Philip Model Research Articles

Modified Green-Ampt model for infiltration analysis in loess area and its parameter determination and verification

Water infiltration into soil is important in geotechnical engineering. The classical Green-Ampt (GA) infiltration model is widely used in soil infiltration due to its physical significance, but it ignores the actual unsaturated layer in the infiltration process and has some deficiencies. Thus, the present study established a modified GA infiltration model (MLGA model) using Darcy’s infiltration law and continuity equation to fully consider the variation characteristics of the soil water profile in the infiltration process. The Philip model and the GA model have the same physical basis. By combining the internal relationship between the infiltration rate and cumulative infiltration of the two models, the expression of matrix suction of the MLGA model was obtained. The existing measured data was used to verify the correctness and applicability of the MLGA model. Finally, the sensitivity analysis of the critical parameters of the model was performed. The results showed that the MLGA model is reliable and can be used for water infiltration analysis in loess sites. When the MLGA model is used to calculate the infiltration depth, the maximum relative error between the calculated value and the measured data is less than 10%, and the average relative error is 5.54%, which indicates that the model has a high calculation accuracy. The average error of the MLGA model is 24.47% of the Kostiakov model and 80.42% of the existing modified GA model (LGAM model). Sensitivity analysis of the saturated permeability coefficient, initial water content, saturated water content, and matrix suction was performed using the single-factor disturbance method. The influence of each parameter on infiltration depth was summarized, and the sensitivity of each parameter was quantitatively evaluated, which revealed that saturated water content is a highly sensitive parameter. When using the MLGA model to calculate infiltration depth, the accuracy of saturated water content should be ensured first. Finally, the difference between the MLGA model and the LGAM model in describing the whole process of water infiltration is discussed, and the influence mechanism of critical parameters on the water infiltration process is deeply analyzed. The established MLGA model provides theoretical support for further study of the loess water infiltration mechanism.

Water Infiltration and Evaporation Process with ATP Addition in Newly Reclaimed Soil

The newly reclaimed soil is an important reserve land resource, while it faces challenges such as poor water retention and low fertility. Therefore, it requires improvement through the use of soil amendments. Attapulgite (ATP) is abundant in northwest China with excellent properties and can be used as an amendment for newly reclaimed soil. The effects of ATP and its addition rate on infiltration and evaporation characteristics in newly reclaimed soil were studied by experiments and model simulation. Three addition gradients (2%, 4%, and 6%) were set in this study, and no ATP addition was used as a control (CK). The results show that ATP treatment prolonged the infiltration duration, reduced the wetting front migration distance, and reduced the accumulated evaporation. Both the Philip model and the Kostiakov model can accurately describe the infiltration process of newly reclaimed soil with ATP addition; the soil evaporation process can be fitted well with the Rose model. In this study, ATP addition affected both sorptivity and the stable infiltration rate of the reclaimed soil. During the evaporation, the soil evaporation effect was inversely proportional to the addition rates of ATP, and the ATP addition rate at 2% had the best effect on reducing soil evaporation. In summary, the ATP addition was beneficial top soil infiltration and evaporation, thus improving the poor water retention of newly reclaimed land and is a reasonable choice for efficient construction of new reclaimed land.

Use of rice straw nano-biochar to slow down water infiltration and reduce nitrogen leaching in a clayey soil

Biochar exhibits numerous advantages in enhancing the soil environment despite a few limitations due to its lower surface energy. Nanomodified biochar combines the advantages of biochar and nanoscale materials. However, its effects on water infiltration and N leaching in a clayey soil remain unclear. Therefore, this study prepared rice straw nano-biochar by a ball milling method, and investigated its physicochemical properties and effects of bulk biochar and nano-biochar at various addition rates (0 %, 0.5 %, 1 %, 2 %, 3 %, and 5 %) on wetting peak migration, cumulative infiltration, water absorption and retention, and N leaching. The results showed that, compared with bulk biochar, nano-biochar presented a more abundant pore structure with an increase in specific surface area of approximately 1.5 times, accompanied by a 20 % increase in acid functional groups. Compared with those for clayey soil without biochar addition, the wetting front migration time was increased by 10.2 %–123.9 % and 17.0 %–257.9 %, and the cumulative infiltration volume at 60 min was decreased by 26.0 %–48.4 % and 14.1 %–62.4 % for bulk biochar and nano-biochar, respectively. The parameter S of Philip model and the parameter a of Kostiakov model for nano-biochar were lower than those for bulk biochar, whereas the parameter b of Kostiakov model was greater, indicating that nano-biochar decreased initial soil infiltration rate and increased attenuation degree of the infiltration rate. Nano-biochar increased water absorption by 8.03 % and subsequently enhanced water retention capacity relative to bulk biochar. In addition, bulk biochar and nano-biochar reduced NH4+-N leaching by 3.0 %–13.1 % and 5.7 %–39.2 %, respectively, and NO3−-N leaching by 2.7 %–3.6 % and 9.0 %–43.3 %, respectively, by decreasing N concentration and leachate volume relative to those with no biochar addition. This study provides new knowledge for nano-biochar application in a clayey soil.

Changes and influence factors of soil matrix infiltration in Chinese fir plantations with different stand ages in northern Guangxi

Soil matrix infiltration is an important pathway for plantations to obtain water, which affects ecological benefits and water conservation function of plantations. The changes of soil matrix infiltration and its influencing factors in different growth stages of Chinese fir plantations remain unclear. We measured soil matrix infiltration process using a tension infiltrometer in Chinese fir plantations (5, 8, 11, and 15 years old) of Beijiang River Forest Farm in Rongshui, Guangxi, and analyzed soil basic physicochemical properties to identify the dominant factors influencing soil matrix infiltration. The results showed that initial infiltration rate, stable infiltration rate, and cumulative infiltration increased with stand ages. The ranges of different stand ages were 141-180 mm·h-1, 109-150 mm·h-1, and 188-251 mm, respectively. The initial infiltration rate, stable infiltration rate, and cumulative infiltration were significantly positively correlated with soil capillary porosity, soil organic matter, soil water stable macroaggregate, sand content, and clay content, while negatively correlated with soil bulk density and silt content. Early thinning had a positive effect on soil matrix infiltration, but thinning measures after 11 years did not enhance soil matrix infiltration further. Philip model was optimal for describing soil matrix infiltration process in this region. In conclusion, soil matrix infiltration capacity of Chinese fir plantations gradually increased from young to middle-aged stands, but matrix infiltration capacity tended to stabilize after 11 years old. Silt content and water stable macroaggregate were the dominant factors influencing matrix infiltration.

Coupled heat and water transfer in heterogeneous and deformable soils: Numerical model using mixed finite element method

We present a generic model framework for coupled heat and water transfer (CHWT) in deformable (non-rigid) soils with spatial variations of soil properties. The model backbone is a mixed finite element method (FEM), which solves the Philip and de Vries (1957) CHWT model and achieves conservation of mass and energy on both local and global scales. Spatial variations occur in soil hydraulic and thermal properties due to transient water content and temperature distributions. Based on the mixed FEM scheme, a gradient measure and a clustering model (“k-means”) are proposed to trace the regions with large spatial variations of soil properties, and an adaptive mesh refinement technique is developed to improve the spatial resolution and simulation accuracy. Deformation perturbates local soil topography and alters transient soil water and temperature regimes in the deformed regions. A quasi-static deformation model is presented, and the deformation effects are incorporated into the mixed FEM scheme. When external load exists, soil deformation is simulated with an updated Lagrangian formulation, and the local water content and temperature variations due to soil volume changes are also updated in the CHWT model. Numerical examples, including thermally induced soil water transfer and water infiltration, illustrate the model ability to provide plausible CHWT results, especially the refined solutions near the wetting fronts and the water content and temperature distributions when the soil is deformable. In conclusion, the proposed model framework provides an effective pipeline to incorporate and process the spatial variations of soil properties and soil deformation in CHWT simulations.

Water Infiltration in Different Soil Covers and Management in the Cerrado–Amazon Ecotone, Brazil

Soil water infiltration is an important component of the hydrological cycle, and it is best evaluated when the raindrop impacts the ground surface. For this reason, it is affected by changes in land use and land cover and by the characteristics and physical–hydric properties of the soil. This study aimed to evaluate soil water infiltration in areas occupied by annual crops (soybean and corn) and pastures in two watersheds of the Teles Pires River-MT, using simulated rainfall, physical models, and principal component analysis. Infiltration rates were evaluated based on simulated rainfall with an average intensity of 75 mm h−1, with four repetitions per region (upper, middle, and lower) of the hydrographic sub-basins of the Caiabi and Renato rivers, and soil use with cover, without cover, and disturbed. Soil tillage provided higher water infiltration rates into the soil, especially in pasture areas in the two hydrographic sub-basins. There were significant adjustments to the mathematical models based on the infiltration rate data for all land use and land cover conditions. The soil attributes that most interfered with the infiltration rate were microporosity, bulk density, and total porosity in the crop areas of the middle Caiabi and microporosity, clay content, total porosity, and silt content in the areas farming at the source of the Renato River. The Horton and Philip models presented the best adjustments in the hydrographic sub-basins of the Caiabi and Renato Rivers, which are recommended for estimating the water infiltration rate into the soil in different uses, coverages, and regions.

Comparison of infiltration model performance based on basic infiltration rate for small watersheds in Papua region, Indonesia

Research on soil water infiltration in equatorial climates like Indonesia is limited. Despite Papua accounting for 29% of Indonesia’s surface water, there’s a shortage of hydrological data. This study aimed to identify the best infiltration model tailored to the characteristics of basic infiltration rates in Papua’s small watersheds. Observations were made at 95 points across 11 small watersheds in Papua. Based on equatorial basic infiltration rate theories, analysis classified infiltration values against observation time. The performance of four infiltration models — Horton, Philip, Kostiakov, and Green Ampt — were compared. The results indicated the Philip model as superior, with average scores of 0.901 (R), 0.814 (NSE), and 0.424 (RSR), followed by the Horton and Green Ampt models. These three models showed excellent performance. However, the Kostiakov model was found lacking and needs modification. Further research on rapid and very rapid classifications is vital for enhancing infiltration rate predictions in small equatorial watersheds.

Estimation of Infiltration Parameters: The Role of Pedotransfer Functions and Initial Moisture Conditions

Infiltration is one of the key components of rainfall-runoff processes at small catchment scale and is therefore a vital component of hydrological models. However, small catchments typically lack direct infiltration measurements and associated soil hydraulic characteristics, which are being substituted with soil databases and pedotransfer functions built upon these databases. We utilized two sets of pedotransfer functions Rosetta 3 and EUPTFv2 derived from two well known soil databases: UNSODA, based on US and global soil data, and EU-HYDI, based on EU soil data. Our study evaluates the impact of choosing one of these pedotransfer functions on modeled infiltration in relation to variable initial moisture content- It investigates the behavior of the simplified infiltration models of Green-Ampt and Philip under different initial conditions, in comparison with Richards’ complex solution, which is used as a benchmark. Our evaluation was conducted using soil property data available in the Czech Republic, covering ten USDA soil textures that are prevalent within the European Union. The applied initial moisture conditions were derived for specific suction pressure values that correspond to hydrological initial conditions ranging from near saturation to near the permanent wilting point. Variation in the derived parameters for the Green-Ampt and Philip models across the pedotransfer function sources results in considerable variation in the modeled infiltration. Our results imply different sensitivities of the simplified infiltration models to the initial moisture for different pedotransfer functions. The Green-Ampt and Philip infiltration models demonstrate better alignment with Richards’ complex solution with a low and consistent RMSE when using the Rosetta 3 pedotransfer function. By contrast, the EUPTFv2 model scenarios, show a clear trend of increasing RMSE towards dry initial conditions. As the European soil database is not an open data source, we only hypothesize that the distributions of soil characteristics in the European soil database differ systematically from those in UNSODA, and that this would cause different results of pedotransfer functions for different initial moisture conditions. The findings of this study are important for selecting appropriate infiltration models and, appropriate pedotransfer functions for estimating model parameters, and for assessing uncertainties connected with varying initial conditions.

Evaluation of infiltration models in clay loam and laterite soils under field conditions

The purpose of the investigation is to calculate soil infiltration rates with the help of infiltration models. The infiltration model helps to design and evaluate surface irrigation systems. The study calculated constant infiltration for two types of soils (clay loam soil and laterite soil) under field conditions (Unploughed and Ploughed). The double-ring infiltrometer has been implemented to experiment. The value of various constants of the models was calculated using the approach of averages counselled through a graphical technique. Fitting infiltration test data to prominent infiltration models such as Philip’s, Horton's and Kostiakov’s and The Nash- Sutcliffe efficiency (NSE), coefficient of determination (R2) and root mean square error (RMSE) statistics are used to evaluate the effectiveness of the model. The results indicate that Philip's model is the most reliable, with R2, NSE, and RMSE values ranging from 0.9044-0.9677, 0.294-0.957 and 1.2647-5.7129, respectively. Therefore, under identical circumstances and without any kind of infiltration information, the above model can be employed to artificially produce infiltration information.

Simulation model of water infiltration in soil using combination technique

Due to the limited groundwater resources, the appropriate and optimal utilization of these resources is an imperative aspect of the hydrological cycle, hydrological studies, water conservation and management, implementation of irrigation and drainage projects, and control of soil erosion in watersheds. The objective of this paper was to accurately simulate soil water permeability. The findings demonstrated that the Philip mathematical models, as well as the Philip, Green-Ampt, and three-component Philip models, exhibited significant efficacy in simulating water permeability behavior in soil. However, like all modeling methods, these approaches are not without errors, despite their considerable capabilities. Consequently, several combined techniques, including SMA, WAM, MMSE, and M3SE, were employed to enhance the simulation of water infiltration in soil. Thus, the aim of this study was to ascertain the impact of different combination techniques on the level of simulation accuracy of various models. The outcomes revealed that all combined techniques, with the exception of M3SE, yielded improved results in terms of infiltration models and accuracy. Among the methods, the combined M3SE technique proved superior in clay loam, loam, and sandy loam soils, with error values of 0.007 cm, 0.012 cm, and 0.009 cm, respectively. However, in the context of soil physics and saturated conductivity, M3SE did not exhibit satisfactory performance, serving as one of the possible explanations. This investigation demonstrated that multi-model simulations surpass uncontrollable single-model simulations, even when utilizing the best-calibrated single-model simulations.

Effects of Subsoiling with Different Wing Mounting Heights on Soil Water Infiltration Using HYDRUS-2D Simulations

Subsoiling is an essential practice in conservation tillage technology. The amount of disturbed soil at various depths resulting from subsoilers with different parameters has an important effect on soil properties (e.g., bulk density and water infiltration). The information regarding the effects of subsoiling on the characteristics of soil water infiltration is essential for the design of subsoiling tools. In this study, the effects of the wing mounting height (h) (75–155 mm) of the subsoiler on soil disturbance and soil water infiltration were modelled using HYDRUS-2D and validated using field experiments. Results showed that reducing h values resulted in larger soil disturbance area ratios, soil water infiltration rates (f(t)), distances of vertical wetting front movement (DVWs), accumulative infiltrations (AINs), and soil moisture contents at depths of 10–30 cm. The relationships among characteristics of soil water infiltration, h and time (t), were developed. The stable infiltration rates (fs) varied quadratically with h and the corresponding coefficient of determination (R2) was 0.9869. The Horton model is more suitable for describing the relationship between f(t) and t under the tested soil conditions, as compared with the Kostiakov and Philip models. According to the results of soil water content at different depths from the HYDRUS simulations and field experiments, the developed soil water infiltration model had a good accuracy, as indicated by RMSEs of <0.05, R2 values of >0.95, and mean relative errors of <12%. The Above results indicated that increasing the hardpan disturbance by optimizing wing parameters of the subsoiler could improve soil water infiltration characteristics.

Infiltration Measurements during Dry Conditions in an Urban Park in Ljubljana, Slovenia

A thorough understanding of the hydrologic mechanisms that control the movement of water through the soil is essential for developing effective stormwater management strategies. Infiltration is critical for determining the amount of water entering the soil and controlling surface runoff. Spatial and temporal variations in soil properties strongly affect infiltration rates, which underscores the importance of evaluating field-specific values for hydraulic conductivity, which are also highly dependent on the chosen measurement and evaluation methods. The objective of this study is to determine and compare soil hydraulic conductivity under dry conditions using two field measurement techniques, namely the double-ring infiltrometer (DRI) and the mini-disk infiltrometer (MDI). The results demonstrate the importance of performing multiple replicates of infiltration tests, especially during the dry season, as the initial dry surface caused deviations in hydraulic conductivity estimates for both methods used (DRI and MDI). Significant spatial variability was observed within the radius of the test replicates over short distances (<1 m). In addition, experimental infiltration curves for a selected site were used to evaluate and compare soil hydraulic parameters through infiltration modeling. In general, the Philip, Green-Ampt, and Smith-Parlange theoretical models showed a better fit to the experimental DRI data than the semi-empirical Horton model.

A Study on Infiltration Characteristics and One-Dimensional Algebraic Model Simulation in Reclaimed Soil with Biochar

The cultivated land area in China is approaching the red line of farmland protection. The newly reclaimed land will become a vital reserved land resource, and it possesses a large exploratory potential. Newly reclaimed soil usually has low productivity with poor physical and chemical properties as well as weak fertility, and it is prone to serious soil erosion. The effects of corn straw biochar and rice husk biochar (at the mass ratio of 2%, 4%, and 8%) on the soil infiltration process and soil moisture distribution in the soil profile were studied. The results showed that the infiltration duration was prolonged, and the wetting front migration distance and infiltration rate were decreased under biochar addition treatments, except under the low addition rate for rice husk biochar. The Philip model and Kostiakov model accurately described the water infiltration process of the newly reclaimed soil with both kinds of biochar. The two kinds of biochar used in this study affected both the initial infiltration rates and stable infiltration rates, and water infiltration was more sensitive to rice husk biochar and its addition rate. The moisture in the soil profile after infiltration was simulated using a one-dimensional algebraic model. The surface soil moisture was improved with both kinds of biochar addition, and the water retention ability was enhanced with an increased biochar addition rate. In conclusion, corn straw biochar with a high addition rate is beneficial for inhibiting soil water infiltration and improving weak water retention ability in the newly reclaimed area, which is a recommended choice for efficient soil construction in newly reclaimed land.

Field‐scale measurements of soil physico‐chemical profiles of the Potohar region in the Indus basin of Pakistan

AbstractSoil physico‐chemical properties are important for best management practices. We measured infiltration, bulk density, texture, water retention and chemical profiles from the surface to 1.0 m and lithology to 50 m depths at 30 sites. The infiltration data were fitted to the cumulative and infiltration rate models of Philip and Horton. The same sites were used for water retention, physico‐chemical properties and lithological assessment. The cumulative models fit persistently better than their infiltration rate forms. The Horton cumulative model fitted statistically better than the corresponding Philip model. The dominant steady‐state infiltration rates were 15–30 and 30–45 mm h−1 over the entire profile. Sandy loam, loam and silt loam were the dominant soils. The percentages of sandy loam decreased, whereas silt loam increased, with depth. Water retention parameters and lithological strata were diverse and in harmony with physiography. Soil organic matter varied up to 2.5%. No sodicity or salinity was detected except in sparse saline seeps. The central tendency and extrema of the measured parameters were compatible with the literature, and the CVs of the soil hydraulic parameters were greater than those of the physical parameters. Comprehensive data are presented, which will serve as an important reference for regional and global repositories.

Changes of preferential flow in short-rotation eucalyptus plantations: field experiments and modeling

As an important part of the hydrological cycle, preferential flow significantly improves infiltration properties and limits the ability of soil to store, filter, and buffer water. However, the effect of roots on the preferential flow infiltration process in forest ecosystems is still unclear. This study measured the preferential flow infiltration process in short-rotation eucalyptus plantations (four forest ages of 1, 2, 3, and 5 years) with the surface-positioned double-ring infiltrometer in south subtropical area, China. Overall, the cumulative infiltration (CI), initial infiltration rate (IIR), and stable infiltration rate (SIR) increased with forest age. The CI, IIR, and SIR of the 5-year-old eucalyptus plantation were the highest in four aged eucalyptus plantations. Correlation analysis showed that root biomass was positively and significantly correlated with CI (p < 0.05), IIR (p < 0.01), and SIR (p < 0.01), which showed that the preferential flow increased with root biomass. However, the correlations between total porosity (TP) and IIR, SIR, and CI were all not significant (p > 0.05). The dye coverage of the inner and outer ring tangents, which were used to observe the strength of lateral preferential flows, was significantly and positively correlated with CI (p < 0.01), IIR (p < 0.01), and SIR (p < 0.01). The dye coverage of the outer ring tangent was significantly and positively correlated with root biomass (p < 0.05). So, the lateral preferential flows depended on root biomass and increased with forest age. The Horton model, which had higher stability and accuracy than the Kostiakov and Philip models, was the most suitable model to describe the preferential flow infiltration process in eucalyptus plantations. As important factors influencing the evolution of preferential flow in eucalyptus plantation, root biomass was used in predicting the parameters of the Horton model through regression analysis. Then, a unified model predicting the preferential flow infiltration process in short-rotation eucalyptus plantations was proposed and verified. This study achieved the quantitative measurement of preferential flow infiltration process, explored the importance of roots in the production of preferential flow channels, and found the lateral preferential flow played an important role in infiltration in forests. These results can provide a theoretical basis for improving the efficiency of water resource management in plantation, and optimizing the model of preferential flow infiltration process in plantation.

Infiltration Model of Mediterranean Soil with Clay Texture

Infiltration plays an essential role in increasing the soil water content as a part of the hydrological cycle. Infiltration affects surface runoff and soil conservation. It also determines the sustainability of the groundwater system. Heavy rain intensity exceeding the infiltration capacity will result in surface runoff, and excessive surface runoff will cause soil erosion. This study aims to investigate the suitable infiltration rate model in the Mediterranean soil of clay textured with various soil conditions. Infiltration rate measurement employed a double-ring infiltrometer in soil without and with tillage. The applied infiltration rate model was an empirical model and the function of time, which includes the Kostiakov, Horton, and Philip Models. The results demonstrated that the Mediterranean soil infiltration rate with a clay texture was 0.91 cm/min and was relatively higher in the soil without tillage. The suitable infiltration rate model to be applied in soil conditions without and with tillage is the Kostiakov Model f = 0.700 t-0.25 and f = 0.682 t-0.22, respectively. The Kostiakov model is the most suitable infiltration rate model in Mediterranean textured clay, without tillage conditions, with a determination value of 0.988 and a deviation value of 0.005. Keywords: Horton model, Philip model, Infiltrometer; Kostiakov model, Tillage

Development and uncertainty analysis of infiltration models using PSO and Monte Carlo method

AbstractThe present research aims to calibrate infiltration models including the Kostiakov (KM), modified Kostiakov (MKM), Novel (NM), Philip (PM), Horton (HM) and Soil Conservation Service (SCSM) models using the particle swarm optimization (PSO) algorithm. To satisfy this end, the published data related to the double‐ring test in the Davood Rashid and Hunam regions located in Lorestan and Ilam provinces (western Iran) were applied. Then, Monte Carlo analysis (MCA) was used to model the uncertainty of the coefficients of the mentioned models. The lowest accuracy in the Hunam region is related to MKM with the statistical indices coefficient of determination (R2) = 0.901 and root mean square error (RMSE) = 0.023, while in the same region, the highest accuracy is related to the NM with the statistical indices R2 = 0.988 and RMSE = 0.008. For the Davood Rashid region, the lowest accuracy is related to the HM with the statistical indices R2 = 0.890 and RMSE = 0.038. In this region, the highest accuracy is related to the NM and MKM with the statistical indices R2 = 0.987 and RMSE = 0.012. To determine the uncertainty of the parameters of the infiltration models, 10,000 datasets were generated based on observed data and the MCA, and then their range at the 95% confidence level was calculated. According to the MCA, among the models used in the study areas, the NM has less uncertainty and the results of this model can be adopted with more reliability.

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.

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.