Bulk Soil Electrical Conductivity Research Articles

Determining Drought and Salinity Stress Response Function for Garlic

Garlic (Allium sativum L.) is an important crop cultivated in arid and semi-arid climates. To quantify the tolerance of garlic to drought and salinity stresses in terms of parameter values of the stress response function, we conducted pot experiments in a greenhouse for two years. Nine 1/5000a Wagner pots were used for three treatments, namely drought-treated, salinity-treated, and control pots, for estimating the relative transpiration. Daily transpiration rates were observed by weighing pots, and the soil surface of each pot was covered. The soil water contents were measured hourly using two soil moisture probes for drought-treated pots, and two salinity probes for both soil water content and bulk electrical conductivity were monitored for salinity-treated pots. When the ratio of actual to potential transpiration fell below 50%, the root length distributions were obtained by dismantling the pots. The parameter values for both drought-stress and salinity-stress functions were estimated using inverse-analysis and bulk-analysis methods. The parameter values of drought-stress and salinity-stress functions obtained by the simpler and cheaper bulk method gave similar results to the inverse method when the root length distributions were relatively uniform.

Evaluation of soil water content and bulk electrical conductivity across the U.S. Climate Reference Network using two electromagnetic sensors

AbstractSoil bulk electrical conductivity (BEC) was evaluated alongside soil volumetric water content (VWC) and soil temperature measurements using the HydraProbe (model HydraProbe, Stevens Water Monitoring Systems, Inc.) (hereafter called HP) with accuracy range of BEC ≤ 0.3 S m−1, and the time domain reflectometry (TDR)‐315L Probe (model TDR‐315L, Acclima, Inc.) (hereafter called AP) suitable for BEC up to 0.6 S m−1, at 23 stations of the U.S. Climate Reference Network. Previous evaluations revealed inconsistent performance of both sensors in some clay soils using manufacturer‐recommended calibrations in converting dielectric permittivity measurements to VWC. Here, we found that hourly values of BEC reached 0.6 S m−1 in high clay content soils and exceeded 2 S m−1 in high saline soils, and these high values of BEC were associated with poor performance and failures of both HP and AP sensors. Large values of BEC occurred in predominantly saturated soils where VWC values reached about 0.5 m3 m−3 for saline soils and about 0.7 m3 m−3 for clay soils, while low magnitudes of BEC were associated with low soil water content and seldomly saturated soils. Low hourly BEC values of less than 0.1 S m−1 were observed in wide variety of soil types, where sensor performance was typically excellent. The most influential factor on BEC was high soil water content conditions. Although dielectric permittivity measurements in estimating the soil water content were sensitive to BEC as some high clay content and high salinity soils increased BEC, the impact of large BEC on dielectric permittivity measurements was smaller in the well‐drained top soil layers than in deep soil layers that remained near saturation. Soil temperature had only a small impact on BEC. With high clay content and high salinity, the specific area of clay minerals was also associated with the magnitude of BEC.

Mapping and monitoring peatlands in the Belgian Hautes Fagnes: Insights from Ground-penetrating radar and Electromagnetic induction characterization

Peatlands are vital ecosystems providing crucial ecological services such as significant carbon storage in the context of climate change. These sensitive ecosystems are subjected to degradation due to land use change. In this context, it is important to understand the actual state of degraded peatlands and their recovery potential for regaining important functions. This study focuses on a disturbed peatland in the Belgian Hautes Fagnes, previously drained and planted with spruce, and characterized by a topographic gradient. We aimed to elucidate the use of Ground-penetrating radar (GPR) and Electromagnetic induction (EMI) techniques in characterizing such peatlands, with a specific focus on their implications for peat depth and electrical conductivity assessment, related to peatland degradation. The GPR revealed a high spatial heterogeneity in peat depth, ranging from 0.2 to more than 2 m on the site. In contrast, an EMI instrument used with single coil spacing proved to be unsuccessful to deduce peat depth but demonstrated potential for the delineation of zones of mineral soil. It is also shown that the links between soil physical and chemical properties and its bulk soil electrical conductivity (ECa) measured by EMI are complex in zones of shallower peat. Additionally, this study highlights the role of pore water conductivity in influencing temporal variations in ECa. Our findings explain the intricate interplay between peat depth, topography and ECa in disturbed peatlands. The results of this study may be of substantial societal interest, as it provides insights into techniques for the rapid non destructive characterization of the conditions of previously drained peatlands.

Response of the TEROS 12 Soil Moisture Sensor under Different Soils and Variable Electrical Conductivity.

In this work, the performance of the TEROS 12 electromagnetic sensor, which measures volumetric soil water content (θ), bulk soil electrical conductivity (σb), and temperature, is examined for a number of different soils, different θ and different levels of the electrical conductivity of the soil solution (ECW) under laboratory conditions. For the above reason, a prototype device was developed including a low-cost microcontroller and suitable adaptation circuits for the aforementioned sensor. Six characteristic porous media were examined in a θ range from air drying to saturation, while four different solutions of increasing Electrical Conductivity (ECw) from 0.28 dS/m to approximately 10 dS/m were used in four of these porous media. It was found that TEROS 12 apparent dielectric permittivity (εa) readings were lower than that of Topp's permittivity-water content relationship, especially at higher soil water content values in the coarse porous bodies. The differences are observed in sand (S), sandy loam (SL) and loam (L), at this order. The results suggested that the relationship between experimentally measured soil water content (θm) and εa0.5 was strongly linear (0.869 < R2 < 0.989), but the linearity of the relation θm-εa0.5 decreases with the increase in bulk EC (σb) of the soil. The most accurate results were provided by the multipoint calibration method (CAL), as evaluated with the root mean square error (RMSE). Also, it was found that εa degrades substantially at values of σb less than 2.5 dS/m while εa returns to near 80 at higher values. Regarding the relation εa-σb, it seems that it is strongly linear and that its slope depends on the pore water electrical conductivity (σp) and the soil type.

Carbon emissions from Australian Sphagnum peatlands increase with feral horse (Equus caballus) presence

Peatlands are globally significant carbon sinks, but when disturbed, have the potential to release carbon back to the atmosphere as greenhouse gases. Feral horse populations in the Australian Alps degrade Sphagnum peatlands, which are highly sensitive to disturbance. However, the link between this degradation and peatland carbon cycling is not understood. Here, we compared the autumn daytime carbon dioxide (CO2) and methane (CH4) fluxes of 12 alpine and subalpine Sphagnum peatlands in Kosciuszko National Park, Australia. The presence of feral horses at these sites was correlated with higher carbon loss: sites with horses were losing carbon to the atmosphere (4.83 and 8.18 g CO2-e m−2 d−1 in areas of Sphagnum moss and bare soil, respectively), whereas sites without horses were removing carbon from the atmosphere (−6.39 g CO2-e m−2 d−1). Sites with feral horses also had higher soil bulk density, temperature, and electrical conductivity (EC), and higher water pH, EC, and turbidity, than sites without horses. Our findings suggest that excluding feral horses from peatland areas could reduce rates of carbon loss to the atmosphere, in addition to improving overall site condition, peat soil condition, and water quality. We discuss potential management applications, further research, and restoration opportunities arising from these results.

Impacts of repeated coastal flooding on soil and groundwater following managed dike realignment

Coastal defense structures (e.g., dikes, seawalls) protect vulnerable communities along marine coastlines and estuaries from the physical and chemical influences of adjacent water bodies. These structures are susceptible to overtopping or breaching by tides and waves, with risks amplified by climate change-induced sea-level rise. Repeated inundation by saline water can contaminate freshwater resources and salinize soil, impacting land-use activities, including agricultural productivity. Managed ecosystem-based dike realignment and salt marsh restoration can provide alternatives to traditional coastal adaptation approaches. We assess the changes to soil salinity at a managed dike realignment project prior to the transformation from a diked terrestrial environment to an estuarine environment. Baseline data are compared to conditions following 8–10 months of intermittent flooding at spring tides.Results show that an increase in salinity occurred over the entire site in the shallow subsurface, with the most significant contamination occurring in low-lying areas. Bulk soil electrical conductivity (salinity proxy) measured from geophysical surveys increased from the previous freshwater condition of ∼300 μS/cm to over 6000 μS/cm following <20 flood events, while successive flooding resulted in increased soil moisture as infiltrated floodwater propagated to greater depths. Sediment deposition occurred at high rates, with up to 4 cm of sediment deposited per flood, converting much of the previously cultivated land into tidal mudflats. Deeper sediments and groundwater (i.e., >1.8 m depth) were not impacted over the time scale of this research. This study demonstrates that intermittent shallow flooding can rapidly increase moisture content and soil salinity in surficial sediments and, in turn, adversely impact conditions suitable for agricultural crop production. The realignment zone serves as an engineered analog of coastal flooding, presenting an opportunity to investigate how low-lying coastal environments may experience regular flooding in the future due to sea-level rise and intensifying coastal storms.

Research on vehicle-mounted soil electrical conductivity and moisture content detection system based on current–voltage six-terminal method and spectroscopy

To provide real-time, online, and accurate measurements of soil electrical conductivity (EC) and moisture content (SM) in large-scale agricultural fields and guide field management, vehicle-mounted online EC and SM measurement system based on the fusion of current–voltage six-terminal method and near-infrared spectral information was developed and the predictive accuracy of the system was tested in field and laboratory experiments. The traditional current–voltage six-terminal method is used to fuse the spectral information at the moisture-sensitive wavelength of 1450 nm to predict SM and then a correction factor Q was proposed to eliminate the influence of SM on EC. In addition, the linear relationship between soil apparent electrical conductivity (or bulk soil electrical conductivity, ECa) and SM, the exponential relationship between SM and spectral reflectance (R) were used to indirectly obtain the exponential relationship between ECa and R. And then, the binary model of EC is established using the electrical conductivity values of the univariate model (ECeq) obtained from the current–voltage six-terminal method and the univariate model (EClq) obtained from the relationship between the conductivity of the ECa and the R index as an input variable. The experimental data of the univariate model EClq and ECeq and the binary model were analyzed. The field electrical conductivity detection accuracy R2 of the univariate model EClq and ECeq is 0.790 and 0.829 respectively, and the RMSE is 10.113 and 8.078 respectively. While the field electrical conductivity detection accuracy R2 and RMSE of the binary model are 0.899 and 6.535 respectively. The laboratory electrical conductivity detection accuracy of R2 for the univariate models EClq and ECeq were 0.874 and 0.893, and the RMSE were 7.129 and 6.663 respectively. The laboratory electrical conductivity detection accuracy of R2 and RMSE for the binary model were 0.942 and 5.346 respectively. From the above result, it can be seen that R2 for the binary model has improved and the RMSE of the model has decreased. Analysis result of the SM prediction model shows that the accuracy of the SM prediction model R2 in the field and laboratory is 0.888 and 0.938 respectively, and the RMSE is 0.339 and 0.239 respectively, which indicates that the accuracy of the SM prediction model can meet the system requirements. The overall experimental results show that the electrical conductivity detection accuracy of the binary model of the detection system fused with spectral data is significantly improved, and the SM prediction accuracy can meet the needs of farmland detection, which can guide scientific and precise management of farmland.

In situ Soil Moisture Sensors in Undisturbed Soils.

Soil moisture directly affects operational hydrology, food security, ecosystem services, and the climate system. However, the adoption of soil moisture data has been slow due to inconsistent data collection, poor standardization, and typically short record duration. Soil moisture, or quantitatively volumetric soil water content (SWC), is measured using buried, in situ sensors that infer SWC from an electromagnetic response. This signal can vary considerably with local site conditions such as clay content and mineralogy, soil salinity or bulk electrical conductivity, and soil temperature; each of these can have varying impacts depending on the sensor technology. Furthermore, poor soil contact and sensor degradation can affect the quality of these readings over time. Unlike more traditional environmental sensors, there are no accepted standards, maintenance practices, or quality controls for SWC data. As such, SWC is a challenging measurement for many environmental monitoring networks to implement. Here, we attempt to establish a community-based standard of practice for in situ SWC sensors so that future research and applications have consistent guidance on site selection, sensor installation, data interpretation, and long-term maintenance of monitoring stations. The videography focuses on a multi-agency consensus of best-practices and recommendations for the installation of in situ SWC sensors. This paper presents an overview of this protocol along with the various steps essential for high-quality and long-term SWC data collection. This protocol will be of use to scientists and engineers hoping to deploy a single station or an entire network.

Biochar benefits carbon off-setting in blue-green infrastructure soils - A lysimeter study

Carbon sequestration with amendments in blue-green infrastructure soils could off-set anthropogenic greenhouse gas emissions to alleviate climate change. In this 3-year study, the effects of wheat straw and its biochar on carbon sequestration in an urban landscaping soil were investigated under realistic outdoor conditions using two large-scale lysimeters. Both amendments were carried out by incorporating pellets at 0–15 cm soil depth with an equivalent initial total carbon input of 2% of the dry soil weight. Soil carbon, carbon isotope ratios, dissolved carbon in leachates, CO2–C emissions, carbon fixed in above ground vegetation, soil water content, soil bulk electrical conductivity, and water infiltration rates, were then compared between the 2 lysimeters. After 3 years, we observed that, despite having a 17.2% lower vegetation growth, soil organic and inorganic carbon content was higher by 28.8% and 41.5%, respectively, in biochar as compared to wheat straw amended soil. Carbon isotope analysis confirmed the greater stability of the added carbon in the biochar amended soil. Water content was on average 23.2% and 13.0% in the straw pellet and biochar amended soil, respectively, whereas water infiltration rates were not significantly different between the two lysimeters. Overall, the incorporation of wheat straw biochar into soil could store an estimated 30 tonnes of carbon per hectare in city blue-green infrastructure spaces. Interviews involving institution stakeholders examined the feasibility of this biochar application. Stakeholders recognized the potential of biochar as an environment-friendly means for carbon offsetting, but were concerned about the practicality of biochar production and application into soil and increased maintenance work. Consequently, additional potential benefits of biochar for environmental management such as improving the quality of polluted run-off in stormwater treatment systems should be emphasized to make biochar an attractive proposition in sustainable urban development.

Seasonal variation modifies the spatial patterns of soil microbial community structure and enzyme activity in a meadow steppe

Understanding how spatial heterogeneity in soil microbial community structure and enzyme activities vary seasonally, and identifying the underlying mechanisms, are crucial for predicting how soil organic matter dynamics and nutrient cycling may respond to environmental change. We examined spatial variability in microbial community structure and enzyme activity and measured associated changes in plant biomass, soil microclimate, soil nutrients and other soil characteristics for 75 sampling points across a 15 × 15 m area of a Leymus chinensis meadow steppe in northeastern China over three seasons (summer, fall and spring). We observed seasonal variation in the spatial patterns of soil microbial community structure and enzyme activity, and the plant and soil variables associated with this variation also changed over time. Specifically, the microbial community structure exhibited strong spatial dependence, with high a relative spatial variance [C / (C + C0) ≥ 0.9] in summer, whereas it was more homogeneous in spring and fall. In summer, the spatial patterns of plants, soil dissolved inorganic N and dissolved organic C were the most significant predictors of spatial variation in microbial community structure. In fall, a mix of plant and soil physical explanatory variables explained 22–46 % of the spatial variation in microbial community structure. Meanwhile, only soil physical variables (soil bulk density and electrical conductivity) were strongly associated with spatial variation in microbial community structure in spring. The spatial links between microbial community structure and enzyme activity were reshaped throughout the growing season. We observed strong spatial links between soil microbial community structure and enzyme activity in spring and fall. In summer, the association between soil enzyme activities and microbial biomass was decoupled, indicating that microbial biomass showed higher turnover than soil enzymes at this time. Overall, our results reveal the drivers of spatial variation in soil microbial community structure and enzyme activity shift seasonally, highlighting the value of seasonal sampling to accurately estimate the heterogeneity and complexity of ecosystem-level processes in grasslands.

Soil water and solute transport in an Andosol apple orchard including the dormancy period in a snowy cold region

Early spring corresponds to the snowmelt season in apple orchards of the northern hemisphere. This has a significant effect on the initial growth of shoots and flower buds of apple trees. Understanding the soil environment of the orchard during the non-growth period as monitored by farmers is important for managing year-round apple production. However, the details of mass transport, such as that of soil water and solute, during the non-growing season in the Andosols remain unclear. This study conducted soil environment monitoring in an Andosol apple orchard in Aomori Prefecture, Japan, during the non-growing season in winter to examine the year-round changes in the soil environment, using a field monitoring system that is necessary for understanding the soil environment. Volumetric water content, soil bulk electrical conductivity, and soil temperature were measured, and the cumulative changes in total soil moisture (ΣΔTSM) were calculated from the monitored volumetric water content. Results showed that although ΣΔTSM tended to increase (i.e., dry out) annually with periodicity, the variation was small compared to that of apple orchards with gravelly brown forest soil. These results could significantly influence fertilization management of apple orchard soil during the summer drought season and early spring when the roots of apple trees begin taking up nutrients. In particular, it was revealed that if sufficient nutrients remain in the soil pore water in early spring, the negative impact of excessive fertilization on the surrounding environment can be reduced. Therefore, this study constitutes an innovative step in the implementation of field monitoring system to understand the details of mass transport in the Andosol apple orchard soil.

Yield Performance of Wheat Under Different Practices of Tillage and Integrated Inorganic and Organic Fertilizers

Tillage management and fertilizer application are important components of wheat plant growth and productivity. Yet limited data are available on the consequences of simultaneous tillage and integrated fertilization on wheat production and soil chemical characteristics in the heavy soil of Sothern parts of Iraq. Hence, split-split plots were used to conduct a field experiments at two locations. The primary plots were divided into three tillage techniques that are no tillage (NT), tine cultivator (TC) and moldboard plow (MP). Five selected combinations of organic and inorganic nutrient sources were arranged in sub plots including the traditional chemical fertilizer application of nitrogen, phosphorus and potassium (CF), farm yard manure (FYM), poultry manure (PM), 50% CF+FYM and 50% CF+PM application, in addition to control treatment, and three wheat cultivars (Al-Rasheed, IPA-99 and Abu Ghraib-3) were allocated to sub-sub plots. The results showed positive superiority of MP and TC in the growth parameters, yield components, wheat yield and some soil properties at both experimental locations. Likewise, the MP and TC had the lowest bulk density, while MP had the lowest electrical conductivity and the highest soil pH. The results also revealed that organic and inorganic amendments affected plant growth, yield components, grain yield significantly. The 50% CF+PM and 50% CF+FYM gave significantly higher thousand grain weight, spikes number at the 2nd location, wheat yield, and tillers per square meter at the 2nd location. Furthermore, soil bulk density, pH and electrical conductivity were significantly affected by all organic and inorganic treatments. The results also indicated that the highest spikes number, grain yield, chlorophyll content SPAD were recorded by IPA-99 cultivar at both locations. Moreover, under experiment conditions, the flag leaf chlorophyll content was significantly related to grain yield.

Development of a crop water use monitoring system using electromagnetic induction survey

Monitoring soil water use at the plot level is essential for studying the plant’s response to drought or irrigation. However, the current soil monitoring system using moisture sensors is impractical. Soil electromagnetic induction (EMI) surveys can be a rapid, convenient, and non-invasive solution for monitoring soil moisture changes at the plot level. This study developed a crop water use monitoring system for the plot level using an EMI instrument that collects measurements at 0, 20, 40, 60, and 80 cm above the ground surface. The EMI data were converted to bulk soil electrical conductivity (σ) to the depth 1.5 m via an inversion technique and correlated with measured volumetric moisture contents. The EMI system was first tested for variation in ambient temperature. Within the temperature range of 25.5–34 °C, the standard deviation varied between 0.84 and 3.45 mS m−1 with coefficient of variations 1.54–9.26%. The system was then tested on a field trial at Narrabri, New South Wales, Australia, to measure the water use of chickpea genotypes grown over a season. The total water use of chickpeas obtained from EMI surveys correlated highly with values obtained from the Neutron Moisture Meter (NMM) (R2 = 0.73). Time-series of water content, as measured by the EMI survey, could differentiate the water use of different genotypes. In conclusion, the EMI survey is an efficient technique for monitoring crop water use.

Causes and implications of the seasonal dissolution and precipitation of pedogenic carbonates in soils of karst regions – A thermodynamic model approach

Red Mediterranean Soils developed over carbonate rocks can precipitate pedogenic carbonates at the base of their profiles, forming an evolutionary stage of calcretes. We studied a 0.6 m deep soil profile in Dalmatia (Croatia) where the lowest section of the soil is a calcic horizon formed by diffuse calcite particles and small nodules. These nodules record different events of dissolution and precipitation. Using a 3-month period of soil environmental monitoring, where soil temperature, soil water content, soil bulk electrical conductivity and soil air CO2 were measured, we implemented a thermodynamic model for dissolution and precipitation of calcite in the soil. The simulation shows a stage dominated by calcite dissolution during spring and early summer followed by a stage dominated by calcite precipitation. Soil air CO2 is the main control of the calcite reactions, with concentration of solutes also being of some importance during the stage of calcite precipitation. Soil water content and temperature, both affect soil air CO2. Precipitation events also have high-frequency impact on soil air CO2, but the response is complex. The model enables soil water solutions to be supersaturated in relation to calcite without precipitation of that mineral. Simulated soil water reached variable values of supersaturation in relation to calcite before its precipitation was triggered, suggesting that there is no fixed threshold value for the precipitation of calcite in a particular soil. During the 3-month simulated period, 83% of the calcite dissolved was reprecipitated as pedogenic carbonate. Most of the initially dissolved calcite, was expected to be diffuse pedogenic carbonate particles, although nodules and bedrock at the base of the soil should also have contributed to the solutes dissolved. Therefore, karst landscapes where soils have pedogenic carbonates are expected to record less denudation rates than those regions without calcretes.

Effects of Vermicompost Application on Growth and Heavy Metal Uptake of Barley Grown in Mudflat Salt-Affected Soils

China is facing a shortage of arable land resources, and the mudflat salt-affected soil along the east coast of China is an important reserve arable land resource. In this study, we conducted a randomized field trial to investigate the effects of vermicompost application rate (0, 25, 50, 125, and 250 t ha−1) on barley growth and heavy metal accumulation in mudflat salt-affected soil. We found that vermicompost application decreased bulk density, electrical conductivity (EC), and pH of mudflat salt-affected soil while increasing its organic carbon, nitrogen, and phosphorus contents. With the increase in vermicompost application rate, the yield of grain and total biomass of barley plants increased. The yield of grain in the vermicompost application treatments of 25, 50, 125, and 250 t ha−1 increased by 66.0%, 226.0%, 340.0%, and 512.0%, respectively, relative to the control. In addition, the concentrations of heavy metals (Cd, Cr, Cu, and Zn) in mudflat salt-affected soil and barley plant increased as the vermicompost application rate increased.

Effect of Gas Flaring on Physico-Chemical Properties of Soil under Tea Plantation in Assam, India

Gas flaring is a major contributor to the emission of toxic gases and other gaseous pollutants into the atmosphere. A study was undertaken to establish gas flaring effects on physic-chemical properties of soil under tea plantation in Assam, India. The experimental plot was laid out in 5 x 2 factorial RCBD. The experiment was carried out in small tea grower’s gardens adjacent to OCS-6 at Merbil Majuli and Kothaloni OCS in Dibrugarh district of Assam in the year 2019-20. The experimental plots were laid out at 11 metres away from the gas flaring point. Plots were selected at an interval of 20 metres within the experimental design i.e. D1 (11-31m), D2 (31-51m), D3 (51-71m), D4 (71-91m) and DC (150-170m) where, DC denotes control plot. Soil samples for the study were obtained for two tea growing season i.e. rainy and autumn season from the selected gardens. Soil physical parameters such as bulk density, porosity, hydraulic conductivity, soil temperature and soil moisture and chemical parameters such as pH, organic carbon content, available NPK and electrical conductivity of both effected and control plots were evaluated in the laboratory to check the effect of gas flaring and the results obtained were compared with those from the control plot. The results showed that the soil temperature, soil moisture content, soil organic carbon and available NPK of both Merbil Majuli and Kothaloni were significantly affected by gas flaring with respect to distances. But, the bulk density, soil porosity, hydraulic conductivity, soil pH and electrical conductivity of soil were not affected by gas flaring.

Influences of grassland to cropland conversion on select soil properties, microbiome and agricultural emissions

Context Conversion of grasslands to croplands can usually result in the degradation of soils and increased greenhouse gas (GHG) emissions such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). However, little is known about the impacts of grassland conversion to recently tilled croplands on soils and GHG fluxes. Aims A field experiment was established in 2016 to evaluate the impacts of grassland conversion to tilled cropland under different landscape positions (upslope, backslope, and footslope) on select soil properties and soil GHG fluxes. Key results The findings showed that the grassland conversion significantly increased soil bulk density and electrical conductivity but reduced pH and total nitrogen (TN). The conversion impacted soil biome community grassland and tilled croplands. The landscape position significantly impacted soil pH (footslope &lt; upslope) and TN (footslope &gt; upslope). The grassland conversion significantly decreased soil CO2 fluxes, but increased soil CH4 and N2O fluxes. The landscape position significantly impacted soil CO2 (footslope &gt; upslope and backslope) and CH4 (upslope &gt; footslope and backslope) fluxes for some periods. Soil CO2 and N2O fluxes generally followed upward and downward trends over time, respectively. Conclusions These results indicate that grassland conversion was able to lose soil N, increase soil compaction, acidity, salts, and soil N2O and CH4 fluxes, and decrease the diversity of abundant genera and CO2 fluxes. Footslope increased TN, soil acidity, CO2, and CH4 fluxes, compared with upslope and backslope. CO2 fluxes under grassland and tilled cropland significantly increased over time, whereas N2O fluxes under grassland significantly reduced. Implications Conversion of grassland to tilled cropland significantly impacted on sol quality. It caused a loss in soil N and increased soil compaction, acidity and salts. Grassland conversion also decreased the abundance and diversity soil microbiome.

Rhizosphere soil properties, microbial community, and enzyme activities: Short-term responses to partial substitution of chemical fertilizer with organic manure

The partial substitution of chemical fertilizers with organic manure has positive effects on crop productivity and sustainable development. Nevertheless, few studies have focused on major grain crops. Herein, we report the short-term effects of the partial substitution of chemical fertilizers with organic manure on the physicochemical properties, microbial community, and enzyme activities in the rhizosphere soil of a maize (Zea mays L.) field. A decrease in soil bulk density, pH, and electrical conductivity, concomitant with an increase in soil urease, invertase, and alkaline phosphatase activities, and a high level of nutrients were observed in organic manure-treated soil. The influence of the organic substitution treatment on bacterial diversity was greater than that on fungal diversity, particularly on alpha diversity. Among dominant bacterial phyla, Actinobacteria abundance changed the most, with significantly increase under organic manure treatment. In turn, among fungi, only Ascomycota responded substantially to organic substitution. Binding spatial ordination analysis revealed that relative soil water content and soil organic carbon, and nitrate and total nitrogen contents had a stronger effect on bacteria and fungi, respectively, than any other soil physicochemical property. Additionally, the changes in bacterial and fungal communities influenced soil enzymatic activities. Moreover, partial least squares path model revealed that soil physicochemical properties indirectly affected soil enzymatic activities by their direct effects on microbial (both bacteria and fungi) community. Overall, our results indicate that the substitution of chemical fertilizers by organic manure changed the composition of the soil microbial community, and that the effects of the substitution were more significant on bacteria than on fungi.

Synergetic variations of active layer soil water and salt in a permafrost-affected meadow in the headwater area of the Yellow River, northeastern Qinghai–Tibet plateau

The coupling effects and mechanisms of water, heat, and salt in frozen soils are considered to be one of the core scientific issues in frozen soil studies. This study was based on in situ observation data of active layer soil volumetric water content (VWC), temperature, and bulk electrical conductivity (EC) obtained at an alpine meadow site from October 2016 to November 2019. The site is located in the headwater area of the Yellow River (HAYR). We analyzed the synergetic variations of active layer soil VWC, temperature, and bulk EC during the freeze and thaw processes and discussed the underlying mechanisms. When the thaw process occurred from 10 to 80 cm depths, the VWC and bulk EC at a 10 cm depth showed synchronous high-frequency fluctuations and both increased linearly. The linear decreasing rate of the VWC (bulk EC) at an 80 cm depth in the freeze depths between 0 and 40 cm was 2 (1.6–2.3) times that of the VWC (bulk EC) at an 80 cm depth in the freeze depths occurring 0–10 cm. As soil temperature decreased in the frozen layer, unfrozen water content (bulk EC) decreased nonlinearly along with the absolute value of soil temperature (|T|), following a power (logarithmic) function. This study provided data that partly elucidate the interactions among permafrost, meadow, and ecohydrological processes in the HAYR. Also, our results can be used as a scientific basis for decision making on the protection and restoration of alpine grasslands, as well as for soil salinization studies.

Investigation of Soil Physicochemical Effects on the Corrosion of Buried Iron Pipes

Soil corrosivity was an active problem of water pipeline damaged by corrosion that affects the performance of pipe manufacturers. In Addis ababa, groundwater pipelines were facing breakage and like due to corrosion damage of the pipes. The population of nearly four million were facing a shortage of clean and continuous water supply. Maintenace and replacing old pipes with new ones increased additional cost and delay of water supply for the city. For this investigation of corrosion, causes were conducted which soil property is the one factor. Investigation of soil corrosivity for a given specific location before installation is important to design robust pipes that can serve for long life. Soil physicochemical behaviors of the soil parameters were pH, moisture content, and electrical resistivity for any type of soil. In addition, soil bulk density, total nitrogen, soil texture, and electrical conductivity were also the main factors to be studied. The laboratory result indicated that pH of 6.98-7.04, moisture content of 23.7-37.5%, and electrical conductivity of 0.105-313 ds/m were observed. Total nitrogen was small as 0.06-0.10 for a type of soil were class and loam soils. From the analysis of eight soil samples taken from different cities. The results show that the corrosivity behavior of buried iron pipes in the capital city of Ethiopia was moderately corrosive. As confirmed from various soil samples tested from corroded pipes at different depths of 40, 80, and 120 cm. The influence of soil corrosiveness factors initiates pits formation and propagates its width and depth on the surface of pipes.