Changes In Soil Hydraulic Conductivity Research Articles

Coupled hydromechanical modelling of cone penetration in layered liquefiable soils

Soil layering modifies cone penetration measurements when the cone is close to layer boundaries. Transition zone and thin-layer effects appear, complicating interpretation. To help identify the mechanisms underlying transition and thin-layer effects, several series of realistic simulations of cone penetration in layered soils are presented. Cone penetration tests are simulated using fully coupled hydromechanical models solved with the particle finite-element method. A constitutive model capable of representing flow liquefaction is employed to explore the effect of embedded layers with different initial state parameter and/or hydraulic conductivity than the host soil. Sensing and development distances for tip resistance and excess pore pressure are examined, as well as the effect of layering on dissipation tests. It is shown how distortion of layer interfaces by the cone is captured, explaining several characteristics of pore pressure and dissipation records. It is also shown that looser soil states may be hidden in the tip resistance trace by simultaneous changes in soil hydraulic conductivity.

Changes in soil hydraulic conductivity in sweet potato field with living mulch

AbstractLiving mulch (LM) is used in agricultural fields to suppress weeds, control diseases, and mitigate erosion. It also enhances soil nutrient supply at the root death and decay stage during the growing season. However, benefits of LM to soil hydraulic properties related to soil pore structure have not been elaborated here. We focus on temporal changes in soil hydraulic conductivity (K) in a field where sweet potato was grown with and without LM (barley, Hordeum vulgare L.). K was measured in the field using a mini‐disk infiltrometer at three different pressure heads. In the plots with LM, K decreased significantly in August and then increased in October compared to plots without LM (at –0.5 cm pressure head). Changes in soil pore structure due to root growth or death and decay may alter soil hydraulic conductivity.

Evaluation of Cracking in Biochar-Amended Clayey Soil Under Freeze–Thaw Cycles

Biochar has been identified as an efficient soil amendment, and it shows promising results in inhibiting desiccation cracks. However, the effects of biochar on soil freeze–thaw cycle behavior on surface cracking have not been considered. This study focuses on the influence of wood biochar dosages on surface cracking under freeze–thaw cycles on clayey soils, and the mechanism was investigated through image analysis and water evaporation. Samples were prepared with different biochar dosages of 0%, 5%, 10%, and 15%, and maintained for 12 h constant temperature freeze (−20°C) and thaw (21°C) cycles. Every 12 h, sample weight, 2D images, and 3D scans were taken. Also, a parallel desiccation experiment was conducted at room temperature for comparison purposes. Results show that with an increased dosage of biochar for the freeze–thaw samples, the crack ratio, fractal dimension, total crack length, and average crack width decrease. Also, the crack propagation rate decreased with the increased amount of biochar. Further, the water evaporation rate decreased with increasing biochar for the freeze–thaw samples; the reasons can be correlated with the reduced thermal conductivity of soil with added biochar, and the reduction in bulk density causing reduced thermal conductivity. Results indicate that the final crack patterns are associated with the initial ice crystal patterns. Samples with low biochar produced larger-sized parallel layered texture ice crystals, and increased biochar content caused homogeneous massive ice crystal texture; these responses can be correlated with changes in soil hydraulic conductivity.

Temporal changes in soil hydraulic conductivity in saturated and unsaturated fields

Soil hydraulic conductivity ( $$K$$ ) is an important soil property that exhibits relatively large uncertainty. The temporal variability of $$K$$ is often ignored when calculating water movement in soil. Various factors such as tillage, rain, temperature, wetting/drying, soil surface crusting, solution concentration, and biological activity can influence field $$K$$ . We investigated soil $$K$$ in a central Iowa field as a function of time and tillage by using tension infiltrometer measurements with pressure head tension settings of 0 cm and − 3 cm. No clear relationship was found between bulk density ( $$\rho_{\text{b}}$$ ) and $$K$$ . Path analysis was conducted to assess the contribution ratios and causal relationships between factors affecting $$K$$ . The $$K$$ values were influenced by physical impacts such as tillage, precipitation, and surface crusting with contributions of 24%, − 32%, and 49%, respectively, and with error of 60%. Soil surface crusting had a particularly large impact on saturated $$K$$ . The maximum volume fraction influenced $$K$$ . Earthworm activity that impacted the soil pore structure was also noticed in the field. Owing to this biological mechanism, no relationship was observed between $$\rho_{\text{b}}$$ and $$K$$ . It is important to recognize the multiple combined effects of soil physical processes and biological activities when documenting $$K$$ in field soils.

Reclaiming Tropical Saline-Sodic Soils with Gypsum and Cow Manure

Saline-sodic soils are a major impediment for agricultural production in semi-arid regions. Salinity and sodicity drastically reduce agricultural crop yields, damage farm equipment, jeopardize food security, and render soils unusable for agriculture. However, many farmers in developing semi-arid regions cannot afford expensive amendments to reclaim saline-sodic soils. Furthermore, existing research does not cover soil types (e.g., Luvisols and Lixisols) that are found in many semi-arid regions of South America. Therefore, we used percolation columns to evaluate the effect of inexpensive chemical and organic amendments (gypsum and cow manure) on the reclamation of saline-sodic soils in the northeast of Brazil. Soil samples from two layers (0–20 cm and 20–40 cm in depth) were collected and placed in percolation columns. Then, we applied gypsum into the columns, with and without cow manure. The experiment followed a complete randomized design with three replications. The chemical amendment treatments included a control and four combinations of gypsum and cow manure. Percolation columns were subjected to a constant flood layer of 55 mm. We evaluated the effectiveness of sodic soil reclamation treatments via changes in soil hydraulic conductivity, chemical composition (cations and anions), electrical conductivity of the saturated soil-paste extract, pH, and the exchangeable sodium percentage. These results suggest that the combined use of gypsum and cow manure is better to reduce soil sodicity, improve soil chemical properties, and increase water infiltration than gypsum alone. Cow manure at 40 ton ha−1 was better than at 80 ton ha−1 to reduce the sodium adsorption ratio.

Changes in soil hydraulic conductivity after prescribed fires in Mediterranean pine forests

Prescribed fire removes or reduces the plant material that is prone to forest fires by creating fuel discontinuity and minimising fire intensity. This forest management tool potentially impacts Mediterranean ecosystems hydrological response by influencing water infiltration into soil. As direct measurements (e.g. by infiltrometers) of unsaturated infiltration in soil subjected to prescribed fires are scarce, this study has evaluated changes in soil hydraulic conductivity (SHC) using Minidisk infiltrometer after prescribed fires in representative plots of forests in the Iberian Peninsula under Mediterranean semi-arid conditions: (i) pure forest of Black pine Arnold ssp salzmannii; (ii) mixed forest of Maritime and Black pine; (iii) mixed forest of Aleppo and Maritime pine. The results have shown that fire reduced the organic layer thickness and its organic matter content. Consequently, after the prescribed fire the water content of burned plots was always lower than in untreated soils; conversely, the reverse soil behaviour was noticed before applying fire. Compared to the untreated soils, and with very few exceptions, prescribed fire did not cause significant changes in SHC. No general patterns in the comparisons between treatments (burned/unburned soils), in time evolution after fires and in the interactions between these effects were detected. This means that the SHC of burned soils followed the temporal variations of untreated soils. The lack of significance of these differences between treatments could be due to the low-fire severity and the limited effect of temperature in the mineral layer on soil hydraulic properties. This effect was expected and agrees with other studies. Overall prescribed fires did not alter SHC in Mediterranean forest ecosystems under unsaturated conditions since fire was of low-severity.

Estimation of runoff mitigation by morphologically different cover crop root systems

Summary Hydrology is a major driver of biogeochemical processes underlying the distinct productivity of different biomes, including agricultural plantations. Understanding factors governing water fluxes in soil is therefore a key target for hydrological management. Our aim was to investigate changes in soil hydraulic conductivity driven by morphologically different root systems of cover crops and their impact on surface runoff. Root systems of twelve cover crop species were characterized and the corresponding hydraulic conductivity was measured by tension infiltrometry. Relations of root traits to Gardner’s hydraulic conductivity function were determined and the impact on surface runoff was estimated using HYDRUS 2D. The species differed in both rooting density and root axes thickness, with legumes distinguished by coarser axes. Soil hydraulic conductivity was changed particularly in the plant row where roots are concentrated. Specific root length and median root radius were the best predictors for hydraulic conductivity changes. For an intensive rainfall simulation scenario up to 17% less rainfall was lost by surface runoff in case of the coarsely rooted legumes Melilotus officinalis and Lathyrus sativus , and the densely rooted Linum usitatissimum . Cover crops with coarse root axes and high rooting density enhance soil hydraulic conductivity and effectively reduce surface runoff. An appropriate functional root description can contribute to targeted cover crop selection for efficient runoff mitigation.

Soil hydraulic conductivity as affected by vegetation restoration age on the Loess Plateau, China

The Loess Plateau of China has experienced extensive vegetation restoration in the past several decades, which leads to great changes in soil properties such as soil bulk, porosity, and organic matter with the vegetation restoration age. And these soil properties have great effect on the soil infiltration and soil hydraulic conductivity. However, the potential changes in soil hydraulic conductivity caused by vegetation restoration age have not been well understood. This study was conducted to investigate the changes in soil hydraulic conductivity under five grasslands with different vegetation restoration ages (3, 10, 18, 28 and 37 years) compared to a slope farmland, and further to identify the factors responsible for these changes on the Loess Plateau of China. At each site, accumulative infiltration amount and soil hydraulic conductivity were determined using a disc permeameter with a water supply pressure of –20 mm. Soil properties were measured for analyzing their potential factors influencing soil hydraulic conductivity. The results showed that the soil bulk had no significant changes over the initial 20 years of restoration (P>0.05); the total porosity, capillary porosity and field capacity decreased significantly in the grass land with 28 and 37 restoration ages compared to the slope farmland; accumulative infiltration amount and soil hydraulic conductivity were significantly enhanced after 18 years of vegetation restoration. However, accumulative infiltration amount and soil hydraulic conductivity fluctuated over the initial 10 years of restoration. The increase in soil hydraulic conductivity with vegetation restoration was closely related to the changes in soil texture and structure. Soil sand and clay contents were the most influential factors on soil hydraulic conductivity, followed by bulk density, soil porosity, root density and crust thickness. The Pearson correlation coefficients indicated that the soil hydraulic conductivity was affected by multiply factors. These results are helpful to understand the changes in hydrological and erosion processes response to vegetation succession on the Loess Plateau.

Modeling changes in hydraulic conductivity due to siltation using soil columns from Alshuwaib dam site, United Arab Emirates

Changes in soil hydraulic conductivity (K) as a function of total suspended solids (TSS) concentration in the infiltrating water were studied in the laboratory using the constant-head technique. Soil samples collected from Alshuwaib dam site in the United Arab Emirates were selected for the study. The soil samples were collected from two distinct layers at the dam site; an upper layer which is composed of silt and clay and a lower layer which is mainly composed of sand. Formation of the upper layer is believed to be due to deposition of TSS originally present in the intercepted stormwater or due to dust deposition at the site. Temporal variations in the saturated K of the soil were studied using water with various TSS concentrations. The infiltrating turbid solution was prepared using tap water mixed with soil samples collected from the upper layer. Results show that presence of TSS in the water introduced into the columns caused a drop in K over time. Changes in K follow a sharp drop shortly after injecting the turbid solution and a slower drop at later times. The sharp initial drop was more pronounced for cases with higher injected TSS concentration. For an experimental time of about 80 h, K dropped an order of magnitude for cases with low influent concentration. Changes in K were simulated using a mechanistically based model that assumes formation of new layers with lower K values as a result of particle entrapment below the soil surface followed by particle deposition on the surface. The developed layers model closely predicts variations of K over time, with no observed particle entrapment, except at low TSS concentration. Meanwhile, predicted deposited masses of TSS are in agreement with those determined after the completion of the experiments. Results presented here could also be useful to managers of surface recharge facilities in the country and elsewhere.

The effect of mineral-ion interactions on soil hydraulic conductivity

The reuse of winery wastewater (WW) could provide an alternative water source for vineyard irrigation. The shift of many wineries and other food processing industries to K+-based cleaners requires studies on the effects of K+ on soil hydraulic conductivity (HC). Depending on clay content and mineral composition, K+ additions can affect the HC either positively or negatively. Soil mineralogy was anticipated to exhibit a strong influence on HC responses and, therefore, soils of contrasting mineralogy were evaluated for changes in soil HC resulting from applications of solutions elevated in Na+ and K+. To examine the impact of mineral-ion relationships on HC, soils dominant in montmorillonite, vermiculite, or kaolinite from the Napa and Lodi wine regions of California, were packed into soil columns to observe changes in leachate chemistry and HC. Irrigation with Na+- and K+-rich WW was simulated by applying solutions at sodium absorption ratio (SAR) values of 3, 6, and 9 and potassium absorption ratio (PAR) values of 1, 2, 4, and 9. While HC was reduced in the 2:1 clay soils (montmorillonite and vermiculite) for all SAR treatments, the vermiculite and the kaolinite rich soils exhibited equal or greater reductions in HC for PAR treatments, as compared with the SAR treatments. Findings from this evaluation of the interaction of Na+ and K+ with three different mineral soils suggest that the reuse of WW with increasing PAR are least problematic for montmorillonite dominated soils and most detrimental to the HC of the vermiculite dominated soil. The presence of minerals with a high affinity for K+ (e.g., vermiculite, mica) in this soil suggest that the interlayer binding of K+ could lead to greater reductions in HC. Full analysis of soil and WW is recommended prior to all land applications.

Biochar-induced changes in soil hydraulic conductivity and dissolved nutrient fluxes constrained by laboratory experiments.

The addition of charcoal (or biochar) to soil has significant carbon sequestration and agronomic potential, making it important to determine how this potentially large anthropogenic carbon influx will alter ecosystem functions. We used column experiments to quantify how hydrologic and nutrient-retention characteristics of three soil materials differed with biochar amendment. We compared three homogeneous soil materials (sand, organic-rich topsoil, and clay-rich Hapludert) to provide a basic understanding of biochar-soil-water interactions. On average, biochar amendment decreased saturated hydraulic conductivity (K) by 92% in sand and 67% in organic soil, but increased K by 328% in clay-rich soil. The change in K for sand was not predicted by the accompanying physical changes to the soil mixture; the sand-biochar mixture was less dense and more porous than sand without biochar. We propose two hydrologic pathways that are potential drivers for this behavior: one through the interstitial biochar-sand space and a second through pores within the biochar grains themselves. This second pathway adds to the porosity of the soil mixture; however, it likely does not add to the effective soil K due to its tortuosity and smaller pore size. Therefore, the addition of biochar can increase or decrease soil drainage, and suggests that any potential improvement of water delivery to plants is dependent on soil type, biochar amendment rate, and biochar properties. Changes in dissolved carbon (C) and nitrogen (N) fluxes also differed; with biochar increasing the C flux from organic-poor sand, decreasing it from organic-rich soils, and retaining small amounts of soil-derived N. The aromaticity of C lost from sand and clay increased, suggesting lost C was biochar-derived; though the loss accounts for only 0.05% of added biochar-C. Thus, the direction and magnitude of hydraulic, C, and N changes associated with biochar amendments are soil type (composition and particle size) dependent.

Temporal changes in soil hydraulic conductivity with different soil types and irrigation methods

The soil hydraulic conductivity (K) is an important parameter for understanding soil hydrologic processes. K varies with time, soil type, and irrigation method. Understanding and predicting the temporal variability of K are required for irrigation design and numerical analyses. The objective of this study was to investigate and evaluate the temporal variability in K from April to September of 2008 in two soils, clay loam (CLS) and sandy loam (SLS), and two irrigation methods, furrow irrigation (FIM) and drip irrigation (DIM). Five sets of infiltration measurements with five replications were taken in grape fields using a tension infiltrometer at supply h values of −15, −6, −3, and 0cm. The results showed that K had significant temporal differences under all supply h values. Generally, K initially exhibited high values and decreased from April to September. K of SLS was always significantly higher than that of CLS. K values were lower and varied more for FIM than for DIM, but showed no statistically significant difference between the two irrigation methods. About 1.3 to 2.9 times differences existed between the maximum mean K (in April) and minimum mean K values (in July/September) through the whole growing period. However, the relative errors between the calculated K and measured K diminished within 10% when K was estimated using a regression to adjust K to the number of irrigation events. These results contribute to a more accurate description of K for irrigation design and water flow modeling.

The relative effects of sodium and potassium on soil hydraulic conductivity and implications for winery wastewater management

The relative effects of Na+ and K+ on soil structural stability are not clearly defined by the existing literature. This is an important issue for the application of winery wastewater on soils as it contains high levels of K+ and varying levels of Na+. To evaluate the relative effects of Na+ and K+ on soil structural stability both surface and subsoil from a land application site for winery wastewater were used to assess changes in soil hydraulic conductivity in repacked soil columns. The soil was rich of smectite, 51–56%, with minor presence of illite, 5–8%, and kaolinite 10% clays. Solutions with sodium adsorption ratio (SAR) and potassium adsorption ratio (PAR) of 5–40, where the monovalent cation was Na+ or K+ and the divalent cation was Ca2+ or Mg2+ were used to leach the soil columns, at electrolyte concentrations ranging from 2.5 to 640meqL−1. In both surface and subsoil, percolating solutions with PAR or SAR, comprising all cation combinations, of 20 and 40 caused a decrease in hydraulic conductivity as electrolyte concentrations reduced. However, in PAR solutions the decreases in hydraulic conductivity were significantly smaller than the corresponding SAR solutions. These results indicated greater soil stability in the presence of K+ relative to Na+.

Changes in soil hydraulic conductivity, runoff, and soil loss due to irrigation with different types of saline–sodic water

Irrigation with saline–sodic water causes sodic conditions in the soil which reduces soil productivity. We evaluated the changes in a number of important indices related to soil structural stability when treated wastewater (TWW), albeit with higher loads of organic matter and suspended solids, was used instead of more saline–sodic irrigation water, under different degrees of aggregate slaking. We studied soil saturated hydraulic conductivity (HC) using disturbed samples packed in columns, and soil infiltration rate, runoff and erosion under simulated rainfall. Aggregate slaking was manipulated by wetting the samples prior to all tests at either a slow (1–2 mm h − 1 ) or a fast (50 mm h − 1 ) rate. Samples of a calcareous silty clay (Typic Calciorthids) from the Bet She'an Valley, Israel, were taken from plots irrigated for three years with either TWW, saline–sodic Jordan River water (JRW), or moderately saline–sodic spring water (SPW), and also from a non-cultivated area (control). With little or no aggregate slaking (use of slow wetting), higher HC values and lower amounts of total runoff and soil loss were measured compared to when more severe aggregate slaking was induced (use of fast wetting). The HC values for the TWW treatment were similar to, or lower than, those for the control and significantly higher than those for the JRW treatment. For the runoff and soil loss data, differences among the water quality treatments were, generally, more pronounced when aggregate slaking was substantially reduced, and were related to soil sodicity. Under the latter condition, runoff and soil loss from the TWW treatment were comparable with those from the control and significantly lower than those from the JRW treatment. Our results suggested that replacing saline–sodic irrigation water with TWW could have favorable effects on soil structural stability, especially under conditions where aggregate slaking can be reduced (e.g., in regions with low to moderate rain intensities; and/or use of low intensity irrigation systems).

Modeling the soil water balance based on time-dependent hydraulic conductivity under different tillage practices

A simulation model with time-dependent hydraulic conductivity parameters was used to predict the effects of three different tillage practices: conventional tillage (CT), no-tillage (NT) and subsoiling tillage (ST) on the components of the soil water balance during the summer maize growing season. The predictive capability of the model was improved, particularly for the subsoiling tillage case. The simulation results show that temporal changes in soil hydraulic conductivity induced by different tillage practices can affect percolation, water storage, transpiration and evaporation. Differences in the simulated components of the water balance were found to be small between CT and NT practices, but larger in the ST case. Compared with the conventional and no-tillage methods, subsoiling promotes infiltration and deep percolation, thereby favoring a possible recharge of the groundwater. Actual evaporation is always lower in the subsoiled plots, whatever the hydrological year. Transpiration is similar for the three treatments, suggesting no significant differences in water availability, except in wet years where it is higher in subsoiled soils.

SWBCM: a soil water balance capacity model for environmental applications in the UK

The paper presents a daily-time step, multi-horizon capacity model of soil-water balance (SWBCM—Soil Water Balance Capacity Model) suitable for ecological and environmental applications investigating the spatial and temporal variability of soil water content determined by changes in soil hydraulic conductivity, soil water storage capacity and the pathways of water movement through the soil and across soil types. SWBCM simulates soil water content at horizon level and encompasses limits on the amount of drainage from one horizon to the next to allow the formation of temporary perched water tables, lateral drainage, matric potential and surface runoff. The model incorporates a dynamic sub-model of grass growth (SWARD—Dowle, K., Armstrong, A.C., 1990. A model for investment appraisal of grassland drainage schemes on farms in the UK. Agric. Water Manage. 18, 101–120; Armstrong, A.C., Castel, D.A., Tyson, K.C., 1995. SWARD: a model of grass growth and the economic utilisation of grassland. In: Pereira L.S., van den Broek B.J., Kabat P., Allen R.G. (Eds.), Crop-Water Simulation Models in Practice. Wageningen Press, Wageningen, The Netherlands, pp. 189–197). SWBCM’s predictive ability is tested across a range of soil types under permanent grass in the UK and outputs are compared with predictions made by MACRO (Jarvis, N.J., 1994. The MACRO Model Version 3.1. Technical Description and Sample Simulations. Swedish University of Agricultural Sciences, Department of Soil Sciences, Reports and Dissertations 19, Uppsala, Sweden, 51 pp.), a mechanistic solute transport model which incorporates a physically-based preferential flow model in which total soil porosity is divided into two flow domains (macro-pores and micro-pores), each characterised by a flow rate; soil water flow in the micro-pore domain is modelled using Richards’ equation. In the modelling experiment, SWBCM simulations have been shown to provide good approximations of point-scale experimental data under a range of soil, climate and drainage management conditions in the UK. SWBCM simulations are close to those developed by the mechanistic MACRO model, suggesting that the capacity model can be applied to describe the water balance of multi-horizon UK soil profiles. The modelling approach used is considered to be applicable to the wide range of soil lower boundary conditions, ranging from free-draining to impermeable, occurring in the field and to simulate transient perched water tables that commonly occur in most temperate, high latitude countries such as the UK.