Wetting Front Research Articles

Intermittent Drip Irrigation Soil Wet Front Prediction Model and Effective Water Storage Analysis

The depth and width of drip infiltration play a critical role in designing effective irrigation strategies. However, existing models primarily focus on continuous irrigation and fail to predict wetting patterns under intermittent drip irrigation. This study developed an infiltration model to estimate soil moisture depth and width under intermittent drip irrigation and identified strategies that enhance effective water storage. Indoor soil box simulations were conducted, with continuous drip irrigation as the control. Results showed that intermittent irrigation increased infiltration width and reduced depth, maximizing water storage efficiency. We recommend adopting an intermittent irrigation system with 1.5 h of irrigation followed by a 0.5 h interval, repeated four times. This system increased effective water storage by up to 16.23% compared to continuous irrigation. The proposed method is suitable for sandy loam farmland in southern Xinjiang and can significantly improve water use efficiency in arid regions.

Spontaneous imbibition in thin anisotropic fibrous media: Experiments and numerical modeling

In this study, we investigate the temporal and spatial evolution of wetting saturation during spontaneous imbibition in anisotropic fibrous porous media using both experimental and numerical methods. We present a novel experimental approach to systematically study spontaneous imbibition in these media, allowing for a comprehensive assessment of how microstructure influences wicking performance. The experimental method, which exhibits high reproducibility, was used to validate the numerical model. The numerical model was parameterized using only the porosity and filament diameter of the porous media in conjunction with the material properties of the imbibing fluid. The essential capillary saturation curve for the numerical model was derived using the pore morphology method. The numerical results effectively replicated the experimental results. Our experimental and numerical observations revealed a diffusive wetting front within the porous media, which progressively expanded and decelerated during the imbibition process. The results highlight the significant influence of filament size on the wetting saturation dynamics and the height of the wetting front during spontaneous imbibition.

Monitoring of stable isotope composition of precipitation reveals thunderstorm dynamics

ABSTRACT The summer of 2019 is particularly well known for the famous heatwaves that swept across the European continent, with its associated drought and record-breaking air temperatures. This was followed by powerful thunderstorms, characterised by hail and heavy rain that damaged the crops on a regional scale. Here, we investigated one of the largest storm cells, lasting more than 6 h, which struck southwestern Romania. High-temporal resolution sampling of storm precipitation was performed for stable isotope measurements, rainfall and air temperature, to follow the storm dynamics. Hydrogen and oxygen isotope measurements show an abrupt decreasing temporal trend followed by superimposed V-shaped patterns interpreted as reflecting moisture replenishment by successive rain bands. To model the stable isotope values of precipitation in relation to the general trend of decreasing air temperatures, we applied a numerical Rayleigh condensation model for a non-constant α isotopic fractionation factor between liquid water and water vapour. The storm is powered by four consecutive moisture fronts, each following a Rayleigh distribution. About 40 % of the water vapour condenses during the sampled storm due to adiabatic expansion and cooling, which lowers saturation. Condensation ceases when cooling and absolute humidity can no longer sustain the dew point, stopping the rain. The timing of the event, occurring late at night and early in the morning, its duration of over 6 h as well as its synoptic scale may indicate a mesoscale convective complex.

Numerical analysis on crystallization inside porous sandstone induced by salt phase change

The behavior of water and salt inside porous sandstone is crucial for determining the durability of stone heritage. This involves multiphase coupled processes, yet previous analyses have paid insufficient attention to the spatial and temporal characterization of solution-crystal phase change. Based on the salt crystallization experiments, theoretical models and numerical computational frameworks are synthesized to simulate multiphase processes. Subsequently, equations are established for coupled water-salt-heat-mechanical interactions in the multiphase media. Then, the critical state of solution-crystal phase change is analyzed through the evolution of saturation, crystallization pressure, and porosity. The findings indicate rapid solution saturation growth at positions with minimal wetting front fluctuations, leading to initial crystallization. Further tracing reveals that crystallization evolves through discrete crystallization, annular crystallization, and crystallization expansion stages. By investigating the crystallization pressure and the crystal morphology, it is possible to quantify the dynamics of crystal pressure on constraint surfaces and solution pressure. In addition, the change in porosity can be observed by simulation of dry and wet cycles to obtain crystallization initiation. The numerical calculations agree well with the experimental results, providing valuable insights into the deterioration mechanism induced by salt crystallization in the porous sandstone of Dazu Rock Carvings.

3D in situ observation of the capillary infiltration of molten silicon in a SiC/SiC composite by X-ray tomography

The Liquid Silicon Infiltration (LSI) process is used to decrease residual porosity of SiC/SiC composite materials. However, it is not fully mastered since the mechanisms involved at 1500 °C under high vacuum are complex to analyze, especially without direct observation. Previous work had demonstrated the feasibility of using X-ray radiography to observe the front rise of silicon in a SiC/SiC composite material during the LSI process. 2D observations, as a first approach, could give a basic understanding of the mechanisms but raised several interrogations due to the superposition of these phenomena along the thickness preventing any quantification. The setup has been improved in order to make X-ray tomography using a fully integrated DC motor in place of the rotation stage commonly used. The sets of X-ray tomographs confirm two successive fillings. First, the molten silicon rapidly and non uniformly invades the accessible intergranular micro porosity of the powder. Then, the liquid slowly fills the remaining isolated powder areas. Once the SiC matrix is fully saturated, the liquid fills the bigger porosities such as cracks and intra yarn macro porosities. In addition, this 3D analysis enabled to give a better comprehension of the non uniform wetting front in the SiC matrix powder. During the 1st step, the accessibility of the powder was known to have a major effect on the speed of progression. Also, the cracks network plays a key role in the filling of the isolated areas in the powder matrix.

Revealing the mechanisms of water permeability enhancement of urban loess subgrades due to vibration application

Urban loess subgrades are affected by considerable vibrations from traffic, especially when the underground pipelines leak, and seepage under vibrations often causes road damage. However, the influence of vibrations on the water permeability of loess subgrades remains elusive. Here we address this issue by performing vibration-assisted permeability tests and scanning electron microscopy, mercury intrusion porosimetry, and suction–nuclear magnetic resonance measurements. This allowed the evolution of the saturated hydraulic conductivity (Ks), water-air migration, soil microstructure, and pore water forms to be evaluated. The water permeability of the loess subgrade is promoted by vibrations due to the increase in Ks, the acceleration of wet front migration, and the escape of entrapped air. Moreover, the value of Ks under vibration is 3–14 times greater than that without vibration, and the maximum increase occurs at a vibration frequency near the natural frequency of the loess. Furthermore, a theoretical framework of loess vibration permeability is proposed, and the mechanisms by which vibration accelerates the permeability behavior of the loess subgrade are revealed. Vibration promotes the expansion of soil pores, a decrease in the binding capacity of pore water, the mobilization of fine particles, and the formation of local low-permeability layer. Moreover, it accelerates the opening of entrapped air bubbles and the displacement of water-air, the reduction in seepage resistance. Thus, seepage water flows rapidly along infiltration channels. These findings are highly important for the road safety performance and the sustainable development of the traffic environment in loess regions.

Multifactor analysis of the infiltration characteristics of film hole irrigation under muddy water conditions

Film hole irrigation under muddy water conditions is a new and effective water-saving irrigation technology. In order to determine the influence of multiple factors on the infiltration process of film hole irrigation under muddy water conditions, 12 sets of indoor infiltration tests were conducted to investigate the effects of four key influencing factors (muddy water sand content, hole diameter, soil bulk density, and infiltration time) on the infiltration characteristics of irrigation with film holes under muddy water conditions, in this study. Based on the experimental data, accurate and effective soil water infiltration and vertical and horizontal wetting front transport models were constructed. Based on the modeling results, the standard regression coefficients of each influencing factor against the fitted parameters were calculated and the effects of the factors on the fitted parameters were analyzed. Error analysis showed that both models could effectively simulate the soil water infiltration process under experimental conditions. Infiltration time was the dominant factor influencing the cumulative infiltration per unit of film hole area, followed by hole diameter, muddy water sand content and lastly, soil bulk density. Infiltration time was also the main influencing factor of the vertical wetting front transport distance, followed by soil bulk density, muddy water sand content, and lastly, hole diameter. Similarly, infiltration time exerted the greatest effect on the horizontal transport distance, followed by hole diameter, soil bulk density and muddy water sand content. The model validation revealed that both the calculated and measured values were distributed around the 1:1 line, reflecting the accuracy of the models. The results of this study can provide theoretical support for the design of film hole irrigation systems under muddy water conditions.

Approximate analytical solution of a soil water movement equation under different ponding radii on the basis of numerical simulation

AbstractThis study addresses the problem of 2D soil water movement under ponding radii of 1, 2, and 3 cm. The soil water movement characteristics (shape parameters of the water content profile, ratio of horizontal wetting front to vertical wetting front, relationship between infiltration time and horizontal wetting front, and relationship between infiltration time and cumulative infiltration) under the above three kinds of water ponding radius were analyzed. On the basis of the assumption that the soil wetting body is a semi‐ellipse and the analytical solution of the 1D soil water movement equation at any angle, the approximate analytical solution of the 2D soil water movement equation under ponding conditions is optimized. The function relationships between infiltration time, wetting front, and cumulative infiltration are established. We applied the numerical data simulated by HYDRUS‐3D to validate the parameters in proposed analytical solutions and evaluated the relationships between the wetting front and hydraulic parameters. The results indicate that as the water ponding radius increases, the wetting body and 2D water content distribution becomes larger. When the water ponding radius was 2 cm, the numerical and analytical solution of 1D soil water distribution showed the best comparison results, and the model error was the smallest. The ratio of wetting fronts was linearly increased with the increase of air‐entry suction with R2 = 0.9969.

Seepage rate and uniformity of the stalk composite pipe for subsurface irrigation

AbstractAn orthogonal experiment with three factors and three levels was conducted to study the seepage rate and uniformity of stalk composite pipe (SCP) under subsurface SCP irrigation (SSI). Furthermore, to determine the best application mode for SSI, the pipeline length, irrigation volume and inner–outer diameter of the SCP were considered at a 0.4 m working pressure. The three levels corresponding to each factor were 20, 40 and 60 m; 30, 45 and 60 L m⁻¹; and 28–60, 40–80 and 50–100 mm, respectively. The results indicated that the seepage rate gradually decreased with increasing pipeline length. The pattern of the change in the seepage rate with irrigation volume was not obvious. There was a positive correlation between the seepage rate and the inner–outer diameter of the SCP. The irrigation uniformity coefficient, which was calculated based on the width of the surface wetting front, gradually decreased with increasing pipeline length. The impact patterns of irrigation volume and inner–outer diameter on irrigation uniformity were ambiguous. The seepage rate reached its maximum at the pipeline length, irrigation volume and inner–outer diameter, which were 20 m, 30 L m⁻¹ and 50–100 mm, respectively. There was the highest irrigation uniformity, with a pipeline length, irrigation volume and inner–outer diameter of the SCP of 20 m, 60 L m⁻¹ and 40–80 mm, respectively.

Boiling induced atomization of liquid film produced by oblique jet impingement on superheated wall

For the thermal management of industrial devices, a reduction in the net coolant flow rate by droplet dispersion from a liquid film is important because it can cause unexpected thermal failure. To understand the process of droplet dispersion from a liquid film better, we experimentally and theoretically evaluated the characteristics of boiling-induced atomization in a liquid film formed by oblique jet impingement on a superheated wall. Atomization processes were visualized using magnified high-speed imaging using a backlight technique. In this study, two types of droplets were observed using high-speed-magnification imaging. These were large droplets that disintegrated from the ligament formed on a relatively high-temperature wall, and small droplets from the ligament formed via bubble bursting in the nucleate boiling regime. For the atomization induced by nucleate boiling, larger droplets were produced via bubble bursting further downstream from the impingement point because the bubble size and liquid film thickness increased. Finally, the total volume of the droplets produced by nucleate boiling was estimated from the frequency of bubble bursting and droplet size measured from the visualization results. The estimation results suggest that the ratio of the total volume flow rate of the ejected droplets to the injection flow rate of the liquid was negligible (2%). Thus, most of the injected liquid eventually reached the wetting front of the sheet, separating it from the wall before drying out.

Soil Organic Matter Input Promotes Coastal Topsoil Desalinization by Altering the Salt Distribution in the Soil Profile

Organic amendment is an effective method to reclaim salt-affected soil. However, in coastal land with shallow saline groundwater, it is limited known about the mechanism of organic amendment on soil desalinization. Thus, to examine the effect of topsoil organic matter content on soil water/salt transport and distribution, two-year field observations in Bohai coastal land, North China, and soil column experiments simulating salt accumulation and salt leaching were conducted, respectively. There were different organic fertilizer amendment rates in 0–20 cm topsoil, 0% (CK), 50% (OA 0.5), and 100% (OA 1.0) (w/w) for soil column experiments. Field observation showed that after organic amendment (OA), the soil’s physical structure was improved, and less of the increase in topsoil salt content was observed, with more salt accumulated in deep soil layers during the dry season. In addition, OA greatly promoted salt leaching during the rainy seasons. The results of the soil column tests further indicated that OA treatments significantly inhibited soil evaporation, with less salt accumulated in the topsoil. Although there was no difference in soil water distribution between the CK and OA 0.5 treatment, the topsoil EC for the OA 0.5 treatment was significantly lower than that for CK. During soil water infiltration, the OA 0.5 and OA 1.0 treatments significantly increased the infiltration rates, enhanced the wetting front, and promoted salt leaching to deeper soil layers, compared with CK. The improvement of soil organic amounts could make the soil more self-resistant to the coastal salinization. The findings of this study provide some insights into soil water/salt regulation in heterogeneous soil masses and on the permanent management of coastal saline farmland.

A critique on “Modeling the spontaneous imbibition of non-Newtonian fluids into the fractal porous media of tight reservoirs”

In February 2022, this journal published the paper “Modeling the spontaneous imbibition of non-Newtonian fluids into the fractal porous media of tight reservoirs” (Zhu et al., 2022), which develops and validates an analytical model for the capillary absorption of (non-)Newtonian liquids in sandstone, founded on a fractal-based bundle-of-tubes model. This critique – a post-publication review – expresses concerns on that model development and validation. It is shown that agreement between calculated and measured absorbed moisture masses and moisture front heights is only attained with two strongly distinct sets of material and fluid properties, a dichotomy that is however not disclosed in the paper. It is moreover revealed that the input material and fluid properties and the output absorbed moisture masses and moisture front heights often defy physical plausibility. Detailed scrutiny of the mathematical model complementarily exposes concrete defects in the calculation of the ‘sample’ cross-section. It is displayed that this cross-section calculation is exclusively governed by the material properties, implying that the measured cross-section can (almost) never be equated. It is furthermore established that the cross-section calculation assumes the equality of the areal and volumetric porosity, which is incorrect for a bundle-of-tubes with tortuous capillaries. Additionally it is demonstrated that the cross-section calculation merges two conflicting relations between the porosity and the fractal properties. All these concerns bring about doubts concerning the reliability of (Zhu et al., 2022)'s model development and validation, and the authors are hence invited to placate these concerns in their reply.

Experimental and numerical investigations on soil–water dynamics in Moistube irrigation under dynamically regulated working pressure heads: scenario simulations under maize cultivation

Moistube irrigation (MTI) accurately delivers moisture to root zone through subsurface nanotube irrigators. How to dynamically adjust the working pressure head (WPH) considering crop evapotranspiration remains unstudied. Here, the Moistube discharge characteristics, wetting front (WF) morphology, and soil water content (SWC) distribution under adjusted WPH (0 → 1, 0 → 2, 1 → 2, 1 → 0, 2 → 0 and 2 → 1 m) were experimentally investigated. HYDRUS 2D model was employed to reproduce the soil water dynamics and validated against the experimental data. Maize growth scenarios under regulated WPH for three representative regions (Nanjing, Hami, and Siping in China) with typical hydrological years were performed. The relatively long-term Moistube discharge, SWC, and deep percolation were analyzed. Results demonstrated that flexible WPH adjustment regulated Moistube discharge, the advance velocity of WF, and SWC within the wetting patterns. With increased (or decreased) WPH, the Moistube discharge rate precipitously raised (or descended) to values positively correlated with WPHs. WPHs of 0, 1, and 2 m corresponded to discharge rates of 0.63–0.76, 2.15–3.34, and 5.53–6.41 cm2 h−1, respectively. WF also noticeably accelerated (or decelerated) as WPH, meanwhile SWC within the wetting pattern increased (or decreased). Upon WPH increase, the elevated SWC intensified the deviation (δ) of wetting body centroid from Moistube. HYDRUS 2D model accurately reproduced the Moistube discharge rate and WF advance (R2 ≥ 0.90, NSE ≥ 0.70, RSR close to 0), corroborating the feasibility of treating Moistube as a heavy clay. Surprisingly, the Moistube discharge rate obeyed exponential decreasing trend over time after WPH increased but abnormally displayed restrained trends followed by rebounding after WPH decreased. SWC and the deviation of wetting body centroid from Moistube exhibited discrepancies in absolute values but consistencies in trends between the observed and simulated data. Scenario analyses of maize cultivation revealed that regulating WPH accurately replenished crop evapotranspiration and maintained appropriate SWC environments. Regulated WPH in MTI was efficacious in reducing deep percolation and suitable for arid regions. These results could contribute to intelligent MTI by automatically maintaining a balance between Moistube discharge and crop water requirements.

The Impact of Long-Term Mulched Drip Irrigation on Soil Particle Composition and Salinity in Arid Northwest China

The evaluation of soil particle composition and salt dynamics is essential for promoting the sustainable development of oasis agriculture in arid regions under long-term mulched drip irrigation (MDI). In this study, we employed the space-for-time substitution method to investigate the long-term effects of MDI on soil particle composition and salinity. Additionally, seven fields, with MDI durations ranging from 0 to 16 years, were selected to represent the primary successional sequence though time in Northwest China. Soil samples were collected from three soil depths (0–30 cm, 30–60 cm, and 60–100 cm) and then analyzed in the laboratory for soil particle composition and salt content. Our findings demonstrated that influenced by the depth of mechanical cultivation and the maximum wetting front depth, the long-term application of MDI significantly altered both the structure of soil layers and the composition of soil particles after 8 years. Soil sand content and soil salinity gradually decreased, whereas the content of soil silt and clay increased with increasing MDI duration throughout 0–100 cm soil depth. Furthermore, the rates of soil desalination stabilized after 10 years of MDI application, with desalination levels exceeding 90% in the 0–100 cm soil layer. Additionally, the soil mass fractal dimension (Dm) exhibited an upward trend across 0–100 cm soil depth. The changes in soil particle composition indirectly influenced the variations in Dm and salt content. Our study demonstrated that long-term application of MDI effectively mitigated soil salinity, changed soil structure, and ultimately enhanced soil quality and cotton yield.

Infiltration and Leaching Characteristics of Soils with Different Salinity under Fertilizer Irrigation

Salt and nutrient transport and transformations during water infiltration directly influence saline soil improvement and the efficient use of water and fertilizer resources. The effects of soil initial salinity (18.3 g/kg, 25.5 g/kg, 42.2 g/kg, 79.94 g/kg, and 165 g/kg, respectively, labeled S1 to S5) on the infiltration and leaching characteristics of water, salt, and nitrogen were analyzed via a one-dimensional vertical fertilizer infiltration experiment. Meanwhile, the estimation models of cumulative infiltration and wetting front, including the effect of soil initial salinity, were established. The results showed that, with the increase in soil initial salinity, the cumulative infiltration within the same time decreased, and the migration time of wet front to 45 cm was longer. The time required for S5 to reach the preset cumulative infiltration was more than six times that of S1, and, for the wet front migration to 45 cm, the time requirement for S5 was about four times that of S1. In the established Kostiakov model and wetting front model, the coefficients all decreased with the increase in soil initial salinity, and the test index R2 values both reached 0.999. In the Kostiakov model, coefficient K had a linear relationship with the natural logarithm of initial soil salt content, while index a had a direct linear relationship with initial soil salt content. The cumulative leachate volume decreased with the increase in soil initial salinity, and the corresponding data of S3 and S5 were reduced by 37% and 57.3%, respectively, compared with S1. The electrical conductivity values of S1, S3, and S5 were 15.4, 209.8, and 205.6 ms/cm, respectively, being affected by the initial content in soil, soil moisture transport rate, and exogenous potassium nitrate (KNO3) addition. The NO3−-N concentrations in the leachates of S1, S3, and S5 at the end of leaching were 55.26, 16.17, and 3.2 mg/L, respectively. Based on the results of this study, for soil with high initial salinity, the conventional irrigation amount (2250 m3/ha) of the general soil in the study area could not meet the requirements of leaching salt. These results can provide a reference for the formulation of irrigation and fertilization strategies for soils with different salinity and contribute to the sustainable development of saline soil agriculture and the ecological environment.

Unsteady wetting of soft solids

HypothesisSpreading of liquids on soft solids often occurs intermittently, i.e., the liquid's wetting front switches between sticking and slipping. Studies of this so-called stick-slip wetting on soft solids mostly are confined within quasi-static or forced spreading conditions. In these situations, because the sticking duration is set much larger than the viscoelastic relaxation time of the solid, a ridge is persistently and fully developed at the wetting front as the soft solid yields to the liquid's surface tension. The sticking duration and spreading velocity, therefore, were shown to have little impact to the contact angle change required for stick-to-slip transitions. For unsteady wetting of soft solids, a commonly encountered but largely unexplored situation, we hypothesize that the stick-to-slip transition is controlled not only by a combination of sticking duration and the spreading velocity, but also by an increasing depinning threshold caused by the growing ridge at the wetting front. ExperimentWe performed unsteady wetting experiment on soft solids by letting water droplets spread freely on soft solid surfaces of various stiffness. We capture both the stick-slip spreading behavior and growing wetting ridges using synchronous high-speed imaging and high-speed interferometry. Recorded data of liquid spreading and solid deforming at the wetting front were analyzed to shed light on the relation between stick-slip characteristics and the growing wetting ridge. FindingsWe find that intermittent wetting on a soft solid surface results from a competition between three key factors: liquid inertia, capillary force change during sticking, and growing pinning force caused by the solid's viscoelastic response. We theoretically formulate their quantitative contributions to predict how stick-to-slip transitions occur, i.e., how the contact angle change and sticking duration depend on the liquid's spreading velocity and the solid's viscoelastic characteristics. This provides a mechanistic understanding and methods to control unsteady wetting phenomena in diverse applications, from tissue engineering and fabrication of flexible electronics to biomedicine.

Evaluation of wet front under foundation at “El Chocón dam” using electrical tomography

El Chocón dam is located on Limay River in the province of Neuquén (Argentina) and is one of the most important in the country and in Latin America due its reservoir capacity. Currently, the dam is at full operation stage, while its structural health is monitored through a significant number of instruments installed in the dam body and its foundation. In the sector of the closure of the dam on its left margin, the measurements of some piezometers that monitor the deep rock foundation, showed some changes that gave rise to the hypothesis of the advance of wet front, despite fact that the work has practically 50 years from commissioning. To confirm or rule out this hypothesis, research work was started using the 2D electrical tomography method. The methodology was selected based on the good correlation that exists between the electrical resistivity and the volumetric content of water in a rock formation. Tomographic image obtained made it possible to determine different sectors in which wet front is detected and to define its extension, also evidencing a good correlation with what was recorded in the rock auscultation instruments, confirming the slow advance of wet front to downstream.

Research on Underground Drip Irrigation and Soil Redistribution - Take Heshan District of Yiyang City as an Example

Abstract: The drip flow and the buried depth of drip irrigation zone are not only important parameters of subsurface irrigation design and operation management, but also important factors affecting the migration and redistribution of soil water and fertilizer. Crop growth is closely related to soil water and nitrogen leaching, water and fertilizer transport patterns and redistribution characteristics. It is of great significance to study the migration and redistribution of soil water and fertilizer under subsurface drip irrigation for improving the utilization efficiency of water and fertilizer and improving the system of subsurface drip irrigation. In this paper, the migration mode and redistribution characteristics of water and nitrogen in subsurface drip irrigation were studied and analyzed by means of laboratory soil box experiment, considering the two factors of drip flow and the buried depth of drip irrigation belt. The main research conclusions are as follows: Ⅰ. Different drip flows had effects on soil moisture front, soil moisture content and soil water redistribution. If other conditions remain unchanged, increasing the drip flow can increase the moist body area of soil and increase the moisture content of soil. The distance between vertical and horizontal directions increased with the large drip flow, and the soil water content decreased with the increase of distance. Large drip flow can promote the redistribution of soil water after drip irrigation. Ⅱ. Different drip depth had effects on soil moisture content and soil water redistribution. When the drip depth was 0cm, the surface shape of the wet body was a "horizontal" semi-ellipse after drip irrigation. When the drip depth was 10cm and 20cm, the surface of the wet body was an "upright" semi-ellipse after drip irrigation. The larger the buried depth of the drip can make the distribution of soil moisture more uniform, and the larger the buried depth of the drip can promote the migration of water in the soil. Ⅲ. Different drip discharge had an effect on soil nitrogen redistribution, and large drip discharge promoted soil nitrogen redistribution after drip irrigation. The Nitrate Nitrogen (NO3--N) content in the moist body is lower than that near the edge of the wetting front. The content of Ammonium Nitrogen (NH4+-N) near the edge of the wetting peak is higher than that inside the wetting body. Ⅳ. The redistribution of soil nitrogen was affected by different buried depth of drip head, and the greater buried depth of drip head could promote the redistribution of soil nitrogen. In terms of vertical and horizontal migration of ammonium nitrogen and nitrate nitrogen, on the day after drip irrigation, the cumulative effect of Nitrate Nitrogen (NO3--N) buried at a depth of 20cm was more significant near the wetting front edge at a larger vertical downward distance, and the cumulative effect of Nitrate Nitrogen (NO3--N) buried at a depth of 20cm was more significant inside the wetting body at a larger vertical downward distance. At the same time, the drip buried depth of 20cm can spread the cumulative effect inside the wet body and near the edge of the wet front to a longer horizontal distance.

Efficacy Of Single Drip Lateral Design For Two Plant Rows Of Grain Maize In Konya-Kadinhani-Kolukisa Province, Turkey

The purpose of this research was to evaluate the effectiveness of trickle irrigation on grain-corn production as well as soil wetting geometry under single drip lateral design for two plants rows at Konya-Kadınhanı-Kolukısa province of Turkey under farmer’s practices. The seasonal applied water varied from 416.78 to 441.98 mm in research farms. The grain yield was found between 14200 and 16750 kg/ha in those study farms. Irrigation Water Use Efficiency, IWUE, varied from 3.21 and 3.93 kg/m3. The both the lateral and vertical wetting front was around 50 cm under 140 cm lateral space. The field inspection clearly showed that it is impossible to obtain sufficient wetted soil volume by use of one trickle lateral design, 140 cm, for two plant rows so one drip lateral design,70 cm, for each crop row was strongly recommended for facilitating better wetted soil volume within plant rooting depth consequently increasing grain production. Maize plant is very sensitive to the water deficiency so water amount should be met enough in soil rooting environment during the whole plant growing cycles.

Coupled hydrogeophysical inversion of an artificial infiltration experiment monitored with ground-penetrating radar: synthetic demonstration

Abstract. In this study, we investigate the use of ground-penetrating radar (GPR) time-lapse monitoring of artificial soil infiltration experiments. The aim is to evaluate this protocol in the context of estimating the hydrodynamic unsaturated soil parameter values and their associated uncertainties. The originality of this work is to suggest a statistical parameter estimation approach using Markov chain Monte Carlo (MCMC) methods to have direct estimates of the parameter uncertainties. Using the GPR time data from the moving wetting front only does not provide reliable results. Thus, we propose to use additional information from other types of reflectors to optimize the quality of the parameter estimation. Water movement and electromagnetic wave propagation in the unsaturated zone are modeled using a one-dimensional hydrogeophysical model. The GPR travel time data are analyzed for different reflectors: a moving reflector (the infiltration wetting front) and three fixed reflectors located at different depths in the soil. Global sensitivity analysis (GSA) is employed to assess the influence of the saturated hydraulic conductivity Ks, the saturated and residual water contents θs and θr, and the Mualem–van Genuchten shape parameters α and n of the soil on the GPR travel time data of the reflectors. Statistical calibration of the soil parameters is then performed using the MCMC method. The impact of the type of reflector (moving or fixed) is then evaluated by analyzing the calibrated model parameters and their confidence intervals for different scenarios. GSA results show that the sensitivities of the GPR data to the hydrodynamic soil parameters are different between moving and fixed reflectors, whereas fixed reflectors at various depths have similar sensitivities. Ks has a similar and strong influence on the data of both types of reflectors. Concerning the other parameters, for the wetting front, only θs and α have an influence, and only at long time steps since the total variance is zero at the very beginning of the experiment. On the other hand, for the fixed reflectors, the total variance is not zero at the very start and the parameters θs, θr, α and n can have an influence from the very beginning of the infiltration. Results of parameter estimation show that the use of calibration data from the moving or fixed reflectors alone does not enable a good identification of all soil parameters. With the moving reflector, the error between the estimated mean value and the exact target value for θr and α is 9 % and 45 %, respectively, and less than 3 % for the other parameters. The best reduction of the size of the parameter distribution is obtained for n, with a posterior distribution 9 times smaller than the prior one. For the others, this reduction ratio varies between 1 and 5. For the fixed reflectors, the estimated mean values are far from the target values for α, θr and n, representing for a reflector located at 120 cm 15 %, 27 %, and 121 %, respectively. On the other hand, when both data are combined, all soil parameters can be well estimated with narrow confidence intervals. For instance, when using both data from the moving wetting front and a fixed reflector located at 120 cm for calibration, the estimated mean values of the errors of all parameters are less than 5 %. Moreover, all parameter distributions are well reduced, with a maximum reduction for Ks, leading to a posterior distribution being 46 times smaller than the prior one, and the worst but still satisfactory being for θr for which the posterior distribution is 8 times smaller than the prior one. The methodology was applied to fine, medium, and coarse sands with very good results, particularly for the finest soil. The thickness of the unsaturated zone was also tested (0.5, 1, and 2 m) and a better estimation of the hydrodynamic parameters is obtained when the water table is deeper. In addition, the height of water applied in the infiltrometry test influences the speed of the test without affecting the performance of the proposed method.