Effluent-irrigation induced water repellent soils

In semi-arid and arid regions that suffer from fresh water shortages, the use of marginal waters such as treated sewage effluent is indispensable for support and sustenance of agriculture. Even in areas not stressed by water shortage, land application of effluent is considered a viable disposal option, preferable over other alternatives such as release to surface water bodies. Irrigation with treated sewage effluent has been found to have positive impacts on soil fertility, and to improve or maintain soil physical properties. Certain environmentally detrimental aspects of effluent-irrigation have also been documented in field studies, including enhanced downward transportation of pesticides, increased soil sodicity, and excessive nitrate leaching. Consequently, land application of treated effluent needs to be accompanied by sustainable soil management practices so as to maximize benefits while minimizing harm. In our studies we document, apparently for the first time, the development of soil water repellency under irrigation with secondary treated sewage effluent. We found that soil water repellency that was developed in a commercial orchard affected the uniformity of moisture content distribution in the soil profile following irrigation events in the summer and rainfall events in the winter. Such non-uniform wetting can adversely affect agricultural production and lead to contamination of underlying groundwater resources. Flow chamber studies of soils taken from this orchard indicated that unstable flow is developed in water repellent soil. The fingers shape, size, and the water content distribution within the fingers during wetting and redistribution are shown in the attached presentation.

Pollution of surface runoff by soil-applied agrochemicals

Pesticides, nutrients, and other agricultural chemicals which are transferred from the soil to surface runoff water are potentially important pollutants of nearby surface waters. This research focuses on identifying the main mechanisms controlling the fate and transport of the soil chemicals toward the soil surface and their transfer to overland flow. A physically based mathematical model has been developed and is currently being modified to increase its flexibility for predicting overland-flow pollution due to different agricultural practices. The model includes different soil and hydrological parameters which can be independently determined in the field. By running different scenarios, one can select an appropriate management scheme for the local conditions that would minimize the pollution of surface runoff.

Fertigation management of container media

Optimization of irrigation and fertilization (fertigation) regimes in greenhouses and other controlled environments requires a knowledge of the physical and hydraulic properties of different mineral and organic soil substitutes. Their characterization can then eanble a study of irrigation-water flow within the containers, its uptake by the plant roots and its drainage at the bottom of the container. Although the principles are the same as those used for irrigation management in the open field where plants grow on natural soils, there are significant differences between the two management approaches. Major differences in hydraulic properties between soils and soil substitutes and the limited root volume within the containers cause large fluctuations in water availability to the plant. This imposes management involving frequent irrigation of short duration. The long-term goal of this research is to determine the frequent-irrigation schedule as dictates by the transient needs of the plants. The research is based on laboratory and greenhouse studies, as well as on modeling the processes that control water availability to the plant roots.

Irrigation scheduling by time domain reflectometry (TDR)

Soil-water monitoring is necessary to obtain reliable estimates of actual irrigation-water use, in order to adjust the actual crop's water demand and to optimize irrigation scheduling. Continuous soil monitoring is needed to assess changes in the wetted volume and to monitor the accumulation of salt and other chemicals in the root zone. The TDR method offers a fast and reliable tool to monitor these parameters at different locations within the root zone. An analysis of the measured data enables us to monitor the rate of water uptake at different depths and lateral distances as a function of time and soil-water content. In field studies, we are comparing the data from the TDR to other measured plant and climatic parameters that hae been widely used for irrigation scheduling. To date, the TDR measurements have provided important data on the dynamics of soil-water uptake by plant roots at different depths. This data is highly valuable for the design of optimal irrigation management for different irrigation methods (e.g. sprinklers and mini-sprinklers, surface and subsurface drip).

Preferential flow in structured porous media

Many experimental observations have shown that preferential flow and transport takes place in the structured soil profiles commonly found under most field conditions. In most cases, the volume of water within the preferential paths is much smaller than that of the stagnant fluid, but a particular, not negligible part of the solution may be moving within the well-defined preferential paths ahead of the main flow. These preferential paths could be macropores with a certain spatial distribution, or subsurface channels, such as fractures, fissures or cracks, which are an intrinsic part of the soil structure. Preferential transport of fluids through structured soils can also take place through fingers caused by dynamic instabilities of the wetting front due to density and/or viscosity differences between the displacing and displaced fluids. The purpose of this study is to look more closely at the processes of chemical transport in the preferential paths and their interaction with the stagnant matrix that surrounds these paths; moreover, we aim to predict the concentration distribution with time at a certain depth of structured soil. Both laboratory-scale measurements and modeling are being used in this study. The mathematical model, which includes linear and nonlinear partial differential equations, is simplified by taking advantage of the processes' different time scales.

Recent Publications

(5-years) manuscripts in refereed journals (out of 100) (h-index – 36)

1. Baver CE, Parlange J-Y, Stoof CR, DiCarlo DA, Wallach R, Durnford DS, Steenhuis TS, 2014. Capillary pressure overshoot for unstable wetting fronts is explained by Hoffman’s velocity-dependent contact-angle relationship. Water Resour. Res. 50, 5290–5297, doi:10.1002/2013WR014766

2. Moshelion M, Halperin O, Wallach R, Oren R, Way DA, 2014. The role of aquaporins in determining transpiration and photosynthesis in water-stressed plants: crop water-use efficiency, growth and yield. Plant Cell and Environ. doi: 10.1111/pce.12410.

3. Xu P, Moshelion M, Wu X, Halperin O, Wang B, Luo J, Wallach R, Wu X, Lu Z, Li G, 2015. Natural variation and gene regulatory basis for the responses of asparagus beans to soil drought. Front. Plant Sci. 6:891. doi: 10.3389/fpls.2015.00891

4. Zhang K, Wang Q, Li S, Wallach R, 2016. Gravity-driven unsteady-state slug fall in capillaries – modeling and experimental verification. Journal of Adhesion Science and Technology 30(19):1-11 DOI: 10.1080/01694243.2016.1176661

5. Bugichi, T, Wallach R, 2016. Formation of soil-water repellency in olive orchards and its influence on infiltration patterns. Geoderma, 262, 1-11.

6. Halperin O,  Gebremedhin A, Wallach R, Moshelion M, 2016. High-throughput physiological phenotyping and screening system for characterization of plant-environment interaction. The Plant J. doi: 10.1111/tpj.13425

7. Nissan A, Wang Q, Wallach R, 2016. Kinetics of gravity-driven slug flow in partially wettable capillaries of varying cross section. Water Resour. Res. 52, doi:10.1002/2016WR018849.

8. Brindt N, Wallach R, 2016. The moving-boundary approach for modeling gravity-driven stable and unstable flow in soils. Water Resour. Res. 53, doi:10.1002/2016WR019252.

9. Rahav M, Brindt N. Yermiyahu U, Wallach R, 2017. Induced heterogeneity of soil water content and chemical properties by treated wastewater irrigation and its reclamation by freshwater irrigation. Water Resour. Res., 53, doi:10.1002/2016WR019860.

10. Aidoo M, Quansah L, Galkin E, Batushansky A, Wallach R, Moshelion M, Bonfil DJ. Fait A, 2017. A combination of stomata deregulation and a distinctive modulation of amino acid metabolism are associated with enhanced tolerance of wheat varieties to transient drought. MEBO 13, 138-

11. Leuther F, Weller U, Wallach R, Vogel H-J, 2018. Quantitative analysis of wetting front instabilities in soil caused by treated wastewater irrigation. Geoderma 319, 132–141 doi.org/10.1016/j.geoderma.2018.01.004.

12. Galkin E, Dalal A, Evenko A, Friedman E, Kan I, Wallach R, Moshelion M, 2018. Risk-management strategies and transpiration rates of wild barley in uncertain environments. Physiologia Plantarum 164, 412-428

13. Leuther F, Schluter S, Wallach R, Vogel H-J, 2019. Structure and hydraulic properties in soils under long-term irrigation with treated wastewater. Geoderma 333, 90-98 doi.org/10.1016/j.geoderma.2018.07.015 doi:10.1111/ppl.12814.

14. Liu Z, Rahav M, Wallach R, 2019. Spatial variation of soil water repellency in a commercial orchard irrigated with treated wastewater. Geoderma 333 214-224doi.org/10.1016/j.geoderma.2018.07.021

15. Brindt N, Rahav M, Wallach R, 2019. ERT and salinity - A method to determine whether ERT-detected preferential pathways in brackish water-irrigated soils are water-induced or an artifact of salinity. J. Hydrology (in press).

Prof. Rony Wallach

71601: Fundamentals of Irrigation Science

Instructor: Prof. Rony Wallach

Course Level: undergraduate
Course Description: Climatic factors and soil characters as the basis of irrigation planning. Water sources and methods of infiltration. Methods for bringing water to the field. Storage of water in the soil and the availability of such water to crops. Evapotranspiration and the water consumption of crops. Irrigation methods and their relations to the field water regime. Efficiency of water application and efficiency of crop water use. Special problems in irrigation: drainage, salinity, plant diseases, regulation of micro-climate. Covered crops.

71607: Fundamentals of Irrigation Engineering

Instructor: Prof. Rony Wallach

Course Level: undergraduate
Course Description: Definition of essential data for irrigation system design and of the design process. Criteria for choice of irrigation method. Determination of discharge required for single fields and for entire farm; the daily and seasonal irrigation schedule. Stage-wise planning of an irrigation system from the single emitter to the main supply network for sprinkler and drip systems. The principles of gravity irrigation. Accessories for measurement and control of discharge and pressure, filtration, fertilizer injection. Various levels of automated irrigation control.

71624: Groundwater Hydrology

Instructor: Prof. Rony Wallach

Course Level: undergraduate
Course Description: Basic concepts: Darcy's Law, water potential, hydraulic conductivity, porosity, transmissivity, storativity, specific yield. Limitations of the Darcian approach. Laminar, steady and transient flow. Case studies in groundwater flow in aquifers. Flow in a fracture medium. Well hydraulics. Solute and contaminant transport in aquifers.

71918: Movement of Solutes in the Soil

Instructor: Prof. Rony Wallach

Course Level: graduate
Course Description: Simultaneous transport of solutes and water - emphasizing plant nutrition, salinity and pollution problems. Classic theory of diffusion and application to transport of ions, organic complexed, and organic compounds through soils and onto plant roots. Classical theory of water movement and application to irrigation. Effect of clay and soil properties on water-salt movement. Effect of combined convection and diffusion on transport phenomena. Mathematical-physical models describing simultaneous flow of mass and energy in charged porous media.

Visiting Scholars

Dr. Zhipeng Liu (Nanjing Agric. Univ., China) – Biochar hydrophobicity and its effect on flow in soil with biochar additament.

Ph.D. Students

Naaran Brindt – The moving boundary approach for prediction of gravity-driven unstable flow in porous media

Ziv Attia - The rule of CK and ABA in regulating plant water status and as a shoot to root long signal during biotic and abiotic stress (co-supervisor: Prof. Menachem Moshelion, Plant Sci.).

Ayelet Karmon – Water retention in unwoven porous substrates.

M.Sc. Students

Ronny Burstein – Measuring the response of pine trees to abiotic stress by the acoustic emission method.

Matan Rahav – The effect of prolonged irrigation with treated wastewater on soil wettability and the later's effect on water and chemical spatial distribution in the root zone of a commercial citrus orchard.

Adi Haft Characterizing stormwater quantity and quality in Israeli Cities (co- supervisor: Prof. Eran Friedler, Technion)

Felix Ogunmokun (Nigeria) – Use of wetting agents to remediate soils that were rendered water repellent by treated wastewater irrigation

Noam Bar-Hadas – Macro-nutrients effects on physiological processes associated with water control of citrus seedlings

Open positions:

MSc and PhD students with background in Civil, Environmental or Chemical Engineering, Soil Science or Environmental Sciences (natural sciences track) for the following projects:

1) Impact of effluent irrigation on soil water dynamics and sustainable land use

2) Water repellent soils reclamation by surfactants application.

3) Characterizing surface runoff (quantity and quality) from urban areas – Kfar-Sava as a case study.

4) Rhizosphere wettability and implications for water availability to plants

5) Simulating water flow in porous media (soils) by alternative models (e.g. a bundle of nonunifrom capillary tubes).