Measurements and simulation of leaf xylem water potential and root water uptake in heterogeneous soil water contents

2019 ◽  
Vol 124 ◽  
pp. 96-105 ◽  
Author(s):  
Faisal Hayat ◽  
Mutez Ali Ahmed ◽  
Mohsen Zarebanadkouki ◽  
Gaochao Cai ◽  
Andrea Carminati
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Uptake ◽  
Root Water Uptake ◽  
Xylem Water Potential ◽  
Heterogeneous Soil ◽  
Water Contents ◽  
Soil Water Contents

An exponential root-water-uptake model

1999 ◽  
Vol 79 (2) ◽  
pp. 333-343 ◽  
Author(s):  
K. Y. Li ◽  
J. B. Boisvert ◽  
R. De Jong
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Root Distribution ◽  
Maximum Error ◽  
Root Water Uptake ◽  
Exponential Model ◽  
Rate Model ◽  
Loam Soil ◽  
Water Contents ◽  
Soil Water Contents

Macroscopic root-water-extraction models often do not adequately account for the non-uniform distribution of roots in the soil profile. We developed an exponential root-water-uptake model, which was derived from a measured root density distribution function. The model, incorporated in the Soil-Water-Atmosphere-Plant (SWAP) simulation model, was tested on a clay loam soil cropped to soybeans and on a sandy loam soil cropped to corn, near Ottawa. Comparisons of measured and simulated soil water contents with the exponential model, a linear depth-dependent model and a constant-extraction-rate model were also made. The exponential model performed satisfactorily (average relative errors <20%) when used to simulate measured field soil water contents at various depths. The constant-extraction-rate model overestimated the soil water contents in the upper part of the soil profile (maximum error 0.24 cm3 cm−3) and underestimated them (maximum error −0.09 cm3 cm−3) in the lower part. The exponential model and the linear model performed fairly similarly at the lower depths, but the exponential model gave better results in the near-surface horizons. The exponential model was sensitive to the root distribution coefficient and to the rooting depth, when the latter was approximately less than 40 cm. The results of this study suggest that the exponential root-water-uptake model as incorporated in SWAP is an improvement over those models, which do not account for the root distribution in the soil. Key words: SWAP, soil water simulation, root distribution, corn, soybeans, sensitivity analysis

scholarly journals The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

2021 ◽  
Vol 13 (4) ◽  
pp. 1759
Author(s):  
Said A. Hamido ◽  
Kelly T. Morgan
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Salinity ◽  
Planting Density ◽  
Stem Water Potential ◽  
Irrigation Rate ◽  
Biological Stress ◽  
Stem Water ◽  
Water Contents ◽  
Soil Water Contents

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

scholarly journals Water and salt transport in daily irrigated root zone.

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)

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

1989 ◽  
Vol 16 (5) ◽  
pp. 415 ◽  
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.

Impact of soil water potential pattern on root water uptake distribution and leaf water potential

2021 ◽  
Author(s):  
Ali Mehmandoost Kotlar ◽  
Mathieu Javaux
Keyword(s):  
Water Potential ◽  
Root System ◽  
Soil Water ◽  
Water Flow ◽  
Water Uptake ◽  
Leaf Water Potential ◽  
Root Water Uptake ◽  
Leaf Water ◽  
Hydraulic Lift ◽  
Water Potentials

&lt;p&gt;Root water uptake is a major process controlling water balance and accounts for about 60% of global terrestrial evapotranspiration. The root system employs different strategies to better exploit available soil water, however, the regulation of water uptake under the spatiotemporal heterogeneous and uneven distribution of soil water is still a major question. To tackle this question, we need to understand how plants cope with this heterogeneity by adjustment of above ground responses to partial rhizosphere drying. Therefore, we use R-SWMS simulating soil water flow, flow towards the roots, and radial and the axial flow inside the root system to perform numerical experiments on a 9-cell gridded rhizotrone (50 cm&amp;#215;50 cm). The water potentials in each cell can be varied and fixed for the period of simulation and no water flow is allowed between cells while roots can pass over the boundaries. Then a static mature maize root architecture to different extents invaded in all cells is subjected to the various arrangements of cells' soil water potentials. R-SWMS allows determining possible hydraulic lift in drier areas. With these simulations, the variation of root water and leaf water potential will be determined and the role of root length density in each cell and corresponding average soil-root water potential will be statistically discussed.&lt;/p&gt;

Tree/pasture interactions at a range of tree densities in an agroforestry experiment. II. Water uptake in relation to rooting patterns

1990 ◽  
Vol 41 (4) ◽  
pp. 697 ◽  
Author(s):  
J Eastham ◽  
CW Rose ◽  
DM Cameron ◽  
SJ Rance ◽  
T Talsma ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Unit Root ◽  
Evaporation Rate ◽  
Surface Soil ◽  
Tree Density ◽  
Soil Horizons ◽  
Rooting Patterns ◽  
Water Contents ◽  
Soil Water Contents

Patterns of water uptake throughout a drying period of approximately one year were investigated under trees and pasture at three tree densities in an agroforestry experiment, and related to tree and pasture rooting patterns and water use. A greater proportion of soil water was extracted from deep in the soil profile under the densely planted trees, owing to lower soil water contents in upper horizons and deeper and more dense rooting systems than at lower tree densities. As the drought period progressed, the ratios of tree transpiration rate and pasture evaporation rate to equilibrium evaporation rate tended to decrease at each tree density as soil water contents in upper horizons decreased, and an increasing proportion of water was extracted from deeper soil horizons. At each tree density, the rate of water uptake per unit root length was lowest in surface soil horizons and tended to increase with increasing soil depth. The rate of water uptake per unit root length tended to increase with time in deeper, wetter soil horizons and decrease with time in surface soil horizons as soil water content decreased.

scholarly journals Formulation of root water uptake in a multi-layer soil-plant model: does van den Honert's equation hold?

1998 ◽  
Vol 2 (1) ◽  
pp. 31-39 ◽  
Author(s):  
J.-P. Lhomme
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Uptake ◽  
Transpiration Rate ◽  
Plant Resistance ◽  
Soil Water Potential ◽  
Root Water Uptake ◽  
Layer Model ◽  
Ohm’S Law ◽  
Ohm's Law

Abstract. The withdrawal of water from soil by vegetation, which in steady state conditions is equivalent to the transpiration rate, can be written in terms of water potential in the form of an Ohm's law analogy, known as van den Honert's equation: The difference between an effective soil water potential and the bulk canopy water potential is divided by an effective soil-plant resistance. This equation is commonly used, but little is known about the precise definition of its parameters. The issue of this paper is to bridge the gap between the bulk approach and a multi-layer description of soil-plant water transfer by interpreting the bulk parameters in terms of the characteristics of the multi-layer approach. Water flow through an elementary path within the soil or the root is assumed to follow an Ohm's law analogy, and the soil and root characterisics are allowed to vary with depth. Starting from the basic equations of the multi-layer approach, it is proved that the total rate of transpiration can also be expressed in the form of an Ohm's law analogy. This means that van den Honert's equation holds at canopy scale, insofar as the assumptions made on the physics of root water uptake hold. In the bulk formulation derived, the effective soil-plant resistance appears as a combination of the elementary resistances making up the multi-layer model; and the effective soil water potential is a weighted mean of the water potentials in each soil layer, the weighting system involving the complete set of elementary resistances. Simpler representations of soil-plant interaction leading to Ohm's law type formulations are also examined: a simplified multi-layer model, in which xylem (root axial) resistance is neglected, and a bulk approach, in which soil-root interaction is represented by only one layer. Numerical simulations performed in different standard conditions show that these simpler representations do not provide accurate estimates of the transpiration rate, when compared to the values obtained by the complete algorithm.

scholarly journals Analysis of Soil Water Response to Grass Transpiration

2013 ◽  
Vol 1 (No. 3) ◽  
pp. 85-98
Author(s):  
Dohnal Michal ◽  
Dušek Jaromír ◽  
Vogel Tomáš ◽  
Herza Jiří
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Preferential Flow ◽  
Water Movement ◽  
Control Volume ◽  
Water Pressure ◽  
Lower Boundary ◽  
Root Water Uptake ◽  
Water Dynamics ◽  
Soil Water Dynamics

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&rsquo; 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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