A two-dimensional model of root water uptake for single apple trees and its verification with sap flow and soil water content measurements

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.

Download Full-text

Estimation of root water uptake parameters by inverse modeling with soil water content data

Water Resources Research ◽

10.1029/2003wr002046 ◽

2003 ◽

Vol 39 (11) ◽

Cited By ~ 39

Author(s):

F. Hupet ◽

S. Lambot ◽

R. A. Feddes ◽

J. C. van Dam ◽

M. Vanclooster

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Inverse Modeling ◽

Root Water Uptake

Download Full-text

On the identification of macroscopic root water uptake parameters from soil water content observations

Water Resources Research ◽

10.1029/2002wr001556 ◽

2002 ◽

Vol 38 (12) ◽

pp. 36-1-36-14 ◽

Cited By ~ 39

Author(s):

F. Hupet ◽

S. Lambot ◽

M. Javaux ◽

M. Vanclooster

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Root Water Uptake

Download Full-text

Using measured soil water contents to estimate evapotranspiration and root water uptake profiles – a comparative study

Hydrology and Earth System Sciences ◽

10.5194/hess-19-409-2015 ◽

2015 ◽

Vol 19 (1) ◽

pp. 409-425 ◽

Cited By ~ 17

Author(s):

M. Guderle ◽

A. Hildebrandt

Keyword(s):

Time Series ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Root Water Uptake ◽

Performance Criteria ◽

Sensor Calibration ◽

Vertical Flow ◽

Sink Term

Abstract. Understanding the role of plants in soil water relations, and thus ecosystem functioning, requires information about root water uptake. We evaluated four different complex water balance methods to estimate sink term patterns and evapotranspiration directly from soil moisture measurements. We tested four methods. The first two take the difference between two measurement intervals as evapotranspiration, thus neglecting vertical flow. The third uses regression on the soil water content time series and differences between day and night to account for vertical flow. The fourth accounts for vertical flow using a numerical model and iteratively solves for the sink term. None of these methods requires any a priori information of root distribution parameters or evapotranspiration, which is an advantage compared to common root water uptake models. To test the methods, a synthetic experiment with numerical simulations for a grassland ecosystem was conducted. Additionally, the time series were perturbed to simulate common sensor errors, like those due to measurement precision and inaccurate sensor calibration. We tested each method for a range of measurement frequencies and applied performance criteria to evaluate the suitability of each method. In general, we show that methods accounting for vertical flow predict evapotranspiration and the sink term distribution more accurately than the simpler approaches. Under consideration of possible measurement uncertainties, the method based on regression and differentiating between day and night cycles leads to the best and most robust estimation of sink term patterns. It is thus an alternative to more complex inverse numerical methods. This study demonstrates that highly resolved (temporally and spatially) soil water content measurements may be used to estimate the sink term profiles when the appropriate approach is used.

Download Full-text

Time-lapse monitoring of root water uptake using electrical resistivity tomography and Mise-à-la-Masse: a vineyard infiltration experiment

10.5194/soil-2019-28 ◽

2019 ◽

Author(s):

Benjamin Mary ◽

Luca Peruzzo ◽

Jacopo Boaga ◽

Nicola Cenni ◽

Myriam Schmutz ◽

...

Keyword(s):

Electrical Resistivity ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Electrical Resistivity Tomography ◽

Time Lapse ◽

Root Water Uptake ◽

Resistivity Tomography ◽

Infiltration Experiment

Abstract. This paper presents a time-lapse application of electrical methods (Electrical Resistivity Tomography – ERT – and Mise-à-la-Masse – MALM) for monitoring plant roots and their activity (root water uptake) during a controlled infiltration experiment. The use of non-invasive geophysical monitoring is of increasing interest as these techniques provide time-lapse imaging of processes that otherwise can only be measured at few specific spatial locations. The experiment here described was conducted in a vineyard in Bordeaux (France) and was focused on the behaviour of two neighbouring grapevines. The joint application of ERT and MALM has several advantages. While ERT in time-lapse mode is sensitive to changes in soil electrical resistivity and thus to the factors controlling it (mainly soil water content, in this context), MALM uses DC current injected in a tree stem to image where the plant-root system is in effective electrical contact with the soil at locations that are likely to be the same where root water uptake (RWU) takes place. Thus ERT and MALM provide complementary information about the root structure and activity. The experiment shows that the region of likely electrical current sources produced by MALM does not change significantly during the infiltration study time in spite of the strong changes of electrical resistivity caused by changes in soil water content. This fact, together with the evidence that current injection in the soil produces totally different patterns, corroborates the idea that this application of MALM highlights the active root density in the soil. When considering the electrical resistivity changes (as measured by ERT) inside the stationary volume of active roots delineated by MALM, the overall tendency is towards a resistivity increase, which can be linked to a decrease in soil water content caused by root water uptake. On the contrary, when considering the soil volume outside the MALM-derived root water uptake region, the electrical resistivity tends to decrease as an effect of soil water content increase caused by the infiltration. The results are particularly promising, and the method can be applied to a variety of scales including the laboratory scale where direct evidence of roots structure and root water uptake can help corroborate the approach. Once fully validated, the joint use of MALM and ERT can be used as a valuable tool to study the activity of roots under a wide variety of field conditions.

Download Full-text

Using measured soil water contents to estimate evapotranspiration and root water uptake profiles – a comparative study

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-10859-2014 ◽

2014 ◽

Vol 11 (9) ◽

pp. 10859-10902 ◽

Cited By ~ 1

Author(s):

M. Guderle ◽

A. Hildebrandt

Keyword(s):

Time Series ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Root Water Uptake ◽

Performance Criteria ◽

Sensor Calibration ◽

Vertical Flow ◽

Sink Term

Abstract. Understanding the role of plants for soil water relations, and thus for ecosystem functioning, requires information about root water uptake. We evaluated four different complex water balance methods to estimate sink term patterns and evapotranspiration directly from soil moisture measurements. We tested four methods: the first two take the difference between two measurement intervals as evapotranspiration, thus neglecting vertical flow. The third uses regression on the soil water content time series and differences between day and night to account for vertical flow. The fourth accounts for vertical flow using a numerical model and iteratively solves for the sink term. Neither of those methods requires any a priori information of root distribution parameters or evapotranspiration, which is the advantage, compared to common root water uptake models. To test the methods, a synthetic experiment with numerical simulations for a grassland ecosystem was conducted. Additionally, the time series were perturbed to simulate common sensor errors, like those due to measurement precision and inaccurate sensor calibration. We tested each method for a range of measurement frequencies and applied performance criteria to evaluate the suitability of each method. In general, we show that methods accounting for vertical flow predict evapotranspiration and the sink term distribution more accurately than the simpler approaches. Under consideration of possible measurement uncertainties, the method based on regression and differentiating between day and night cycles leads to the best and most robust estimation of sink term patterns. It is thus an alternative to more complex inverse numerical methods. This study demonstrates that highly resolved (temporal and spatial) soil water content measurements may be used to estimate the sink term profiles when the appropriate approach is used.

Download Full-text

Disentangling temporal and population variability in plant root water uptake from stable isotopic analysis: a labeling study

10.5194/hess-2019-543 ◽

2019 ◽

Author(s):

Valentin Couvreur ◽

Youri Rothfuss ◽

Félicien Meunier ◽

Thierry Bariac ◽

Philippe Biron ◽

...

Keyword(s):

Water Content ◽

Soil Water ◽

Physical Model ◽

Soil Water Content ◽

Water Uptake ◽

Temporal Dynamics ◽

Plant Root ◽

Root Water Uptake ◽

Leaf Water ◽

Stable Isotopic

Abstract. Isotopic labeling techniques have the potential to minimize the uncertainty of plant root water uptake (RWU) profiles estimated through multi-source (statistical) modeling, by artificially enhancing soil water isotopic gradient. Furthermore, physical models can account for hydrodynamic constraints to RWU if simultaneous soil and plant water status data is available. In this study, a population of tall fescue (Festuca arundinacae cv Soni) was grown in a macro-rhizotron setup under semi-controlled conditions to monitor such variables for a 34-hours long period following the oxygen stable isotopic (18O) labeling of deep soil water. Aboveground variables included tiller and leaf water oxygen isotopic compositions as well as leaf water potential (ψleaf), relative humidity, and transpiration rate. Belowground profiles of root length density (RLD), soil water content and isotopic composition were also sampled. While there were strong correlations between hydraulic variables as well as between isotopic variables, the experimental results underlined the discrepancy between variations of hydraulic and isotopic variables. In order to dissect the problem, we reproduced both types of observations with a one-dimensional physical model of water flow in the soil-plant domain, for 60 different realistic RLD profiles. While simulated ψleaf followed clear temporal variations with little differences across plants as if they were “on board of the same rollercoaster”, simulated δtiller values within the plant population were rather heterogeneous (“swarm-like”) with relatively little temporal variation and a strong sensitivity to rooting depth. The physical model thus suggested that the discrepancy between isotopic and hydraulic observations was logical, as the variability captured by the former was spatial and may not correlate with the temporal dynamics of the latter. For comparison purposes a Bayesian statistical model was also used to simulate RWU. While they predicted relatively similar cumulative RWU profiles, the physical model could differentiate spatial from temporal dynamics of the isotopic signature, and supported that the local increase of soil water content and formation of a peak of labelled water observed overnight were due to hydraulic lift.

Download Full-text

Time-lapse monitoring of root water uptake using electrical resistivity tomography and mise-à-la-masse: a vineyard infiltration experiment

SOIL ◽

10.5194/soil-6-95-2020 ◽

2020 ◽

Vol 6 (1) ◽

pp. 95-114 ◽

Cited By ~ 4

Author(s):

Benjamin Mary ◽

Luca Peruzzo ◽

Jacopo Boaga ◽

Nicola Cenni ◽

Myriam Schmutz ◽

...

Keyword(s):

Electrical Resistivity ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Electrical Resistivity Tomography ◽

Time Lapse ◽

Root Water Uptake ◽

Root Structure ◽

Resistivity Tomography

Abstract. This paper presents a time-lapse application of electrical methods (electrical resistivity tomography, ERT; and mise-à-la-masse, MALM) for monitoring plant roots and their activity (root water uptake) during a controlled infiltration experiment. The use of non-invasive geophysical monitoring is of increasing interest as these techniques provide time-lapse imaging of processes that otherwise can only be measured at few specific spatial locations. The experiment here described was conducted in a vineyard in Bordeaux (France) and was focused on the behaviour of two neighbouring grapevines. The joint application of ERT and MALM has several advantages. While ERT in time-lapse mode is sensitive to changes in soil electrical resistivity and thus to the factors controlling it (mainly soil water content, in this context), MALM uses DC current injected into a tree stem to image where the plant root system is in effective electrical contact with the soil at locations that are likely to be the same where root water uptake (RWU) takes place. Thus, ERT and MALM provide complementary information about the root structure and activity. The experiment shows that the region of likely electrical current sources produced by MALM does not change significantly during the infiltration time in spite of the strong changes of electrical resistivity caused by changes in soil water content. Ultimately, the interpretation of the current source distribution strengthened the hypothesis of using current as a proxy for root detection. This fact, together with the evidence that current injection in the soil and in the stem produces totally different voltage patterns, corroborates the idea that this application of MALM highlights the active root density in the soil. When considering the electrical resistivity changes (as measured by ERT) inside the stationary volume of active roots delineated by MALM, the overall tendency is towards a resistivity increase during irrigation time, which can be linked to a decrease in soil water content caused by root water uptake. On the contrary, when considering the soil volume outside the MALM-derived root water uptake region, the electrical resistivity tends to decrease as an effect of soil water content increase caused by the infiltration. The use of a simplified infiltration model confirms at least qualitatively this behaviour. The monitoring results are particularly promising, and the method can be applied to a variety of scales including the laboratory scale where direct evidence of root structure and root water uptake can help corroborate the approach. Once fully validated, the joint use of MALM and ERT can be used as a valuable tool to study the activity of roots under a wide variety of field conditions.

Download Full-text

Detecting crop water requirements indicators in irrigated agro-ecosystems from soil water content profiles: an application for a citrus orchard

10.5194/egusphere-egu21-9172 ◽

2021 ◽

Author(s):

Giuseppe Provenzano ◽

Daniel Alberto Segovia-Cardozo

Keyword(s):

Soil Moisture ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Water Uptake ◽

Crop Coefficient ◽

Root Water Uptake ◽

Climate Variables ◽

Crop Water ◽

Citrus Orchard

For annual cropping systems sensitive to water stress, such as citrus, efficient water management can allow facing their large water consumption and enhancing crop sustainability. However, to apply water-saving strategies it is necessary to monitoring soil and/or plant water status. In the last decade, a wide number of sensors providing indirect measurements of volumetric soil water content based on soil physical properties, such as dielectric permittivity or matric potential, have been developed. Among the sensors using the frequency domain reflectometry technique, the &#8220;drill and drop&#8221; (Sentek, Inc., Stepney, Australia) multi-sensor probes allow continuous acquisition of soil moisture dynamic every 10 cm starting from the soil surface; these data hide important information on root water uptake and actual crop evapotranspiration.The objective of the paper was to analyze the temporal dynamics of soil water content profiles detected with multi-sensor probes during three years of field observations (July 2017- August 2020) in a citrus orchard, to estimate root water uptake and crop transpiration by three methodologies. Simultaneous measurements of sap fluxes and climate variables also allowed estimating the basal crop coefficient, Kcb, often considered for estimating crop water requirement.The experiments were carried out in a 30 years-old citrus orchard (C. reticulata Blanco cv. Tardivo di Ciaculli) with trees spaced 5.0x5.0 m. The field is irrigated with a subsurface drip system installed in 2018, with two lateral pipes per plant row at 30 depth and distance of 1.1 m from the trunk. Integrated sensing methodologies supported by the Internet of Things and cloud computing technologies (Agrinet/Tuctronics, Walla Walla, WA, USA), linked with a suitable communication infrastructure, were used to acquire continuously, in real-time and from remote soil water contents and climate variables. Four soil moisture profiles corresponding to as many plants were monitored with 120 cm long drill and drop sensors installed at a distance of 30 cm from one emitter. A standard weather station (Spectrum Technologies, Inc) was also installed to acquire, once every half hour, wind speed and direction at 2 m height, solar radiation, air temperature, relative air humidity and precipitation. In both years, sap fluxes were also measured hourly on two citrus trees, by using two Granier&#8217;s thermal dissipation probes (TDP) per tree. Each hour, the difference of temperature between the upper heated and lower un-heated needles, combined with the temperature difference at night allowed to estimate the sap velocity and then the hourly sap fluxes.The analysis evidenced the characteristic declines of soil water content after rainfall events, from which it was possible verifying that the hourly dynamic of root water uptake followed that of the corresponding sap flow sensors. Moreover, the knowledge of daily root water uptake, associated with the simultaneous values of reference evapotranspiration allowed obtaining suitable estimations of the basal crop coefficient. The proposed approach provided interesting insights into the dynamic of root water uptake of citrus trees and can represent a promising tool for precise irrigation scheduling.

Download Full-text