The Impact of Rhizosphere Soil Structure and Mucilage on Root Water Uptake – A Simulation Study

AbstractIn agricultural lands has the soil moisture uptake from the root system a significant effect on the water regime of the soil profile. In texturally heavy soils, where preferential pathways are present, infiltrated precipitation and irrigation water with diluted fertilizers quickly penetrate to a significant depth and often reach an under-root zone or even the ground-water level. Such a scenario is likely to happen during long summer periods without rain followed by heavy precipitation events, when a part of the water may flow through desiccated cracks.Since 2001 the effects of drip irrigation and nitrogen fertilization of potatoes (Solanum tuberosum L., cultivar Agria) have been monitored within the frame of a research project at the experimental site Valecov (Czech Republic). Based upon the measured data an attempt has been made to simulate the water regime of the soil profile at a selected experimental plot, considering the impact of preferential flow and root water uptake. The dual-permeability simulation model S_1D_Dual (VOGEL et al., 2000) was used for the simulation. The soil hydraulic parameters were inversely determined using Levenberg-Marquardt method. Measured and simulated pressure heads were utilized in the optimization criterion. The scaling approach was applied to simplify the description of the spatial variability of the soil profile.The results of simulations demonstrate that during particular rainfall events the water reaches significant depths of the soil profile via preferential pathways. The effect of the root zone is dominant during dry periods, when capillary water uptake from the layers below roots becomes important. This should be taken in account into the optimization of the drip irrigation and nitrogen fertilization schedule.

Download Full-text

Variability assessment of Irrigation Requirement for Winter Wheat Cropping Under Changing Climate.

10.5194/egusphere-egu2020-172 ◽

2020 ◽

Author(s):

Kaushika Gujjanadu Suryaprakash ◽

Hari Prasad Kotnur Suryanarayana Rao

Keyword(s):

Climate Change ◽

Water Uptake ◽

Root Water Uptake ◽

Water Requirement ◽

Richards Equation ◽

Emission Scenarios ◽

Irrigation Requirement ◽

Moisture Movement ◽

The Future ◽

The Impact

India is primarily an agronomic country and most of the cropping in the Rabi season depends on the rainwater availability. With the ill effects of climate change cropping up, the agriculture sector is expected to take a major hit. This study takes a technical approach on the impact of climate change on the irrigation requirement of wheat cropping by studying the future irrigation requirement based on the temperature and rainfall that can be expected to occur in the future timelines. A root water uptake model involving the solution of the non-linear Richards equation to assess the root-zone moisture movement is formulated and validated. The inputs of the model include the crop data, which, in this case is obtained by field experimentation at the irrigation field laboratory at IIT Roorkee and weather data, which is obtained from the CANESM2 General circulation model for the historical and projected timescales. The historical GCM data for thirty years is bias corrected using the observed data from the India Meteorological department (IMD). The validated root water uptake model is applied to the historical and projected data for a 60 year span for two emission scenarios for RCP 4.5 and 8.5. The output was obtained as soil moisture profiles and frequencies of irrigation required. It was seen that for both the mild and high emission scenarios, the number of irrigation events per cropping period increased. This increase is assessed using variability analysis and for its impacts on the water resources management systems. The variability assessment showed the variation of the irrigation water requirement on annual and decadal scales. This is useful in understanding the historical and expected crop water requirement in view of the climate change effects.

Download Full-text

The impact of mucilage on root water uptake—A numerical study

Water Resources Research ◽

10.1002/2015wr018150 ◽

2016 ◽

Vol 52 (1) ◽

pp. 264-277 ◽

Cited By ~ 22

Author(s):

N. Schwartz ◽

A. Carminati ◽

M. Javaux

Keyword(s):

Water Uptake ◽

Numerical Study ◽

Root Water Uptake ◽

The Impact

Download Full-text

Tracing plant water fluxes in ecosystems by stable isotopes along the soil-plant and plant-atmosphere interfaces

10.5194/egusphere-egu2020-11289 ◽

2020 ◽

Author(s):

Christiane Werner

Keyword(s):

Water Uptake ◽

Large Scale ◽

Temporal Dynamics ◽

Root Water Uptake ◽

Plant Water ◽

Water Fluxes ◽

Terrestrial Vegetation ◽

Species Specific ◽

The Impact

Terrestrial vegetation is a main driver of ecosystem water fluxes, as plants mediate the water fluxes within the soil-vegetation-atmosphere continuum. Stable isotopologues of water are efficient tracer to follow the water transfer in soils, uptake by plants, transport in stems and release into the atmosphere through stomata. The development of in-situ methods coupled to isotope spectroscopy does now enable real-time in-situ water vapour isotopologue measurements revealing high spatial and temporal dynamics, such as adaptations in root water uptake depths (within hours to days) or the impact of transpirational fluxes on atmospheric moisture.Examples will be given how isotopes can be used to inform the complex interplay between plant ecophysiological adaptations and hydrological processes. For example, root water uptake is not solely driven by soil water availability but has to be understood in the context of species-specific regulation of active zones in their rooting system determining the conductivity between soil and roots regulating uptake depths. The latter has also to be evaluated in context of the nutrient demand and the spatial nutrient availability. Similarly, plant water transport and losses are a fined tuned interplay between species-specific structural and functional adaptations and atmospheric processes.Finally, first data of a large-scale ecosystem labelling experiment at the Biosphere 2 tropical rainforest of the B2 Wald, Atmosphere, and Live Dynamics (B2WALD) will be presented.

Download Full-text

Root distributions in a laboratory box evaluated using two different techniques (gravimetric and image processing) and their impact on root water uptake simulated with HYDRUS

Journal of Hydrology and Hydromechanics ◽

10.1515/johh-2016-0016 ◽

2016 ◽

Vol 64 (2) ◽

pp. 196-208 ◽

Cited By ~ 2

Author(s):

Aleš Klement ◽

Miroslav Fér ◽

Šárka Novotná ◽

Antonín Nikodem ◽

Radka Kodešová

Keyword(s):

Image Analysis ◽

Water Uptake ◽

Fine Roots ◽

Root Zone ◽

Root Water Uptake ◽

Root Density ◽

Gravimetric Analysis ◽

Lower Root ◽

The Impact ◽

Hydrus 1D

Abstract Knowledge of the distribution of plant roots in a soil profile (i.e. root density) is needed when simulating root water uptake from soil. Therefore, this study focused on evaluating barley and wheat root densities in a sand-vermiculite substrate. Barley and wheat were planted in a flat laboratory box under greenhouse conditions. The box was always divided into two parts, where a single plant row and rows cross section (respectively) was simulated. Roots were excavated at the end of the experiment and root densities were assessed using root zone image processing and by weighing. For this purpose, the entire area (width of 40 and height of 50 cm) of each scenario was divided into 80 segments (area of 5×5 cm). Root density in each segment was expressed as a root percentage of the entire root cluster. Vertical root distributions (i.e. root density with respect to depth) were also calculated as a sum of root densities in each 5 cm layer. Resulting vertical root densities, measured evaporation from the water table (used as the potential root water uptake), and the Feddes stress response function model were used for simulating substrate water regime and actual root water uptake for all scenarios using HYDRUS-1D. All scenarios were also simulated using HYDRUS-2D. One scenario (areal root density of barley sown in a single row, obtained using image analysis) is presented in this paper (because most scenarios showed root water uptakes similar to results of 1D scenarios). The application of two root detecting techniques resulted in noticeably different root density distributions. Differences were mainly attributed to the fact that fine roots of high density (located mostly at the deeper part of the box) had lower weights in comparison to the weight of few large roots (at the box top). Thus, at the deeper part, higher root density (with respect to the entire root zone) was obtained using the image analysis in comparison to that from the gravimetric analysis. Conversely, lower root density was obtained using the image analysis at the upper part in comparison to that from the gravimetric analysis. On the other hand, fine roots overlapped each other and therefore were not visible in the image, which resulted in lower root density values from image analysis. Root water uptakes simulated with HYDRUS-1D using diverse root densities obtained for each cereal declined differently from the potential root water uptake values depending on water scarcity at depths of higher root density. Usually, an earlier downtrend associated with gradual root water up-take decreases and vice versa. Similar root water uptakes were simulated for the presented scenario using the HYDRUS-1D and HYDRUS-2D models. The impact of the horizontal root density distribution on root water uptake was, in this case, less important than the impact of the vertical root distribution resulting from different techniques and sowing scenarios.

Download Full-text

Modeling the Impact of Rhizosphere Bulk Density and Mucilage Gradients on Root Water Uptake

Frontiers in Agronomy ◽

10.3389/fagro.2021.622367 ◽

2021 ◽

Vol 3 ◽

Author(s):

Magdalena Landl ◽

Maxime Phalempin ◽

Steffen Schlüter ◽

Doris Vetterlein ◽

Jan Vanderborght ◽

...

Keyword(s):

Bulk Density ◽

Water Uptake ◽

Hydraulic Properties ◽

Model Simulation ◽

Root Water Uptake ◽

Water Dynamics ◽

Bulk Soil ◽

Soil Hydraulic Properties ◽

Soil Hydraulic ◽

The Impact

In models of water flow in soil and roots, differences in the soil hydraulic properties of the rhizosphere and the bulk soil are usually neglected. There is, however, strong experimental evidence that rhizosphere and bulk soil hydraulic properties differ significantly from each other due to various root-soil interaction processes. Two such processes, which can also influence each other, are rhizosphere loosening or compaction and mucilage deposition. In this work, we identified realistic gradients in rhizosphere bulk density and mucilage concentration using X-ray CT imaging, respectively, model simulation for two different soil types and soil bulk densities and related them to soil hydraulic parameters. Using a 1D-single-root model, we then evaluated both the individual and combined effects of these gradients on soil water dynamics using scenario simulations. We showed that during soil drying, a lower rhizosphere bulk density leads to an earlier onset of water stress and to a reduced root water uptake that is sustained longer. The presence of mucilage led to a faster reduction of root water uptake. This is due to the stronger effect of mucilage viscosity on hydraulic conductivity compared to the mucilage- induced increase in water retention. Root water uptake was rapidly reduced when both mucilage and rhizosphere bulk density gradients were considered. The intensity of the effect of gradients in rhizosphere bulk density and mucilage concentration depended strongly on the interplay between initial soil hydraulic conditions, soil type and soil bulk densities. Both gradients in rhizosphere bulk density and mucilage concentration appear as a measure to sustain transpiration at a lower level and to avoid fast dehydration.

Download Full-text

Influence of soil structure and root water uptake strategy on unsaturated flow in heterogeneous media

Water Resources Research ◽

10.1029/2011wr010651 ◽

2012 ◽

Vol 48 (2) ◽

Cited By ~ 30

Author(s):

A. Kuhlmann ◽

I. Neuweiler ◽

S. E. A. T. M. van der Zee ◽

R. Helmig

Keyword(s):

Water Uptake ◽

Soil Structure ◽

Heterogeneous Media ◽

Unsaturated Flow ◽

Root Water Uptake

Download Full-text

Using dye tracer for visualizing roots impact on soil structure and soil porous system

Biologia ◽

10.1515/biolog-2015-0166 ◽

2015 ◽

Vol 70 (11) ◽

Cited By ~ 5

Author(s):

Radka Kodešová ◽

Karel Němeček ◽

Anna Žigová ◽

Antonín Nikodem ◽

Miroslav Fér

Keyword(s):

Water Uptake ◽

Soil Structure ◽

Preferential Flow ◽

Soil Surface ◽

Water Infiltration ◽

Porous System ◽

Field Scale ◽

Thin Sections ◽

Dye Tracer ◽

The Impact

AbstractPlants influence the water regime in soil by both water uptake and an uneven distribution of water infiltration at the soil surface. The latter process is more poorly studied, but it is well known that roots modify soil structure by enhancing aggregation and biopore production. This study used a dye tracer to visualize the impact of plants on water flow in the topsoil of a Greyic Phaeozem. Brilliant blue was ponded to 10 cm height in a 1 m × 1 m frame in the field immediately after harvest of winter wheat (Triticum aestivum L.). After complete infiltration, the staining patterns within the vertical and horizontal field-scale sections were studied. In addition, soil thin sections were made and micromorphological images were used to study soil structure and dye distribution at the microscale. The field-scale sections clearly documented uneven dye penetration into the soil surface, which was influenced by plant presence and in some cases by mechanical compaction of the soil surface. The micromorphological images showed that root activities compress soil and increases the bulk density near the roots (which could be also result of root water uptake and consequent soil adhesion). On the other hand in few cases a preferential flow along the roots was observed.

Download Full-text