration response of the backfill, seismic earth pressures acting on the wall, and the dynamic increment of the structure's inner force for sand backfills with different relative densities. Particularly, the horizontal seismic coefficient, earth pressure distribution, and dynamic thrust are analyzed in detail. Based on the experimental results, the dynamic thrust development is consistent for peak ground accelerations at bedrock less than 0.12 g and 0.10 g for relavitve densities of 78 % and 54 %, respectively. However, the dynamic thrust starts to increase when the bedrock acceleration exceeds this threshold. Moreover, the varying trend of dynamic thrusts under ground input motion employed during at the initial excitation differs from that of the succeeding input motions, likely due to the changes in relative density caused by backfill disturbance from sequential excitation. The increasing rate of increase on the dynamic thrusts among Northridge, Kobe, and artificial excitations was changed with the amplitude of the acceleration response. Lastly, the wall bending moment and strut axial force increase by up to 97.3 % and 12.9 % of the maximum value of member force on the at-rest condition due to earthquake loading.

Spatiotemporal investigation of geochemical and hydrological controls on release of soluble reactive phosphorus from the shallow aquifer of a riparian zone.

Phosphorus (P) that accumulates in agricultural riparian zones can be released under certain hydrological and biogeochemical conditions, thereby limiting the effectiveness of these zones in reducing P loads from field to stream. The study objective was to explore factors that may be contributing to, or limiting, high soluble reactive phosphorus (SRP) concentrations in the shallow aquifer of an alluvial upland riparian zone located in a continental climate. Field investigations including porewater sampling from six vertical nests, soil sampling, and continuous soil moisture, groundwater table, and redox measurements were conducted over 19 months. Porewater SRP concentrations were generally low in the aquifer considering all sampling times (median=14.7µg/L; interquartile range [IQR]=11.1µg/L, 287 samples). The overall low SRP may be due to low reducible labile soil P (median=21.1 µgP/g dw, IQR=10.9 µgP/g dw, 21 samples). However, high SRP concentrations(>52µg/L, 95% quartile) did occur intermittently in space and time with no clear spatial or temporal patterns. Analyses indicate that most high concentrations were likely not associated with factors previously reported to influence SRP release in riparian aquifers, including redox conditions, pH, and soil drying and wetting. Further, data indicate that internally released or externally supplied SRP may undergo rapid (re-) sequestration within the aquifer, limiting its vertical or horizontal transport. The study findings highlight the complexity of P behavior in riparian zones and the need for caution when assessing the effectiveness of conservation practices and in interpreting potential impacts of subsurface water quality on stream water quality when monitoring locations are distant from the stream.

Performance of soybean cultivars for increased seedling emergence after sowing in dry soil

Performance of soybean cultivars for increased seedling emergence after sowing in dry soil