Initial Infiltration Rate Research Articles

Contribution of root and soil properties on soil infiltration capacity of gramineous and leguminous forages during root decomposition

Soil properties are generally altered during root decomposition, which impacts soil water infiltration. Gramineous and leguminous plants present distinct root properties, but it remains unclear whether the root or soil properties are primarily responsible for the soil infiltration capability during root decomposition. To identifythe differences in the contributions of root and soil properties to soil infiltration capability between these two species during root decomposition, a potted plant in situ decomposition experiment was conducted using Bothriochloa. ischaemum (Gramineae) and Lespedeza. davurica (Leguminosae) during three root decomposition times (the 90th, 270th and 450th day). The results revealed that all the root properties (root length, root volume, average root diameter and root biomass) gradually decreased during root decomposition, especially the root length (RL) and root volume (RV) of L. davurica in 0–40 cm soil layer, with reductions of 55.35% and 58.73% at the 450th day compared with the 90th day. The reverse was true for the soil porosity and mean weight diameter of the soil aggregates. Compared to B. ischaemum, L. davurica presented relatively high initial infiltration rate (IIR), steady infiltration rate (SIR), and average infiltration rate (AIR) values at three root decomposition times. A great increase in the soil infiltration rate was observed for both species at the late decomposition stage (450th day), especially for L. davurica, with increases of 38.32%, 267.7%, and 137.1% in IIR, SIR, and AIR. The GLM analysis results revealed that root properties had a greater contribution to the soil infiltration capability. The key factors controlling the soil water infiltration process have been quantified as RL and RV. The present study indicates that leguminous forage presented greater soil infiltration capability during root decomposition. A great decrease in RL and RV within the upper soil layers increased the soil porosity and facilitated the formation of soil aggregates, thereby promoting water flow and ultimately improving the soil infiltration capability.

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.

Distinct variations of soil infiltrability of contrasting root types in a temperate mosaic-pattern grassland in northern China

Soil infiltration capacity is an important factor affecting soil moisture, and is of great significance to plant growth and groundwater recharge in arid and semiarid areas. Patchiness of grasslands widely exist and have a crucial effect on hydrological processes in water-limited regions. This study investigated soil infiltrability under natural grasslands with patchy mosaic patterns based on a series of in-situ tests. Two dominated natural restoration vegetation communities (Bothriochloa ischaemum (B. ischaemum) with fibrous root systems and Artemisia gmelinii (A. gmelinii) with tap root systems) and abandoned land (as control) were selected in the loess hilly and gully region of the Loess Plateau, China. The results showed that natural restoration grasslands significantly improved soil infiltrability in both plant and bare patches, and the emergence of patchy mosaic patterns can result in infiltration heterogeneity to redistribute water on a hillslope scale. Compared to B. ischaemum, A. gmelinii are more likely to facilitate the formation of preferential flow, contributing to the increased soil infiltration rates. The initial, steady and average infiltration rates (IIR, SIR, and AIR, respectively) and soil infiltration capacity index (SIC) were all negatively correlated with both root length density (RLD) and root surface area density (RSAD) of fine roots (diameter < 2 mm) but positively correlated with those of coarse roots (diameter ≥ 2 mm). The main factors influencing the infiltration capacity were the mean weight diameter in the 10−20 cm layer and the RSAD of the fine roots in the 0−20 cm layer, which can explain 98.6 %, 81.7 %, 63.9 %, and 91.3 % of the total variance of IIR, SIR, AIR, and SIC, respectively. This work highlights the important roles of patchy mosaic patterns in affecting soil water redistribution and the stabilization of ecological systems, providing a scientific basis for vegetation selection in the process of vegetation restoration in water-limited regions.

Colour pervious concrete pavements applied to bikeway track: mechanical, hydraulic and functional performances

ABSTRACT Pervious concrete pavement test sections employing coloured permeable concrete were constructed as an experimental bicycle lane. For two of the sections, coloured concrete was used with pigment addition consisting of Fe2O3 (red) and Cr2O2 (green). The impacts on the resistance and stiffness of the concretes when using these pigments were analysed in relation to the reference concrete (grey). Alterations in plasticiser dosage during mixing were readily observed with the red concrete. The flexural strength increased substantially in the case of the red coloured concrete, as well as the modulus of elasticity of the material. Initial infiltration rates decreased with the use of coloured pigments, especially for red concrete, with expressive drops in permeability. Simultaneously, the resistance to friction given by the British Pendulum Number was reduced due to the use of red or green pigments. The consequences of using red pigment with a very high grains specific surface are discussed, since they are advantageous in the case of mechanical responses eventually inferior in terms of hydraulic and functional aspects.

One-dimensional infiltration in a layered soil measured in the laboratory with the mini-disk infiltrometer

Abstract Layered soils can consist of a thin little permeable upper layer over a more permeable subsoil. There are not many experimental data on the influence of this upper layer on infiltration. The mini-disk infiltrometer set at a pressure head of –3 cm was used to compare infiltration of nearly 40 mm of water in homogeneous loam and clay soil columns with that in columns made by a thin layer (1 and 3 cm) of clay soil over the loam soil. For each run, the Horton infiltration model was fitted to the data and the soil sorptivity was also estimated by considering the complete infiltration run. For the two layered soils, the estimates of initial infiltration rate and decay constant were similar but a thicker upper layer induced 2.4 times smaller final infiltration rates. Depending on the infiltration parameter and the thickness of the upper layer, the layered soils were characterized by 2.2–6.3 times smaller values than the loam soil and 2.2–6.6 higher values than the clay soil. Sorptivity did not differ between the homogeneous clay soil and the layered soil with a thick upper layer and a thin layer was enough to induce a decrease of this hydrodynamic parameter by 2.5 times as compared with that of the homogeneous loam soil. Even a thin upper layer influences appreciably infiltration and hydrodynamic parameters. Layering effects vary with the thickness of the upper layer and the considered parameter. The applied experimental methodology could be used with other soils and soil combinations.

Effect of vegetation restoration type and topography on soil water storage and infiltration capacity in the Loess Plateau, China

Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems.

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.

Mechanical terracing regulates soil physicochemical properties and infiltration processes in the Loess Hilly Region of China

AbstractThe widespread adoption of large‐scale machines has led to a significant shift in terrace construction methods, transitioning from manual labor to mechanical processes. Mechanical terracing, by deeply disturbing the surface and compaction of the soil, has resulted in significant variations in both the soil physicochemical properties (SPCs) and soil infiltration properties (SIPs). However, few studies have been carried out to investigate the impact mechanisms of mechanical terracing on soils. In this study, we conducted detailed field experiments to determine the effects of mechanical terracing on SPCs and SIPs. The results showed that mechanical terracing increased soil compaction and decreased soil porosity and organic matter compared to manual terracing. Moreover, mechanical terracing had lower initial and steady infiltration rates than manual terracing (decreasing by 2.60% and 18.59%, respectively). However, initial and steady infiltration rates significantly improved compared to sloped land, increasing by 20.82% and 54.68%, respectively. The partial least squares path model indicated that bulk weight, organic matter content, and soil texture were the dominant influencing factors of SIPs. The results underscore the critical need to incorporate distinctions between various terrace construction methods into hydrological models for more accurate predictions.

Short‐term conservation tillage degrades soil infiltration properties in the black soil region of Northeast China

AbstractSoil infiltration properties (SIPs) are crucial soil hydraulic parameters for hydrological and erosion models as they regulate the movement of water and nutrients within the soil. Tillage practice can significantly impact the hydrological and erosional processes of sloping farmland by changing SIPs through altering soil structure. Nevertheless, knowledge regarding the effects of short‐term conservation tillage on SIPs is unclear, which greatly limits the management of soil and water resources of sloping farmland. This study aimed to clarify the potential impact and underlying mechanisms of short‐term implementation of conservation tillage on SIPs under three typical tillage management types: conventional downslope tillage (DT), conservation contour tillage (CT), and no‐tillage (NT) in the black soil region of Northeast China. SIPs of initial infiltration rate (IIR), steady infiltration (SIR), and hydraulic conductivity (Ks) were determined by a field disc infiltration experiment under pressure heads (h) of −3, −1.5, and 0 cm. The results revealed that short‐term implementation of conservation tillage management degraded SIPs, with a significant difference observed between DT and NT. In comparison to DT, the mean SIPs of IIR, SIR, and Ks of CT decreased by 27.5%, 31.2%, and 28.6%, and the corresponding reduced values of NT were 54.1%, 65.0%, and 65.5%, respectively. SIPs were significantly correlated with soil texture, bulk density (BD), capillary porosity (CP), total porosity (TP), field capacity (FC), saturated water content (SSWC), and organic matter content (SOM). Among these influencing factors, the variations in SIPs among different tillage management and soil layers were primarily influenced by differences in clay and gravel contents, FC, and SSWC and SSWC played the most critical role. These results highlight the substantial impacts and clarify the mechanisms of short‐term conservation tillage on SIPs, which is helpful for understanding the potential effect of short‐term conservation tillage management on hydrology and erosional processes, thereby improving the sustainable utilization of arable land.

Assessing Horton and Kostiakov models focused on estimating soil water infiltration

Water infiltration into the soil plays key role in proper soil and water conservation and management processes. The aim of the current study is to assess water behavior in soil infiltration processes by using the Horton and Kostiakov models. Double-ring infiltrometer method was used to determine water infiltration into the soil. In addition, soil samples were collected at depths of 0-10 cm, 10-20 cm and 20-30 cm, to determine soil moisture. Cumulative infiltration (IA) and instantaneous infiltration rates per time interval (TiR) were calculated. Equations describing the investigated phenomena were adjusted, according to the Horton and Kostiakov models. High water infiltration rate was observed at the beginning of the process, likely due to low moisture level at the top soil layer. Both models tend to underestimate the initial infiltration rate value. However, the Horton model tends to overestimate most of the instantaneous infiltration values up to 25 minutes. The Kostiakov model, on the other hand, tends to overestimate most of the instantaneous infiltration rate values after 80 minutes. Despite the large fluctuation observed in TiR values in the soil, the assessed models have satisfactorily described the infiltration behavior at the experimental site. Based on the heat map analysis, the Kostiakov model was the one capable of determining the infiltration values closest to actual one.

Influence of soil properties and near-surface roots on soil infiltration process in short-rotation eucalyptus plantations in southern subtropical China

Soil infiltration capacity is a measure of the rate of water infiltrating into a soil. The influence of soil properties and near-surface roots on the soil infiltration process remains unclear in short-rotation eucalyptus plantations. A series of field experiments were conducted to determine the soil infiltration capacities of differently aged (1, 2, 3, and 5 years) eucalyptus plantations by using a surface-positioned double-ring infiltration instrument. The biomass of fine root (<2 mm) and medium root (2–10 mm) on near-surface soil (0–50 cm) and soil samples (0–60 cm with 20 cm interval) was collected for analyzing the effects of near-surface fine root biomass (FRB), medium root biomass (MRB), soil organic matter (SOM), soil bulk density (BD), soil total porosity (TP), soil macroaggregate, and water-stable macroaggregate on soil infiltration. Results showed that the average infiltration rate (762–1463 mm h−1), initial infiltration rate (5420–8454 mm h−1, infiltration rate of stage I (3130–5421 mm h−1), infiltration rate of stage II (1594–2257 mm h−1), infiltration rate of stage III (484–934 mm h−1), and steady infiltration rate (318–510 mm h−1) increased with increasing forest age. The near-surface FRB (4.25–14.71 g) decreased with increasing forest age. Near-surface FRB showed a strong plugging effect on soil infiltration in both initial and steady infiltration stages, but this effect weakened with increasing forest age because of FRB decreasing. Near-surface MRB had no significant effects on soil infiltration. The TP and SOM in near-surface soil promoted soil infiltration capacity. The soil infiltration capacity of short-rotation eucalyptus plantations significantly improved after the third year of planting. Our finding contributes to understanding the effects of near-surface root biomass and soil properties on soil infiltration capacity in eucalyptus plantations, and provides a scientific reference for eco-hydrological study in such plantations.

Soil physicochemical properties and crusts regulate the soil infiltration capacity after land-use conversions from farmlands in semiarid areas

Large scale land-use conversions played important role in regulating the process of soil infiltration, and thus changing soil moisture recharge. However, how the soil properties influence infiltration after farmland conversions remain unclear in the semiarid areas. This study used a double-ring infiltrometer to conduct infiltration experiments in soil surface and subsurface among land-uses on the Loess Plateau, to explore the mechanism of soil physicochemical properties and crusts on infiltration. The results showed that the revegetation lands effectively improved infiltration properties, while no significant differences were observed between the orchards and the farmlands. The loose soil structure, stable aggregates, higher organic matter and root mass density improved while soil crusts impeded infiltration capacity after farmland conversions. The impeding effect of the biocrusts presented throughout the infiltration process while physical crusts impeded infiltration only at the initial stage. Soil physical properties (i.e., bulk density, porosity, macroaggregate, texture, moisture), biochemical properties (i.e., soil organic matter, roots) and crusts were major factors in the variation of the surface (0–20 cm) infiltration properties, while subsurface (20–40 cm) infiltration were mainly influenced by soil physical properties. The deeper soils had a greater impact on steady infiltration rate than initial infiltration rate. Due to the plough pan in agricultural lands, the subsurface soil (20–40 cm) had a strong effect (42.1%) on the steady infiltration rate of the surface (0–20 cm) soil, even close to the surface (0–20 cm) soils (49.8%). These findings improve the comprehensive understanding of the soil hydrological processes after farmlands conversions in semiarid areas.

Impact of Storm Characteristics on Infiltration Dynamics in Sponge Cities Using SWMM

Effective stormwater management in urban areas requires enhancing the permeability of underlying surfaces. However, the impact of storm characteristics on infiltration processes in sponge cities remains insufficiently explored. This study uses the Horton method within the storm water management model to investigate how uniform and Chicago storm parameters affect infiltration rates. Our findings provide valuable insights: (1) Increasing porous pavement area proportionally reduces subarea sizes within subcatchments, and infiltration rates of porous pavements are supply-controlled. (2) Uniform storms result in consistent initial infiltration rates across pervious areas, subcatchments, and the entire catchment. The duration of this stable state decreases with higher return periods. Catchment infiltration volumes exhibit linear growth with greater storm intensities (R-squared = 0.999). (3) Peak infiltration rates and moments for pervious areas, subcatchments, and the overall catchment exhibit correlations with both the return period and the time-to-peak coefficient, with correlation coefficients ranging from −0.9914 to 0.9986 and p-values ranging from 0.0334 to 0.6923. This study quantifies the influence of design storm parameters on infiltration, providing valuable insights for stormwater infrastructure design and urban stormwater control.

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.

A nature-based solution to reduce soil water vertical leakage in arid sandy land

Quick water seepage in sandy soils results in a serious restriction for ecological restoration, becoming a worldwide urgent research issue in arid areas. Search for practical solutions are focused on reserving the limited rainfall into topsoil layer to meet plant water demand. Based on fieldwork, this study evaluates the blocking effects of Pisha sandstone on soil water leakage, by inserting sandstone layers in the different soil depths (10–15 cm, 20–25 cm, 30–35 cm), which act as isolation layers within the sandy soil. Results showed that the inserted Pisha sandstone layers significantly decreased the soil water infiltration rates at the different stages and cumulative infiltration. The inserted sandstone layer at the depth of 10–15 cm presented the highest permeability resistance, and its initial infiltration rate, stable infiltration rate and average infiltration rate decreased by 102.42 mm h−1, 144.30 mm h−1 and 132.79 mm h−1, respectively. Meanwhile, the soil water content in the 5–10, 20–25, and 30–35 cm soil layers increased by 2.17%, 2.20%, and 1.37%, respectively, due to the inserted Pisha sandstones. This experimental study proves that the insertion of Pisha sandstones effectively hinders the downward penetration of soil water in sandy soil. These findings provide a new alternative for an effective solution of the fast water leakage problem of sandy land.

Effects of organic amendments on soil hydraulic characteristics in the Mollisols of Northeast China

AbstractSoil degradation in the Mollisol region of Northeast China is ubiquitous partly due to poor soil hydraulic characteristics. Improving soil hydraulic characteristics thus delivers benefits to soil sustainability. In this study, the effects of organic amendments on soil hydraulic characteristics were explored at the laboratory scale. Soil samples were subjected to three low‐cost and eco‐friendly organic amendments, including corn straw juice (CSJ), fulvic acid (FA), and humic acid (HA). The soil infiltration capacity, soil water characteristic curve (SWCC) and soil water retention capacity were determined by using a steel‐ring method and a centrifuge method. The parameters of the SWCC were fitted by a van Genuchten (VG) model, and the specific water capacity [C(h)] was calculated. In addition, bulk density (BD), macroporosity, and soil organic matter (SOM) were measured, and the relationships between the variables and processes were evaluated. The results indicated that the soil infiltration capacity (i.e., initial infiltration rate, cumulative infiltration, and steady infiltration rate) was significantly increased in the CSJ and FA treatments (p &lt; 0.05) but decreased in the HA treatment compared to the control (CK) treatment. All the selected organic amendments improved the soil water release and supply capacity, and the CSJ2 treatment showed the best effect. The incorporation of CSJ, FA, and HA significantly improved the soil water retention capacity by increasing the saturated soil water content, field capacity, and plant available water capacity (p &lt; 0.05). Such changes were significantly associated with macroporosity and SOM (p &lt; 0.05). In this sense, our results showed that the CSJ treatment with 4 L m−2 and 50% volumetric concentration could be an effective soil amendment to improve the soil hydraulic characteristics in Mollisols and deserves further research.

Variation in soil infiltration properties under different land use/cover in the black soil region of Northeast China

Soil infiltration properties (SIPs) of infiltration rate and saturated hydraulic conductivity significantly affect hydrological and erosion processes, thus, knowledge of SIPs under different land use/cover are vital for land use management to control soil erosion for realizing the sustainable development of the small agricultural watershed. Nevertheless, few studies have been carried out to investigate the differences in SIPs and their dominant influencing factors between different land use/cover in the black soil region of Northeast China. Therefore, eight typical land use/cover were selected to clarify the variations in SIPs between different land use/cover and further identify their dominant influencing factors. SIPs of initial infiltration rate (IIR), steady infiltration rate (SIR), and saturated hydraulic conductivity (Ks) were determined under eight typical land use/cover (forestland, shrub land, grassland, longitudinal shelterbelt, transverse shelterbelt, agricultural road, and cropland of Zea mays L. and Glycine max (Linn.) Merr) using a tension disc infiltrometer with three pressure heads of −3, −1.5, and 0 cm. The results of one-way ANOVA analysis showed that SIPs varied greatly between different land use/cover. Shelterbelt plant with Populus L. had the maximum IIR, SIR, and Ks, and then followed by shrub land, agricultural road, cropland, grassland, and forestland. Spearman correlation analysis indicated that SIPs were significantly correlated with soil and vegetation properties. Redundancy analysis revealed that differences in SIPs between different land use/cover were dominantly attributed to the differences in soil texture, field capacity, and plant root mass density, which explained 79.36% of the total variation in SIPs. Among these dominant influencing factors, the results of structural equation model indicated that the indirect effects of plant root and soil texture played the most important role in variations of SIPs via affecting soil texture and pore characteristics. These results have significant implications for the precise prediction of watershed hydrological and erosion processes, also provide a scientific basis for guiding the distribution pattern of land use in the cultivated watershed.

Hydrodynamic response of a loam soil after wetting with different methods

Different points in a field can be wetted with different natural or artificial rainfall amounts and intensities. Therefore, a non-uniform soil wetting could occur during short-term monitoring of soil hydrodynamic parameters and its global effect on soil characterization is not easily predictable. For an initially dry loam soil, a sequence of three beerkan infiltration runs was performed at fixed sampling points in a period of two weeks. Immediately after the first beerkan run, the soil was perturbed by adding an additional water volume differing with the sampling point by the amount of water (0, 100 or 227 mm) and the application methodology (rainfall simulation, another beerkan run). As compared with the initial conditions, the soil infiltration parameters (mean, initial and final infiltration rates; constant of the Horton’s infiltration model) decreased by 2.9–4.3 times after wetting. A decrease of these parameters by 1.6–2.3 times remained detectable at the end of the sampling period, even if the soil likely returned to wetness conditions close to the initial ones. Relative variability decreased too (coefficients of variation = 52–135%, depending on the parameter, for the initial runs and 36–95% for the final ones). Nevertheless, a link was recognized between the infiltration parameters determined in the subsequent runs of the sequence. The correlation was stronger when the initial runs were compared with the last runs (coefficients of determination, R2 = 0.104–0.749, depending on the parameter; R >0 at P = 0.05 in all cases) than with those performed immediately after the intermediate wetting (R2 varying from a non-significant value of 0.059 to significant 0.196–0.211 values). The hydrodynamic response of a disturbed soil appears overall related to that of the initially undisturbed soil even if the disturbing agent is not exactly the same over the sampled area. Performing other investigations by characterizing the antecedent soil conditions in more detail could help to improve interpretation and modelling of hydrological processes by a more realistic description of temporal variability of soil infiltration parameters.

Specific power or droplet shear stress: Which is the primary cause of soil erosion under low-pressure sprinklers?

Specific power and droplet shear stress are generally considered to be the most critical indicators of soil erosion in sprinkler irrigation, but there is controversy about which indicator has a greater impact. This creates uncertainty in the optimization design of low-pressure sprinkler irrigation systems. In this study, a commonly used low-pressure sprinkler, i.e., Nelson D3000, was used to carry out in soil box experiments, to study the effects of specific power and average droplet shear stress at the end of a spray jet on soil erosion during sprinkler irrigation under three nozzle diameters (3.97, 5.95, and 7.94 mm), two operating pressures (103 and 138 kPa), and two soil textures (loamy sand and silty loam). Overall, the larger specific power or average droplet shear stress resulted in higher initial and steady runoff rates and a shorter time until runoff occurs and stabilizes. Enlarging the specific power or average droplet shear stress could significantly increase the initial infiltration rate, sediment yield, and surface soil bulk density, but the infiltration depth prior to runoff and surface soil porosity decreased. Furthermore, the specific power was observed to have greater correlations than average droplet shear stress with the surface runoff rate, initial infiltration rate, and increase in the soil bulk density and decrease in the soil porosity after irrigation. However, it was weakly related to the infiltration depth prior to runoff and sediment yield, indicating that the specific power could more accurately reflect the soil erosion with respect to the shear stress. To minimize the risk of soil erosion, a small operating pressure (103 kPa) is recommended in the design of center pivot irrigation systems, especially for the overhang of the system with large nozzle diameters. This research can provide the technical support for soil erosion prevention under low-pressure sprinkler irrigation.

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.