The role of biochar particle size and hydrophobicity in improving soil hydraulic properties

Soil Water Retention ◽

The physical properties of biochar have been shown to dramatically influence its performance as a soil amendment. Biochar particle size is one of key parameters, as it controls its specific surface area, shape, and pore distribution. Therefore, this study assessed the role of biochar particle size and hydrophobicity in controlling soil water movement and retention. Softwood pellet biochar in five particle size ranges (>2 mm, 2 &#8211; 0.5 mm, 0.5 &#8211; 0.25 mm, 0.25 &#8211; 0.063mm and <0.063 mm) was used for the experiment. These particle sizes were tested on 2 soil types (sandy loam and loamy sand) at four different application rates (1, 2, 4 and 8%).&#160; Our results showed that biochar hydrophobicity increased with decreasing biochar particle size, leading to a reduction in its water retention capacity. The effect of biochar on soil hydraulic properties varied with different rate of application and particle sizes. With increasing rate of application, water retention increased while hydraulic conductivity decreased. Water content at field capacity, permanent wilting point, and the available water content increased with increasing biochar particle size. The soil hydraulic conductivity increased with decreasing particle sizes apart from biochar particles <0.063mm which showed a significant (p&#8804;0.05) decrease compared to the larger particle sizes. The results clearly showed that both biochar intra-porosity and inter-porosity are important factors affecting soil hydraulic properties. Biochar interpores affected mainly hydraulic conductivity, both interpores and intrapores controlled soil water retention properties. Our results suggest that for a more effective increase in soil water retention in sandy loam and loamy sand, the use of hydrophilic biochar with high intra-porosity is recommended.

The influence of microplastic on soil hydraulic properties

10.5194/egusphere-egu2020-9337 ◽

2020 ◽

Author(s):

Patrizia Hangele ◽

Katharina Luise Müller ◽

Hannes Laermanns ◽

Christina Bogner

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Pore Space ◽

Water Retention Curve ◽

Soil Water Retention ◽

Soil Hydraulic Conductivity ◽

The need to study the occurrence and effects of microplastic (MP) in different ecosystems has become apparent by a variety of studies in the past years. Until recently, research regarding MP in the environment has mainly focused on marine systems. Within terrestrial systems, studies suggest soils to be the biggest sink for MP. Some studies now started to explore the presence of MP in soils. However, there is a substantial lack of the basic mechanistic understanding of the behaviour of MP particles within soils.This study investigates how the presence of MP in soils affects their hydraulic properties. In order to understand these processes, experiments are set up under controlled laboratory conditions as to set unknown influencing variables to a minimum. Different substrates, from simple sands to undisturbed soils, are investigated in soil cylinders. MP particles of different sizes and forms of the most common plastic types are applied to the surface of the soil cylinders and undergo an irrigation for the MP particles to infiltrate. Soil-water retention curves and soil hydraulic conductivity are measured before and after the application of MP particles. It is hypothesised that the infiltrated MP particles clog a part of the pore space and should thus reduce soil hydraulic conductivity and change the soil-water retention curve of the sample. Knowledge about the influence of MP on soil hydraulic properties are crucial to understand transport and retention of MP in soils.

Seasonal changes of hydraulic properties of a Chromic Luvisol under different soil management

Biologia ◽

10.2478/s11756-006-0186-6 ◽

2006 ◽

Vol 61 (19) ◽

Cited By ~ 10

Author(s):

Csilla Farkas ◽

Csaba Gyuricza ◽

Márta Birkás

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Vegetation Period ◽

Saturated Hydraulic Conductivity ◽

Soil Water Retention ◽

Tillage Systems ◽

AbstractIn the present work the effect of five tillage methods on the hydraulic properties and water regime of a brown forest soil was studied. In each treatment, measurements of bulk density and soil water retention characteristics were carried out 3 times (March, June and August) within the vegetation period. Near-saturated hydraulic conductivity and soil water content measurements were performed five and eight times, respectively. Statistically valuable differences were obtained between the soil properties, measured in different tillage treatments. The effect of the tillage treatments on the water retention curves was significant in the low suction range (pF < 2.0) only. Differences between the soil water retention curves, measured at the end of the vegetation period reflected the indirect effect of different tillage systems on soil hydraulic properties. The seasonal variability of both the soil hydraulic functions was proofed. Saturated hydraulic conductivity values, evaluated in the ploughing treatment at the beginning and end of the vegetation period differed up to 4-times. The near-saturated hydraulic conductivity values measured in March were nearly two times higher in all the treatments, except no till, than those, measured in August. The applied tillage systems did not influence the potential amount of water available for the plant; still, valuable differences between the soil water contents were measured. According to the soil hydraulic properties and measured soil water regime, ploughing and deep loosening created the most favourable soil conditions for the plants. The biological activity, however, was the highest in the no till treatment. Further studies on the application of the soil conserving tillage systems under Hungarian conditions are recommended.

Measurement of soil hydraulic properties of structured and repacked soils

10.5194/egusphere-egu21-3985 ◽

2021 ◽

Author(s):

Urša Pečan ◽

Luka Žvokelj ◽

Jure Ferlin ◽

Vesna Zupanc ◽

Marina Pintar

Keyword(s):

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Soil Samples ◽

Measuring System ◽

Soil Water Retention ◽

Undisturbed Soil ◽

Soil Hydraulic ◽

Low Tension

Soil hydraulic properties provide important information about soil behavior under unsaturated and saturated conditions. Often sampling of undisturbed soils is not possible and soil samples have to be repacked for laboratory analysis. The HYPROP&#174; measuring system (METERgroup, Munich, Germany) is a convenient method for determination of soil water retention characteristics and unsaturated hydraulic conductivity of undisturbed soil samples. It measures the matric potential of the saturated and drying soil sample using two tensiometers placed at different depths. Although the tensiometers are based on a new design that theoretically withstands cavitation at higher tension values, they are still considered to operate in the low tension range. Since soil water retention properties in the low tension range are strongly influenced by soil structure and pore size distribution, we were interested in the changes in hydraulic properties when measured on disturbed and then repacked samples, and undisturbed soil samples. Therefore, we investigated the soil hydraulic properties of three different soil types using the evaporation method on undisturbed and repacked samples. The results provide important insights for the interpretation of the results when the collection of undisturbed samples is not possible, and for designing laboratory experiments with repacked soils.

Influence of crust formation under natural rain on physical attributes of soils with different textures

Revista Brasileira de Ciência do Solo ◽

10.1590/s0100-06832011000600006 ◽

2011 ◽

Vol 35 (6) ◽

pp. 1893-1905 ◽

Cited By ~ 6

Author(s):

Selene Cristina de Pierri Castilho ◽

Miguel Cooper ◽

Carlos Eduardo Pinto Juhász

Keyword(s):

Particle Size ◽

Hydraulic Conductivity ◽

Soil Water ◽

Soil Degradation ◽

Water Retention ◽

Sandy Loam ◽

Distribution Analysis ◽

Soil Water Retention ◽

Crust Formation ◽

Soil Crusts

One of the main negative anthropic effects on soil is the formation of crusts, resulting in soil degradation. This process of physical origin reduces soil water infiltration, causing increased runoff and consequently soil losses, water erosion and/or soil degradation. The study and monitoring of soil crusts is important for soil management and conservation, mainly in tropical regions where research is insufficient to explain how soil crusts are formed and how they evolve. The purpose of this study was to monitor these processes on soils with different particle size distributions. Soil crusts on a sandy/sandy loam Argissolo Vermelho-Amarelo (Typic Hapludult), sandy loam Latossolo Vermelho-Amarelo (Typic Hapludox) and a clayey Nitossolo Vermelho eutroférrico (Rhodic Kandiudalf) were monitored. The soil was sampled and data collected after 0, 3, 5 and 10 rain storms with intensities above 25 mm h-1, from December 2008 to May 2009. Soil chemical and particle size distribution analysis were performed. The changes caused by rainfall were monitored by determining the soil roughness, hydraulic conductivity and soil water retention curves and by micromorphological analysis. Reduced soil roughness and crust formation were observed for all soils during the monitored rainfall events. However, contrary to what was expected according to the literature, crust formation was not always accompanied by reductions in total porosity, hydraulic conductivity and soil water retention.

Modeling root water uptake depth driven by climate and soil texture using a simple bucket model approach

10.5194/egusphere-egu21-16434 ◽

2021 ◽

Author(s):

Ruth Adamczewski ◽

Sven Westermann ◽

Anke Hildebrandt

Keyword(s):

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Root Water Uptake ◽

Rooting Depth ◽

Soil Water Retention ◽

Precipitation Patterns ◽

Biogeochemical Models ◽

Root water uptake (RWU) in grasslands is determined by species composition, climate and soil hydraulic properties. Generally, plant communities are adapted to their environment, showing different rooting patterns along climate gradients. Due to climate change, ecosystems are exposed to shifts in precipitation patterns and rising temperatures, causing the need to adapt rooting strategies. RWU is mainly driven by plant transpiration and soil hydraulic status in the rooting zone. Soil hydraulic properties depend strongly on soil texture, which has been observed to influence rooting depth, increasing the root length from fine to coarse soils. Secondly, precipitation patterns affect the typical soil moisture status, and subsequently the rooting depth. Global models suggest that in dry environments RWU should move deeper, to enhance the plant available soil water. However, few studies have at the same time considered the effect of climate and soil properties on RWU depth, although soil properties vary substantially and probably more than precipitation patterns due to climate change.Biogeochemical models suffer from uncertainty in subsurface hydrological processes, RWU being an important part of it. Thus, ecohydrological models are needed for an integration in larger context biogeochemical models. The trend of ecological models is towards high parameterized models, implying high uncertainty and challenging calibration for those parameters. Especially in the subsurface, parameters are often unknown and are usually impossible to derive from direct measurements. In this project, a simple, parsimonious bucket model was implemented, solving the water balance equation for a multi-layer soil profile. The objective of this work is to predict maximum required RWU depth required to satisfy potential evapotranspiration across established experimental grassland sites with different climate and soil water retention properties. For this we use soil moisture measurements, textures and hydraulic properties determined in three grassland sites of the Nutrient-Network (NutNet) across a climate gradient. We test the sensitivity of the model towards climate and soil hydraulic parameters. First model results show a high sensitivity of RWU depth besides to dynamics to climate, also to soil water retention determined by texture and organic matter content in the soils.

Estimating soil hydraulic properties from saturation to complete dryness

10.5194/egusphere-egu21-10481 ◽

2021 ◽

Author(s):

Budiman Minasny ◽

Rudiyanto Rudiyanto ◽

Federico Maggi

Keyword(s):

Soil Moisture ◽

Hydraulic Conductivity ◽

Soil Water ◽

Hydraulic Properties ◽

Water Retention ◽

Pedotransfer Functions ◽

Soil Moisture Dynamics ◽

Soil Hydraulic ◽

Moisture Dynamics

To study the effect of drought on soil water dynamics, we need an accurate description of water retention and hydraulic conductivity from saturation to complete dryness. Recent studies have demonstrated the inaccuracy of conventional soil hydraulic models, especially in the dry end. Likewise, current pedotransfer functions (PTFs) for soil hydraulic properties are based on the classical Mualem-van Genuchten functions.This study will evaluate models that estimate soil water retention and unsaturated hydraulic conductivity curves in full soil moisture ranges. An example is the Fredlund-Xing scaling model coupled with the hydraulic conductivity model of Wang et al. We will develop pedotransfer functions that can estimate parameters of the model. We will compare it with existing PTFs in predicting water retention and hydraulic conductivity.The results show that a new suite of PTFs that used sand, silt, clay, and bulk density can be used successfully to predict water retention and hydraulic conductivity over a range of moisture content. The prediction of hydraulic properties is used in a soil water flow model to simulate soil moisture dynamics under drought. This study demonstrates the importance of accurate hydraulic model prediction for a better description of soil moisture dynamics.&#160;

Multifractal analysis of soil hydraulic properties in arid areas

Soil Research ◽

10.1071/sr15284 ◽

2016 ◽

Vol 54 (8) ◽

pp. 914 ◽

Cited By ~ 1

Author(s):

N. Pahlevan ◽

M. R. Yazdani ◽

A. A. Zolfaghari ◽

M. Ghodrati

Keyword(s):

Spatial Variability ◽

Soil Properties ◽

Soil Water ◽

Multifractal Analysis ◽

Hydraulic Properties ◽

Water Retention ◽

Scaling Analysis ◽

Soil Water Retention ◽

Physical and hydraulic properties of soil are variable at different spatial scales. This indicates the necessity of understanding spatial patterns of soil properties. Scaling analysis, such as multifractal analysis, has been used to determine the spatial variability of soil properties. There are however limited numbers of studies concerning the applications of multifractal techniques applied to characterise spatial variability of soil properties in arid lands. The objective of this study was to quantify the scaling patterns of soil properties measured across a transect and to apply multifractal analysis in arid land areas. A transect with a length of 4.80km was selected, and soil properties were measured at 0–20cm depth every 145m along the transect. The soil properties analysed were: texture (sand, silt, clay), pH, electrical conductivity (EC), bulk density (BD), soil hydraulic properties (saturated hydraulic conductivity Ks and the van Genuchten soil water-retention equation’s parameters nv and αv), saturated water content (θs), and the slope of the soil water-retention curve at its inflection point (S). Results showed that the variability of pH and BD was characterised by quasi-monofractal behaviour. Results showed that soil hydraulic properties such as Ks, αn, nv, S, and θs were characterised by higher multifractal indices in the transects. EC showed the highest tendency to a multifractal type of scaling or the higher degree of multifractality.

Method for Quick Prediction of Hydraulic Conductivity and Soil-Water Retention of Unsaturated Soils

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198118798486 ◽

2018 ◽

Vol 2672 (52) ◽

pp. 108-117 ◽

Cited By ~ 1

Author(s):

Shaoyang Dong ◽

Yuan Guo ◽

Xiong (Bill) Yu

Keyword(s):

Finite Element ◽

Hydraulic Conductivity ◽

Soil Properties ◽

Soil Water ◽

Unsaturated Soil ◽

Unsaturated Soils ◽

Hydraulic Properties ◽

Water Retention ◽

Characteristic Curve ◽

Soil Water Retention

Hydraulic conductivity and soil-water retention are two critical soil properties describing the fluid flow in unsaturated soils. Existing experimental procedures tend to be time consuming and labor intensive. This paper describes a heuristic approach that combines a limited number of experimental measurements with a computational model with random finite element to significantly accelerate the process. A microstructure-based model is established to describe unsaturated soils with distribution of phases based on their respective volumetric contents. The model is converted into a finite element model, in which the intrinsic hydraulic properties of each phase (soil particle, water, and air) are applied based on the microscopic structures. The bulk hydraulic properties are then determined based on discharge rate using Darcy’s law. The intrinsic permeability of each phase of soil is first calibrated from soil measured under dry and saturated conditions, which is then used to predict the hydraulic conductivities at different extents of saturation. The results match the experimental data closely. Mualem’s equation is applied to fit the pore size parameter based on the hydraulic conductivity. From these, the soil-water characteristic curve is predicted from van Genuchten’s equation. The simulation results are compared with the experimental results from documented studies, and excellent agreements were observed. Overall, this study provides a new modeling-based approach to predict the hydraulic conductivity function and soil-water characteristic curve of unsaturated soils based on measurement at complete dry or completely saturated conditions. An efficient way to measure these critical unsaturated soil properties will be of benefit in introducing unsaturated soil mechanics into engineering practice.

Assessing the cover crop effect on soil hydraulic properties by inverse modelling in a 10-year field trial

10.5194/hess-2018-372 ◽

2018 ◽

Author(s):

José Luis Gabriel ◽

Miguel Quemada ◽

Diana Martín-Lammerding ◽

Marnik Vanclooster

Keyword(s):

Soil Water ◽

Cover Crop ◽

Hydraulic Properties ◽

Water Retention ◽

Cover Cropping ◽

Term Change ◽

Soil Hydraulic ◽

The Impact

Abstract. Cover cropping in agriculture is expected to enhance many agricultural and ecosystems functions and services. Yet, few studies are available allowing to evaluate the impact of cover cropping on the long term change of soil hydrologic functions. We assessed the long term change of the soil hydraulic properties due to cover cropping by means of a 10-year field experiment. We monitored continuously soil water content in non cover cropped and cover cropped fields by means of capacitance probes. We subsequently determined the hydraulic properties by inverting the soil hydrological model WAVE, using the time series of the 10 year monitoring data in the object function. We observed two main impacts, each having their own time dynamics. First, we observed an initial compaction as a result of the minimum tillage. This initial negative effect was followed by a more positive cover crop effect. The positive cover crop effect consisted in an increase of the soil micro- and macro-porosity, improving the structure. This resulted in a larger soil water retention capacity. This latter improvement was mainly observed below 20 cm, and mostly in the soil layer between 40 and 80 cm depth. This study shows that the expected cover crop competition for water with the main crop can be compensated by an improvement of the water retention in the intermediate layers of the soil profile. This may enhance the hydrologic functions of agricultural soils in arid and semiarid regions which often are constrained by water stress.

A global data set of soil hydraulic properties and sub-grid variability of soil water retention and hydraulic conductivity curves

Earth System Science Data ◽

10.5194/essd-9-529-2017 ◽

2017 ◽

Vol 9 (2) ◽

pp. 529-543 ◽

Cited By ~ 32

Author(s):

Carsten Montzka ◽

Michael Herbst ◽

Lutz Weihermüller ◽

Anne Verhoef ◽

Harry Vereecken

Keyword(s):

Hydraulic Conductivity ◽

Soil Texture ◽

Hydraulic Properties ◽

Water Retention ◽

Climate Models ◽

Hydraulic Parameters ◽

Soil Water Retention ◽

Data Set ◽

Global Data

Abstract. Agroecosystem models, regional and global climate models, and numerical weather prediction models require adequate parameterization of soil hydraulic properties. These properties are fundamental for describing and predicting water and energy exchange processes at the transition zone between solid earth and atmosphere, and regulate evapotranspiration, infiltration and runoff generation. Hydraulic parameters describing the soil water retention (WRC) and hydraulic conductivity (HCC) curves are typically derived from soil texture via pedotransfer functions (PTFs). Resampling of those parameters for specific model grids is typically performed by different aggregation approaches such a spatial averaging and the use of dominant textural properties or soil classes. These aggregation approaches introduce uncertainty, bias and parameter inconsistencies throughout spatial scales due to nonlinear relationships between hydraulic parameters and soil texture. Therefore, we present a method to scale hydraulic parameters to individual model grids and provide a global data set that overcomes the mentioned problems. The approach is based on Miller–Miller scaling in the relaxed form by Warrick, that fits the parameters of the WRC through all sub-grid WRCs to provide an effective parameterization for the grid cell at model resolution; at the same time it preserves the information of sub-grid variability of the water retention curve by deriving local scaling parameters. Based on the Mualem–van Genuchten approach we also derive the unsaturated hydraulic conductivity from the water retention functions, thereby assuming that the local parameters are also valid for this function. In addition, via the Warrick scaling parameter λ, information on global sub-grid scaling variance is given that enables modellers to improve dynamical downscaling of (regional) climate models or to perturb hydraulic parameters for model ensemble output generation. The present analysis is based on the ROSETTA PTF of Schaap et al. (2001) applied to the SoilGrids1km data set of Hengl et al. (2014). The example data set is provided at a global resolution of 0.25° at https://doi.org/10.1594/PANGAEA.870605.