Cumulative Infiltration Research Articles

Investigating the Spatial Structure of Soil Hydraulic Properties in a Long-Term Field Experiment Using the BEST Methodology

Understanding the spatial structure of soil properties at field scale and introducing this information into appropriate data analysis methods can help in detecting the effects of different soil management practices and in supporting precision agriculture applications. The objectives of this study were: (i) assessing the spatial structure of soil physical and hydraulic properties in a long-term field experiment; (ii) defining a set of spatial indicators for gaining an integrated view of the studied system. In seventy-two georeferenced locations, soil bulk density (BD), initial volumetric soil water content (θi) and cumulative infiltration curve as function of the time (I(t)) were measured. The soil water retention curve (θ(h)) and the hydraulic conductivity function (K(h)) were then estimated using the Beerkan Estimation of Soil Transfer parameters (BEST) methodology. The volumetric soil water contents at soil matrix (h = −10 cm), field capacity (h = −100 cm) and wilting point (h = −15,300 cm) were considered. In addition, a set of capacitive indicators—plant available water capacity (PAWCe), soil macroporosity (PMACe), air capacity (ACe) and relative field capacity (RFCe)—were computed. The data were first analyzed for overall spatial dependence and then processed through variography for structural analysis and subsequent spatial interpolation. Cross-correlation analysis allowed for assessing the spatial relationships between selected physical and hydraulic properties. On average, optimal soil physical quality conditions were recorded; only PMACe values were indicative of non-optimal conditions, whereas mean values of all the other indicators (BD, Ks, PAWCe, ACe, RFCe) fell within optimal ranges. The exponential model was found to be the best function to describe the spatial variability of all the considered variables, except ACe. A good spatial dependence was found for most of the investigated variables and only BD, ACe and Ks showed a moderate autocorrelation. Ks was confirmed to be characterized by a relatively high spatial variability, and thus, to require a more intensive spatial sampling. An inverse spatial cross-correlation was observed between BD and Ks up to a distance of 10 m; significant cross-correlations were also recorded between Ks and PMACe and ACe. This result seems to suggest the possibility to use these soil physical quality indicators as covariates in predictive multivariate approaches.

Magnetic resonance imaging for the diagnosis of muscular dystrophy

To summarize the skeletal muscle magnetic resonance imaging (MRI) features of the lower limbs in common subtypes of muscular dystrophy (MD) and the experience in the application of MRI in the diagnosis of MD. A total of 48 children with MD who were diagnosed by genetic testing were enrolled as subjects. The muscle MRI features of the lower limbs were analyzed. Cumulative fatty infiltration score was calculated for each subtype, and the correlation of cumulative fatty infiltration score with clinical indices was analyzed for Duchenne muscular dystrophy (DMD). DMD was characterized by the involvement of the gluteus maximus and the adductor magnus. Becker muscular dystrophy was characterized by the involvement of the vastus lateralis muscle. Limb-girdle muscular dystrophy was characterized by the involvement of the adductor magnus, the vastus intermedius, the vastus medialis, and the vastus lateralis muscle. For DMD, the cumulative fatty infiltration score of the lower limb muscles was significantly correlated with age, course of the disease, muscle strength, and motor function (P<0.05), while it was not significantly correlated with the serum creatine kinase level (P>0.05). Different subtypes of MD have different MRI manifestations, and MRI may help with the diagnosis and assessment of MD.

Approximate analytical solution to equation for two-dimensional soil-water movement in ponding infiltration based on numerical simulation

A simple analytical solution to two-dimensional (2D) ponding infiltration is essential for designing line-source or drip irrigation. We propose a new and simple approximate analytical method for calculating the 2D distribution of soil water with a 1-cm radius of ponding and uniform initial conditions and for estimating the horizontal and vertical distances of wetting fronts based on soil hydraulic parameters. The method assumes a semi-elliptical soil-wetting pattern and a one-dimensional profile of soil water at an arbitrary infiltration angle to solve the equation for the 2D movement of soil water and cumulative infiltration. We applied the numerical data simulated using HYDRUS-3D to validate the proposed method's parameters and evaluate the relationship between the wetting front and hydraulic parameters. The simulated results indicated that the assumptions were propitious to the fine-texture soils with air-entry suction larger than 10 cm. The ratio between the distances of the horizontal and vertical wetting fronts could be approximately predicted using the air-entry suction by analyzing the numerical results. The fitted results indicated that the parameters of the power function of the relationship between the distances of the horizontal and vertical wetting fronts and infiltration time could be described as polynomial and power functions of the diffusivity of saturated soil water. The approximate analytical solutions for the distance of the horizontal wetting front, depth of the vertical wetting front, and cumulative infiltration agreed well with other numerical simulations.

Quantifying and assessing the infiltration potential of green infrastructure in urban areas using a layered hydrological model

Spatial heterogeneity in hydrological responses is an important element in urbanized watersheds. One of the main challenges in simulating urban hydrology is the lack of layered information and knowledge of the true infiltration potential of stormwater infrastructure systems. In this study, changes in the infiltration characteristics of three green infrastructures (GIs), with and without underground barriers, were simulated during a designed rain event in Xiamen, China, using a layered, one-dimensional infiltration model. The variations in the maximum infiltration rate (MIR) and cumulative infiltration (CI) for permeable pavements, vegetative swales, and rain gardens were found to differ in response to 204 scenarios of pervious material thickness, even though they were linearly correlated. Comparisons between the GIs, with and without barriers, revealed that the MIR was almost unchanged, while CI varied considerably with the depth to the impervious layer. To explore the impacts of barriers on infiltration potential, simulations with depths to the impervious layer from 700 to 1000 mm were compared. We statistically evaluated the infiltration potential with all possible scenarios for the GIs. Identifying the potential impacts of infiltration processes beneath GI can be beneficial in urban stormwater management.

Simplified approach for determination of parameters for Kostiakov's infiltration equation

Abstract Knowledge of soil infiltration characteristics is required increasingly for the proper design and efficient management of irrigation. Various empirical and physically based infiltration models have been used for several years, but the practical use of many is limited by parameter determination problems, which, in turn, are influenced by factors acting at the surface and within the soil, initial and boundary conditions, etc. In this study, a simplified approach for determining parameters for the Kostiakov equation was tested and validated. The equation's linearized form, using logarithmic transformation and field data collected from five sites, was employed. The results show that cumulative infiltration can be described well using the approach. Its quality is also confirmed by performance indices like R2 and standard error, whose values ranged from 0.985 to 0.999 and 0.020 to 0.005, respectively, suggesting that the simplified approach described is sufficient for practical purposes, when data are too scarce to apply other, complex methods to predict cumulative infiltration.

Effect of a Superabsorbent Polymer (Poly-Gamma-Glutamic Acid) on Water and Salt Transport in Saline Soils under the Influence of Multiple Factors.

In order to effectively suppress the negative effects of salt ions contained in saline soils on agricultural soil quality and crop growth, this study took advantage of the water-saving properties and better soil improvement properties of poly-γ-glutamic acid (γ-PGA). By carrying out various experiments, the following relationships have been found. (1) The lab experiment studies the effect of the γ-PGA application on the infiltration of sandy loam soil. The application rates of γ-PGA are 0%, 0.1%, 0.2%, and 0.3%, respectively. (2) HYDRUS-1D is used to simulate water infiltration of sandy loam soil under multiple factors (bulk density, γ-PGA application rate, and the application depth of γ-PGA). (3) The effect of γ-PGA on soil solute (Cl−) transport is also explored in this paper. The results show that bulk density and the application depth of γ-PGA (p < 0.01) have higher effects on cumulative infiltration than the application amount of γ-PGA (p < 0.05). A lower γ-PGA application rate will increase the proportion of unavailable soil water by 3%. The established empirical models have good results. Furthermore, when the γ-PGA application rate is 0.3% (0.02-cm2 min−1), the Cl− hydrodynamic dispersion coefficient is the highest. The study recommends applying the γ-PGA at 1.4 g cm−3, 5–20 cm, and 0.2%. The results of this study are conducive to an in-depth understanding of the physicochemical properties of poly-γ-glutamic acid, improving the utilization rate of salinized land, achieving agricultural water and fertilizer conservation and yield enhancement, and guaranteeing sustainable land use and sustainable development of agroecological environment.

The Effect of Plug Height and Inflow Rate on Water Flow Characteristics in Furrow Irrigation

Despite its wide application across arid land types, furrow irrigation is often associated with numerous environmental problems related to deep percolation, runoff, and soil erosion. In this study, a straightforward approach was proposed to achieve higher uniformity and reduce erosion. Here, the impacts that a moveable “plug” has on the behavior of irrigation water in the furrow were simulated using FLOW-3D and HYDRUS-2D, where three plug heights and two flow rates were set. The effect of inflow rate and plug height on the water advance, water level, cumulative infiltration in the furrow, and uniformity coefficient was determined. Results indicate that the plug was able to slow water velocity by approximately 60% in the furrow and increase the furrow advance time by 3–4 times; the water level was increased by nearly 10 cm compared with no plug. Moreover, an irrigation uniformity range of 90.18–99.22% was associated with this plugging. The addition of a plug in the furrow irrigation practices for smallholder farmers in developing countries demonstrates great potential in reducing the probability of erosion under large slopes and can effectively improve irrigation uniformity.

Comparison of Infiltration Rates of Soils for Run-Off Management and Irrigation Planning in Makurdi Benue State, Nigeria

Understanding of initial infiltration rates and steady state infiltration rates of soil is very important for runoff management and irrigation scheduling. Therefore, a field experiment was conducted at the Teaching and Research Farm of Joseph Sarwuan Tarka University, Makurdi in 2018 to evaluate the initial and steady state infiltration rates of soils in Makurdi, Nigeria. Infiltration test was carried out using double ring infiltrometer at eighteen points. Initial and steady state infiltration rates and the cumulative infiltration were then calculated. Soil samples were collected from the adjacent area of the marked points at 0-15 cm and 15-30 cm depths for routine analysis. Undisturbed soil samples were also collected for the measurement of saturated hydraulic conductivity, bulk density, total porosity and moisture content determination. Simple descriptive statistic of mean, variance and standard deviation was used to analyze the data. The soils were predominantly sandy loan texture, with percentage sand, silt and clay as 710.7, 118.9, and 170.4 g kg-1 respectively. Soil bulk density and saturated hydraulic conductivity were 1.40 g cm-3 and 10.27 cm hr-1 at 0 – 15 cm depth, while soil organic carbon and CEC were 0.67 % and 6.62 cmol/kg respectively. The initial infiltration rate ranged from 7.40 - 87.46 mm hr-1 with a mean of 44.09 mm hr-1, meanwhile, the steady state infiltration rate ranged between 4.99 – 22 mm hr-1, with a mean value of 15.42 mm hr-1. High soil bulk density caused moderate to low infiltration capacity. The mean values for the steady state infiltration rate suggest that the soils of the study area have moderate infiltration capacity, therefore, water application for irrigation should be less or equal to the infiltration capacity of the soils to minimize water loss by surface runoff and erosion.

Numerical investigation on hydraulic and gas flow response of MSW landfill cover system comprising a geosynthetic clay liner under arid climatic conditions

Municipal solid waste (MSW) landfill cover systems are designed to minimize the infiltration of rainwater into waste and to mitigate the biogas emissions to the atmosphere. In the present study, the efficacy of such a landfill cover system consisting of a Geosynthetic clay liner (GCL)in mitigating the hydraulic flow and gas emissions under arid climatic conditions was investigated critically. For this purpose, the water retention curve (WRC), hydraulic conductivity function, and gas flow characteristics of the chosen GCL were studied through experimental methods in the laboratory. The unsaturated transient state seepage analysis utilizing coupled hydraulic and gas flow mechanisms was performed in the study to assess the performance of the cover system. The results obtained from the experiments were used as input parameters. The effect of drying/desiccation and the self-healing nature of GCL due to climatic changes were also analyzed by exposing the GCL directly to the climatic boundary for one year. It was observed that the GCL present in the chosen cover system effectively functions as a hydraulic barrier in arid climatic conditions. However, during the summer and winter seasons, an increase in gas flow from 0.02 g/h/m2 to 24.7 g/h/m2 was observed, probably due to the drying anddesiccation of GCL. Interestingly, due to the self-healing nature of the GCL, gas flow through the cover system was substantially reduced to 0.02 g/h/m2 during the rainy season. The effect of drying was more pronounced when the GCL was exposed to the climatic condition, leading to an early gas breakthrough and an increase in gas flow from 0.02 g/h/m2 to 957 g/h/m2. The percolation through the cover system remains considerably low throughout the year, mostly due to the unsaturation and low hydraulic conductivity in GCL. A cumulative percolation close to 0.1 m3 was observed at the end of one year in arid climatic conditions.

A dual-porosity model for coupled rainwater and landfill gas transport through capillary barrier covers

A two-dimensional dual-porosity model for coupled rainwater and landfill gas transport through capillary barrier covers (CBCs) was established. The proposed model was partially verified using published data from a laboratory loess column test. By fitting the field-measured data using the proposed model, the optimal dual-porosity parameters of the in-situ loess of a loess/gravel CBC in Northwest China were determined to be wf = 0.1 (volume fraction of macropore system), Kf/Km = 150 (intrinsic permeability ratio of macropore to micropore system) and Re = 1 (reduction factor of mass exchange at the interface between macropore and micropore systems). This model was used to predict the performance of the CBC experiencing a 15-day rainfall period followed by a 30-day no-rainfall period. Results showed that the presence of macropores induced an earlier occurrence of percolation accompanied with a higher percolation rate. The cumulative percolation and CH4 emission rate derived from the dual-porosity model were about 50 % and one order of magnitude higher than those predicted by the single-porosity model, respectively. In addition, the existence of gravel layer had remarkable influence on minimizing water percolation and CH4 emission, but these were practically independent of its thickness. The results of this study can provide an effective method, crucial parameters and guidelines for the design of CBCs.

Performance evaluation of infiltration models under different tillage operations in a tropical climate

Land management practices have the propensity to influence soil infiltration characteristics and predictability of infiltration models. This study was conducted to evaluate the performances of the Kostiakov model, the Philip model and the Horton model in predicting cumulative infiltration depth under four tillage systems in a sandy clay loam: (i) No Tillage (NT), (ii) Reduced Tillage (RT), (iii) Ploughing followed by Harrowing and Ridging (PHR), and (iv) Deep tillage followed by Ploughing, Harrowing and Ridging (DPHR). Using the double ring infiltrometer to measure the infiltration rate, the observed data was fitted to the infiltration models and their goodness of fit was verified by Root Mean Square Error (RMSE), Mean Absolute Error (MAE), coefficient of determination (R2), Nash Sutcliffe efficiency (NSE) and paired sample t-test. The results show that the Kostiakov model exhibited the highest accuracy with the highest R2 and NSE values (R2≥0.9967 and NSE ≥ 0.9965) and lowest errors (RMSE≤ 1.16 mm and MAE ≤ 0.98 mm). The comparison of the performances of the models in predicting the cumulative infiltration depth revealed that the Kostiakov model is superior to the Philip and the Horton models under all the Tillage systems, as the Philip and the Horton models underestimated and overestimated the observed data at the initial and latter parts of the experiment, respectively. The observed and predicted cumulative infiltration depth compared using the paired sample t-test showed that the Kostiakov model was better than the Horton and the Philip models under NT, RT and PHR, while the Horton model predicted better on the DPHR than the Kostiakov and the Philip models. The infiltration capacities of the conservation tillage practices (NT and RT) were higher than the conventional tillage conditions (PHR and DPHR). However, the performance of the evaluated models in predicting cumulative infiltration shows that the measured infiltration was best simulated for the DPHR followed by the PHR, RT and NT tillage practices. From our study the Kostiakov model precisely predicted the cumulative infiltration depth relative to the Horton and Philip models. It is, therefore, the preferred choice for modelling cumulative infiltration depth in the ochrosols of the study area and under verified field conditions, these models can be applied to determine the suitable infiltration characteristics to minimise deep percolation and run off losses in irrigation scheduling.

Impacts of Biochar on Hydro-Physical Properties of Sandy Soil under Different Irrigation Regimes for Enhanced Tomato Growth

The performance of biochar application in water conservation, salt distribution, water infiltration, and tomato growth was evaluated under regulated deficit irrigation (RDI) (40%, 60% and 80% of ETc) and partial root drying (PRD) systems by using different quality irrigation water. Date palm derived biochar was applied to sandy soil at 4% (w/w) in pots, and tomato was grown as the test crop under greenhouse conditions. The results indicated that soil moisture was decreased by 27.38% to 24.95% without biochar application at different levels of irrigation, whereas it increased by 8.11% and 5.48% with biochar application, compared with control treatment of 100% of ETc. Soil moisture was decreased by 12.78%, 15.82% and 12.78% for the 1st stage, 2nd stage and 3rd growth stage, respectively, while it increased by 37.93% at the 4th growth stage compared with full irrigation. Soil salinity ranged between 0.5 and 1.4 dS·m−1 with biochar application, while 0.7–2.1 dS·m−1. Cumulative infiltration at one minute varied between 1.89 and 2.79 cm and 1.74 and 2.79 cm for biochar and non-biochar treatments, respectively. Infiltration rate varied from 0.98 to 2.63 cm min−1 and 1.48 to 1.68 cm·min−1 for fresh and saline water, respectively. Overall, the results revealed that biochar application substantially improved the characteristics of sandy soil, subsequently resulting in water conservation.

An approximate solution to one-dimensional upward infiltration in soils for a rapid estimation of soil hydraulic properties

Soil hydraulic properties quantify soil pore structure and are essential input parameters for simulating soil hydrological processes in the vadose zone. Although methods have been proposed to estimate soil hydraulic properties, efficient and applicable ones are still scarce. In this study, we derived an approximate solution for a one-dimensional upward infiltration process with initially uniform soil water content distribution. Founded on our solution, a nonlinearly constrained optimization method was developed to simultaneously estimate the parameters Ks and n, hd of the Brooks-Corey model by measuring the upward infiltration process in a 5-cm high soil column. Numerical experiments simulated with Hydrus-1D were performed on six theoretical soils to evaluate the accuracy of the new method. The results indicate that the approximate solution can accurately simulate the upward infiltration process at the low initial soil water content range, with a relative error (Re) of 2.85% to 5.47% for soil water content distribution in space and time. For the cumulative infiltration curve, the Re ranges from 0.2% to 1.01%. The estimated parameters Ks and n, hd of the Brooks-Corey model are close to the actual parameter values, with a Re of 0.59% to 4.68% for n, 0.00% to 7.91% for hd, and 0.50% to 8.83% for Ks, respectively. It is concluded that the new method provides a simple and valuable tool for the accurate estimation of soil hydraulic properties.

Effect of Sodium Carboxymethyl Cellulose on Water and Salt Transport Characteristics of Saline-Alkali Soil in Xinjiang, China.

The scientific use of sodium carboxymethyl cellulose (CMC) to improve the production capacity of saline–alkali soil is critical to achieve green agriculture and sustainable land use. It serves as a foundation for the scientific use of CMC to clarify the water and salt transport characteristics of CMC-treated soil. In this study, a one-dimensional soil column infiltration experiment was carried out to investigate the effects of different CMC dosages (0, 0.2, 0.4, 0.6, and 0.8 g/kg) on the infiltration characteristics, infiltration model parameters, water and salt distribution, and salt leaching of saline–alkali soil in Xinjiang, China. The results showed that the final cumulative infiltration of CMC-treated soil increased by 8.63–20.72%, and the infiltration time to reach the preset wetting front depth increased by 1.02–3.96 times. The sorptivity (S) in the Philip infiltration model and comprehensive shape coefficient (α) in the algebraic infiltration model showed a trend of increasing first and then decreasing with CMC dosage, revealing a quadratic polynomial relationship. The algebraic model could accurately simulate the water content profile of CMC-treated soil. CMC enhanced the soil water holding capacity and salt leaching efficiency. The average soil water content, desalination rate, and leaching efficiency were increased by 5.18–15.54%, 21.17–57.15%, and 11.61–30.18%, respectively. The effect of water retention and salt inhibition on loamy sand was the best when the CMC dosage was 0.6 g/ kg. In conclusion, the results provide a theoretical basis for the rational application of CMC to improve saline–alkali soil in arid areas.

Short-term Tillage and Soil Nutrient Management on Soil Water Movement in a Lixisol in a Tropical Climate

Aims: The study was conducted to assess the effects of different soil tillage practices and soil amendments on soil hydraulic characteristics.&#x0D; Study Design: The study was a 3 × 4 split-plot experiment arranged in randomized complete block design (RCBD) with 3 replications.&#x0D; Methodology: The treatments comprised 12 main plots, namely no till (NT), plough-plant (PP) and plough-harrow-plant (PHP) and 36 sub-plots, namely no amendment (NA), NPK 60:40:40 (100% NPK), 4 tons/ha poultry manure (100% PM) and 2 tons/ha PM + NPK 30:20:20 [½(NPK + PM)]. Soil bulk density (BD), volumetric moisture content (VMC), total porosity (TP), aggregate stability (ASt), and infiltration parameters were measured under the different treatments.&#x0D; Results: Among the different tillage operations, the NT plot had the lowest BD, but highest TP, VMC and ASt. With regard to the soil amendments, TP was highest under the ½(NPK + PM) treatment. The cumulative infiltration amount (F) and infiltration capacity (K0) were highest in the NT plots. However, sorptivity (S\(\theta\)) was highest and lowest in the PP and NT plots, respectively. The infiltration parameters were highest in the ½(NPK + PM) plots. Further, the combined application of NT + ½(NPK + PM) resulted in the highest F, S\(\theta\) and K0.&#x0D; Conclusion: The, NT, ½(NPK + PM) and NT + ½(NPK + PM) improved the soil hydro-physical properties.

Correspondence between theory and practice of a Beerkan infiltration experiment

AbstractThe Beerkan infiltration experiment is carried out by inserting the ring a short depth into the soil and establishing a positive head of water on the infiltration surface for at least a part of the run. Nevertheless, the data are analyzed by assuming a fully unconfined infiltration process (ring insertion depth, d = 0 cm) and a null ponded depth of water (H = 0 cm). The influence of ring insertion and ponded water on an infiltration process of 2 h sampled every minute was tested in this numerical investigation. Five soils varying from sand to silt loam, three ring radii (5–15 cm), and the Beerkan‐specific range of values for both d and H (between 0 and 1 cm) were considered. The differences between the theoretical (d = H = 0 cm) and the practical (d = H = 1 cm) setups varied from −10.4 to +8.6% for the mean infiltration rate and from −10.2 to +8.3% for the final cumulative infiltration. These differences were small, and they decreased in absolute value by considering a soil‐dependent ring radius. In particular, nearly negligible differences were detected using a small ring in coarse‐textured soils and a large ring in fine‐textured soils. In the coarser soils, inserting the ring and establishing a ponded depth of water did not alter the estimated coefficients of the two‐parameter infiltration model appreciably with the cumulative linearization method, because these coefficients differed between the theoretical and practical setups by no more than 9.2%. In fine soils, linearization could not be possible regardless of the considered setup, or it was the use of d = H = 1 cm instead of d = H = 0 cm that impeded a convincing linearization of the data. In conclusion, the good correspondence, in many circumstances, between the theoretical and the practical Beerkan infiltration experiment reinforced the interest in this simple experiment as a practical means to collect infiltration data in the field.

Evaluation of deep machine learning-based models of soil cumulative infiltration

Evaluation of deep machine learning-based models of soil cumulative infiltration

Effect of biochar on soil properties and infiltration in a light salinized soil: Experiments and simulations

AbstractThe sustainable development of agriculture in Xinjiang Province, China has been threatened by soil salinization. Biochar can be an effective amendment to improve salt‐affected soils. An appropriate amount of biochar application and incorporation depth are key factors for amending performance. However, few studies have investigated the effects of differing biochar application amounts on saline soil properties, including soil water infiltration, using a combination of experiments and simulations. In this study, acidulated biochar was applied at rates of 0, 10, 25, 50 and 100 t ha−1 to a farmland topsoil to investigate the impacts of biochar on Xinjiang saline soil's physical and chemical properties and infiltration characteristics. The soil's physical and chemical properties that were investigated included soil pH, soil organic carbon content, soil salt content, saturated hydraulic conductivity (Ks), soil water retention curves, and infiltration characteristics including cumulative infiltration (CI) and wetting front (Zf). HYDRUS‐1D was applied to predict soil water movement under different biochar incorporation depths. Results showed that the rate of change of soil pH, soil organic carbon content, soil salt content and Ks were −0.009, 0.102 g kg−1, 0.045 g kg−1 and 0.035 cm day−1, respectively, per ton of biochar applied. Soil water retention curves showed that biochar enhanced soil water retention capacity and available soil water content (AWC) in the silt clay loam soil. The Philip model was a good (R2 &gt; 0.80) fit to soil water infiltration and indicated that biochar amendment promoted infiltration rates. The van Genuchten model was good for describing soil hydraulic parameters (R2 &gt; 0.99) and could be used for HYDRUS‐1D simulations (R2 &gt; 0.99, RRMSE &lt;6.8% and NSE &gt;0.98). The optimum biochar application amount for the light salinised soil in Xinjiang was recommended as 25 t ha−1 incorporated to 30 cm depth based on the AWC, soil salt content and incorporation depths. The study provides a reference for future field experiment design.Highlights Effects of biochar on salt‐affected soil studied using a combination of experiments and simulations. Acidulated biochar amendment of saline soils can reduce pH and increase SOC. Biochar incorporation depth was considered to affect soil water infiltration. The biochar application amount at 25 t ha−1 incorporated to 30 cm depth was recommended

Water repellent characteristics of physical and biological crusts and their effects on water infiltration

Soil crust is a normal natural phenomenon with different water hydrophilicity and repellency due to different formation mechanism, thus affecting soil hydraulic characteristics and hydrological cycle. In this study, we measured water repellent characteristics of physical and biological crusts under different vegetations in the field using water drop penetration time (WDPT). The surface morphology of crusts was observed using scanning electron microscopy, and the infiltration characteristics of crusts and their non-crust soils (control) was evaluated with micro-infiltration device. The results showed that: 1) The average WDPT of physical crusts and the control soils was 3.3 s and 0.9 s, respectively, indicating that both were hydrophilic. The average WDPT of biological crusts ranged from 20.9 s to 140.9 s, which was 2.8 to 19 times that of control, and that under Diospyros lotus and Robinia pseudoacacia was 134.5 s and 140.9 s, respectively. 2) Compared with the control, the cumulative infiltration amount, average infiltration rate and moisture absorption force of physical crusts decreased by 0-4.3%, 3.5%-5.1%, and 27.2%-90.1%, respectively, while those of biological crusts decreased by 0-25%, 1.4%-28.2% and 36.0%-84.9%, respectively. 3) Regardless of the presence of crusts or not, there were "hockey-stick-like" curves by using Philip model to fit infiltration data. Before the WRCT point in the "hockey-stick-like" curve, the point source infiltration was mainly horizontal diffusion. After the WRCT point, the infiltration was mainly vertical diffusion. The presence of soil crust prolonged the formation time of the turning point. In all, physical crusts formed by inorganic mineral particles blocking the surface soil did not affect water repellency, while biological crusts that reflected the effects of hydrophobic organic compounds on soil structure enhanced its water repellency. Both physical crusts and biological crusts decreased the cumulative infiltration amount and average infiltration rate of soil. Compared with the control, physical crusts mainly affected soil hygroscopicity, but with limited effects on the steady infiltration rate. Biological crust decreased soil hygroscopicity and increased steady infiltration rate.

Characteristics of runoff and infiltration processes on slope with intergrown biocrusts and herbs

Biocrusts and herbs coexist in arid and semi-arid areas, playing an important role in soil and water conservation. However, the combined effects of biocrusts and herbs on process and mechanism of runoff and infiltration on slope are still unclear. In this study, simulated rainfall experiments with four treatments, including bare soil, biocrusts, Stipa bungeana and S. bungeana+biocrusts, were designed to investigate runoff, infiltration process and hydrodynamic characteristics of herbs and biocrusts on slope. The results showed that the runoff under the two treatments with biocrusts was stable. The total runoff of four treatments was in the following order: biocrusts > S. bungeana+biocrusts > bare soil > S. bungeana, indicating that biocrusts could inhibit soil infiltration and S. bungeana could promote soil infiltration. At soil depths of 16 cm and 24 cm, the cumulative infiltration of biocrusts treatment was significantly less than that of S. bungeana+biocrusts treatment, suggesting that with the increases of soil depth, S. bungeana reduced the negative effect of biocrusts on soil infiltration. The Froude number was greater than 1 under bare soil and less than 1 under other treatments, which was subcritical flow. Compared with the runoff kinetic energy of the bare soil treatment, the treatments of biocrusts, S. bungeana, and S. bungeana+biocrusts were reduced by 83.3%, 59.5%, and 88.1%, respectively. The variations of hydrodynamic parameters indicated that the role of biocrusts is greater than S. bungeana in regulating runoff.