Initial Infiltration Rate Research Articles

Mattic epipedon fragmentation strengthened the soil infiltration capacity of a hillside alpine meadow on the Qinghai‐Tibetan Plateau

AbstractDegradation of hillside alpine meadow ecosystems is a widespread problem that usually results in the fragmentation of the mattic epipedon (ME). The mattic epipedon plays a well‐known role in the hydrological cycle of alpine ecosystems due to its high water‐holding capacity. However, little is known about how ME fragmentation alters soil infiltrability—a key soil property that influences runoff and erosion processes as well as soil moisture dynamics. To address this issue, we contrasted the infiltration rates and soil and plant characteristics of preserved meadow patches (with full ME) and patches at two stages of ME fragmentation, namely, half ME and without ME. Our results showed that mattic epipedon fragmentation reduced aboveground plant biomass (mainly of sedges) by 58.6–65.6 g m−2 and root biomass by 5,643–10,054 g m−2. Soil compressive strength (11.6 kg cm−2) and total soil porosity (52%) of fragmented meadow patches without ME were significantly lower than in those with half (17.9 cm−2 and 62%, respectively) or full ME (31.7 cm−2 and 62.5%, respectively). In contrast, non‐capillary porosity and aggregate stability slightly increased with fragmentation and were highest at patches without ME. Importantly, soil infiltration rates in hillside alpine meadows greatly increased as a result of mattic epipedon fragmentation. Initial infiltration rates were approximately 10 and 20 times higher at patches with half ME and without ME (177 mm h−1 and 326 mm h−1, respectively) than at patches with the full ME (17 mm h−1). Moreover, steady‐state infiltration rates were approximately 6 and 9 times higher at patches with half ME and without ME (60 mm h−1 and 88 mm h−1, respectively) than at patches with the full ME (17 mm h−1). Overall, mattic epipedon fragmentation improved soil infiltrability by changing the soil and plant characteristics. These findings suggest that mattic epipedon fragmentation will lower runoff maintenance and have drastic effects on the water provisioning function of hillside alpine meadows on the Qinghai‐Tibetan Plateau.

Infiltration properties affected by slope position on cropped hillslopes

Soil infiltration properties (SIPs) and their spatial variability are essential for simulating hydrologic and erosion processes. Intensive water erosion likely leads to large spatial heterogeneity of soil particle distribution, thus the large spatial variability of general soil properties, such as SIPs. Nevertheless, little is known about the spatial variabilities of SIPs along long, gentle hillslopes and their dominant controlling factors. This study was conducted to investigate SIPs under different slope positions under agricultural management and to identify dominant SIP-related factors in the Black-soil region of Northeast China. Soil infiltration properties were determined at five slope positions (i.e. upper, middle-upper, middle, middle-lower, and lower) on two approximate 5 % hillslopes using a disc infiltrometer under three pressure heads (-3, −1.5, and 0 cm). Results showed that the initial infiltration rate (IIR), steady infiltration rate (SIR), and saturated hydraulic conductivity (KS) varied from 0.11 to 0.47 mm min−1, 0.04 to 0.30 mm min−1, and 0.04 to 0.29 mm min−1, respectively. Soil infiltration properties generally increased initially, then decreased from the upper to the lower position along the hillslope. The middle-slope position had the numeric maximum SIPs, and SIPs were significantly greater than those of the upper and lower slope positions. Compared to the middle-slope position, IIR, SIR, and Ks of the upper and lower slope positions were lower by 50.9, 61.1, 63.6 and 33.8, 32.3, 34.6 %, respectively. Initial infiltration rate, SIR, and Ks were positively correlated with sand content (r = 0.60, 0.69, 0.69; p < 0.01), total porosity (r = 0.67, 0.71, 0.71, respectively; p < 0.01), saturated soil water content (r = 0.62, 0.70, 0.71, respectively; p < 0.01), and gravel content (r = 0.48, 0.66, 0.70, respectively; p ≤ 0.01), but were negatively correlated with silt (r = -0.50, −0.49, −0.49, respectively; p ≤ 0.01) and clay (r = -0.50, −0.64, −0.63, respectively; p ≤ 0.01) contents, bulk density (r = -0.67, −0.70, −0.70, respectively; p < 0.01), and physical crust thickness (r = -0.63, −0.73, −0.73, respectively; p < 0.01) across positions of the two hillslopes. The result of redundancy analysis indicated that physical crust thickness, bulk density, and water-stable aggregate and clay contents were the dominant factors attributed to the variation in SIPs under different slope positions, and collectively they explained 74.6 % of the total variation of SIPs. Physical crust thickness alone explained the largest proportion (49.9 %) of the variation of SIPs. Results will be helpful for improving precision of hydrologic and erosion processes modeling and sustainable soil management on long, gentle hillslopes in the agricultural region of Northeast China.

Numerical simulation study of urban hydrological effects under low impact development with a physical experimental basis

Global climate change and rapid urbanization led to frequent extreme rainstorms and waterlogging. Low impact development (LID) as an essential measure of urban stormwater control, it is necessary to explore the urban hydrological response under low impact development combined with physical experiment and numerical simulation. This paper takes the Beiyangyuan campus of Tianjin University, where numerous LID practices have been implemented, as the study area. The prototype permeable pavement in the campus was scaled down to a laboratory-scale for infiltration experiments. The results show that the Horton infiltration model could describe the infiltration process of permeable concrete and grass-planting brick. The initial infiltration rate of the permeable concrete is large but decays faster. In contrast, the infiltration process of the grass-planting brick decays slower, and the stable infiltration rate and infiltration capacity are higher than that of the permeable concrete. The mean infiltration rates measured for the permeable concrete and the grass-planting brick were 95 mm/hr and 190 mm/hr, respectively. A SWMM-MIKE21 coupled model was constructed based on the LID experimental results to explore the effects of the removal or density reduction of the LID practices on surface hydrological processes. The results show that permeable pavement performs best in the reduction of runoff volume, inundation area, and inundation depth, while the bio-retention cell takes the second place, and the sunken greenbelt has limited effect. Frequent light rainfall is sensitive to the density of LID practices, and the implementation of even a tiny percentage (4% of the catchment area) of LID practices can be effective in controlling runoff. The removal or density reduction of LID practices has little effect on the inundation region but leads to an increased possibility of flood risk due to increasing inundation depth.

Supporting evidences for vegetation-enhanced stormwater infiltration in bioretention systems: a comprehensive review.

Stormwater mitigation efficiency of bioretention systems relies for a large part on their capacity to infiltrate rapidly received runoff. Within this context, the primary aim of this literature review was to clarify the vegetation influences on bioretention media hydraulic conductivity, with the ultimate goal of improving guidance on plant choice for system durability. A thorough synthesis of studies dealing with the comparison of plant species, functional types, or traits on infiltration-related processes in biofilters was achieved. Overall, results converged to a positive impact of plants on water infiltration and percolation, either under greenhouse or field conditions. In most cases, vegetation selection had a determining role in maintaining initial media infiltration rates, with in terms of improvement: turfgrass < prairie grass < shrubs < trees. Wind-induced movements of rigid foliage or stems are believed to avoid complete surface clogging. Species with thick, rhizomatous or fleshy (with maximum root diameter near the centimeter range), and tap or deep root systems could be preferred to maximize infiltration rates in permeable bioretention media. In fine-textured soils, higher specific root length, root length density, or mass density could also enhance infiltration. Root mass densities (0.1-2.2kg.m3) were positively linked with infiltration rates in unlined systems while roots around 1mm diameter would favor macropore-related preferential flows and increased hydraulic conductivity. Finally, implementation of high-diversity plant communities would ensure the presence of a more functionally rich vegetation community with species possessing adequate physiological adaptations (including root system architecture) to local environmental conditions for perennial cover and proper bioretention hydrological functioning.

Combining soil macropore flow with formation mechanism to the development of shallow landslide warning threshold in South China

Because of the physical character of soil from granite weathering and the typhoon rains in South China, the model for early warnings of existing shallow landslides cannot be well applied in that area. This study developed a new shallow landslide model based on the effect of soil macropores for determining the rainfall threshold to post an early warning of the possibility of a shallow landslide in South China. We studied the hydrological effects of macropore flow and proposed a mechanistic model of the formation of shallow landslides by introducing the macropore coefficient of granite residual soil. The rainfall threshold of each slope unit was calculated by combining the hydrological model with the proposed shallow landslide model. Lastly, we tested the calculated result in the Maguihe watershed, Guangdong province, South China, which experienced a group of massive shallow landslides on 21 September 2010. The study results showed that the macropores of vegetation roots had a significant effect by increasing the permeability of granite residual soil. Coniferous forest land has the highest initial infiltration rate and stable infiltration rate, followed by shrub forest land, and then bare land. Statistical verification showed that the accurate prediction rate of the proposed model was 80.65%, which is adequate for early warning of shallow landslides in South China. We discuss the application conditions and parameter calibrations of the proposed model, and offer recommendations for future research.

Effects of different vegetation restoration types on soil infiltration characteristics in severely eroded subtropical regions of South China

Vegetation restoration could cause variations in soil and near-surface properties, altering soil structure directly or indirectly and consequently affecting soil infiltration characteristics. This study is aimed at exploring the variation of soil physicochemical properties and infiltration characteristics under five vegetation restoration types (including restored forest, restored orchard, restored scrubland, restored grassland, and unrestored eroded land, which are referred to as RF, RO, RS, RG, and EL, respectively) and the main factors affecting infiltration characteristics. The EL was taken as the control group. Five hydraulic heads (0, −3, −6, −9, and −12 cm) were set to continuously measure the soil infiltration characteristics through a disc infiltrometer. Results indicated that vegetation restoration types significantly affected initial infiltration rate (IIR), steady infiltration rate (SIR), and hydraulic conductivity (K), which ranged from 0.56 to 4.40, 0.32 to 2.86, and 6.48 × 10⁻³ to 0.47 mm h⁻¹, respectively (mean value: 2.72, 1.35, and 0.32 mm h⁻¹, respectively). The highest value of soil infiltration rate appeared in the EL, and the lowest value was observed in the RF. Root parameters including root length density and root surface density were highest in RG, and lowest in the control and RF, respectively. In addition, the conceptual path model explained 95%, 96%, and 96% of the variance in IIR, SIR, and K_s, with the goodness-of-fit index of 0.988, 0.988, and 0.997, respectively. This modeling determined biological crust thickness, soil organic matter content, root length density, and sand content as the major factors affecting the process of soil infiltration. These results enhance our understanding of the water erosion process under different vegetation restoration types in the severely eroded subtropical regions of South China.

Evaluating Model Effectiveness for Soil Infiltration Attribute: Comparison of Green-Ampt, Horton and Modified Green-Ampt Infiltration Models

Soil infiltration is a very important concept in hydrology as well as irrigation, which plays a vital role in estimating surface runoff and groundwater recharge. It is a complicated process that varies with numerous factors. Accurate estimation of soil infiltration is required for future irrigation, and many other purposes. To estimate the infiltration process, there are numerous models. The majority of them have some presumptions, a unique calculation method, and some limitations. The purpose of the paper was to assess the model’s performance for a similar hypothetical scenario involving soil infiltration. It compared the infiltration rate, runoff rate, and incremental infiltration versus time for three different infiltration models: the Green-Ampt model (GA), the Horton model and the Modified Green-Ampt (MGA) model. A spreadsheet was used to calculate the Horton model, and HYDROL-INF (V 5.03) was used to simulate the other two models. Among those three models, the MGA model outperformed those three models, while the GA model produced greater infiltration rate than rainfall, which was insensible. The study showed that the MGA model, which provides useful infiltration predictions, outperformed the other two infiltration models. Since the Horton model does not consider ponding conditions, it is only applicable when the effective rainfall intensity exceeds the final infiltration capacity. Moreover, the GA model’s initial infiltration rate is irrational because it disregards the intensity of the rainfall. The results of this study will assist in selecting the most accurate method for estimating soil infiltration for agricultural purposes.

A novel method of estimating dynamic partial contributing area for integrating subsurface flow layer into GIUH model

The partial contributing area (PCA) is a conceptual parameter proposed to approximately quantify the effective surface-runoff region which is directly resulting from the excess rainfall. Previous studies further applied the ratio of PCA, which can determine the separation between the surface- and subsurface-flow regions, to introduce the subsurface-flow mechanism in a geomorphology-based IUH model. The temporal distribution of the simulated hydrograph was found to be sensitive to the ratio of PCA, especially for the stage of flow recession. Therefore, this study focuses on devising a method to estimate the dynamic PCA depending on the initial streamflow, antecedent precipitation, and current infiltration rate, in which the soil type is considered. An artificial neural network model, called long short-term memory (LSTM), is established to provide adequate values of PCA by considering the aforementioned factors associated with the hydrological conditions. A geomorphology-based IUH model is subsequently implemented to demonstrate the importance of using the proposed methodology to seek a reliable PCA by comparing simulated hydrographs with observed discharges. The proposed methodology could be a promising way to avoid the assumption of constant PCA or the complex process of deriving time-varying PCA. Additionally, the results of this study showed that it can significantly ameliorate the performance in terms of relative error of simulated hydrograph as well as the overall similarity compared to the flow records of floods.

Managed aquifer recharge using a borrow pit in connection with the Mississippi River Valley alluvial aquifer in northeastern Arkansas

The Mississippi River Valley alluvial aquifer (MRVAA) is one of the overexploited aquifers in the United States. Agriculture in Arkansas relies significantly on the MRVAA for irrigation, due to its accessibility and high yield. Increased irrigation demand since the early 1900s with continued expansion and inequitable recharge contributions resulted in groundwater decline. Overdraft of the MRVAA in Arkansas has resulted in the designation of critical groundwater areas. Managed aquifer recharge (MAR) methods intentionally replenish stressed groundwater resources. A MAR case study was conducted to determine whether infiltration basins, as repurposed borrow pits, could be used to enhance groundwater decline in critical groundwater areas of northeast Arkansas. This rehabilitation would be a practical solution to alleviate groundwater decline as well as economically feasible as land would not need to be taken out of production. In 2015, the Arkansas Department of Transportation contracted sand excavation of fallow land owned by a collaborating producer. This borrow pit would serve as a test case to measure infiltration rates into the MRVAA using nearby surface water as the recharge source. Initial soil core analyses revealed soil properties within the confining clay layer of red-brown clay and silty clay soils (0 to 3.7 m deep) with sand below. Excavation completed to a depth of ~6 m exposed the uppermost-unsaturated section of the alluvial aquifer, consisting of well-sorted medium grain size sand. The borrow pit floor was ~27 m above the existing water table, and it was hypothesized that this exposed unsaturated aquifer section would provide a natural filter and an avenue for increased water storage underground. Sediment samples were collected from the pit floor and sidewall pre- and postexperiment to characterize particle size, textural class, and organic matter. Submersible pressure transducers were installed within the pit and in a nearby irrigation well to monitor water level changes. Meteorological data were collected on-site to measure the water budget components of precipitation and evaporation. Water level declines and infiltration were evident throughout the experiment. An initial infiltration rate of 192 mm d⁻¹ was measured in February of 2016 that decreased until March, with steady state rates of 4.43 to 136 mm d⁻¹ that varied until June. An overall integrated infiltration rate of 36.4 mm d⁻¹ was calculated from the water budget. Total subsurface storage increased by 9.3 ML from February to June of 2016, and a two-dimensional simulation predicted a maximum groundwater mounding of 2.6 m during the experiment. Additionally, 14 borrow pits that had not been repurposed were identified in the area using remote sensing. Results of this study demonstrate that a relatively inexpensive MAR strategy could be implemented using former borrow pits repurposed as infiltration basins to alleviate groundwater decline in a critical groundwater area of northeastern Arkansas.

Key soil properties influencing infiltration capacity after long-term straw incorporation in a wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation system

Straw incorporation is increasingly being adopted in wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation systems to improve soil physiochemical properties. To identify the main soil properties influencing infiltration capacity under long-term straw incorporation in a wheat–maize rotation system, the study set four treatments: no straw incorporation and fertilizer application, wheat straw incorporation with 276 kg nitrogen/ha, wheat and maize straw incorporation with 276 kg N/ha, and wheat and maize straw incorporation. The initial, average, and final infiltration rates were calculated to represent soil infiltration capacity. Compared with other treatments, wheat straw incorporation with 276 kg nitrogen/ha treatment significantly decreased soil bulk density, soil aggregate (DMWD) mean weight diameter measured using the dry sieving method, and weight rate of soil aggregates with diameters greater than 0.25 mm measured using the wet sieving method, and significantly increased total soil porosity, soil capillary porosity, field capacity, and weight rate of soil aggregates with diameters less than 0.25 mm measured using the wet sieving method. In contrast, wheat and maize straw incorporation treatment significantly increased soil bulk density and noncapillary porosity, but decreased total soil porosity, capillary porosity, and field capacity. The results of partial least squares regression indicated that the soil moisture content and DMWD were the primary factors influencing initial infiltration rate with positive regression coefficient. Higher total soil porosity, capillary porosity, field capacity, and DMWD contributed to higher final infiltration rate, while higher soil bulk density and noncapillary porosity were correlated with a lower final infiltration rate. The key influencing factors of average infiltration rate were soil bulk density, soil moisture content, total soil porosity, capillary porosity, and DMWD. The wheat straw incorporation with 276 kg nitrogen/ha treatment had higher infiltration rates than no straw incorporation and fertilizer application treatment. However, with an increase in straw amount, the influence of straw on infiltration showed a law of diminishing marginal returns. Therefore, wheat and maize straw incorporation with 276 kg nitrogen/ha treatments had a lower infiltration rate than wheat straw incorporation with 276 kg nitrogen/ha treatment. In addition, wheat and maize straw incorporation treatment had the lowest average and final infiltration rates of all treatments, indicating that excessive straw incorporation without nitrogen fertilizer had adverse effects on infiltration rates. This study furthers understanding of the influence of long-term straw incorporation on soil hydrological processes and helps rationally use straw resources in wheat–maize rotation systems.

Clipping decreases plant cover, litter mass, and water infiltration rate in soil across six plant community sites in a semiarid grassland

Water infiltration in the soil is a crucial hydrological function in the land water cycle, especially in the semiarid region where water is relatively scarce. The semiarid grassland in Northern China represents the regional vegetation in the vast area of Eurasian continent and is sensitive to land use change. However, no clear patterns exist regarding the comprehensive examination of water infiltration in relation to clipping across six plant community sites. This study aimed to test the effect of clipping and plant community sites, which were dominated by Agropyron cristatum, Stipa krylovii, Leymus chinensis, Potentilla tanacetifolia, Artemisia frigida, or Lespedeza davurica, on the water infiltration rate in the semiarid grassland. Clipping significantly decreased the water initial, steady, and average infiltration rates by 39.13, 4.36, and 12.46 mm h−1, respectively, across the six plant community sites. Clipping-induced changes in the average infiltration rate positively correlated with the changes in the plant cover (r = 0.60, P < 0.01), litter mass (r = 0.53, P < 0.01), forb functional group ratio (r = 0.46, P = 0.03), and total porosity (r = 0.49, P = 0.02), and negatively with water-holding capacity (r = −0.45, P = 0.03). Further, the water infiltration rate significantly differed among the six plant community sites. The L.davurica site had the highest water initial infiltration rate with a value of 137.63 ± 17.76 mm h−1, while the L. chinensis site had the lowest rate with a value of 74.08 ± 5.26 mm h−1. Principal component analysis showed that the total porosity, litter mass, plant cover, and forb functional group ratio were the main factors affecting water infiltration rates in the control grassland. Overall, our findings suggested that local governments and herders should implement unclipping as a potential sustainable management for improving hydrological function in the semiarid grassland.

Capillary infiltration kinetics in highly asymmetric porous membranes and the resulting debonding behaviors

Reliable bonding of high-performance membranes onto polymeric supporting structures is critical for capitalizing their potentials within practical filtration applications. The successful bonding typically requires infiltration of the membrane pores by a thermoplastic polymer, driven by capillary pressure and/or external pressure. In this work, we systematically examine the capillary infiltration of a polypropylene (PP) within polyethersulfone (PES) membranes with a highly asymmetric pore structure, a nominal pore size of 20 nm, and varying degrees of hydrophilicity. Most significantly, the infiltration kinetics was strongly influenced by the asymmetric pore structure in two aspects: (1) the time to achieve full infiltration from the large-pore side was approximately 4 times shorter than that from the tight-pore side; (2) When bonding from the tight-pore side, the infiltration depth, L(t) showed L (t) ∼ t1.6, instead of characteristic L (t) ∼ t0.5. The accelerated infiltration rate over time was successfully modelled with the Cai model using depth-dependent pore size that captures the asymmetric pore structure. Furthermore, chemical modification reduced the initial infiltration rate only, which is attributed to the reduction in surface porosity. No significant difference in infiltration kinetics at the later stage was observed. Mechanical integrity tests of the bonded samples display complex debonding behaviors including complete peeling, incomplete peeling, and complete membrane failure. The peel force corresponding to membrane failure appeared larger than the other two debonding modes, all of which showed insignificant dependence on the membrane chemistry or infiltration depth. Post-mortem analysis of the completely peeled sample showed PP nanofibers were pulled out of the PES membranes during debonding, emphasizing relatively weak mechanical interlocking due to the low surface porosity.

The Impact of Tillage and Weed Control Methods on Physical Properties of Sandy Clay Loam Forest Ochrosol in Cassava Cultivation

The field study was carried out on a sandy clay loam forest ochrosol at Hodzo, near Ho in Ghana, from July 2017 to May 2018. The objective was to determine how tillage and weed control techniques affect the physical properties of the soil. The split-plot design was used in the study, with tillage serving as the main factor and weed control serving as the subplot factor. The tillage treatments were no tillage (NT), minimum tillage (MT), and ploughing followed by harrowing and ridging (PHR) and deep tillage followed by Ploughing, harrowing, and ridging (DPHR). On the other hand, the weed control treatments comprised hoe weeding, machete weeding, and no weeding. It was realised during the study that, in the upper layer (0–15 cm), the PHR treatment produced lower soil penetration resistance (38.57 kPa), high dry bulk density (1.019 Mgm−3), and slightly lower soil moisture content (5.0%) in comparison with the other tillage treatments at three months after planting (3 MAP). The results on initial and basic infiltration rates portrayed a trend where the more intensive the tillage regime (hence, soil disturbance), the lower the initial and basic infiltration rates, and vice versa. Moreover, tillage had a higher impact on the physical characteristics of the soil than weed control methods. Nonetheless, tillage with machete weeding resulted in lower soil dry bulk density and higher moisture content, while tillage with hoe weeding reduced penetration resistance and increased infiltration rates. Given similar weather and soil conditions, the study recommends that farms and farmers in the Ho Municipality and the Volta Region adopt conservative tillage methods such as heaping with machete or hoe weeding and use the savings to expand their farm sizes. Therefore, the adoption of conservation tillage practices is more crucial than ever in order to ensure sustainable food production with minimal impact on the soil and environment.

Rancang Bangun Double Ring Infiltrometer Untuk Pengukuran Pengaruh Penambahan Ketinggian Pasir

Double ring infiltrometer is a tool to measure the rate of infiltration into the soil. The design of the double ring infiltrometer has 3 stages, the first using 304 stainless steel material, the next stage is the rolling process using a rolling machine 6 × 1300 mm BB613RL, and the last stage is the welding process using TIG welding. The effect of adding sand on changes in the infiltration rate that occurs in the two rings, in this change the slowing of the infiltration rate does occur because the sand blocks the infiltration of water directly into the soil. However, the slowdown in the infiltration rate that occurs tends to be very small so that it can be said that it has no significant effect on the infiltration rate without sand. The results of the measurements showed that the initial and constant infiltration rates slowed down with a change in the average infiltration rate that occurred, namely 0.005 mm/s at the initial infiltration rate and 0.002 mm/s at a constant infiltration rate. Thus it can be concluded that the addition of sand as a ground cover does not have much impact on the rate of water infiltration into the soil, especially in the direction of water infiltration perpendicular to the soil. So that this sand can be said to be a safe material to use as a ground cover compared to concrete, castings, or asphalt.

Rancang Bangun Double Ring Infiltrometer Untuk Pengukuran Penambahan Ketinggian Sabut Kelapa

Infiltrometer technology is a water infiltration system that can measure water levels in a certain area to determine the maximum water infiltration rate so that natural disasters can not occur arising from the lack of infiltration land. The purpose of this study is to determine the design of the double ring infiltrometer to determine the effect of increasing the height of coconut husk, the stages in the fabrication process of the double ring infiltrometer, the effect of adding the height of coconut husk, and the validation results in the infiltrometer rate measurement process. The fabrication method carried out is by rolling process and welding process. The material used in this study is stainless steel grade 304 (SS 304). The measurement results show that the addition of coconut husk will inhibit the rate of water absorption into the soil when compared to open soil with an average change in infiltration rate for 0.006 mm/s for the initial infiltration rate and 0.004mm/s for the constant infiltration rate. Thus, it can be concluded that the addition of coconut husk as a ground cover does not have much impact on the rate of water infiltration into the soil, especially in the direction of water infiltration perpendicular to the ground. So that coconut coir can be said to be a safe material to use as a ground surface cover compared to concrete, castings, or asphalt.

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.

Assessing the Effects of Plant Roots on Soil Water Infiltration Using Dyes and Hydrus-1D

Forestry eco-hydrology is closely related to root architecture, and soil water infiltration has been always associated with root architecture. In this study, dye infiltration experiments and HYDRUS-1D were used to quantify the effects of different root architectures on the dynamics of soil water infiltration, volumetric water content, and soil water pressure head. The results provide evidence that root channels acted as preferential flow paths for water infiltration and percolation into the soil. Maize fibrous roots, rubber trees fine roots, and Spartina alterniflora smooth roots easily penetrated the plough layer of an agriculture site, the hard soil layer of a forest site, and the alternating sandy and mud layers of an intertidal zone, respectively. The initial and final infiltration rates were significantly different between the rooted and rootless soil profiles. The root-induced infiltration events lowered the propagation time of the wetting front across the rooted soil profile by 33%–113% than the rootless soil (p &lt; 0.05), and the volumetric water content of the saturation zone of the rooted soil profile increased by 12%–19% relative to the rootless soil (p &lt; 0.05). Furthermore, the soil water pressure head increased from negative (i.e., unsaturated) to positive (i.e., saturated) in the saturated soil. This change was more pronounced in the maize fibrous roots soil profile, but less pronounced in the rubber fine roots’ soil profiles or the S. alterniflora smooth roots. The results indicate that the downward movement, volumetric water content, and soil water pressure head were higher in soil profiles having plant roots than the rootless soil, and the degree of roots effects depended on roots architectures, soil hardness, and soil layer configuration. The findings provide evidence that root channels can act as preferential flow paths for water infiltration and percolation into the soil.

Soil Water Behavior of Sandy Soils under Semiarid Conditions in the Shendong Mining Area (China)

The soil water behavior of sandy soils was studied under semiarid conditions in the Shendong mining area (China). The soil water content (θ) was measured under different depths and topographies using an HH2 moisture meter. The infiltration process was studied using a Guelph soil permeameter. A set of hydrodynamic variables was calculated in the laboratory. The θ of the first 20 cm was the lowest and increased with depth. The content of soil water increased from the top slope to the bottom slope. The infiltration experiments showed that the steady state infiltration rate was &gt;40 mm h−1 in most cases. Owing to the higher contents of sand and soil macropores at the top of the slope and the top 0–20 cm of surface soil, the initial infiltration rate and steady infiltration rate were higher. The average available water capacity was 18.28%, which was consistent with the predominance of a sandy textural fraction. The results of a soil water retention curve and a rainfall simulation experiment showed that there was a low soil water retention capacity throughout the whole profile. This study contributes to the understanding of several aspects of the soil water behavior of sandy soils and provides key information for environmental management and land reclamation under semiarid conditions in the Shendong mining area.

Effects of simulated grazing disturbance on soil water infiltration of biocrust slope in the hilly Loess Pla-teau, China

Water is the key factor for vegetation restoration in the Loess Plateau region. Biological soil crust (biocrust), a widely distributed soil surface cover, significantly affects soil infiltration. Disturbance would affect soil water infiltration of biocrust. The effects of different intensities of disturbance on soil water infiltration of biocrust are still unclear. By simulating the trampling disturbance of sheep, we examined the effects of disturbance intensity (10%, 20%, 30%, and 40%) estimated by the coverage of broken biocrust on the surface cover of biocrust slope in the Hegou catchment of Wuqi County, Shaanxi Province. Soil water infiltration under different intensities were measured by the linear source infiltration method. The influence mechanisms of disturbance on soil water infiltration of biocrust slope were investigated with a structural equation model and correlation analysis. Results showed that compared to that without disturbance, the coverage of cyanobacterial crust was increased by 33.6% at 10% of disturbance intensity, no difference at 20% of disturbance intensity, and decreased by 36.1% and 75.0% at 30% and 40% of disturbance intensities, respectively. Litter coverage was increased by 34.3% under 40% of disturbance intensity, while that of other treatments were not changed. Surface roughness was decreased by 22.3%, 11.1%, and 5.6% at 10%, 20%, and 30% of disturbance intensities, respectively, but increased by 8.2% at the 40% of disturbance intensity. The initial infiltration rate at 40% of disturbance intensity was 77.1% higher than that without disturbance, while other treatments had no significant difference at the initial infiltration rate. Furthermore, distur-bance did not affect the stable and average infiltration rate. Our results confirmed that disturbance mainly promoted the initial infiltration by reducing the coverage of cyanobacterial crust, increasing the coverage of litter, and changing soil roughness. This study would provide scientific basis for the management of biocrust of rehabilitated lands in the Loess Plateau region.

Effects of moss biocrust on soil water infiltration in the Three Gorges Reservoir Area, China

We examined the effects of moss-dominated biocrusts on soil infiltration properties in Wangjiaqiao watershed of the Three Gorges Reservoir Area. Five levels of coverage (1%-20%, 20%-40%, 40%-60%, 60%-80% and 80%-100%) were set, with a nearby bare land as the control. We collected soil samples and conducted infiltration process observation by double cutting ring method. The results showed that biocrusts could appreciably increase soil cohesion, porosity, clay content, water-stable aggregates and organic carbon of topsoil, but significantly reduce soil bulk density and sand content. Biocrusts promoted soil water infiltration, with the initial infiltration rate (Ii), stable infiltration rate (If), average infiltration rate and cumulative infiltration amount being two times or more of that in bare land. Withbiocrust coverage increasing, soil infiltration properties firstly increased and then decreased, and peaked at 40%-60% coverage level. Results of path analysis indicated that Ii was mainly affected by biocrust coverage, soil bulk density, and organic carbon content, while If was mainly affected by biocrust coverage and soil bulk density. The simulation results of four infiltration models demonstrated that Horton model was the best fitting on the water infiltration process of biocrusted soil in the Three Gorges Reservoir Area.