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6 pages, 203 KiB

Open AccessEditorial

Soil Water Conservation: Dynamics and Impact

by Simone Di Prima, Mirko Castellini, Mario Pirastru and Saskia Keesstra

Water 2018, 10(7), 952; https://doi.org/10.3390/w10070952 - 18 Jul 2018

Cited by 6 | Viewed by 5435

Abstract

Human needs like food and clean water are directly related to good maintenance of healthy and productive soils. A good understanding of human impact on the natural environment is therefore necessary to preserve and manage soil and water resources. This knowledge is particularly [...] Read more.

Human needs like food and clean water are directly related to good maintenance of healthy and productive soils. A good understanding of human impact on the natural environment is therefore necessary to preserve and manage soil and water resources. This knowledge is particularly important in semi-arid and arid regions, where the increasing demands on limited water supplies require urgent efforts to improve water quality and water use efficiency. It is important to keep in mind that both soil and water are limited resources. Thus, wise use of these natural resources is a fundamental prerequisite for the sustainability of human societies. This Special Issue collects 15 original contributions addressing the state of the art of soil and water conservation research. Contributions cover a wide range of topics, including (1) recovery of soil hydraulic properties; (2) erosion risk; (3) novel modeling, monitoring and experimental approaches for soil hydraulic characterization; (4) improvement of crop yields; (5) water availability; and (6) soil salinity. The collection of manuscripts presented in this Special Issue provides more insights into conservation strategies for effective and sustainable soil and water management. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

Research

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15 pages, 5762 KiB

Open AccessArticle

Use of a Non-Ionic Water Surfactant in Lettuce Fertigation for Optimizing Water Use, Improving Nutrient Use Efficiency, and Increasing Crop Quality

by Alessandra Trinchera and Valentina Baratella

Water 2018, 10(5), 613; https://doi.org/10.3390/w10050613 - 8 May 2018

Cited by 10 | Viewed by 5404

Abstract

The use of water surfactants in fertigation constitutes a viable approach to increase soil wetting, potentially improving crop nutrient uptake and quality. An in-field demonstration test was carried out by applying an innovative, eco-friendly, non-ionic surfactant to fertigation water in Lactuca sativa (var. [...] Read more.

The use of water surfactants in fertigation constitutes a viable approach to increase soil wetting, potentially improving crop nutrient uptake and quality. An in-field demonstration test was carried out by applying an innovative, eco-friendly, non-ionic surfactant to fertigation water in Lactuca sativa (var. Iceberg) production to increase nutrient use efficiency and improve the crop’s access to water. A non-ionic methyl-oxirane surfactant (methyl-oxirane + 2-methyl-oxirane) was added at an increasing rate to the fertigation solution (Hoagland). Upon harvesting, the main growth and nutritional parameters were determined on the aboveground and belowground portions of the lettuce. Leaf nitrate content, water, and nitrogen use efficiency were recorded; the relationship of lettuce aboveground dry biomass with nutrient uptake was evaluated using vectorial analysis; and ultrastructural analysis of lettuce roots was performed by scanning electron microscopy. The surfactant, applied by fertigation at the rate of 1.0 mL × L_Hoagland⁻¹, improved crop P, K, Mn, and Fe use efficiency. When applied by fertigation, although the surfactant did not increase the water use efficiency index, it induced a significant decrease of the specific leaf water content (−8.8%) and an increase of the leaf area (+13.3%). By comparison with the recent literature, we inferred a positive physiological response by more expanded and less thick leaves in lettuce, likely by the optimization of the crop water and nutrient root uptakes mediated by the abundant but shortest lateral roots. This finding corresponded to the lowest leaf nitrate content, indicating an improvement of the lettuce quality without losing the crop yield. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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12 pages, 2051 KiB

Open AccessArticle

Translocation of Soil Particles during Secondary Soil Tillage along Contour Lines

by Novák Petr and Hůla Josef

Water 2018, 10(5), 568; https://doi.org/10.3390/w10050568 - 27 Apr 2018

Cited by 5 | Viewed by 3779

Abstract

A high percentage of arable land and erosion risk on agricultural land are typical of current agriculture. While tillage erosion is a less frequently studied issue, it impacts vast areas of agricultural land. Not all relationships between cultivation equipment, the gradient of the [...] Read more.

A high percentage of arable land and erosion risk on agricultural land are typical of current agriculture. While tillage erosion is a less frequently studied issue, it impacts vast areas of agricultural land. Not all relationships between cultivation equipment, the gradient of the plot and other factors have been known until now. Intensive soil tillage can be a crucial erosive factor mainly when the cultivation equipment moves in a fall line direction. Nevertheless, even when the equipment moves along contour lines, soil particles can be translocated perpendicular to the direction of the equipment movement (in a fall line direction). This phenomenon has not yet been adequately studied. For measurements, a field trial with secondary tillage of soil was laid out (a seedbed preparation implement was used). The objective of the trial was to evaluate the effect of the working tools of the cultivation equipment on the crosswise and lengthwise translocation of soil particles during soil tillage. Aluminium cubes, with a side length of 16 mm, were used as tracers. Before the operation, the tracers were inserted in a row perpendicular (at a right angle) to a direction of the equipment passes. After the equipment passes, position of tracers was evaluated within a two-axis grid. The trial was performed at three gradients of the plot (2°, 6° and 11°). For each gradient, the 1-pass, 2-pass and 3-pass treatments were tested. The equipment always moved along the plot contour line. After the equipment passes in all treatments, all tracers were localized on an orthogonal grid. The results of the trial demonstrate the effect of the slope gradient on the crosswise translocation of particles during secondary tillage of soil in the slope direction. The tillage equipment translocated particles in the fall line direction even if it passed along the contour line. With the increasing intensity of passes, the effect of the equipment on crosswise translocation increases. During secondary tillage of soil, the working tools of the equipment have an erosive effect (causing tillage erosion), even though the equipment moves along the contour line. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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8 pages, 572 KiB

Open AccessCommunication

Individual Local Farmers’ Perceptions of Environmental Change in Tanzania

by Lina Röschel, Frieder Graef, Ottfried Dietrich, Meike Pendo Schäfer and Dagmar Haase

Water 2018, 10(4), 525; https://doi.org/10.3390/w10040525 - 22 Apr 2018

Cited by 11 | Viewed by 4405

Abstract

Climatic and environmental changes are expected to affect in particular those regions where the economy is primarily based on the agricultural sector and where the dependency on water availability is high. This study examines how smallholder farmers in rural Tanzania perceived climatic and [...] Read more.

Climatic and environmental changes are expected to affect in particular those regions where the economy is primarily based on the agricultural sector and where the dependency on water availability is high. This study examines how smallholder farmers in rural Tanzania perceived climatic and environmental changes over the past 20 years and the resulting effects on water availability and food security. The study is based on a household survey of 899 farmers in a semi-arid and a sub-humid region in Tanzania. It was found that (a) significant differences in perceptions of the environment by farmers can be attributed to agro-climatic location, while the distance to a water source has less impact on individual perception; (b) differently perceived changes affect individual water availability and food security; and (c) the farm level adaptation methods applied are linked to vulnerability to changes and the household dependence on the immediate environment. The authors conclude that the specific environmental surroundings paired with socio-economic factors can severely compound the negative effects of water scarcity on rural farmers. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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17 pages, 7012 KiB

Open AccessArticle

Comparing Transient and Steady-State Analysis of Single-Ring Infiltrometer Data for an Abandoned Field Affected by Fire in Eastern Spain

by Simone Di Prima, Laurent Lassabatere, Jesús Rodrigo-Comino, Roberto Marrosu, Manuel Pulido, Rafael Angulo-Jaramillo, Xavier Úbeda, Saskia Keesstra, Artemi Cerdà and Mario Pirastru

Water 2018, 10(4), 514; https://doi.org/10.3390/w10040514 - 20 Apr 2018

Cited by 23 | Viewed by 5021

Abstract

This study aimed at determining the field-saturated soil hydraulic conductivity, K_fs, of an unmanaged field affected by fire by means of single-ring infiltrometer runs and the use of transient and steady-state data analysis procedures. Sampling and measurements were carried out in [...] Read more.

This study aimed at determining the field-saturated soil hydraulic conductivity, K_fs, of an unmanaged field affected by fire by means of single-ring infiltrometer runs and the use of transient and steady-state data analysis procedures. Sampling and measurements were carried out in 2012 and 2017 in a fire-affected field (burnt site) and in a neighboring non-affected site (control site). The predictive potential of different data analysis procedures (i.e., transient and steady-state) to yield proper K_fs estimates was investigated. In particular, the transient WU1 method and the BB, WU2 and OPD methods were compared. The cumulative linearization (CL) method was used to apply the WU1 method. Values of K_fs ranging from 0.87 to 4.21 mm·h⁻¹ were obtained, depending on the considered data analysis method. The WU1 method did not yield significantly different K_fs estimates between the sampled sites throughout the five-year period, due to the generally poor performance of the CL method, which spoiled the soil hydraulic characterization. In particular, good fits were only obtained in 23% of the cases. The BB, WU2 and the OPD methods, with a characterization based exclusively on a stabilized infiltration process, yielded an appreciably lower variability of the K_fs data as compared with the WU1 method. It was concluded that steady-state methods were more appropriate for detecting slight changes of K_fs in post-fire soil hydraulic characterizations. Our results showed a certain degree of soil degradation at the burnt site with an immediate reduction of the soil organic matter and a progressive increase of the soil bulk density during the five years following the fire. This general impoverishment resulted in a slight but significant decrease in the field-saturated soil hydraulic conductivity. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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16 pages, 7100 KiB

Open AccessFeature PaperArticle

Previous Land Use Affects the Recovery of Soil Hydraulic Properties after Forest Restoration

by Sergio E. Lozano-Baez, Miguel Cooper, Silvio F. B. Ferraz, Ricardo Ribeiro Rodrigues, Mario Pirastru and Simone Di Prima

Water 2018, 10(4), 453; https://doi.org/10.3390/w10040453 - 9 Apr 2018

Cited by 27 | Viewed by 6533

Abstract

Knowledge of soil hydraulic properties after forest restoration is essential for understanding the recovery of hydrological processes, such as water infiltration. An increase of forest cover may improve water infiltration and soil hydraulic properties, but little is known about the response and extent [...] Read more.

Knowledge of soil hydraulic properties after forest restoration is essential for understanding the recovery of hydrological processes, such as water infiltration. An increase of forest cover may improve water infiltration and soil hydraulic properties, but little is known about the response and extent to which forest restoration can affect these properties. The purpose of this study was to investigate the effect of forest restoration on surface-saturated soil hydraulic conductivity (K_s), and to verify the K_s recovery to the pre-disturbance soil conditions. We sampled field K_s at the surface in Campinas municipality, São Paulo State, Brazil, at 18 plots under three land-cover types: (i) a pasture; (ii) a restored forest using a high-diversity mix of plantings (85 regional native species) of 9 years of age; and (iii) a remnant forest patch. We used the Beerkan method for soil hydraulic characterization. Bulk density (ρ_b), soil organic carbon content (OC), soil porosity and particle size data were also sampled. We found considerable differences in soil hydraulic properties between land-cover classes. The highest K_s were observed in remnant forest sites and the lowest K_s were associated with pasture sites. The K_s recovery differs markedly between restored forests. Our results strongly suggest that soil attributes and K_s recovery are influenced by the duration and intensity of land use prior to forest restoration. Attention needs to be given to management activities before, during and after forest restoration, especially where the soil is still compacted and K_s is low. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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17 pages, 698 KiB

Open AccessArticle

Redrawing Soil Salinity Innovation-Focused Stakeholder Interaction for Sustainable Land Management in Khorezm Province, Uzbekistan

by Akmal Akramkhanov, Muhammad Mehmood Ul Hassan and Anna-Katharina Hornidge

Water 2018, 10(2), 208; https://doi.org/10.3390/w10020208 - 15 Feb 2018

Cited by 7 | Viewed by 4210

Abstract

Addressing soil salinity in irrigated drylands is tightly linked with water and land management decisions thus requiring interdisciplinary engagement. The salinity mapping approaches in Central Asia are undertaken through field sampling and laboratory analysis, which is a time consuming process. As a consequence, [...] Read more.

Addressing soil salinity in irrigated drylands is tightly linked with water and land management decisions thus requiring interdisciplinary engagement. The salinity mapping approaches in Central Asia are undertaken through field sampling and laboratory analysis, which is a time consuming process. As a consequence, salinity maps are not available on time to estimate water requirements to cope with varying levels of soil salinity. Reducing the time lag between assessment and delivery of such maps would enable authorities to determine in advance appropriate water volumes for leaching the salts before and during the growing season. Research initiated in Uzbekistan context explored transdisciplinary and participatory approach to innovation development with local stakeholders. As one of the innovations, an electromagnetic induction meter (EM), a tool for rapid salinity assessment, was chosen and jointly with local salinity mapping related institutions tested, validated, and local capacities for its use developed. This paper redraws this process of innovation-focused stakeholder interaction and transdisciplinary research and discusses it with reference to ongoing debates on participatory and/or transdisciplinary innovation research. The existence of strong path dependencies within implementation oriented organizations could be observed, meaning that the innovation demands many changes to the existing system. Furthermore, the encountered challenges of participatory, transdisciplinary research in the hierarchically shaped setting of post-soviet Uzbekistan are illustrated in selected qualitative field notes and assessed. For improved joint learning and research in a transdisciplinary team, feedback cycles of mutual learning and critical reflection of how to theoretically and practically work in a transdisciplinary manner turned out to be crucial and not to be underestimated. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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16 pages, 8098 KiB

Open AccessArticle

Application of EMI and FDR Sensors to Assess the Fraction of Transpirable Soil Water over an Olive Grove

by Giovanni Rallo, Giuseppe Provenzano, Mirko Castellini and Àngela Puig Sirera

Water 2018, 10(2), 168; https://doi.org/10.3390/w10020168 - 8 Feb 2018

Cited by 24 | Viewed by 4561

Abstract

Accurate soil water status measurements across spatial and temporal scales are still a challenging task, specifically at intermediate spatial (0.1–10 ha) and temporal (minutes to days) scales. Consequently, a gap in knowledge limits our understanding of the reliability of the spatial measurements and [...] Read more.

Accurate soil water status measurements across spatial and temporal scales are still a challenging task, specifically at intermediate spatial (0.1–10 ha) and temporal (minutes to days) scales. Consequently, a gap in knowledge limits our understanding of the reliability of the spatial measurements and its practical applicability in agricultural water management. This paper compares the cumulative EM38 (Geonics Ltd., Mississauga, ON, Canada) response collected by placing the sensor above ground with the corresponding soil water content obtained by integrating the values measured with an FDR (frequency domain reflectometry) sensor. In two field areas, characterized by different soil clay content, two Diviner 2000 access tubes (1.2 m) were installed and used to quantify the dimensionless fraction of transpirable soil water (FTSW). After the calibration, the work proposes the combined use of the FDR and electromagnetic induction (EMI) sensors to measure and map FTSW. A strong correlation (R² = 0.86) between FTSW and EM38 bulk electrical conductivity was found. As a result, field changes of FTSW are due to the variability of soil water content and soil texture. As with the data acquired in the field, more structured patterns occurred after a wetting event, indicating the presence of subsurface flow or root water uptake paths. After assessing the relationship between the soil and crop water status, the FTSW domain includes a critical value, estimated around 0.38, below which a strong reduction of relative transpiration can be recognized. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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16 pages, 1857 KiB

Open AccessArticle

Do As They Did: Peer Effects Explain Adoption of Conservation Agriculture in Malawi

by Andrew Reid Bell, Jennifer Zavaleta Cheek, Frazer Mataya and Patrick S. Ward

Water 2018, 10(1), 51; https://doi.org/10.3390/w10010051 - 10 Jan 2018

Cited by 28 | Viewed by 8944

Abstract

Adoption of the trinity of practices known commonly today as conservation agriculture (CA)—maintaining soil cover, reducing tillage, and enhancing soil nitrogen through legumes—is a critical process to the management of erosion in rural landscapes, and maintenance of aquatic habitats and hydropower potential. However, [...] Read more.

Adoption of the trinity of practices known commonly today as conservation agriculture (CA)—maintaining soil cover, reducing tillage, and enhancing soil nitrogen through legumes—is a critical process to the management of erosion in rural landscapes, and maintenance of aquatic habitats and hydropower potential. However, the large literature on the benefits and risks of CA fails to find any universal determinants of adoption, with competing uses for crop residues, availability of labor, and access to physical inputs common constraints appearing in different contexts. We conduct a study in the specific context of Malawi, using ethnographic interviewing to draw out possible decision criteria and machine learning to identify their explanatory power. This study is structured to inform the question: “How do farmers decide to adopt the specific activities of CA in Malawi?” We find that more than any other factor, adoption by neighbors (i.e., peer effects) matters, with possible implications for the overall cost of encouraging CA (e.g., through subsidies) as it is taken up across a landscape. Further, we note that little else within our household survey (save for more detailed articulation of neighbor and neighborhood characteristics) offers greater explanatory power than those factors identified by farmers themselves. Finally, we note that decisions made in the presence of an incentive are structurally different than those made without incentives, validating previous concerns in the literature regarding the basis most CA adoption studies, within CA promotion interventions. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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7559 KiB

Open AccessArticle

The Impact of the Age of Vines on Soil Hydraulic Conductivity in Vineyards in Eastern Spain

by Vincenzo Alagna, Simone Di Prima, Jesús Rodrigo-Comino, Massimo Iovino, Mario Pirastru, Saskia D. Keesstra, Agata Novara and Artemio Cerdà

Water 2018, 10(1), 14; https://doi.org/10.3390/w10010014 - 25 Dec 2017

Cited by 20 | Viewed by 6112

Abstract

Soil infiltration processes manage runoff generation, which in turn affects soil erosion. There is limited information on infiltration rates. In this study, the impact of vine age on soil bulk density (BD) and hydraulic conductivity (K_s) was assessed on a [...] Read more.

Soil infiltration processes manage runoff generation, which in turn affects soil erosion. There is limited information on infiltration rates. In this study, the impact of vine age on soil bulk density (BD) and hydraulic conductivity (K_s) was assessed on a loam soil tilled by chisel plough. Soil sampling was conducted in the inter row area of six vineyards, which differed by the age from planting: 0 (Age 0; just planted), 1, 3, 6, 13, and 25 years (Age 1, Age 3, Age 6, Age 13, and Age 25, respectively). The One Ponding Depth (OPD) approach was applied to ring infiltration data to estimate soil K_s with an α* parameter equal to 0.012 mm⁻¹. Soil bulk density for Age 0 was about 1.5 times greater than for Age 25, i.e., the long-term managed vineyards. Saturated hydraulic conductivity at Age 0 was 86% less than at Age 25. The planting works were considered a major factor for soil compaction and the reduction of hydraulic conductivity. Compared to the long-term managed vineyards, soil compaction was a very short-term effect given that BD was restored in one year due to ploughing. Reestablishment of K_s to the long-term value required more time. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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6392 KiB

Open AccessArticle

Transient Modeling of Flow in Unsaturated Soils Using a Novel Collocation Meshless Method

by Cheng-Yu Ku, Chih-Yu Liu, Jing-En Xiao and Weichung Yeih

Water 2017, 9(12), 954; https://doi.org/10.3390/w9120954 - 7 Dec 2017

Cited by 22 | Viewed by 4487

Abstract

In this paper, a novel meshless method for the transient modeling of subsurface flow in unsaturated soils was developed. A linearization process for the nonlinear Richards equation using the Gardner exponential model to analyze the transient flow in the unsaturated zone was adopted. [...] Read more.

In this paper, a novel meshless method for the transient modeling of subsurface flow in unsaturated soils was developed. A linearization process for the nonlinear Richards equation using the Gardner exponential model to analyze the transient flow in the unsaturated zone was adopted. For the transient modeling, we proposed a pioneering work using the collocation Trefftz method and utilized the coordinate system in Minkowski spacetime instead of that in the original Euclidean space. The initial value problem for transient modeling of subsurface flow in unsaturated soils can then be transformed into the inverse boundary value problem. A numerical solution obtained in the spacetime coordinate system was approximated by superpositioning Trefftz basis functions satisfying the governing equation for boundary collocation points on partial problem domain boundary in the spacetime coordinate system. As a result, the transient problems can be solved without using the traditional time-marching scheme. The validity of the proposed method is established for several test problems. Numerical results demonstrate that the proposed method is highly accurate and computationally efficient. The results also reveal that it has great numerical stability for the transient modeling of subsurface flow in unsaturated soils. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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4239 KiB

Open AccessArticle

Measurement and Simulation of Soil Water Contents in an Experimental Field in Delta Plain

by Wenjuan Hua, Chuanhai Wang, Gang Chen, Hai Yang and Yue Zhai

Water 2017, 9(12), 947; https://doi.org/10.3390/w9120947 - 6 Dec 2017

Cited by 6 | Viewed by 4697

Abstract

Variation in soil water content in the delta plain has its own particularity and is significant for agricultural improvement, the utilization of water resources and flood risk mitigation. In this study, experimental data collected from a plot of farmland located in the Taihu [...] Read more.

Variation in soil water content in the delta plain has its own particularity and is significant for agricultural improvement, the utilization of water resources and flood risk mitigation. In this study, experimental data collected from a plot of farmland located in the Taihu Basin were used to investigate the temporal and vertical variation of soil water content, as well as the effects of individual rainfall on soil water and shallow groundwater and their interaction. The results showed that the variation of soil water content is dependent on the comprehensive influence of soil hydraulic properties, meteorological factors and shallow groundwater and the correlation to the groundwater table is the strongest due to the significant capillary action in the delta plain. A saturated-unsaturated three-dimensional soil water numerical model was developed for the study area in response to rainfall and evapotranspiration. Scenario simulations were performed with different soil depths for soil water content and the error source was analyzed to improve the model. The average RMSE, RE and R² values of the soil water content at the five depths between the measured and simulated results were 0.0192 cm³·cm⁻³, 2.09% and 0.8119, respectively. The results indicated that the developed model could estimate vertical soil water content and its dynamics over time at the study site at an acceptable level. Moreover, further research and application to other sites in delta plains are necessary to verify and improve the model. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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4710 KiB

Open AccessFeature PaperArticle

Lateral Saturated Hydraulic Conductivity of Soil Horizons Evaluated in Large-Volume Soil Monoliths

by Mario Pirastru, Roberto Marrosu, Simone Di Prima, Saskia Keesstra, Filippo Giadrossich and Marcello Niedda

Water 2017, 9(11), 862; https://doi.org/10.3390/w9110862 - 6 Nov 2017

Cited by 10 | Viewed by 6842

Abstract

Evaluating the lateral saturated hydraulic conductivity, K_s,l, of soil horizons is crucial for understanding and modelling the subsurface flow dynamics in many shallow hill soils. A K_s,l measurement method should be able to catch the effects of soil heterogeneities governing [...] Read more.

Evaluating the lateral saturated hydraulic conductivity, K_s,l, of soil horizons is crucial for understanding and modelling the subsurface flow dynamics in many shallow hill soils. A K_s,l measurement method should be able to catch the effects of soil heterogeneities governing hydrological processes at the scale of interest, in order to yield K_s,l representative values over large spatial scales. This study aims to develop a field technique to determine spatially representative K_s,l values of soil horizons of an experimental hillslope. Drainage experiments were performed on soil monoliths of about 0.12 m³ volume, encased in situ with polyurethane foam. Median K_s,l of 2450 mm·h⁻¹ and 552 mm·h⁻¹ were estimated in the A and B horizon, respectively. In the upper part of the B horizon, the median K_s,l was 490 mm·h⁻¹, whereas it mostly halved near the underlying restricting layer. The decline of K_s,l values with depth was consistent with the water-table dynamics observed at the same site in previous studies. Moreover, the K_s,l from the monoliths were in line with large spatial-scale K_s,l values reported from the hillslope in a prior investigation based on drain data analysis. This indicated that the large-scale hydrological effects of the macropore network were well represented in the investigated soil blocks. Our findings suggest that performing drainage experiments on large-volume monoliths is a promising method for characterizing lateral conductivities over large spatial scales. This information could improve our understanding of hydrological processes and can be used to parameterize runoff-generation models at hillslope and catchment scale. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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5328 KiB

Open AccessArticle

Optimization of Multiple Seepage Piping Parameters to Maximize the Critical Hydraulic Gradient in Bimsoils

by Yu Wang, Changhong Li, Yanzhi Hu and Yonggang Xiao

Water 2017, 9(10), 787; https://doi.org/10.3390/w9100787 - 15 Oct 2017

Cited by 10 | Viewed by 5662

Abstract

Seepage failure in the form of piping can strongly influence the stability of block-in-matrix-soils (bimsoils), as well as weaken and affect the performance of bimsoil structures. The multiple-factor evaluation and optimization play a crucial role in controlling the seepage failure in bimsoil. The [...] Read more.

Seepage failure in the form of piping can strongly influence the stability of block-in-matrix-soils (bimsoils), as well as weaken and affect the performance of bimsoil structures. The multiple-factor evaluation and optimization play a crucial role in controlling the seepage failure in bimsoil. The aim of this study is to improve the ability to control the piping seepage failure in bimsoil. In this work, the response surface method (RSM) was employed to evaluate and optimize the multiple piping parameters to maximize the critical hydraulic gradient (CHG), in combination with experimental modeling based on a self-developed servo-controlled flow-erosion-stress coupled testing system. All of the studied specimens with rock block percentage (RBP) of 30%, 50%, and 70% were produced as a cylindrical shape (50 mm diameter and 100 mm height) by compaction tests. Four uncertain parameters, such as RBP, soil matrix density, confining pressure, and block morphology were used to fit an optimal response of the CHG. The sensitivity analysis reveals the influential order of the studied factors to CHG. It is found that RBP is the most sensitive factor, the CHG decreases with the increase of RBP, and CHG increases with the increase of confining pressure, soil matrix density, and block angularity. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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4108 KiB

Open AccessArticle

Integrating Topography and Soil Properties for Spatial Soil Moisture Storage Modeling

by Xiaohua Xiang, Xiaoling Wu, Xi Chen, Qifeng Song and Xianwu Xue

Water 2017, 9(9), 647; https://doi.org/10.3390/w9090647 - 30 Aug 2017

Cited by 12 | Viewed by 5683

Abstract

The understanding of the temporal and spatial dynamics of soil moisture and hydraulic property of soil is crucial to the study of hydrological and ecological processes. The purpose of this study was to derive equations that describe spatial soil water storage deficit based [...] Read more.

The understanding of the temporal and spatial dynamics of soil moisture and hydraulic property of soil is crucial to the study of hydrological and ecological processes. The purpose of this study was to derive equations that describe spatial soil water storage deficit based on topography and soil properties. This storage deficit together with the topographical index can be used to conclude the spatial distribution curve of storage capacity in a (sub-) basin for developing hydrological model. The established model was able to match spatial and temporal variations of water balance components (i.e., soil moisture content (SMC), evapotranspiration, and runoff) over the Ziluoshan basin. Explicit expression of the soil moisture storage capacity (SMSC) in the model reduced parameters, which provides a method for hydrological simulation in ungauged basins. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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Review

Jump to: Editorial, Research

25 pages, 17909 KiB

Open AccessReview

Crop Upgrading Strategies and Modelling for Rainfed Cereals in a Semi-Arid Climate—A Review

by Festo Richard Silungwe, Frieder Graef, Sonoko Dorothea Bellingrath-Kimura, Siza Donald Tumbo, Frederick Cassian Kahimba and Marcos Alberto Lana

Water 2018, 10(4), 356; https://doi.org/10.3390/w10040356 - 22 Mar 2018

Cited by 16 | Viewed by 6410

Abstract

Spatiotemporal rainfall variability and low soil fertility are the primary crop production challenges facing poor farmers in semi-arid environments. However, there are few solutions for addressing these challenges. The literature provides several crop upgrading strategies (UPS) for improving crop yields, and biophysical models [...] Read more.

Spatiotemporal rainfall variability and low soil fertility are the primary crop production challenges facing poor farmers in semi-arid environments. However, there are few solutions for addressing these challenges. The literature provides several crop upgrading strategies (UPS) for improving crop yields, and biophysical models are used to simulate these strategies. However, the suitability of UPS is limited by systemization of their areas of application and the need to cope with the challenges faced by poor farmers. In this study, we reviewed 187 papers from peer-reviewed journals, conferences and reports that discuss UPS suitable for cereals and biophysical models used to assist in the selection of UPS in semi-arid areas. We found that four UPS were the most suitable, namely tied ridges, microdose fertilization, varying sowing dates, and field scattering. The DSSAT, APSIM and AquaCrop models adequately simulate these UPS. This work provides a systemization of crop UPS and models in semi-arid areas that can be applied by scientists and planners. Full article

(This article belongs to the Special Issue Soil Water Conservation: Dynamics and Impact)

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