Effects Of Soil Hydraulic Properties Research Articles

A modelling approach to discriminate contributions of soil hydrological properties and slope gradient to water stress in Mediterranean vineyards

Grapevine is a widespread crop for grape and wine production, often cultivated on hilly areas. Moderate vine water stress plays an important role in determining high-quality viticulture. However, a precise quantification of the effect of hydraulic properties and slope gradient on hilly soil water balance and consequently on vine stress has not yet been addressed in the literature. The slope-gradient effect is generally taken for granted, without providing experiments validating such a qualitative assumption. We tested the hypothesis that soil hydraulic properties play a greater role than slope gradient in driving soil water status and vine stress. In two consecutive years, we studied an “Aglianico” vineyard grown along a 90 m slope, with up-slope soil having lower water holding capacity than down-slope. Up-slope vines were more stressed, as shown by lower leaf water potential, stomatal conductance, leaf CO2 assimilation and leaf area index, than down-slope vines.Water flow was simulated by using the Hydrus (2D/3D) model, calibrated and validated towards a two-year set of soil water content measurements. Significantly lower soil pressure head and higher transpiration occurred in the up- than the down-slope site.A viable procedure was developed to separate the effects of soil hydraulic properties and slope gradient by modelling soil water balance and therefore vine transpiration with and without the slope gradient. The simulations indicated that the difference in seasonal relative transpiration of 8% in 2011 and 5% in 2012 between the two sites was due to their differing soil hydraulic properties, and that the slope gradient had no contribution to this variation.

Effects of water table on ground-borne vibration screening effectiveness by using open trenches

The seasonal variations in groundwater table would significantly change the dynamic responses of the ground and the screening performances of wave barriers. This paper develops a two-dimensional finite element model based on COMSOL to describe the propagation of waves in a layered ground with open trenches. This layered ground is modelled as a dry layer resting on a saturated half-space. The influence of the moving groundwater table on isolation efficiency of barriers is then investigated, considering the infiltrated water in trenches. The effects of soil hydraulic properties and geometrical parameters of the trench are also analyzed respectively. Results show that a low value of the permeability coefficient of saturated half-space may have a significantly detrimental effect on the screening performance due to the low frequency behaviors of the medium. Placing a trench in vibration-strengthening (weakening) zones results in a better (worse) isolation effect, and with a critical water table (Hw,c), increasing trench depth and width can hardly achieve a satisfactory screening efficiency (75% reduction) due to the occurrence of resonance in the dry layer. In addition, a multiple trench isolation system is simulated in the condition of high water levels and its shielding performance is compared to the single trench barrier. A triple trench barrier is found to be a preferred alternative because it can achieve a much better screening efficiency. Specially for Hw,c, a multiple trench barrier can effectively eliminate the adverse effect of the resonance and achieve more than 75% reduction of ground vibration.

The role of soil hydraulic properties in crop water use efficiency: A process-based analysis for some Brazilian scenarios

The need for improvements in the water use efficiency by agricultural ecosystems requires a holistic assessment of the hydraulic functioning of cropped soils, taking into consideration the most relevant interactions and feedbacks that control the soil water budget. We implemented a mechanistic approach to isolate the effects of soil hydraulic properties (K-θ-h) of layered soils on water balance components and land and water productivity, adopting comprehensive scenarios of soil water availability and requirements. The agro-hydrological simulations were performed using the SWAP model integrated with the WOFOST crop growth module. The simulated scenarios included the rainfed crop growth of maize and soybean in three climate zones, evaluating the current climate scenarios as well as two future scenarios, a wetter and a drier one, totaling 108 scenarios simulated for 30 years each. Simulations were performed for six soils, grouped pairwise (3 × 2), where each pair represented the same soil group with two different long-term land uses: natural forest (proxy of a no-tillage system) and conventional agricultural use. The K-θ-h relationships were obtained simultaneously by inverse modeling for the full range of soil water contents commonly found in the domain of crop available water. The agro-hydrological simulations showed that the soil hydraulic properties affect dynamically water balance components and land productivity by relating soil hydraulic functioning to climate patterns and crop water requirements. In general, maize productivity was more sensitive to soil hydraulic properties under future climate scenarios than soybean. While land productivities of maize and soybean increased under the wetter climate scenario, water productivity of both crops was consistently reduced by both future climate scenarios. The K-θ-h of soils under conventional agricultural use over-performed their counterparts under long-term natural forest use, especially regarding land productivity during growing seasons with pronounced dry spells. Depending on the length and timing of drought stress during the growing season, the yield response is determined by soil-specific conditions strictly related to water availability. The long-term average revealed that the sampled loamy sand soils have more favorable hydraulic properties for crop growth; moreover, the reduced unproductive water losses, especially runoff, increased the dynamic water storage of those soils.

Effect of soil hydraulic properties on water infiltration of containerised soil

The development of infrastructure in an urban city, such as road widening and building work, will inevitably result in the removal of trees. Therefore, innovative solutions such as containerised tree in the manner of increasing the portability of trees would be necessary to facilitate efficient transplanting in order to maintain a sustainable green urban environment. Differences in soil hydraulic properties between soil mixture and in situ soil naturally occur in tree planting, but this difference becomes more important in the use of container due to the limited tree root movement. The objective of this research was to examine the effects of soil hydraulic properties between the soils inside and outside of the container with focus being placed on moisture infiltration both in and out of the container. Field instrumentation and laboratory tests were carried out together with parametric study using numerical model. The results suggested that the higher the ratio between the saturated permeability of the soils inside and outside the container, the lower was the ability of water to flow in and out of the container.

Assessing effects of soil hydraulic properties on the temporal stability of absolute soil moisture content and soil moisture anomaly under different climatic conditions

Due to the complex interactions of soil moisture with its controlling factors, numerical models are more suitable for quantifying different controls on the temporal pattern of soil moisture. Here, the effects of soil hydraulic properties on the temporal stability of absolute soil moisture content (TS SMC) and soil moisture anomaly (TS SMA) under different climatic conditions were assessed using a vadose zone model. To run the model, two soil datasets with van Genuchten parameters were generated and hydrometeorological data from four study sites with a significant precipitation gradient were obtained. The TS SMC analysis revealed that the patterns of mean relative difference (MRD) and standard deviation of relative difference (SDRD) of soil moisture partly depended on climatic conditions. With increasing precipitation, the range of MRD generally decreased; whereas, the range and mean value of SDRD increased, indicating that soil moisture was temporally more stable under drier climatic conditions. Based on the Spearman rank correlation coefficient, the results showed that the dependence of MRD on soil hydraulic parameters was partly determined by climatic conditions. With decreasing precipitation, the effects of residual soil moisture content, saturated hydraulic conductivity, and the parameter l that accounts for pore tortuosity and connectivity strengthened, while the effects of saturated soil moisture content and the parameter n that is a measure of pore size distribution weakened. Finally, according to the Pearson correlation coefficient, the results revealed that the control of soil hydraulic properties was shown to be reduced in the TS SMA analysis, thus confirming the previously made conjecture that the use of soil moisture anomalies in the temporal stability analysis reduces the impacts of static soil properties.

Effects of Soil Hydraulic Properties on the Spatial Variability of Soil Water Content

Effects of Soil Hydraulic Properties on the Spatial Variability of Soil Water Content

Effects of Soil Hydraulic Properties on the Spatial Variability of Soil Water Content: Evidence from Sensor Network Data and Inverse Modeling

Understanding the spatial variation of soil water content and its relation with hydraulic properties is important for the application of hydrologic models. In this study, we investigated whether soil hydraulic properties are related to soil water content variability at the field scale. We used the mean relative difference (MRD) of soil water content and saturation degree to describe the spatial soil water content variability of a 2-yr time series of soil water content measured with a sensor network at 41 locations in the Rollesbroich catchment (Germany). Hydraulic properties were described by the van Genuchten–Mualem (VGM) model and were estimated by inverse modeling of soil water content data using the Hydrus-1D model for each location. The feasible parameter space for the inverse modeling was derived using the Rosetta pedotransfer functions from information on sand, silt, and clay contents and bulk density from 273 soil samples taken in the catchment. Our inverse modeling results were able to reproduce the observed time series of soil water content with a root mean square error <0.08 cm3 cm−3 and R2 > 0.75. We found that the MRDs of soil water content were positively correlated with the saturated water content (θs) and shape-fitting n parameters and negatively correlated with the shape-fitting α and saturated hydraulic conductivity (Ks) parameters of the VGM model. Moreover, the MRDs of the saturation degree were strongly correlated with the α and n parameters that determine the shape of the VGM model.

Mapping soil hydraulic conductivity and matric potential for water management of cranberry: Characterisation and spatial interpolation methods

Spatial interpolation methods are required for analysing the effects of soil hydraulic properties on irrigation management. This study was conducted to determine which interpolation methods are best suited to map these properties. During the summer of 2012 we mapped the spatial variability of soil physical properties, soil matric potential, water table depth and yield of two cranberry fields located near Quebec City, Canada. Three spatial interpolation methods, inverse distance weighting (IDW), thin plate splines (TPS) and kriging with external drift (KED), were compared by means of cross-validation. The best interpolation method for a given property was used to produce maps and perform HYDRUS 1D simulations for the purpose of irrigation management. Results show that even in highly constructed fields, such as for cranberries, spatial patterns of soil hydraulic properties exist. The TPS method was the best interpolation method based on the cross-validation analyses and generated maps. Spatial variability of crop yield showed a strong relationship with soil hydraulic properties and simulations suggest that irrigation can be reduced by 75% when accounting for the spatial variability of soil hydraulic properties.

SIMULATION OF SOIL WATER AND SALINITY DISTRIBUTION UNDER SURFACE DRIP IRRIGATION

ABSTRACTHigher crop production and better water use efficiency are usually achieved with surface drip irrigation as compared to traditional surface irrigation methods. Increasing competition for fresh water also means a greater use of brackish water in agriculture. For this reason, the effects of soil hydraulic properties, initial soil moisture content (θi), and irrigation regime on soil water and salinity distribution under surface drip irrigation (DI) with brackish irrigation water were investigated. Model simulations were performed using the HYDRUS‐2D/3D model assuming tomato crop in saline soil. Simulation scenarios were conducted including sand, loamy sand, and sandy loam soils, together with daily and alternate‐day irrigation regimes. Two θi values were considered in the simulations. Results revealed that the effect of the irrigation regime on wetting patterns differed according to the soil's hydraulic properties, while the effect of the initial soil moisture content disappeared after a few days. The irrigation regime and θi value did not display any significant effect on soil salinity distribution. Higher soil salinity occurred along the soil surface by the end of the simulation period. The higher soil salinity was more close to the emitter in sand as compared to loamy sand and sandy loam. Water balance calculations showed that as the initial soil moisture content increased, the free drainage component increased. However, the irrigation regime and initial soil moisture content did not affect the evaporation rate and root water uptake rate. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Root growth and water uptake by wheat during drying of undisturbed and repacked soil in drainage lysimeters

The dynamics of root development and water uptake in undisturbed and repacked clay soil were studied during increasing soil water deficit pre- and post-anthesis to find how root distribution, soil type and plant development affect plant available water (PAW). Volumetric water fraction was measured with a neutron probe, while root distribution was measured non-destructively using a series of horizontal perspex observation tubes. Soil modification affected the downward root growth which changed little over time for undisturbed (U) soil (6.7-13.6 mm/d) compared with the repacked (R) soil (7.5-42.9 mm). In the well-watered treatments root distribution was mostly above the 0.55 m depth in U soil, while there was a reasonably uniform vertical distribution in R soil. The rate of root growth during post-anthesis drying was 61% of that during pre-anthesis drying. The specific root water uptake rate (vol./unit root length/time) was linearly related to the relative root growth rate, indicating the importance of root growth in supplying water during soil drying. Estimated PAW values reflected effects of soil hydraulic properties, root distribution and a propensity to grow new roots during soil drying. Differences in grain yield between treatments were thought to result from the effects of different root distributions and the propensity to grow roots during soil drying.

Drainage of Soil Profiles

The scaled approximations of Brooks and Corey for water content versus capillary pressure and capillary conductivity versus water content were used to obtain a scalded diffusion function that was dependent only upon the pore-size distribution index, λ. A predictor-corrector finite difference scheme was used to obtain numerical solutions for the scaled differential equation for drainage from vertical soil columns. Results of several numerical solutions were presented for two soil profiles and for two greatly different pore-size distributions. The effects of soil hydraulic properties upon drainage were discussed and used to interpret the term field capacity. Experimental data obtained by several independent investigators were compared with theoretical solutions of discharge as a function of time using the Brooks-Corey approximations. The comparisons between experiment and theory were reasonable and some explanations for lack of agreement were presented.