ROOT WATER UPTAKE MODEL DEPENDING ON SOIL WATER PRESSURE HEAD AND MAXIMUM EXTRACTION RATE

This paper focuses on numerical modelling of soil water movement in response to the root water uptake that is driven by transpiration. The flow of water in a lysimeter, installed at a grass covered hillslope site in a small headwater catchment, is analysed by means of numerical simulation. The lysimeter system provides a well defined control volume with boundary fluxes measured and soil water pressure continuously monitored. The evapotranspiration intensity is estimated by the Penman-Monteith method and compared with the measured lysimeter soil water loss and the simulated root water uptake. Variably saturated flow of water in the lysimeter is simulated using one-dimensional dual-permeability model based on the numerical solution of the Richards’ equation. The availability of water for the root water uptake is determined by the evaluation of the plant water stress function, integrated in the soil water flow model. Different lower boundary conditions are tested to compare the soil water dynamics inside and outside the lysimeter. Special attention is paid to the possible influence of the preferential flow effects on the lysimeter soil water balance. The adopted modelling approach provides a useful and flexible framework for numerical analysis of soil water dynamics in response to the plant transpiration.

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Modelling the Impact on Root Water Uptake and Solute Return Flow of Different Drip Irrigation Regimes with Brackish Water

Water ◽

10.3390/w11030425 ◽

2019 ◽

Vol 11 (3) ◽

pp. 425 ◽

Cited By ~ 3

Author(s):

Fairouz Slama ◽

Nessrine Zemni ◽

Fethi Bouksila ◽

Roberto De Mascellis ◽

Rachida Bouhlila

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Brackish Water ◽

Deficit Irrigation ◽

Root Zone ◽

Root Water Uptake ◽

Return Flows ◽

Semi Arid

Water scarcity and quality degradation represent real threats to economic, social, and environmental development of arid and semi-arid regions. Drip irrigation associated to Deficit Irrigation (DI) has been investigated as a water saving technique. Yet its environmental impacts on soil and groundwater need to be gone into in depth especially when using brackish irrigation water. Soil water content and salinity were monitored in a fully drip irrigated potato plot with brackish water (4.45 dSm−1) in semi-arid Tunisia. The HYDRUS-1D model was used to investigate the effects of different irrigation regimes (deficit irrigation (T1R, 70% ETc), full irrigation (T2R, 100% ETc), and farmer’s schedule (T3R, 237% ETc) on root water uptake, root zone salinity, and solute return flows to groundwater. The simulated values of soil water content (θ) and electrical conductivity of soil solution (ECsw) were in good agreement with the observation values, as indicated by mean RMSE values (≤0.008 m3·m−3, and ≤0.28 dSm−1 for soil water content and ECsw respectively). The results of the different simulation treatments showed that relative yield accounted for 54%, 70%, and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full. and farmer’s irrigation, respectively. Root zone salinity was the lowest and root water uptake was the same with and without solute stress for the treatment corresponding to the farmer’s irrigation schedule (273% ETc). Solute return flows reaching the groundwater were the highest for T3R after two subsequent rainfall seasons. Beyond the water efficiency of DI with brackish water, long term studies need to focus on its impact on soil and groundwater salinization risks under changing climate conditions.

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SIMULATING SOIL WATER FLOW WITH ROOT-WATER-UPTAKE APPLYING AN INVERSE METHOD

Soil Science ◽

10.1097/01.ss.0000112018.97541.85 ◽

2004 ◽

Vol 169 (1) ◽

pp. 13-24 ◽

Cited By ~ 13

Author(s):

Qiang Zuo ◽

Lei Meng ◽

Renduo Zhang

Keyword(s):

Soil Water ◽

Water Flow ◽

Water Uptake ◽

Inverse Method ◽

Root Water Uptake ◽

Soil Water Flow

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Towards the consideration of soil-root resistances in root water uptake models with macroscopic representations of hydraulic root architecture

10.5194/egusphere-egu21-8151 ◽

2021 ◽

Author(s):

Jan Vanderborght ◽

Valentin Couvreur ◽

Felicien Meunier ◽

Andrea Schnepf ◽

Harry Vereecken ◽

...

Keyword(s):

Root System ◽

Soil Water ◽

Water Uptake ◽

Root Distribution ◽

Root Architecture ◽

Soil Layer ◽

Root Water Uptake ◽

Hydraulic Architecture ◽

Root Segments ◽

Soil Volume

Plant water uptake from soil is an important component of terrestrial water cycle with strong links to the carbon cycle and the land surface energy budget. To simulate the relation between soil water content, root distribution, and root water uptake, models should represent the hydraulics of the soil-root system and describe the flow from the soil towards root segments and within the 3D root system architecture according to hydraulic principles. We have recently demonstrated how macroscopic relations that describe the lumped water uptake by all root segments in a certain soil volume, e.g. in a thin horizontal soil layer in which soil water potentials are uniform, can be derived from the hydraulic properties of the 3D root architecture. The flow equations within the root system can be scaled up exactly and the total root water uptake from a soil volume depends on only two macroscopic characteristics of the root system: the root system conductance, Krs, and the uptake distribution from the soil when soil water potentials in the soil are uniform, SUF. When a simple root hydraulic architecture was assumed, these two characteristics were sufficient to describe root water uptake from profiles with a non-uniform water distribution. This simplification gave accurate results when root characteristics were calculated directly from the root hydraulic architecture. In a next step, we investigate how the resistance to flow in the soil surrounding the root can be considered in a macroscopic root water uptake model. We specifically investigate whether the macroscopic representation of the flow in the root architecture, which predicts an effective xylem water potential at a certain soil depth, can be coupled with a model that describes the transfer from the soil to the root using a simplified representation of the root distribution in a certain soil layer, i.e. assuming a uniform root distribution.

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A thermodynamic formulation of root water uptake

Hydrology and Earth System Sciences ◽

10.5194/hess-20-3441-2016 ◽

2016 ◽

Vol 20 (8) ◽

pp. 3441-3454 ◽

Cited By ~ 8

Author(s):

Anke Hildebrandt ◽

Axel Kleidon ◽

Marcel Bechmann

Keyword(s):

Soil Water ◽

Water Uptake ◽

Water Distribution ◽

Bound Water ◽

Root Water Uptake ◽

Flow Path ◽

Thermodynamic Evaluation ◽

Entire Flow ◽

Soil Water Distribution

Abstract. By extracting bound water from the soil and lifting it to the canopy, root systems of vegetation perform work. Here we describe how root water uptake can be evaluated thermodynamically and demonstrate that this evaluation provides additional insights into the factors that impede root water uptake. We derive an expression that relates the energy export at the base of the root system to a sum of terms that reflect all fluxes and storage changes along the flow path in thermodynamic terms. We illustrate this thermodynamic formulation using an idealized setup of scenarios with a simple model. In these scenarios, we demonstrate why heterogeneity in soil water distribution and rooting properties affect the impediment of water flow even though the mean soil water content and rooting properties are the same across the scenarios. The effects of heterogeneity can clearly be identified in the thermodynamics of the system in terms of differences in dissipative losses and hydraulic energy, resulting in an earlier start of water limitation in the drying cycle. We conclude that this thermodynamic evaluation of root water uptake conveniently provides insights into the impediments of different processes along the entire flow path, which goes beyond resistances and also accounts for the role of heterogeneity in soil water distribution.

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Water and salt transport in daily irrigated root zone.

Netherlands Journal of Agricultural Science ◽

10.18174/njas.v35i3.16734 ◽

1987 ◽

Vol 35 (3) ◽

pp. 395-406

Author(s):

C. Dirksen

Keyword(s):

Soil Water ◽

Water Uptake ◽

Gamma Ray ◽

Root Zone ◽

Root Water Uptake ◽

Salt Transport ◽

Soil Water Retention ◽

Transport Models ◽

Leaching Fraction ◽

Water Contents

With closed, high-frequency irrigation systems, the water supply can be tailored to the instant needs of plants. To be able to do this optimally, it is necessary to understand how plants interact with their environment. To study water uptake under a variety of non-uniform conditions in the root zone, lucerne was grown in laboratory soil columns with automated gamma ray attenuation, tensiometer and salinity sensor equipment to measure soil water contents, pressure potentials and osmotic potentials, respectively. The columns were irrigated with water of different salinity at various frequencies and leaching fractions. This paper presents results obtained in a column irrigated daily with water of conductivity 0.33 S/m (h0 = -13.2 m) at a target leaching fraction of 0.08. This includes the drying and wetting patterns under daily irrigations in deficit and excess of evapotranspiration, respectively. After 230 days the salination of the column had still not reached a steady state. Salinity increased rapidly with depth and root water uptake was shallow for the deep-rooting lucerne. Water and salt transport under daily irrigation cannot be described without taking hysteresis of soil water retention into account. The data presented are suitable for testing various water uptake models, once numerical water and salt transport models of the required complexity are operational. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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Leaf Gas Exchange and Water Relations of Lupins and Wheat. II. Root and Shoot Water Relations of Lupin During Drought-Induced Stomatal Closure

Functional Plant Biology ◽

10.1071/pp9890415 ◽

1989 ◽

Vol 16 (5) ◽

pp. 415 ◽

Cited By ~ 13

Author(s):

CR Jensen ◽

IE Henson ◽

NC Turner

Keyword(s):

Water Potential ◽

Soil Water ◽

Water Transport ◽

Water Uptake ◽

Water Relations ◽

Leaf Gas Exchange ◽

Stomatal Closure ◽

Soil Water Potential ◽

Root Water Uptake ◽

Leaf Conductance

Plants of Lupinus cosentinii Guss. cv. Eregulla were grown in a sandy soil in large containers in a glasshouse and exposed to drought by withholding water. Under these conditions stomatal closure had previously been shown to be initiated before a significant reduction in leaf water potential was detected. In the experiments reported here, no significant changes were found in water potential or turgor pressure of roots or leaves when a small reduction in soil water potential was induced which led to a 60% reduction in leaf conductance. The decrease in leaf conductance and root water uptake closely paralleled the fraction of roots in wet soil. By applying observed data of soil water and root characteristics, and root water uptake for whole pots in a single-root model, the average water potential at the root surface was calculated. Potential differences for water transport in the soil-plant system, and the resistances to water flow were estimated using the 'Ohm's Law' analogy for water transport. Soil resistance was negligible or minor, whereas the root resistance accounted for 61-72% and the shoot resistance accounted for about 30% of the total resistance. The validity of the measurements and calculations is discussed and the possible role of root- to-shoot communication raised.

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How to put plant root uptake into a soil water flow model

F1000Research ◽

10.12688/f1000research.7686.1 ◽

2016 ◽

Vol 5 ◽

pp. 43

Author(s):

Xuejun Dong

Keyword(s):

Water Stress ◽

Soil Water ◽

Water Uptake ◽

Root Distribution ◽

Plant Root ◽

Root Water Uptake ◽

Root Uptake ◽

Water Dynamics ◽

Rooting Depth ◽

Plant Root Uptake

The need for improved crop water use efficiency calls for flexible modeling platforms to implement new ideas in plant root uptake and its regulation mechanisms. This paper documents the details of modifying a soil infiltration and redistribution model to include (a) dynamic root growth, (b) non-uniform root distribution and water uptake, (c) the effect of water stress on plant water uptake, and (d) soil evaporation. The paper also demonstrates strategies of using the modified model to simulate soil water dynamics and plant transpiration considering different sensitivity of plants to soil dryness and different mechanisms of root water uptake. In particular, the flexibility of simulating various degrees of compensated uptake (whereby plants tend to maintain potential transpiration under mild water stress) is emphasized. The paper also describes how to estimate unknown root distribution and rooting depth parameters by the use of a simulation-based searching method. The full documentation of the computer code will allow further applications and new development.

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Root water uptake and profile soil water as affected by vertical root distribution

Plant Ecology ◽

10.1007/s11258-006-9163-y ◽

2006 ◽

Vol 189 (1) ◽

pp. 15-30 ◽

Cited By ~ 54

Author(s):

Gui-Rui Yu ◽

Jie Zhuang ◽

Keiichi Nakayama ◽

Yan Jin

Keyword(s):

Soil Water ◽

Water Uptake ◽

Root Distribution ◽

Root Water Uptake ◽

Vertical Root Distribution

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Examining the effect of pore size distribution and shape on flow through unsaturated peat using computed tomography

Hydrology and Earth System Sciences ◽

10.5194/hess-13-1993-2009 ◽

2009 ◽

Vol 13 (10) ◽

pp. 1993-2002 ◽

Cited By ~ 43

Author(s):

F. Rezanezhad ◽

W. L. Quinton ◽

J. S. Price ◽

D. Elrick ◽

T. R. Elliot ◽

...

Keyword(s):

Computed Tomography ◽

Hydraulic Conductivity ◽

Pore Structure ◽

Pore Size ◽

Soil Water ◽

Water Pressure ◽

Peat Soil ◽

Pressure Head ◽

Peat Soils ◽

Unsaturated Hydraulic Conductivity

Abstract. The hydraulic conductivity of unsaturated peat soil is controlled by the air-filled porosity, pore size and geometric distribution as well as other physical properties of peat materials. This study investigates how the size and shape of pores affects the flow of water through peat soils. In this study we used X-ray Computed Tomography (CT), at 45 μm resolution under 5 specific soil-water pressure head levels to provide 3-D, high-resolution images that were used to detect the inner pore structure of peat samples under a changing water regime. Pore structure and configuration were found to be irregular, which affected the rate of water transmission through peat soils. The 3-D analysis suggested that pore distribution is dominated by a single large pore-space. At low pressure head, this single large air-filled pore imparted a more effective flowpath compared to smaller pores. Smaller pores were disconnected and the flowpath was more tortuous than in the single large air-filled pore, and their contribution to flow was negligible when the single large pore was active. We quantify the pore structure of peat soil that affects the hydraulic conductivity in the unsaturated condition, and demonstrate the validity of our estimation of peat unsaturated hydraulic conductivity by making a comparison with a standard permeameter-based method. Estimates of unsaturated hydraulic conductivities were made for the purpose of testing the sensitivity of pore shape and geometry parameters on the hydraulic properties of peats and how to evaluate the structure of the peat and its affects on parameterization. We also studied the ability to quantify these factors for different soil moisture contents in order to define how the factors controlling the shape coefficient vary with changes in soil water pressure head. The relation between measured and estimated unsaturated hydraulic conductivity at various heads shows that rapid initial drainage, that changes the air-filled pore properties, creates a sharp decline in hydraulic conductivity. This is because the large pores readily lose water, the peat rapidly becomes less conductive and the flow path among pores, more tortuous.

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