Soil Infiltration Rate Research Articles

Effects of Design and Climate on Bioretention Effectiveness for Watershed-Scale Hydrologic Benefits

Bioretention areas are a common form of green stormwater infrastructure (GSI). There is significant research on the performance of individual bioretention cells, but the watershed-scale benefits of GSI are still unclear. Furthermore, differences in bioretention design and rainfall patterns make it difficult to compare results between studies. We used the Storm Water Management Model (SWMM) to assess the effects of bioretention size, soil infiltration rate, storm size, and climate on the watershed-scale performance of GSI. We first divided the contiguous US into 10 rainfall regions based on similarities in precipitation amount, intensity, and other storm characteristics. We then modeled the effects of bioretention areas in a single watershed under these different rainfall regimes. Bioretention areas did provide watershed-scale benefits, although performance declined as (1) bioretention areas became smaller, (2) soil infiltration rates decreased, and (3) precipitation depth increased. High-intensity rainfall was the primary cause of outflow from bioretention areas, although back-to-back storm events also caused outflow in some climates. There were some clear discrepancies between subbasin-scale and watershed-scale GSI performance. Generally, runoff volume reduction was greater when measured at the subbasin scale. Peak flow reduction, however, was greater at the watershed-scale, likely because bioretention areas changed the shape of subbasin runoff hydrographs, leading to watershed-scale peak flow reduction that was greater than the sum of the parts. We provide recommendations for design, management, and future research to help advance effective application of GSI for achieving watershed-scale hydrologic benefits.

Review of Adoption and Impact Assessment on Conservation Agriculture in Ethiopia

Conservation agriculture plays a great role in improving farming land productivity and mitigating climate change impact. It is a concept for resource-saving agricultural crop production that strives to achieve acceptable profits together with high and sustained production levels while concurrently conserving the environment. The paper initially investigates theoretical concepts of conservation agriculture in Ethiopia. It then reviews the adaptation level of conservation agriculture by farm households and its impact on their productivity. The various challenges for the adoption of Conservation agriculture are lack of knowledge in CA at the expertise and farmers' level; the belief of farmers on tillage, technical, social, financial, and policy issues; the market does not supply them with the necessary seeds to carry out intercropping; high input costs, low input availability, and associated high opportunity costs for crop residue; and also lack biomass and residues. Its major impacts are increased labor productivity at the time of soil preparation; it helps with water harvesting strategy; the benefit of crop residue retention is a higher content of organic matter in the soil and higher water infiltration rates, which reduces surface runoff and soil erosion significantly.

Soil Infiltration Properties Are Affected by Typical Plant Communities in a Semi-Arid Desert Grassland in China

A process of infiltration from the soil surface to form soil water is known as soil infiltration; this is the only way for plants to absorb and use soil water. This process is closely related to nutrient migration, surface runoff, and soil erosion. The objectives of this study were to quantify the effect of typical plant communities on soil infiltration performance, reveal the interaction between soil infiltration rate and soil characteristics and plant roots, and determine the primary influencing elements on the Xilamuren grassland. The ring knife method was used to determine the soil infiltration rate at the 0–30 cm soil layer of six typical vegetation communities. The results indicated that the infiltration rate of the Koeleria macrantha community was highest at the soil depth of 0–5 cm, while that of the Convolvulus ammannii community was lowest, reaching 4.25 mm·min−1 and 0.53 mm·min−1, respectively. The soil infiltration rate of different plant communities gradually declined with the increment of soil depth. The strongest correlations were found between bulk density, total porosity, organic matter, root characteristics, and soil infiltration rate. The bulk density, initial water content, capillary porosity, and clay content were the primary influencing factors acting on soil infiltration in the region. Other factors indirectly impacted the infiltration rate by modifying bulk density, which was a crucial limiting factor determining the infiltration rate in the research region. The study’s findings will give theoretical and practical assistance for the prevention and management of soil deterioration and grassland restoration in this area.

Differential effects of soil texture and root traits on the spatial variability of soil infiltrability under natural revegetation in the Loess Plateau of China

Soil infiltrability controls precipitation input to soil and plays a crucial role in regulating soil eco-hydrological processes and ecosystem production in water-limited areas worldwide. The effects of root traits on soil infiltrability have been widely investigated at individual sites, but root-soil interactions and their effects on soil water infiltration over large spatial scales remain poorly understood. This study aimed to identify the unique characteristics of soil infiltration processes and different contributions of soil texture and root morphological traits to soil infiltrability. For this purpose, 153 plots of natural revegetated land with two contrasting plant species (Artemisia gmelinii Web. with tap root systems and Stipa bungeana Trin. with fibrous root systems) and bare land were selected in three regions along a texture gradient in the Loess Plateau of China. The results showed a distinct spatial variability of soil infiltration rates across the three regions with soil texture explaining the variability more strongly than plant species at several infiltration stages. Rooted soils had higher infiltration rates than bare soils, with nonsignificant inter-species difference under three soil texture types. Furthermore, soil texture and root morphological traits explained 92.03% and 74.75% of the total variance of soil properties (soil organic matter, aggregate stability, and soil porosity), and their interaction effects (73.09%), accounted for a considerable proportion. These findings suggest that soil texture and root morphological traits indirectly affect soil infiltrability by modulating soil properties, with soil texture having a higher contribution. In addition, the effects of root morphological traits on soil infiltrability were found to be dependent of soil texture on the regional scale. Therefore, the effects of soil texture and root-soil interaction deserves further attention in assessing soil hydrological processes on large spatial scales in the future.

Hydrological and Geological Analysis of Cohesive Soil and its Potential Risk in Middle Mountain Region: A Case Study of Naunuko Pahiro along Madi River, Kaski, Nepal

Middle Mountain region of Nepal is most often vulnerable in hydrological and geological aspect. Rainfall pattern, runoff, infiltration rate, different losses and soil parameters of cohesive soil (Silty clay) along with slope of slide (i) and depth of slide (H), factor of safety (F.O.S) along with probabilistic approach (correlation) are decisive factors pertaining to re-occurrence of landslide. Rainfall intensity, catchment area (A), runoff coefficient plays vital role in the estimation of flood frequency over a various period of time (25 years, 50 years and 100 years) respectively. The civil engineering structures along with middle mountain river are always vulnerable. Hence, its risk identification is prerequisite which is encompasses in the study. This study include hydrological and geological analysis of Taprang landslide (Naunuko Pahiro) which prevail at middle mountain region at an elevation ranging from 937m to 1047m of Kaski district, Gandaki Provenance, Nepal. Soil test data, rainfall data, probability and statistical approach along with different empirical formulas are used to analyse hydrological and geological hazard. Factor of safety (F.O.S) is calculated on the basis of altering value of slope of slide (i) and depth of slide (H) from slope ranging 50° to 70°. With increase depth of slide greater than 10m, F.O.S. is less than one which is unstable. The slope stability found to be critical at depth of slide10m with 50° slopes.Higher ground water table, higher rate of run-off with an average rainfall 446.50cm and higher shear stress contribute to risk of landslide along with increase discharge at down- stream of landslide with possibility of flood hazard at Madi river bank. The result would give insight on nature of landslide and flood discharge which could support Madi Village Municipality, as well as other rural Municipality of middle mountain region of almost same elevation consisting of cohesive (Silty Clay) soil for shaping disaster risk reduction policies and strategies such that death and injuries as well as impact on civil engineering structures can be minimized.

Evaluation of the Relationship Between Infiltration Rate and Some Soil Properties under Different Land-Use

Soil infiltration rate (IR) is an important parameter and a good indicator of soil quality and fertility. The most influential factors for all conditions where the best performance in infiltration surveys is achieved are soil properties and land-use type. Therefore, a detailed understanding of infiltration is required for different land-use complexes. In this study, the effects of soil properties on IR in soils under different land-uses (pasture, fallow, and orchard) were investigated. Soil samples were taken from 30 points determined by GPS from 3 land-uses within the border of the Çubuk district of Ankara Province, Turkey. IR (with Minidisc infiltrometer, MDI), bulk density, and penetration resistance were measured in undisturbed soil samples. Saturated hydraulic conductivity (Ks) and sorptivity were obtained from infiltration measurements. Soil parametric analyses and morphological descriptions were made in disturbed soil samples. In order to digitize the morphological properties, the coding system was created with the help of soil identification cards. The average IR value was found to be the highest in the orchard and the lowest in pasture samples. Correlation analysis, one-way ANOVA, and factor analyses were used to evaluate the relationships between soil variables and IR. IR showed the highest correlation with sorptivity (0.72), sand (0.69), and Ks (0.86) in the pasture, fallow, and orchard, respectively. IR in different land-uses was loaded on the same factors with different soil variables. Due to different land management practices, such additional measurements need to be made to accurately assess the potential impact of land-use and management changes on agricultural activities.

Optimal Sprinkler Application Rate of Water–Fertilizer Integration Machines Based on Radial Basis Function Neural Network

The application rate for sprinkler irrigation of water–fertilizer integration machines is an important technical parameter for efficient operation. If the value is too large, the equipment will produce runoff; if it is too small, the equipment will run too long and waste energy. Therefore, it is necessary to provide a feasible scientific and theoretical basis for developing a reasonable application rate. In this study, a mathematical model of soil infiltration for sprinkler irrigation with water and fertilizer integration machines was developed. Soil water accumulation time for different soil’s initial water content, bulk density, sprinkler application rate and soil texture were derived by the finite element method, and these data were used as a training database for the neural network. To make the neural network convenient for predicting the optimal application rate of sprinkler irrigation (the maximum application rate of sprinkler irrigation without runoff) in practice, the time of waterlogging, was multiplied by the optimal application rate of sprinkler irrigation to obtain the total irrigation volume. The optimal application rate of the sprinkler irrigation prediction model of radial basis function (RBF) neural network was constructed with total irrigation water, soil bulk density, initial water content and soil texture as inputs and compared with BP neural network and generalized regression neural network. The highest prediction accuracy of RBF neural network was obtained, and its average relative error was 0.11. To verify the accuracy of the RBF neural network application rate of sprinkler irrigation prediction model in real life, a sprinkler experiment was conducted in the laboratory of Guangzhou University, and the collected soil and lawn of Guangzhou University were used to simulate the actual environment. The results showed that the relative error between the RBF neural network prediction results and the actual values was generally around 10%, while for a total irrigation volume of 58 mm, the optimal application rate of sprinkler irrigation calculated with the model was 42 (mm/h), which can save 70% of irrigation time compared to the case of using the stable infiltration rate of soil as the application rate of sprinkler irrigation without water and fertilizer. Water and fertilizer losses were not observed. This indicates that the model proposed in this study is of practical value in determining the optimum application rate of sprinkler irrigation for water–fertilizer integration machines.

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.

Evaluating the effects of temperature on soil hydraulic and mechanical properties in the collapsing gully areas of south China

The soil hydrologic and mechanical properties play an important role in the slope stability in the red soil hilly region of southern China. In this study, the red soil layers in a collapsing gully wall were used to investigate the effects of temperature on the soil water retention curve (SWRC) and shear strength. The results showed that the SWRCs of the red soil under different temperatures could be accurately described by the van Genuchten (VG) model (R2 > 0.95, root mean square error (RMSE) < 0.024). An increasing temperature significantly decreased the soil water holding capacity (WHC), especially in the intermediate range of the SWRCs of the red soil. The soil saturated hydraulic conductivity (Ks) increased linearly with temperature. The soil cohesion and soil friction angle decreased by approximately 44.13% and 30.40% respectively when the soil water content increased from 0.24 cm3 cm−3 to 0.42 cm3 cm−3. The mean soil cohesion and soil friction angle decreased approximately 8.56 kPa and 1.34° respectively when the soil temperature increased from 25 °C to 40 °C. Regression analysis showed that the soil cohesion increased as the power function with increasing matric suction (0–2000 kPa), and friction angle increased as the linear function with increasing matric suction. These results illustrated that an increase in temperature will decrease soil matric suction and shear strength but enhance the soil infiltration rate under certain soil moisture levels. Therefore, the stability of a collapsing gully wall will sharply decrease under the conditions of high temperature and heavy rain in summer.

Effect of soil physical properties on soil infiltration rates

The physical properties of the soil are studied to understand the influence of soil properties on infiltration rate. The effect of soil physical properties on infiltration rates on logged-over forests was measured with a mini-disk infiltrometer across various levels of soil disturbances. Results of soil analysis suggest are mostly loamy texture and the bulk density has varied from 0.74 - 1.02 g cm−3, respectively. The basic infiltration rate has varied from a minimum of 0.61 mmhr−1 to a maximum of 45.22 mmhr−1 with an average of 3.81 mmhr−1. The results of simple regression analyses showed that there was little association between the physical properties of the soil and the infiltration rate. This study suggests that the high variation of infiltration rate in this study site is attributed to the high spatial variability of soil properties.

Impact of Land Use Change and Afforestation on Soil Properties in a Mediterranean Mountain Area of Central Spain

Afforestation can improve hydrological processes, such as infiltration, in basins and, therefore, reduce the impact on human populations of floods, soil erosion, landslides, droughts, and climate variation. The aim of this work was to analyze how afforestation and other changes in land use influence infiltrability and the evolution of soils. Infiltration rates, soil water repellency, and physical and chemical properties of sandy loam soils were measured in four types of land: native holm oak forest, afforested 20-year-old pine forest, shrubs, and grasslands. Non-forest covers are the result of the degradation of native oak forests for centuries, while the pine afforestation in this study took place on a perennial wet mountain pasture (cervunalito). Our results show that soil infiltration rates are much higher in pine afforestation areas (857.67 mm·h−1) than in holm oak forest (660.67 mm·h−1), grasslands (280.00 mm·h−1), or shrubs (271.67 mm·h−1). No statistically significant differences in fertility, organic matter content, bulk density, or effective porosity were found between afforestation areas and other types of cover; however, pine afforestation improved the drainage of the soil, as its infiltration rate was higher than that of the native holm oak forest.

The Water Storage Function of Litters and Soil in Five Typical Plantations in the Northern and Southern Mountains of Lanzhou, Northwest China

Soil and water conservation is an important function of forest ecosystems; however, it remains unclear which forest type is best suited for water and soil conservation under the same site conditions. In order to clarify the soil and water conservation function of different plantations in the northern and southern mountains of Lanzhou city, we investigated several soil and water conservation function indicators (thickness and accumulation of litter, maximum water holding capacity and rate of litter, water holding capacity and water absorption rate of litter, soil infiltration rates, soil water content, soil bulk density, soil porosity, and soil water storage) of five plantation types (Platycladus orientalis plantations (Po), Robinia pseudoacacia plantations (Rp), Populus alba var. pyramidalis plantations (Pa), P. alba var. pyramidalis + R. pseudoacacia mixed plantations (Pa + Rp), and P. orientalis + R. pseudoacacia mixed plantations (Po + Rp)) and evaluated them using the gray correlation method. The results indicated the accumulation of litter varied from 13.50 to 47.01 t·hm−2 and increased in the order of Pa &lt; Rp &lt; Po &lt; Po + Rp &lt; Pa + Rp. The maximum water holding capacity of litter varied from 35.29 to 123.59 t·hm−2 and increased in the order of Pa &lt; Rp &lt; Po &lt; Po + Rp &lt; Pa + Rp. The soil physical properties (soil infiltration, porosity, and bulk density) of mixed plantations were better than those of pure plantations. The soil maximum water storage was significantly different among plantation types (p &lt; 0.05), with an average varying from 3930.87 to 4307.45 t·hm−2, and was greater in mixed plantations than in pure plantations. Gray correlation analysis revealed that mixed plantations had the best conservation function of the five plantation types, followed by broad-leaved plantations and coniferous plantations. This suggests that the planting of mixed plantations dominated by Pa + Rp is therefore recommended in the future construction of plantations in the northern and southern mountains of Lanzhou to realize sustainable forest development.

Backpressure effects on emitters flow rate in subsurface drip irrigation

Subsurface drip irrigation success depends on surpassing the backpressure obstacle, a phenomenon which occurs when the water application intensity exceeds the infiltration rate of soil, which reduces the emitter flow rate. Thus, this study aimed to determine the flow rate variation, in relation to surface flow, of four drip emitters when buried at two depths in a loam soil (Yolo Loam soil), and the backpressure generated by the soil on subsurface condition. The cavity radius developed around the emitters outlet was also obtained. The experiment was conducted in a completely randomized design, in a strip-plot scheme, with three treatments: installation depth of driplines (two levels: 0.10 and 0.20 m); dripline type (four levels: D5000, JardiLine, TalDrip and and Hydro PCND) and irrigation time (three levels: 0.5, 1.0 and 3.0 h). The results showed that the flow rate variation between the surface and subsurface application on Yolo Loam soil, with inlet pressure of 145 kPa, was greater the higher was the emitter flow rate. For pressure-compensating emitters, even under backpressure influence, this was not enough to cancel the pressure-compensating device operation, of the emitters. The emitters installation depth, as well the irrigation time, did not affect the backpressure and, consequently, the flow rate variation.

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.

Soil and Water Conservation Nexus Agricultural Productivity in Ethiopia

Soil and water conservation practices contribute to long-term agricultural sustainability and sustainable agriculture. This review examines the primary agronomic practices and their role in soil and water conservation. The review revealed that Ethiopia's significant agronomic soil and water conservation practices are strip cropping, mixed cropping, intercropping, fallowing, mulching, contour plowing, crop rotation, preservation of tillage, and agroforestry. A significant difference was found between conserved and nonconserved land in terms of soil chemical and physical properties, soil organic matter, total N, available phosphorous (P), bulk density, infiltration rate, and soil texture. The non-conserved land had lower soil organic matter, total N, and infiltration rate with higher bulk density, clay content, and available P. Soil organic matter content positively correlated with infiltration rate and total N, and it negatively correlated with soil bulk density. Cation exchange capacity (CEC) positively correlated with soil pH and available P. The undulating lands were moderately suitable for rain fed agriculture. The plant canopies, litter, and mulching intercept rain by decreasing the amount, intensity, and spatial distribution of the precipitation reaching the soil surface, protecting the soil surface from the direct impact of raindrops that can cause splash and sheet erosion. In soil and water conservation, this practice is higher than others because crops and leguminous woody perennials improve and enrich soil conditions through atmospheric nitrogen fixation, organic matter through litterfall and dead and decaying roots, nutrient cycles, modification of soil porosity, and contribution to infiltration rates. It also relieves and maintains salinity, alkalinity, acid, and water retention problems. To increase the water table and increase soil moisture, water conservation is based on trapping as much of this water as possible and storing it on the surface (intanks) or allowing it to sink into the soil. Even where storage pans are dug, they are small and cannot keep the premises afloat when the drought lasts for days, as they have done recently. It is strongly recommended that the productivity of soil and water conservation measures is promoted through an integrated approach in which farmers are intensively involved in every implementation stage.

Experimental Investigation of the Different Polyacrylamide Dosages on Soil Water Movement under Brackish Water Infiltration.

The use of soil conditioners in conjunction with brackish water irrigation is critical for the efficient development and use of brackish water as well as the enhancement of the structure of saline soil and stimulating crop growth. This study investigated the effects of different polyacrylamide (PAM) dosages (0, 0.02%, 0.04%, and 0.06%) on the water flow properties of sandy loam during brackish water infiltration using one-dimensional vertical and horizontal soil column infiltration experiments. The results showed that: (1) PAM could lower the soil infiltration rate and increase soil water retention performance under brackish water infiltration conditions. (2) PAM had a significant effect on the parameters of the Philip and Kostiakov infiltration models. The soil sorption rate S and the empirical coefficient λ were the smallest, and the empirical index β was the largest when the PAM dosage was 0.04%. (3) PAM dosage displayed a quadratic polynomial connection with the soil saturated water content and the saturated hydraulic conductivity. The soil saturated water content was highest when the PAM dosage was 0.04%, the intake suction hd of the Brooks-Corey model increased by 15.30%, and the soil water holding capacity was greatly improved. (4) Soil treated with PAM could absorb more water under the same soil water suction, whereas the soil unsaturated hydraulic conductivity and its growth rate decreased. The soil saturated diffusion rate Ds, as well as the soil water diffusion threshold, rose. Finally, the 0.04% PAM dosage could improve soil hydrodynamic characteristics under brackish water infiltration, which is beneficial for the efficient utilization of brackish water.

Multi‐Stage Soil‐Hydraulic Recovery and Limited Ravel Accumulations Following the 2017 Nuns and Tubbs Wildfires in Northern California

AbstractWildfire can impact soil‐hydraulic properties by reducing saturated hydraulic conductivity and sorptivity, making recently burned landscapes prone to debris flows and flash floods. The post‐fire hazard window can range from years to decades. In Northern California, where wildfire frequency is steadily increasing, the impact and soil‐hydraulic recovery from wildfires is unknown. Following the October 2017 Nuns and Tubbs fires in the Northern Bay Area of California, we established 41 monitoring sites for repeat tension‐disc infiltrometer measurements of field‐saturated hydraulic conductivity (Kfs) over 3.5 years. Our site arrays, which encompass grasslands, chaparral, and oak and conifer forests across a range in lithology, show a marked decrease in Kfs following the wildfires and a swift partial recovery following the initial post‐fire rainy season. Our time series reveals a complex path to soil‐hydraulic recovery marked by distinct seasonal stages. Analysis of changing Kfs, sorptivity, and infiltration model residuals collectively suggests that these stages are related to transitions between soil‐hydraulic processes like structural soil sealing from rainsplash, thermal cracking of bare soil, and vegetation regrowth. While soil infiltration rates were strongly impacted by the 2017 fires, dry ravel estimates are an order of magnitude less for similar slopes than the 2009 Station fire in the San Gabriel mountains of Southern California, suggesting that limited ravel flux may insufficiently load channels for debris flows that initiate from within‐channel failure. Our analysis suggests that burned landscapes in the Northern Bay Area of California may experience rapid soil‐hydraulic recovery and limited pathways toward post‐fire debris flow initiation.

The influence of African elephants on litter and soil nitrogen attributes in mopane woodland in Hwange National Park, northwest Zimbabwe

Little is known about modification of nutrient fluxes through elephant-induced woodland change. We assessed litter quality, soil N attributes, and N transformations in five 20 × 20 m plots each established on sites of low, medium, and high elephant utilization categorized using dung-count surveys in three mopane woodland patches in Hwange National Park, Zimbabwe. Litter standing crop significantly declined but litter N, lignin, lignin:N, condensed tannins, and total phenols increased with increasing elephant utilization, peaking at intermediate levels of elephant utilization. Medium elephant utilization sites had more than twice the nitrate pools in low and high elephant utilization sites (p < 0.001). Ammonium concentration at low elephant utilization was lower by 65% and 92% than at high and medium elephant utilization, respectively. Soil moisture, infiltration rates, N mineralization, and nitrification decreased with increasing elephant utilization. Nitrogen mineralization and nitrification were up to four times greater in low than in medium and high elephant utilization sites. Ammonium, N mineralization, and nitrification were positively correlated to litter N but negatively correlated to condensed tannins. These results indicate that elephant-induced woodland change plays an important role in carbon and nutrient fluxes potentially increasing resources heterogeneity and reinforcing the patch dynamics of savanna.

Effect of Zinc Oxide Nanoparticles and Soil Amendments on Wheat Yield, Physiological Attributes and Soil Properties Grown in the Saline – Sodic Soil

ABSTRACT Soil degradation with salinity and sodicity has become a major issue in Egypt causing a decline in soil quality and crop productivity in these soils. The addition of gypsum (G), rice straw compost (C) and foliar application of ZnO nanoparticles (Z) as foliar application and their combinations to improve soil quality and physiology of wheat plants in saline-sodic soil is unclear. We studied the effects of G, C, Z and their integrated application in the field experiment during the two winter seasons in full form design on some soil properties, proline content, antioxidant enzyme activity and yield of wheat plants grown in the saline – sodic soil. The results showed that the addition of G, C or Z alone or their integrated application led to a significant increase in soil total porosity, infiltration rate, organic matter (OM), nitrogen (N), phosphorus (P), potassium (K) and zinc (Zn) uptake, the yield of wheat plant and a decrease in soil salinity and exchangeable sodium percentage in both seasons. The proline, superoxide dismutase and peroxidase content increased by 605.0%, 20.5% and 12.1% for Z while it increased by 617.5%, 34.4% and 15.2% for G + Z, respectively, compared to the control. The experimental results confirmed that integration of G or C with foliar application of Z can be a promising strategy to alleviate abiotic stresses wheat plants grown under saline-sodic soil and improve their quality.

Effect of brackish water irrigation on the movement of water and salt in salinized soil

Abstract In China, fresh water resources are scarce, while brackish water resources are abundant. Reasonable utilization of brackish water is one of the important measures to alleviate the contradiction of water shortage. In order to study the effect of brackish water irrigation on water and salt transport in saline-alkali soils, one-dimensional brackish water infiltration experiments of soil columns were conducted. The influence of brackish water with different salinities on water and salt transport in salinized soil was compared and analyzed. The results showed that under brackish water irrigation, the Kostiakov model could better simulate the change in soil infiltration rate with time, the soil infiltration capacity had a positive response to the salinity of irrigation water. There was a good linear relationship between cumulative infiltration and the wetting front distance. Under different salinity conditions, the depth of soil desalination, Na+, and Cl− removal is different, which are inversely proportional to the degree of salinity; with the increase in the salinity of irrigation water, the water salt content and the concentration of Na+ and Cl− increased gradually, but the difference in the desalination zone was not obvious. Therefore, brackish water irrigation has a certain effect on the distribution of water and salt in saline soil.