Wide Range Of Soil Textures Research Articles

A generalized van Genuchten model for unsaturated soil hydraulic conductivity

AbstractThe hydrodynamics of variably saturated soils or porous media in general are described via nonlinear functions of water retention and hydraulic conductivity, which facilitate the simulation of various mass and energy transport processes (e.g., water, heat, contaminants, colloids) within the porous medium. We set out to derive improved functions for more accurate estimations of soil hydraulic functions to advance the simulation of porous medium hydrodynamics. A new model is proposed for estimating the unsaturated hydraulic conductivity (UHC) from a soil water retention (SWR) function that is parameterized via nonlinear regression of measured data. The function can be viewed as a generalized van Genuchten (1980) model (GVG). We tested the new SWR and UHC expressions for numerous data sets from literature that cover a wide range of soil textures. Our comparisons reveal more accurate estimations using the GVG model by comparison with the original van Genuchten model.

A sigmoidal model for predicting soil thermal conductivity-water content function in room temperature

Apparent thermal conductivity of soil (λ) as a function of soil water content (θ), i.e., λ(θ) is needed to determine the heat flow in soil. The function of λ(θ) can be used in heat and water flow models for simplicity. The objective of this study was to develop a sigmoidal model based on logistic equation for entire range of soil water contents and a wide range of soil textures that can be used in simulation of heat and water flow in respected modes. Further, performance of the developed sigmoidal model along with two other models in literature was evaluated. In the proposed sigmoidal model, the constants of this model are estimated based on empirical multivariate equations by using soil sand content and bulk density. The sigmoidal model was validated with good accuracy for a wide range of soil textures, as the relationship between the measured and predicted λ showed slope and intercept values of nearly 1.0 and 0.0, respectively. Comparison of the results obtained by sigmoidal model with those obtained from Johansen and Lu et al. models indicated that, the sigmoidal model was superior to the other two models in prediction of λ for a wide range of soil textures and soil water contents. Furthermore, comparison with a recently proposed model by Xiong et al. indicated that our sigmoidal model is superior. Therefore, our developed sigmoidal model can be used in heat and water flow models to predict the soil temperature and heat flow.

New empirical-point pedotransfer functions for water retention data for a wide range of soil texture and climates

Knowing soil hydraulic properties is essential to support soil use and management practices; however, their measuring is commonly expensive and time-consuming. Thus, pedotransfer functions (PTFs) have been used to quantify physical properties such as the soil water retention curve (SWRC). SWRC relates the volumetric soil water content (θ) as a function of the matric potential (h) and plays a vital role in soil hydraulic modeling. Point-PTFs estimate key-points of the SWRC, often from measured texture, bulk density, and organic matter. This study aimed to formulate new point-PTFs to estimate θ(h) data ranging from θ(-0.1 m) to θ(-150 m) to be applied in subtropical, tropical and temperate soils. The PTF equations were derived from linear and non-linear regressions of measured soil physical properties against to the water retention data. The prediction performance of the new-formulated PTFs overcame the performance of already existing and widely-known PTFs recognized in the literature and can be, therefore, applied in soil water retention topics under a wider textural range.

Soil water retention and hydraulic conductivity measured in a wide saturation range

Abstract. Soil hydraulic properties (SHPs), particularly soil water retention capacity and hydraulic conductivity of unsaturated soils, are among the key properties that determine the hydrological functioning of terrestrial systems. Some large collections of SHPs, such as the UNSODA and HYPRES databases, have already existed for more than 2 decades. They have provided an essential basis for many studies related to the critical zone. Today, sample-based SHPs can be determined in a wider saturation range and with higher resolution by combining some recently developed laboratory methods. We provide 572 high-quality SHP data sets from undisturbed, mostly central European samples covering a wide range of soil texture, bulk density and organic carbon content. A consistent and rigorous quality filtering ensures that only trustworthy data sets are included. The data collection contains (i) SHP data, which consist of soil water retention and hydraulic conductivity data, determined by the evaporation method and supplemented by retention data obtained by the dewpoint method and saturated conductivity measurements; (ii) basic soil data, which consist of particle size distribution determined by sedimentation analysis and wet sieving, bulk density and organic carbon content; and (iii) metadata, which include the coordinates of the sampling locations. In addition, for each data set, we provide soil hydraulic parameters for the widely used van Genuchten–Mualem model and for the more advanced Peters–Durner–Iden model. The data were originally collected to develop and test SHP models and associated pedotransfer functions. However, we expect that they will be very valuable for various other purposes such as simulation studies or correlation analyses of different soil properties to study their causal relationships. The data are available at https://doi.org/10.5880/fidgeo.2023.012 (Hohenbrink et al., 2023).

Interactions among soil texture, pore structure, and labile carbon influence soil carbon gains

Perennial vegetation with high plant diversity, e.g., restored prairie, is known for stimulation of soil carbon (C) gains, due in part to enhanced formation of pore structure beneficial for long-term C storage. However, the prevalence of this phenomenon across soils of different types remains poorly understood. The aim of the study was to assess the associations between pore structure, soil C, and their differences in monoculture switchgrass and polyculture restored prairie vegetation across a wide range of soils dominating the Upper Midwest of the USA. Six experimental sites were sampled, representing three soil types with texture ranging from sandy to silt loams. The two vegetation systems studied at each site were (i) monoculture switchgrass (Panicum virgatum L.), and (ii) polyculture restored prairie, also containing switchgrass as one of its species. X-ray computed micro-tomography (µCT) was employed to analyze soil pore structure. Structural equation modeling and multiple path analyses were used to assess direct and indirect effects of soil texture and pore characteristics on microbial biomass C (MBC), particulate organic matter (POM), dissolved organic C (DOC), short-term respiration (CO2), and, ultimately, soil organic C (SOC). Across studied sites, prairie increased fractions of medium (50–150 µm Ø) pores by 11–45 %, SOC by 3–69 %, and MBC by 18–59 % (except for one site). The greater were the prairie-induced increases in the medium pore volumes, the greater were the prairie-induced SOC gains. Greater C losses via CO2 and DOC contributed to slower C accumulation in the prairie soil. We surmise that the interactive feedback loop relating medium pores and soil C acts across a wide range of soil textures and is an important mechanism through which perennial vegetation with high plant diversity, such as restored prairie, promotes rapid SOC gains.

A Family of Soil Water Retention Models Based on Sigmoid Functions

AbstractThe soil water retention curve is the fundamental soil hydraulic property to characterize soil water movement and solute transport. Many efforts have been devoted in the past decades to developing models to describe soil water retention curves. However, most of them are empirical equations or assume that soil pore size distributions conform to a lognormal distribution. Yet, few effects have been undertaken to systematically propose and compare a series of possible alternative probability density functions to describe the sigmoid retention curves with parameters physically explainable. Here, we proposed a family of five soil water retention models based on sigmoid functions with parameters of clear physical implications coinciding with the statistical measures of soil pore size distribution. Compared with the widely used models (i.e., Brooks & Corey, 1964; Kosugi, 1996; van Genuchten, 1980), the proposed models have somewhat improved performances to characterize water retention data for a wide range of soil textures without introducing additional model parameters. Two of the proposed models are capable of characterizing the observed two local extrema in the moisture capacity curves. The associated unsaturated hydraulic conductivity models of the proposed soil water retention models are also derived, which show superior performance in characterizing the observed hydraulic conductivities compared with competing models, especially in macropore regimes. Additionally, we analyzed the parameter‐equivalent conversion between the proposed and the existing models, and a simple linear regression equation can be used to derive the parameters of the proposed models from the existing and other alternative different proposed models.

Nesting of ground‐nesting bees in arable fields is not associated with tillage system per se, but with distance to field edge, crop cover, soil and landscape context

Abstract Ground‐nesting wild bees are crucial for the pollination of wild plants and crops and thus human wellbeing. Arable land currently covers 14 million km2 globally, but little is known about the role of arable fields as potential nesting habitats and how agricultural management, such as tillage system, affects nesting. We quantified nest density and nesting incidence (plot‐level nest presence/absence) of ground‐nesting bees in 12 conventionally tilled and 13 no‐till winter cereal fields in southwestern Switzerland. In each field, nests were quantified in eight belt transects at increasing distances from field edges within an area of 400 m2, and vegetation cover and soil properties were measured at nest sites and sites without nests. Nest density ranged from 0 (32% of fields) to 16 nests (mean: 4.0 nests) per 400 m2, corresponding to 0 to 400 nests ha−1 (mean: 101 nests ha−1). Fifteen nesting species were captured. Nest density was not significantly different between tillage systems. Nest density declined exponentially with distance from the field edge. Nest density and incidence were positively related to proportion of bare ground. Nests occurred across a wide range of soil textures and tended to increase with soil bulk density and sand content. Moreover, nest density tended to increase with the proportion of and proximity to areas under agri‐environment scheme in the surrounding landscape. Synthesis and applications. Our study shows that arable fields, irrespective of tillage system, are used as nesting sites by various ground‐nesting bee species, including important crop pollinators. The concentration of nests along field edges suggests that incentives to maintain small field sizes and to increase edge density have a great potential to support nesting of ground‐nesting bees in agricultural landscapes. Moreover, measures to reduce crop cover, for example, through increased row spacing, offer a promising way to promote nesting opportunities in arable fields, in particular, if floral‐rich agri‐environment scheme areas are locally available. Further studies are needed to better understand to what extent tilled arable fields are suitable nesting habitats for ground‐nesting bees or whether they act as ecological traps due to the adverse effects of tillage on bee offspring.

Assessment and application of an alternative formula to describe the hydraulic conductivity over the full moisture range

AbstractMotivated by a versatile three‐parameter water retention curve (WRC) formula of Fredlund and Xing, we proposed an alternative expression to describe the relative hydraulic conductivity (RHC) for soils that can capture oven‐dry to water‐saturated conditions (full moisture range) with a single, closed‐form equation (without having to explicitly partitioning the capillary and film flow components). This RHC expression was tested using an existing data set that includes a wide range of soil textures, and shown to be more accurate than the other two RHC expressions. Subsequently, the new RHC expression was combined with the WRC formula of Fredlund and Xing, generating an alternative model (hereafter called the FL model) applicable to describe soil hydraulic properties over the full moisture range. The FL model requires both the known WRC and RHC data since three additional fitting parameters are involved in the present RHC expression. Furthermore, the FL model was employed in a HYDRUS‐1D numerical model for simulating the soil moisture redistribution within a lysimeter. The numerical simulation with using the FL model can accurately predict the moisture redistribution, in turn confirming the validity of the FL model despite without partitioning the capillary and film flow components.

New Erodibility Parameterization for Applying WEPP on Rangelands Using ERMiT

HighlightsA practical parameterization approach to estimate erodibility was developed for WEPP applications on rangelands.Soil texture had a greater effect on rill erodibility than vegetation cover.Vegetation cover had a greater effect on interrill erodibility than soil texture.A new set of erodibility input parameters was defined for ERMiT applications on rangelands.Abstract. The USDA Water Erosion Prediction Project (WEPP) is a process-based soil erosion prediction model. WEPP uses three soil erodibility parameters: rill erodibility (Kr), interrill erodibility (Ki), and critical hydraulic shear stress (tc). In this study, a new parameterization approach for estimating erodibility was developed for WEPP applications on rangelands. Data from overland flow experiments on disturbed and undisturbed rangelands were used to develop empirical equations to predict rill erodibility variation as a function of vegetation cover and soil texture. Data from rainfall simulation experiments were analyzed by piecewise regression to develop empirical equations for predicting the variability of interrill erodibility before and after disturbance and across a wide range of soil textures as a function of vegetation cover and soil texture. Critical shear values corresponding to the developed rill and interrill erodibility parameters were proposed. Our results show that the new erodibility approach predicts erosion at the plot scale with a satisfactory range of error (PBIAS =35.6 and Nash-Sutcliffe efficiency = 0.49). The new approach was used to provide soil erodibility values for the Erosion Risk Management Tool (ERMiT), which uses WEPP as the runoff and erosion calculation engine. Keywords: ERMiT, Erosion, Interrill, Rangeland management, Rill, Shrub, Soil burn severity, WEPP.

Infiltration under Ponded Conditions

Ponded infiltration processes occur in agricultural lands irrigated by flooding of their soil surface or under insufficient drainage conditions. The existing equations describing the phenomenon of vertical infiltration under ponded conditions have not considered the actual contribution of the pressure head gradient to the flow. In this study, simple equations are proposed to describe the horizontal and vertical infiltration under various ponding heads incorporating the actual contribution of the pressure head gradient to the flow. Six soils with known hydraulic properties, covering a wide range of soil textures, were used. Horizontal and vertical infiltration data are obtained by numerical simulation for all soils studied using the Hydrus-1D code. To validate the accuracy of the proposed equations, the solutions of horizontal and vertical infiltrations provided by the proposed equations were compared with numerically simulated ones provided by the Hydrus 1-D. The analysis of the results showed a very good agreement in all soils studied. The proposed vertical infiltration equation was also compared to a simple and accurate equation which does not incorporate the actual contribution of the pressure head gradient to the flow and differences between them were observed in all soils studied.

Analysis of soil cohesion by fluidized bed methodology using integrable differential pressure sensors for a wide range of soil textures

Measuring cohesion (Co) as a simple and reliable factor with the fluidized bed approach to assess the inherent resistance of soils against destructive forces corresponding to the separation of particles from the soil mass is considered a promising research area in place of alternative methods by rainfall–runoff experiments. However, the approach has only been tested for very limited soil types, and there is a need to analyze its suitability for more diverse soil conditions, especially for cohesive soils having higher clay, organic matter, or lime contents. This study aimed to evaluate cohesion for twenty soil types representing nine different texture classes that differed significantly in terms of their intrinsic properties with an “Automated Soil Cohesion Measurement Apparatus”. This device was equipped with modern electronic sensor technologies designed to function and measure cohesion with the fluidized-bed approach. In the measurements, pressure drops that occur while the water pressure increases gradually as it passes through the soil mass are visually and electronically monitored and continuously recorded during the experiments with the help of precise differential pressure and weight sensors. Effects of the changes in intrinsic soil properties such as particle sizes, organic matter contents, and lime contents in terms of coagulation potentials on cohesive forces were observed with the designed apparatus. Related to that, the analysis of variance and the Fisher’s least significant difference tests indicated that the cohesion (Co) and the flow velocity at fluidization (Vf) values were significantly different by soil type (p < 0.05). Fraction of the fine silt-sized particles (FNSI) was highly correlated with Co and Vf, and explained much of the variance for the cohesive conditions. In addition, the Co values in coarse-textured soil types with low cementing components and soils having greater sand contents were four times lower than those of heavy textured and clay-bound soils. The approach and the designed apparatus successfully simulated changes in internal soil conditions in terms of measured Co and Vf values.

Evaluation of CH4 Emission in Two Paddy Field Areas, Khonkaen and Ayutthaya, in Thailand

It is well known that submerged soils emit high levels of methane (CH4) due to oxygen deprivation and free iron oxide causing a quick reduction. However, there are other soil properties that control the reduction processes in soil, especially the amount of soil organic carbon (SOC). This study aimed to investigate the major factors controlling CH4 production potential (CH4PP) in Thai paddy fields. Two provinces, Ayutthaya, a clay soil region, and Khonkaen, a sandy soil region, were selected to represent a wide range of soil textures. Soil characteristic analysis pre- and post-incubation, and weekly gas detection in an incubation experiment over two months, was conducted. Stepwise multiple regression analysis was employed to analyze major soil factors controlling CH4PP. For the regional prediction of CH4PP, a map dataset of Ayutthaya and Khonkaen by the Land Development Department, Thailand, and a soil texture map (with intersected point data using the soil property map in ArcGIS) by OpenLandMap, were used. CH4PP was correlated with 1:10 pH, Fe2+, and water-soluble organic carbon (WSOC) measured after incubation. Although CH4PP showed no significant correlation with any soil properties measured before incubation, CH4PP was correlated with SOC, 1:10 electrical conductivity (EC), exchangeable ammonium (ExNH4), and sand content. It was thought that SOC and ExNH4 were related to organic matter decomposition, 1:10 EC was related to SO42− reduction and sand content was related to free oxides. Predicted regional CH4PP was similar in Ayutthaya and Khonkaen, although SOC, ExNH4 and 1:10 EC was higher, and sand content was lower in Ayutthaya than in Khonkaen. In both regions, the distribution of CH4PP corresponded to SOC, and CH4PP was lower with lower sand content and higher 1:10 EC. In clayey Ayutthaya, higher CH4PP was observed in the area with higher ExNH4. This indicates that soil properties other than soil texture and SOC influence CH4PP in the paddy fields in Thailand.

An empirical model for estimating soil penetrometer resistance from relative bulk density, matric potential, and depth

Soil penetrometer resistance (PR), an indicator of soil strength, is often used to denote the force that roots need to exert to penetrate the soil. In this study, we propose an empirical model, which has a simplified form and fewer parameters than the previous ones, to estimate PR from relative bulk density, matric potential of soil water, and soil depth. The model was established by using field measurements of PR, bulk density, water content, and laboratory water retention data at various soil depths in a long-term tillage experiment during maize growing season in 2017. Relative bulk density was determined from soil texture, bulk density, and organic matter content. Model performance was evaluated by comparing the predictions from the new model against those obtained from four earlier models using independent field data collected from four soils of different textures in 2015, 2018 and 2019. The root mean square error of the new model ranged from 0.358 to 0.879 MPa, significantly lower than that of the other four models (0.404–2.689 MPa), indicating that the new model could be applied to estimate PR for a wide range of soil textures with improved accuracy.

Quantifying microbial growth and carbon use efficiency in dry soil environments via 18 O water vapor equilibration.

Soil microbial physiology controls large fluxes of C to the atmosphere, thus, improving our ability to accurately quantify microbial physiology in soil is essential. However, current methods to determine microbial C metabolism require liquid water addition, which makes it practically impossible to measure microbial physiology in dry soil samples without stimulating microbial growth and respiration (namely, the “Birch effect”). We developed a new method based on in vivo 18O‐water vapor equilibration to minimize soil rewetting effects. This method allows the isotopic labeling of soil water without direct liquid water addition. This was compared to the main current method (direct 18O‐liquid water addition) in moist and air‐dry soils. We determined the time kinetics and calculated the average 18O enrichment of soil water over incubation time, which is necessary to calculate microbial growth from 18O incorporation in genomic DNA. We tested isotopic equilibration patterns in three natural and six artificially constructed soils covering a wide range of soil texture and soil organic matter content. We then measured microbial growth, respiration and carbon use efficiency (CUE) in three natural soils (either air‐dry or moist). The proposed 18O‐vapor equilibration method provided similar results as the current method of liquid 18O‐water addition when used for moist soils. However, when applied to air‐dry soils the liquid 18O‐water addition method overestimated growth by up to 250%, respiration by up to 500%, and underestimated CUE by up to 40%. We finally describe the new insights into biogeochemical cycling of C that the new method can help uncover, and we consider a range of questions regarding microbial physiology and its response to global change that can now be addressed.

Simple functions for describing soil water retention and the unsaturated hydraulic conductivity from saturation to complete dryness

Many applications require accurate soil hydraulic functions that can describe the dynamics of water in variably saturated systems from full saturation to complete dryness. Current functions considering zero water content at the dry end involve the summation of capillary and adsorption functions. This study proposes relatively simple yet complete soil hydraulic functions from full saturation to oven dryness that can be incorporated into existing models. The proposed water retention model is constructed by scaling the saturation function of Fredlund and Xing (1994) to describe capillary and adsorptive water retention as well as zero water content at oven dryness. To describe the hydraulic conductivity due to capillary and film flow, the model of Wang et al. (2018) is used. We further incorporated hysteresis in the water retention function of Wang et al. (2018). Testing on 241 hydraulic property data sets covering a wide range of soil textures from sands to clays, shows good agreement with laboratory observations, especially for coarse-textured soils. The proposed model accounts for the following processes: hysteretic capillary and adsorptive water retention, hysteretic hydraulic conductivity as a function of pressure head, non-hysteretic hydraulic conductivity as a function of water content, the effects of entrapped air, and closed scanning curves. This paper successfully derives the parameters of the main wetting curve from the main drying curve. Using the proposed functions for soil water flow modelling should lead to improved dynamic flow predictions, especially for drying soil conditions.

Modeling Distribution of Potassium in the Soil in Under Drip Irrigation

In recent years, use of drip irrigation has been increased for many products, in a wide range of soil textures and structures. So far, any model has not been provided for distribution of potassium in the soil during irrigation. The purpose of this, research is modeling distribution of potassium in the soil, under drip irrigation.

Normalized concept for modelling effective soil thermal conductivity from dryness to saturation

AbstractEffective soil thermal conductivity (λ eff) is a critical parameter for environmental and earth science as well as engineering applications. Models to predict λ eff are required in diverse global and community land surface schemes as well as climate models to investigate coupled water and heat transport in soils and heat exchange at the earth surface. Among the many soil thermal conductivity models, models based on the normalized concept are most often developed and utilized for estimating λ eff. However, at present no systematic study has been performed to investigate the origin and evolution of the normalized thermal conductivity models, nor to evaluate their performance with large datasets. The objectives of this study were to: (a) review the development and evolution of the normalized thermal conductivity models, and (b) assess their performance with datasets consisting of soils with a full range of water saturation and a wide range of soil textures and bulk densities. A total of 38 normalized thermal conductivity models were critically reviewed and their relationships were clearly outlined. Their performance was evaluated by five categories according to model characteristics with a compiled dataset consisting of 71 soils and 669 tests collected from nine studies. Our analysis demonstrated key roles of the quartz content, solid thermal conductivity and choice of the Kersten functions in the model applicability and accuracy of estimating λ eff. The results showed that the Y2018, CK2005, CK2006, J1975, L2007 and T2009 models have the best performance among the models without fitting parameters, but further improvements are required to apply them universally. Although the models of H2017, LD2015, M2006 and K2007 are the best performing models with fitting parameters, approaches to calculate these parameters are required so they can be easily applied. Future studies on parametrization of currently well‐performing models for wider and more accurate application, development of a soil thermal conductivity database for model evaluation and calibration purposes, and connecting soil thermal conductivity models to hydraulic properties are recommended.Highlights The history and evolution of normalized thermal conductivity models and the potential Kersten (K e) functions are collated and synthesized. A total of 38 models were reviewed and their performance was evaluated with a total of 71 soils and 669 tests from nine studies. The Y2018, CK2005, CK2006, J1975, L2007 and T2009 are the best ranked models without fitting parameters. The models of H2017, LD2015, M2006 and K2007 are the best ranked models with fitting parameter.

Evaluation and application of the modified van Genuchten function for unsaturated porous media

Proper soil hydraulic functions of the water retention curve (the WRC) and relative hydraulic conductivity (the RHC) are essential for studies of unsaturated groundwater flow in soils. Various mathematical expressions of these functions have been proposed, including the widely used van Genuchten-Mualem model combining the van Genuchten formula for the WRC and the Mualem formula for the RHC. Here we validate a model based on the van Genuchten function for the both WRC and RHC (termed the MVG model), against published experimental data covering a wide range of soil textures from sand to silt clay loam. The results show that the MVG model is more accurate and flexible than existing soil hydraulic functions, especially for predicting the RHC. The fitting of the model to the data also reveals a relationship of model parameters between the MVG-WRC and MVG-RHC functions. Both functions can be integrated and differentiated to attain simple analytical expressions for characteristic parameters of soil water flow, for example, the wetting front pressure ψf used in the Green and Ampt model for ponded infiltration analysis and the characteristic length Lc as a key factor in determining various flow processes (e.g., drainage or evaporation) in unsaturated soils.

Soil state variables in space and time: first steps towards linking proximal soil sensing and process modelling

The benefits of process-oriented modelling for management recommendations at the field scale are constrained by high spatial variability of soil properties and lack of dense information on soil types, variability and patterns. Geo-electrical mapping provides dense information about the soil, but sensor output is influenced by several factors. The agro-ecosystem model HERMES simulates nitrogen and water flow in the soil–plant–atmosphere system and was applied to 60 soil sampling points from a well-documented field with a wide range of soil texture in North Rhine-Westphalia, Germany. Validation of HERMES resulted in satisfactory root mean square errors for yield (0.62 t ha−1), water (36.08 mm) and nitrogen in the soil (74.93 kg ha−1) over the whole simulation period of 3 years. For the same field, values of electrical conductivity (ECa) ranged from 20 to 90 mS m−1. Clay and sand contents of three soil layers were highly correlated with the measured ECa. Derived regression models showed R2 values between 0.69 and 0.85, and cross-validation of the statistical equations resulted in a very good reflection of observed soil texture for two of the three soil layers. The subsequent calculation of soil texture at the mapping points of ECa produced an improved resolution of this key attribute to initialize model simulation. The temporal and spatial patterns derived from this work linking the ECa sensor to a process model allow the designation of sub-areas within the field according to the soil nitrogen and water supply. However, results could be improved by considering more than one up-scaled soil property for process-modelling.

A New Drainpipe‐Envelope Concept for Subsurface Drainage Systems in Irrigated Agriculture

AbstractOn irrigated lands, drainpipe performance is often below standard due to clogging, siltation and root growth inside the pipe. To tackle these problems, an innovative pipe–envelope concept was tested on a 50 ha pilot area in Harran, Turkey, in 2015 and 2016. The new concept, HYDROLUIS, consists of a corrugated inner pipe with three rows of perforations at the top and an unperforated outer pipe that covers about 2/3 of the inner pipe leaving only the unperforated bottom part of the inner pipe in contact with the soil. The main advantages of the new concept are that it works for a wide range of soil textures and there is better protection against root growth inside the pipe. The new concept was compared with a geotextile envelope, a gravel envelope and a control with no envelope. The HYDROLUIS and gravel envelopes had a significantly lower entrance resistance compared to the geotextile, the best drain performance and no signs of sedimentation nor of root growth inside the pipe. The production costs of the HYDROLUIS envelope are comparable to those of pre‐wrapped synthetic envelopes and considerably lower than gravel envelopes. It can be concluded that the HYDROLUIS envelope is a promising alternative for sand/gravel or synthetic envelopes in irrigated lands. © 2018 The Authors. Irrigation and Drainage published by John Wiley &amp; Sons Ltd on behalf of International Commission for Irrigation and Drainage