Volumetric Soil Water Content Research Articles

Cenostigma pluviosum Tree Stem Growth and Carbon Storage in a Subtropical Urban Environment: A Case Study in Sao Paulo City

Our aim is to contribute to understanding the role of subtropical trees on carbon storage and CO2 removal in the city of Sao Paulo/Brazil, besides highlighting the surrounding environment implications to sibipiruna trees (Cenostigma pluviosum)’s performance. The case study was conducted with three trees, one planted on a sidewalk in Pinheiros neighborhood, a highly sealed area, and two in a green area, the Ibirapuera Park. To define the stem basal area growth and its pattern, local measurements were taken over a year and a segmented linear regression model was adjusted. The stem growth dependency on microclimate was tested by a Spearman Correlation. The trees’ active stem growth presented a similar pattern. The soil volumetric water content and soil temperatures were the variables with more impact. The total mean radial stem growth for the IBIRA1 and IBIRA2 trees was 1.2 mm year−1 and 3 mm year−1, while at PIN1 it was 1.3 mm year−1. The total biomass increment in IBIRA1 and IBIRA2 was 4.2 kg C year−1 and 12.8 kg C year−1, while in PIN it was 4.9 kg C year−1 and the removal was 15.3 C year−1, 47.1 kg CO2 year−1 and 17.9 kg CO2 year−1, respectively. The results indicated that the land cover difference implies a significant interference with the promotion of carbon fixation and CO2 removal, demonstrating that planting urban trees in soils with better water storage conditions is more efficient.

Effect of soil compaction on the measurements of complex dielectric permittivity spectrum with an open-ended antenna probe and the coaxial cell system

The paper proposes the use of dielectric spectroscopy to measure changes in dielectric permittivity for soil subjected to compression. Density-dependent dielectric permittivity characteristics of soils for the entire range of obtained density, and thus for a significant parameter of soil properties corresponding with ideal conditions for plant growth as well as those inhibiting their growth were presented. Measurements were carried out for three soil types with different moisture content using an open-ended antenna probe (OE-A), operating in the frequency range of 20 MHz–1.2 GHz and a coaxial cell system in frequency range of 20 MHz–3 GHz. Experimental results showed that an increase in bulk density and volumetric water content of soil affects the complex dielectric permittivity spectrum – a model for this relationship was proposed. Soil dielectric permittivity as a parameter reflecting soil moisture and density can be useful in assessing soil quality.

Effects of drip irrigation coupled with controlled release potassium fertilizer on maize growth and soil properties

Drip irrigation and the application of controlled-release fertilizers are two effective and important technical measures to conserve water and fertilizer resources and promote the growth and development of maize. However, the underlying physiological mechanism of how drip irrigation combined with controlled release potassium chloride affects maize production and soil properties remains unknown. In different soil water conditions, pot experiments were conducted during the summer maize growing season in 2022 and 2023 to measure maize grain yield, irrigation water productivity, apparent recovery efficiency of potassium, plant physiological characteristics, and soil enzyme activities under the coupling of two irrigation methods (flood irrigation and drip irrigation) and three potassium fertilizer types (potassium chloride (KCl), controlled release potassium chloride (CRK), and 70 % CRK mixed with 30 % KCl). The results revealed that drip irrigation had 6.5–8.1 % and 6.7–9.4 % higher average soil volumetric water content and 3.8–8.1 % and 4.5–13.0 % higher irrigation water productivity than flood irrigation in the two maize growth seasons, respectively. Under the drought conditions, the treatments of 70 % CRK-30 % KCl application led to a significant increase in maize yield by 9.5–10.7 % and 12.2–16.8 % and apparent recovery efficiency of potassium by 8.3–14.2 % and 10.7–10.8 % compared to CRK application treatments in 2022 and 2023, respectively. Compared with the other treatments, the treatment of drip irrigation coupled with 70 % CRK-30 % KCl application under drought conditions (DIDMK) resulted in 4.5–28.7 % and 1.1–31.9 % higher grain yield, 8.2–64.4 % and 8.6–66.8 % higher irrigation water productivity, and 5.9–28.0 % and 6.7–18.9 % higher apparent recovery efficiency of potassium in 2022 and 2023, respectively. Meanwhile, the leaf net photosynthetic rate, rubisco, catalase, peroxidase, and soil enzyme activities of DIDMK treatment were also maintained at a high level. Our results indicated that drip irrigation coupled with 70 % CRK-30 % KCl application were the optimal water and potassium supply modes for maize production. This study can provide useful information regarding summer maize sustainable production and provide theoretical and technical support for summer maize irrigation and potassium fertilizer application technologies in water-scarce regions of China and other similar regions around the world.

Effects of Conversion of Rubber to Oil Palm Plantations on Soil Properties and Hydrological Dynamics in the Low Country Wet Zone of Sri Lanka

A study was conducted to investigate the impacts of converting rubber plantations into oil palm plantations on soil properties and soil hydrology. Soil organic carbon (SOC), bulk density (BD), aggregate stability (AS), saturated hydraulic conductivity (Ks), soil water retention, texture, thermal properties, and pH were determined using soil samples collected from different depths of a twelve-year-old oil palm and rubber cultivated fields located in low country wet zone of Sri Lanka. In each field, volumetric water content (VWC) of soil was continuously measured at four soil depths (0-25, 25-50, 50-75, and 75-100 cm) over a seven-month period. While the study revealed a 40% lower SOC in 0-25 cm soil layer of the oil palm field compared to the rubber field, no significant changes were observed in BD, porosity, pore size distribution, AS, and Ks for the two fields. However, the volumetric heat capacity of rubber grown soil was significantly higher than that of the oil palm grown soil. Oil palm utilized the most water from 25-75 cm soil layer; whereas, rubber extracted more water from deeper soil layers (75-100 cm). Soil water depletion in oil palm field was faster during dry periods than in rubber fields highlighting the need to examine the soil water extraction patterns of oil palm during extended dry spells in future studies. Overall, the conversion of rubber into oil palm plantations showed no significant impact on most of the soil properties and soil hydrology after twelve years of conversion.

Drivers of cocoa yield and growth in young monoculture and agroforestry systems

CONTEXTThe expansion of cocoa farming has been linked to deforestation and biodiversity loss in West Africa. Agroforestry systems could potentially increase the sustainability of cocoa production. However, despite the long history of cocoa cultivation in agroforestry systems, the exact mechanism or the combination of factors that drive cocoa growth and yield in these agroecosystems, especially at the cocoa establishment stage, is unclear. OBJECTIVEThe present study aims to analyse how resource availability, stand characteristics and cocoa tree morphology interact to determine the performance of cocoa during the establishment phase among different cocoa cultivation systems. METHODSWe studied seven different agroforestry systems and one monoculture system in 53 plots located in a 12-ha cocoa agroforestry trial recently established in Côte d'Ivoire. We characterized each system with 16 variables that described five system components: 1) cocoa yield (number of pods, pods weight, number of productive trees) and cocoa growth (basal diameter), 2) cocoa tree morphology (crown depth, diameter, area, and volume), 3) stand characteristics (number and size of shade trees), 4) light (leaf area index) and 5) water (soil volumetric water content). We used a Structural Equation Modelling (SEM) approach to understand and quantify interactions between the five components. RESULTS AND CONCLUSIONSThe models were able to largely explain cocoa early yield and juvenile growth variability (respective determination coefficients: 0.45 and 0.92). We observed improved cocoa establishment in certain designs of agroforestry systems compared with monoculture. However, SEM revealed that stand characteristics (i.e. increase in the number and height of shade trees) had a negative effect on cocoa yield and growth via changes in cocoa tree morphology, having path coefficients of −0.48 and − 0.72, respectively. Conversely, we found a positive relationship between the cocoa tree morphology and cocoa early yield, for which the path coefficient was 0.74, the strongest relation. Cocoa tree morphology was more important than stand characteristics, leaf area index, and soil volumetric water content in controlling cocoa yield and growth. Taken together, our results suggest a competition for space between shade trees and cocoa plants. Finding the optimal design of agroforestry systems can help enhance cocoa establishment in the first years, improving the long-term performance of the system. SIGNIFICANCEThis finding suggests that the competition effect depends on spatial planting pattern and species composition, offering an opportunity to meet the goals of a sustainable intensification of cocoa plantations through the design and management of optimal agroforestry systems.

Evaluation of agricultural non-point source pollution using an in-situ and automated photochemical flow analysis system

Off-line leachate collection from agricultural landscapes cannot guarantee precise evaluation of agricultural non-point source (ANPS) due to geospatial variations, time, and transportation from the field to the laboratory. Implementing an in-situ nitrogen and phosphorous monitoring system with a robust photochemical flow analysis is imperative for precision agriculture, enabling real-time intervention to minimize non-point source pollution and overcome the limitations posed by conventional analysis in laboratory. A reliable, robust and in-situ approach was proposed to monitor nitrogen and phosphorous for determining ANPS pollution. In this study, a home-made porous ceramic probe and the frequency domain reflectometer (FDR) based water content sensors were strategically placed at different soil depths to facilitate the collection of leachates. These solutions were subsequently analyzed by in-situ photochemical flow analysis monitoring system built across the field to estimate the concentrations of phosphorus and nitrogen. After applying both natural and artificial irrigation to the agricultural landscape, at least 10 mL of soil leachates was consistently collected using the porous ceramic probe within 20 min, regardless of the depth of the soil layers when the volumetric soil water contents are greater than 19%. The experimental results showed that under different weather conditions and irrigation conditions, the soil water content of 50 cm and 90 cm below the soil surface was 19.58% and 26.08%, respectively. The average concentrations of NH4+-N, NO3−-N, PO43− are 0.584 mg/L, 15.7 mg/L, 0.844 mg/L, and 0.562 mg/L, 16.828 mg/L and 0.878 mg/L at depths of 50 cm and 90 cm below the soil surface, respectively. Moreover, the comparison with conventional laboratory spectroscopic analysis confirmed R2 values of 0.9951, 0.9943, 0.9947 average concentration ranges of NH4+-N, NO3−-N, and PO43−, showcasing the accuracy and reliability of robust photochemical flow analysis in-situ monitoring system. The suggested monitoring system can be helpful in the assessment of soil nutrition for precision agriculture.

Carbon dioxide fluxes in Alpine grasslands at the Nivolet Plain, Gran Paradiso National Park, Italy 2017–2023

We introduce a georeferenced dataset of Net Ecosystem Exchange (NEE), Ecosystem Respiration (ER) and meteo-climatic variables (air and soil temperature, air relative humidity, soil volumetric water content, pressure, and solar irradiance) collected at the Nivolet Plain in Gran Paradiso National Park (GPNP), western Italian Alps, from 2017 to 2023. NEE and ER are derived by measuring the temporal variation of CO2 concentration obtained by the enclosed chamber method. We used a customised portable non-steady-state dynamic flux chamber, paired with an InfraRed Gas Analyser (IRGA) and a portable weather station, measuring CO2 fluxes at a number of points (around 20 per site and per day) within five different sites during the snow-free season (June to October). Sites are located within the same hydrological basin and have different geological substrates: carbonate rocks (site CARB), gneiss (GNE), glacial deposits (GLA, EC), alluvial sediments (AL). This dataset provides relevant and often missing information on high-altitude mountain ecosystems and enables new comparisons with other similar sites, modelling developments and validation of remote sensing data.

Evaluation of electrical resistivity of cement-based materials using time domain reflectometry

Time domain reflectometry (TDR) is a widely used electromagnetic wave–based technique for evaluating the volumetric water content of soils, although its use for moisture measurement in cement-based materials is limited. This paper presents a comprehensive analysis of the electrical properties of cement pastes and cement paste–slime mixtures using TDR. Both TDR and electrical resistivity probes are used to estimate the electrical resistivities of various cement-based materials over their curing period. The study reveals that these properties are significantly influenced by curing time, water–cement ratio, and water–solid ratio. The experimental results demonstrate a consistent increase in electrical resistivity with curing time, underscoring the significant role of hydration-induced water evaporation and microstructural changes. Furthermore, the interpretation of characteristic voltages on the TDR waveform significantly influences resistivity estimates. Thus, this study highlights the potential of TDR in accurately evaluating the electrical resistivity of cement-based materials.

Root Zone Water Management Effects on Soil Hydrothermal Properties and Sweet Potato Yield.

Sufficient soil moisture is required to ensure the successful transplantation of sweet potato seedlings. Thus, reasonable water management is essential for achieving high quality and yield in sweet potato production. We conducted field experiments in northern China, planted on 18 May and harvested on 18 October 2021, at the Nancun Experimental Base of Qingdao Agricultural University. Three water management treatments were tested for sweet potato seedlings after transplanting: hole irrigation (W1), optimized drip irrigation (W2), and traditional drip irrigation (W3). The variation characteristics of soil volumetric water content, soil temperature, and soil CO2 concentration in the root zone were monitored in situ for 0-50 days. The agronomy, root morphology, photosynthetic parameters, 13C accumulation, yield, and yield components of sweet potato were determined. The results showed that soil VWC was maintained at 22-25% and 27-32% in the hole irrigation and combined drip irrigation treatments, respectively, from 0 to 30 days after transplanting. However, there was no significant difference between the traditional (W3) and optimized (W2) drip irrigation systems. From 30 to 50 days after transplanting, the VWC decreased significantly in all treatments, with significant differences among all treatments. Soil CO2 concentrations were positively correlated with VWC from 0 to 30 days after transplanting but gradually increased from 30 to 50 days, with significant differences among treatments. Soil temperature varied with fluctuations in air temperature, with no significant differences among treatments. Sweet potato survival rates were significantly lower in the hole irrigation treatments than in the drip irrigation treatments, with no significant difference between W2 and W3. The aboveground biomass, photosynthetic parameters, and leaf area index were significantly higher under drip irrigation than under hole irrigation, and values were higher in W3 than in W2. However, the total root length, root volume, and 13C partitioning rate were higher in W2 than in W3. These findings suggest that excessive drip irrigation can lead to an imbalance in sweet potato reservoir sources. Compared with W1, the W2 and W3 treatments exhibited significant yield increases of 42.98% and 36.49%, respectively. The W2 treatment had the lowest sweet potato deformity rate.

Winter cover crop performance in the Southern Piedmont region of South Carolina

AbstractCover crops (CCs) offer in‐field and environmental benefits when integrated into cropping systems. Low CC adoption in the Southern Piedmont region of South Carolina is partially due to the lack of information on CC performance and benefits within the region. To address this, eight winter CCs and a fallow/pigweed (Amaranthus spp.) treatment were investigated for their influence on soil temperature, volumetric water content (VWC), percent cover, biomass, and the occurrence of soil water repellency (SWR). A randomized complete block design experiment was conducted in the fall and winter of 2021–2022 (EXP A) and repeated in 2022–2023 (EXP B). Experiments were treated separately as methods were revised for EXP B. CCs minimally influenced soil VWC over both experiments with no consistent trend. CC did not influence soil temperatures during EXP A. In EXP B, the fallow/pigweed had the highest soil temperatures on two (out of 10) measuring events (p < 0.05). No SWR was found in either experiment. Establishment and fresh and dry CC biomass were most likely influenced by air temperatures and daylight hours driving germination during days with minimal rainfall. In both experiments, annual rye (Lolium multiflorum) produced cover quickly and yielded high biomass. Crimson clover (Trifolium incarnatum) took longer to establish but also yielded one of the highest biomasses. This study demonstrated that winter CCs had little influence on soil physical properties and that while cereal rye (Secale cereale) is a common CC utilized for erosion control, the greater biomass and surface roots of annual rye make it a superior CC for use in Southern Piedmont agroecosystems.

Temporal variability in water content, temperature, and electrical conductivity of sandy soil: Responses to soil-improving cropping systems (SICS)

There is little information on the effect of soil-improving cropping systems (SICS) on the temporal variability of soil volumetric water content (WC), temperature (T), soil temperature amplitude (A_T), and electrical conductivity (EC) in low-quality sandy soils although they are increasingly being used in agriculture. The objective of this study was to determine the effects of the following SICS: liming (L), leguminous catch crops for green manure (LU), farmyard manure (M), and liming + leguminous catch crops for green manure + farmyard manure together (LLUM), and the control (C) on temporal changes in the three properties simultaneously in a field experiment on sandy soil established in 2016 in Poland. The monitoring was performed using TEROS 12 sensors in the soil layers of 5–10, 20–25, and 30–35 cm from 25 April 2019–30 April 2020 with spring wheat as the main crop. The results showed that the average WC over the entire investigation period in the 5–10 cm layer was 0.206 m3 m–3 in the control and increased in the L, LU, M, and LLUM variants to 0.245, 0.219, 0.241, 0.262 m3 m–3, respectively. The highest WC was recorded in the LLUM system during most of the investigation period. The average T in the 5–10 cm layer increased in L, LU, and M by 0.221–0.262 °C and in LLUM by 0.052 °C. The average monthly soil temperature amplitudes in the soil layer 5–10 cm tended to be higher under all SICS vs. C except LLUM vs. C. The average EC in the 5–10 cm layer in variant C (0.066 mS cm–1) increased in the L, LU, M, and LLUM systems to 0.067, 0.090, 0.151, and 0.107 mS cm–1, respectively. The shapes of the temporal variability of WC and EC were similar in all SICSs, while the increase in the response to the combined effects of the SICSs and precipitation during the growing season was greater for the EC. The temporal variability of all soil properties in response to the SICSs and weather course and their averages declined with depth. The amplitudes of soil T in all treatments were lowest in the 30–35 cm layer. This study provides helpful information for the selection of the most suitable SICS in terms of soil properties influencing productivity and other soil functions.

Light thinning effectively improves forest soil water replenishment in water-limited areas: Observational evidence from Robinia pseudoacacia plantations on the Loess Plateau, China

Soil water plays a key role in vegetation growth and recovery, mainly replenished by rainfall in the water-limited areas. Thinning is an important practice for forest reconstruction and soil water regulation. However, the effects of different thinning intensities on the dynamics of soil water and its replenishment by rainfall have been inadequately quantified, which could provide a guide for reasonable thinning intensity determination for in high-density forests from a hydrological perspective. In this study, one nonthinning plot and 5 plots with different thinning intensities, i.e., 35 % (light), 45 % (medium), 55 % (moderate), 65 % (heavy) and 80 % (extremely heavy) in Robinia pseudoacacia plantations, which are widely planted on the Loess Plateau, were set up. The volumetric soil water content (SWC) at 0–200 cm depths and rainfall were observed simultaneously and continuously for up to two years. The soil properties and vegetation structure in each plot were also measured regularly. The results showed that (1) the SWC in all the thinning plots was significantly greater than that in the nonthining plot (P < 0.05). (2) The replenishment increased with increasing thinning intensity, and then decreased after reaching a maximum at T35 % under most rainfall events except for light events. (3) The variations in the soil water response characteristics among the plots with different thinning intensities were mainly significantly correlated with the initial soil water content (ISWC), leaf area index (LAI) and understorey vegetation characteristics (P < 0.05). (4) Based on the relationship between soil water replenishment and retention with thinning intensity and stand density, quantitative equations were fitted to determine the reasonable thinning intensity (22–28 %) and retained stand density (1019–1091 trees/ha), respectively. Our study concluded that thinning could effectively improve soil water, especially light thinning, which could obviously enhance the replenishment of soil water by rainfall in Robinia pseudoacacia plantations. This study can provide a reference for determining forest thinning intensity or stand retention density, which is beneficial for water and reforestation management in water-limited regions.

Effects of gravel-sand and plastic film mulching on soil water and temperature retention in cold and arid regions without irrigation

Gravel-sand mulch (GSM) and plastic film mulch (PFM) are important ways of farming in cold and arid regions without irrigation. Nevertheless, there has been a lack of studies of the system response to live weather conditions. To quantify the effects of GSM and PFM on soil moisture and temperature retention, in-situ monitoring experiments were carried out in the arid belt of central Ningxia, China, using continuous monitoring of the field soil water and meteorological conditions at a 30-mimute time-step under three treatments: a bare soil (CK), soil covered by a layer of GSM, and soil covered by GSM and a layer of plastic film (i.e., GSM + PFM). Results show that: (1) With a limited precipitation of 221 mm during the growing season, the average volumetric soil water content (SWC) in the top 30-cm soil layer was lowest for CK, medium high for GSM, and highest for GSM + PFM. Compared to CK, the soil water storage increased by 54 % under GSM and 75.2 % under GSM + PFM; (2) The most frequently occurring low-intensity rainfalls are more efficiently stored in soil under GSM + PFM; (3) Similarly, the soil temperature was significantly increased under GSM and GSM + PFM conditions. Compared to CK, the average soil temperature in the top 5-cm layer increased by 2.5 °C under GSM and 4.8 °C under GSM + PFM during the germination period, which had effectively extended the growing season for about 30 and 50 days, respectively; (4) Although dewfall is only 4 % of rainfall, the total number of dew day was more than twice that of rain day. Thus, dewfall is a more frequent and dependable source of water for native plants and animals. Our results demonstrate that the benefits of GSM and PFM can be applied globally where either insufficient rainfall or low temperatures are limiting factors.

Time stability of soil volumetric water content and its optimal sampling design in contrasting forest catchments

Characterizing the temporal variation across a forest catchment soil volumetric water content (VWC) with different environmental conditions at different depths for different seasons requires a robust point-scale sampling strategy that balances monitoring cost with predicting accuracy. In the study, the most time-stable locations (MTSLs) using the time-stable concept and the minimum number of required samples (NRS) based on random selection method were studied to explore the optimal sampling design for catchment-mean VWC with an acceptable error (the relative bias (RBIAS) less than 10 %). VWC monitoring was conducted at approximately 25 plots throughout the year in five forest catchments with varying areas and VWC status. Results revealed that the number of MTSLs for mean-VWC estimation with RBIAS within 10 % was directly related to the spatial variability of VWC. Specifically, one MTSL was feasible for accurately estimating mean VWC at different depths in high-VWC catchments with area around or less than 100 ha; one MTSL was adequate for each depth in the catchment with moderate-level VWC; whereas more than one MTSL were necessary for each depth in low-VWC catchment with a larger are of 1800 ha. To identify the MTSL for each catchment, the location with mean VWC was typically situated at the mid-elevation or soil apparent electrical conductivity (ECa) at a certain spatial scale. The NRS for catchment-mean VWC could be determined based on the combination of VWC status, its temporal stability, and potential catchment size, and could be ranked based on the spatial variation of each catchment. If the MTSL cannot be guaranteed for a catchment, the NRS might be a better alternative for optimum sampling design. These finding could be useful in providing guidelines for optimizing VWC monitoring in forest catchments by sampling at a few selected locations representative of the catchment-scale behavior.

Precision Irrigation Soil Moisture Mapper: A Thermal Inertia Approach to Estimating Volumetric Soil Water Content Using Unmanned Aerial Vehicles and Multispectral Imagery

To address the issue of estimating soil moisture at a hyper-resolution scale, a methodology referred to as Precision Irrigation Soil Moisture Mapper (PrISMM), that includes three key components, is developed: high-resolution remotely sensed optical and thermal data, surface energy balance modeling, and site-specific soil analysis. An Unmanned Aerial Vehicle/System (UAV or UAS) collects high-resolution multispectral imagery in the Dallas–Fort Worth metropolitan study area. Orthomosaics are converted to thermal inertia estimates in a spatially distributed format using the remotely sensed data combined with a set of surface energy balance modeling equations. Using thermal and physical properties of soil gained from site-specific soil analysis, thermal inertia estimates were further converted from thermal inertia to daily volumetric soil water content (VSWC) with a horizonal resolution of 8.6 cm. A ground truthing dataset of measured VSWC values taken from a Time Domain Reflectometer was compared with model results, producing a reasonable correlation with an average coefficient of determination of (R2) = 0.79, an average root mean square error (RMSE) = 0.0408, and mean absolute error (MAE) = 0.0308. This study highlights a practical approach of estimating VSWC for irrigation purposes while providing superior spatio-temporal coverage over in situ methods. The authors envision that PrISMM can be implemented in water usage management by relating VSWC with weather forecasts and evapotranspiration rates to develop time-based spatially distributed irrigation management plans.

A slope management method by monitoring soil volumetric water content and its validation through numerical analysis

Landslides induced by heavy rainfall have become increasingly common in recent years. As the groundwater level rises, the safety factor of slopes tends to decrease. However, traditional monitoring methods, such as employing water-level (pressure) gauges in boreholes, require significant effort. Thus, this study proposes a slope management approach based on monitoring the volumetric water content of the ground surface. The monitored slope, approximately 20 m in height and 30 m in length, consists of topsoil mixed with grass roots and sand with a slight silt admixture, as revealed by two borehole investigations. Soil moisture meters were strategically installed at three locations along the slope (upper, middle, and lower sections) to gauge the volumetric water content. Observations indicated a sensitive increase in ground water content following rainfall. Furthermore, a three-dimensional Finite Element Method (FEM) analysis was employed to explore the correlation between rainfall (intensity and duration) and groundwater content. The FEM analysis also examined the impact of rainfall-induced changes in slope water content on the overall slope safety factor, utilizing 3D point cloud data to model the monitored slope. Qualitative agreement was observed between the monitoring and analysis results, highlighting a decrease in slope safety factor as slope water content increased. These findings underscore the potential of conveniently assessing slope safety factors based on the water content of a slope’s ground surface.

Temperature Effects in AMSR2 Soil Moisture Products and Development of a Removal Method Using Data at Ascending and Descending Overpasses

Soil moisture is among the most essential variables in hydrology and earth science. Many satellite missions, such as AMSR-E/2, have been launched to observe it in broader spatial coverage to overcome the shortage of in situ observations. However, the satellite soil moisture products have been reported to comprise errors caused by the so-called “temperature effects” widely observed in dielectrically measured in situ volumetric soil water content (SWC). In this work, we confirmed the existence of these errors in AMSR2 soil moisture products. A new algorithm was developed to remove these errors using satellite data at ascending and descending overpasses. The application of this algorithm to both satellite and in situ data of SWC and soil temperature at the Mongolia site shows that the difference between SWC values at ascending and descending overpasses caused by temperature effects is effectively removed. We assess the impact of this removal method on satellite data by comparing it with in situ data, utilizing metrics such as the correlation coefficient and other widely adopted evaluation methods. It is shown that the difference between the original and corrected in situ SWC is much smaller than that between AMSR2 and in situ SWC, either corrected or not. The results indicate that the metric values between the corrected AMSR2 and in situ SWC, after removing apparent differences caused by temperature effects, slightly improved compared to those between the original AMSR2 and in situ SWC. Though these findings imply that the removed errors may not be the most dominant, considering the current significant difference between AMSR2 and in situ SWC, the removal makes the ascending and descending data have close characteristics. It may allow using data at both ascending and descending overpasses and double the temporal resolution of AMSR2 SWC data.

Effects of cellulose nanofibers on soil water retention and aggregate stability

Innovative solutions that address global challenges such as water scarcity and soil erosion are critical for maintaining sustainable agriculture. Due to their water-absorbing and soil-binding properties, cellulose nanofibers (CNF) can be applied to soil to enhance soil water retention and aggregate stability. In this study, we analyzed the effects of the drying temperature, dosage, irrigation water quality, and soil type on the efficacy of CNFs. Our results revealed that CNF dried at 5°C is more effective at absorbing water than others, and adding 1% CNF enhanced soil water content up to 98%. The CNF samples absorbed water due to their hydrophilic molecular groups and morphological structure, as confirmed by Fourier-transform infrared spectroscopy and scanning electron microscopy. CNF addition increased the soil volumetric water content and prolonged water retention by 22 days in the paddy soil samples, highlighting its potential for drought-prone areas. Furthermore, irrigation water quality, such as pH and cation values, influenced the interactions between CNF and water molecules, suggesting adjustments to the water retention curve. In its hydrated state, CNF promotes colloid flocculation and binds to soil particles, thereby strengthening the bonds crucial for aggregate formation and stability. CNF enhanced macro-aggregate formation by up to 48% and 59% in the masa and paddy soil samples, respectively. Our study emphasizes the potential of CNF for water conservation, soil health, and overall agricultural sustainability.

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.

Moisture and mould growth risk of cross-laminated timber basement walls: Laboratory and field investigation

Reinforced concrete is a commonly used material for constructing basements in low-rise buildings or residential houses in Canada, and as the use of cross-laminated timber (CLT) advances, the door to think of an alternative basement material to offset greenhouse gas emissions associated with reinforced concrete is open. However, the evaluation of CLT durability in below-grade environments, specifically concerning moisture and mould development, remains an unexplored field in research. Hence, this paper aims to analyze CLT's moisture response and mould growth risk in below-grade environments using field and laboratory experiments. A laboratory experiment was carried out to test a waterproofing membrane solution selected to compose the wall assembly in the field experiment. A large-scale experimental CLT basement was built at a cohesive soil site in Edmonton, Canada. The field experiment involved monitoring the relative humidity, temperature, and soil volumetric water content of the CLT panels, which measure 3 m by 6 m in plan and 2 m deep. Data was collected for an extended period from June 2022 to July 2023. The VVT model, developed by Hukka and Viitanen (1999) and updated by Viitanen et al., 2011 to estimate the mould growth level, was used to predict the risk of mould growth. The laboratory experiment showed that the waterproofing membrane is suitable for protection against moisture in a still-water setup. Field experiment results suggested that the primary moisture source was below the basement floor when the floor was finished inadequately. The moisture content of CLT walls was significantly increased by floor flooding and decreased by heating the basement interior. The acceptable mould index of three was surpassed during periods of abundant water below the basement floor due to flood events, showing that the CLT panels were at risk of mould growth development.