Search

Soil plays a pivotal role in enhancing global water and food security. Irrigation water constitutes more than 70% of the global water demand. The anticipated demographic increase and changing climate will impose more pressures on the global water and food systems. Therefore, and to achieve the target of "more crop per drop per area", water management plans must be based on more accurate quantitative and dynamic approaches. It is increasingly obvious that the unique aggregates structure of the soil medium regulates water and nutrient circulations, and consequently defines soil and water health, productivity, and water use efficiency. However, the soil aggregates structure is not currently well considered in the quantification of soil–water holding properties. The authors applied a thermodynamic and soil structure-based approach to quantify soil–water holding properties. Specifically, the paper aims at providing a methodology, based on the pedostructure concept, to quantify field capacity (FC), permanent wilting point (PWP), and plant available water (AW). Pedostructure is a representative aggregates unit of a soil horizon that describes the structural organization of the soil medium. Four types of soil were analyzed considering various soil texture and aggregates structure: loamy fine sand, silt loam, clay loam, and silty clay loam. The calculated values for FC and PWP, based on the proposed pedostructure method, were compared with the recommended values by the standard FAO method and soil suction method. Results showed good agreement between the calculated values of the two methods. The proposed pedostructure method introduces a shift in quantifying the plant available water from a texture-based estimation to a soil aggregates structure-based calculation. Such a shift will enable capturing the changes in soil aggregates structure due to agro-environmental practices and the associated impact of these changes on soil–water holding properties. [ABSTRACT FROM AUTHOR]

Farmers along the main reach of the Zarqa River Basin (ZRB) commonly utilize treated wastewater for irrigation. Deep percolation is expected to occur as a result of irrigation, and it is expected that preferential flow pathways may facilitate the downward movement of irrigation water. Therefore, the aim of this research was to investigate the susceptibility of soils near Zarqa River to preferential flow, and the HYDRUS and Soil and Water Assessment Tool (SWAT) models were used. The methodology consisted of taking tension infiltrometer measurements along the Zarqa River to determine the main physical properties relevant to preferential flow, such as infiltration rate and macroscopic capillary length, followed by investigating the downward water movement using HYDRUS and SWAT. The HYDRUS simulations were conducted using single porosity (SP) and dual porosity (DP) constitutive functions pertaining to matrix and preferential flow, respectively. The in situ tension infiltrometer measurements were used to parameterize the surface layer of the HYDRUS DP model. HYDRUS simulations showed that preferential flow occurring in the surface layer of the soil profile controlled the vertical movement of soil water in excess of field capacity. The comparison between SWAT, SP and DP showed that both SWAT and DP were capable of simulating preferential flow in arid watersheds. However, SWAT simulations of lateral discharge and deep percolation resemble that of the DP only when the evaporation soil compensation factor (ESCO) was set to a value of 0.8 and the length of the soil slope was set to its maximum value. This research recommends using HYDRUS model to verify SWAT model predictions of soil water redistribution in the soil profile and to improve the parameterization of the SWAT model. The research also suggests an approach for the combined use of both models. [ABSTRACT FROM AUTHOR]

The article presents a speech by the author delivered for the Ven Te Chow Memorial Lecture at the 15th World Water Congress of professional organization International Water Resources Association (IWRA) in Edinburgh, Scotland on May 2015. Topics of the speech include water localization and food security, effects of greywater on soil water-holding capacity, and renewable water resources for North African Arab countries.

Liquid latex was used as a method to seal visible surface-connected preferential flow pathways (PFP5) in the field in an effort to block large surface-connected preferential flow and force water to move through the soil matrix. The proposed approach allows for the quantification of the contribution of large surface-connected cracks and biological pores to infiltration at various soil moisture states. Experiments were conducted in a silty clay loam soil in a field under a no-till corn-soybean rotation planted to corn. Surface intake rates under ponding were measured using a simplified falling head technique under two scenarios: (1) natural soil conditions with unaltered PFPs and (2) similar soil conditions with latex-sealed large macropores at the surface. Resiiltc indicated that the contribution of flow from large surface-connected macropores to overall surface intake rates varied from approximately 34% to 99% depending on the initial moisture content and macroporosity present. However, evidence of preferential flow continued to appear in latex-sealed plots, suggesting significant contributions to preferential flow from smaller structural macropores, particularly in two out of four tests where no significant differences were observed between control and latex-sealed plots. [ABSTRACT FROM AUTHOR]

The subject of this article is the dynamics of water in a soil pedostructure sample whose internal environment is subjected to a potential gradient created by the departure of water through surface evaporation. This work refers entirely to the results and conclusions of a fundamental theoretical study focused on the molecular thermodynamic equilibrium of the two aqueous phases of the soil pedostructure. The new concepts and descriptive variables of the hydro-thermodynamic equilibrium state of the soil medium, which have been established at the molecular level of the fluid phases of the pedostructure (water and air) in a previous article, are recalled here in the systemic paradigm of hydrostructural pedology. They allow access to the molecular description of water migration in the soil and go beyond the classical mono-scale description of soil water dynamics. We obtain a hydro-thermodynamic description of the soil′s pedostructure at different hydro-functional scale levels including those relating to the water molecule and its atoms. The experimental results show a perfect agreement with the theory, at the same time validating the systemic approach that was the framework. [ABSTRACT FROM AUTHOR]

Abstract Wastewater reuse is a practice that has been gaining attention for the past few decades as the world's population rises and water resources become scarce. Wastewater application on soil can affect soil health, and the manner and extent to which this occurs depends heavily on soil type and water quality. This study compared the long-term (15+ years) effects and suitability of using secondary-level treated municipal wastewater and brackish groundwater for irrigation on the water holding capacity of a clayey, calcareous soil on a cotton farm near San Angelo, Texas. The soil-water holding properties were determined from the extracted hydrostructural parameters of the two characteristic curves: water retention curve and soil shrinkage curve based on the pedostructure concept. In the pedostructure concept, these hydrostructural parameters are characteristic properties of the soil aggregates structure and its thermodynamic interactions with water. Results indicate that use of secondary treated wastewater increased available water capacity in the top horizon (0–15 cm) and decreased the available water holding capacity of this particular soil in the sub-horizons (15–72 cm). The brackish groundwater irrigation resulted in no effect on available water capacity in the top horizon, but significantly decreased it in the sub-horizons as well. The rainfed soil was the healthiest soil in terms of water holding capacity, but rainfall conditions do not produce profitable cotton yields. Whereas, treated wastewater irrigated soil is producing the highest yields for the farmer. Thus, this treated wastewater source and irrigation system can serve as a suitable irrigation alternative to using brackish groundwater, enhancing the water resource sustainability of this region. Graphical abstract Graphical representation of field capacity, permanent wilting point, and available water capacity for each horizon such that: (a) Ap horizon = 0 to 15 cm, (b) A horizon = 15 to 30 cm, and (c) B horizon = 30 to 72 cm Unlabelled Image Highlights • Treated wastewater and brackish groundwater are both potential alternative irrigation sources. • Field capacity, permanent wilting point, and available water are indicators of a soil's health. • Treated wastewater and groundwater decreased the soil's water-holding ability in the lower horizons of this soil. • Treated wastewater not degrades soil properties any more than the groundwater and produces higher yields for the farmer. • Water conservation solutions should be specific and localized to each region. [ABSTRACT FROM AUTHOR]