Soil and plant resistances to water absorption by plant root systems

1979 ◽  
Vol 30 (2) ◽  
pp. 279 ◽  
Author(s):  
GJ Burch
Keyword(s):  
Water Absorption ◽  
Root System ◽  
Soil Water ◽  
Water Movement ◽  
Plant Root ◽  
Unit Length ◽  
Water Flux ◽  
Soil Water Potential ◽  
Root Systems ◽  
Soil Resistance

A study of water absorption by root systems of two herbage species, white clover (Trifolium repens L.) and tall fescue (Festuca arundinacea Schreb.), was used to partition the resistances to water flux between the soil and plant. A large and almost constant plant resistance influenced the pattern of water absorption until the soil resistance reached about 1.5 x 103 MPa s cm-3. This corresponded to an extraction of almost 80% of the available soil water. Water absorption from progressively deeper soil layers showed no evidence of any substantial resistance to water flux through the root xylem. Therefore, in wet soils, water movement into and through a root system is predominantly influenced by a large resistance to the radial water flux through root tissues outside the xylem. The radial resistance values for unit (cm) length of root were 6.49 x 106 and 6.54 x 106 MPa s cm-2 for clover and fescue respectively. A model of water uptake has been described which introduces two modified parameters for integrating the soil water potential (ψ) and the soil-root conductance (κ), over an entire root system. This study, along with other evidence from the literature, would indicate that for unit length of root the radial resistance to water absorption is reasonably similar, not only for an entire root system but also for a number of different species. An underestimation of the radial soil resistance (Rsr) to water absorption suggests that a root contact resistance (Rc) exists which could be due to the shrinkage of the soil or root, or both, with drying of the soil. This effect caused an increase in resistance to water absorption of about 48 x Rsr for fescue and 71 x Rsr for clover. This difference in Rc between the two species was attributed to a contrast in root morphology, especially a difference in the average root diameters of the two species.

Root Water Uptake Model of Populus Euphratica in Desert Riparian Forest in Extreme Arid Region

2011 ◽  
pp. 276-288
Author(s):  
Yongzheng Tian ◽  
Jianhua Si ◽  
Qi Feng ◽  
Shengkui Cao
Keyword(s):  
Water Absorption ◽  
Soil Water ◽  
Arid Region ◽  
Water Movement ◽  
Root Zone ◽  
Riparian Forest ◽  
Plant Root ◽  
Populus Euphratica ◽  
Root Water Uptake ◽  
Plant Root System

Plant root water uptake is a key way to transfer soil water to the atmosphere. It is an important part of the research on water transforming patterns in the SPAC (Soil-Plant-Air Continuum). So understanding the water absorption patterns of plant root system is a base to recognize the SPAC. Recently there are many studies on the water absorption patterns of plant root system. However, the researched plants are mostly crops and the main researched areas are regions with adequate precipitation. There are only a few studies on the water absorption of natural plants in extreme arid desert regions. This paper studied the root water absorption patterns of Populus euphratica and established the corresponding mathematical model based on the data of root density and soil water dynamics in root zone in desert riparian forest in extreme arid region. The finite difference method was used to discretize the soil water movement equation with evaporation boundary conditions. Numerical simulation analysis of soil water movement in root zone of Populus euphratica showed that the simulated values were consistent with the measurement values with 92-98% precision. This work provides a theoretical basis for the study of water movement in the SPAC.

Root Absorption of Water and Physiological Responses to Water Deficits by Festuca arundinacea Schreb. And Trifolium repens L

1978 ◽  
Vol 5 (6) ◽  
pp. 859 ◽  
Author(s):  
GJ Burch ◽  
GG Johns
Keyword(s):  
Water Absorption ◽  
Root System ◽  
Soil Water ◽  
Water Uptake ◽  
Leaf Senescence ◽  
Soil Profile ◽  
Festuca Arundinacea ◽  
Physiological Responses ◽  
Root Systems ◽  
Two Parameters

A study of water uptake by white clover (Trifoliurn repens) and tall fescue (Festuca arundinacea cv. Demeter) examined their comparative physiological responses to water deficits and the pattern of water absorptioil by their root systems. Fescue had more deep roots than clover and extracted more water from deep soil layers, finally resulting in a drier soil profile. Poor control of leaf transpiration in clover resulted in low leaf water potentials and increased leaf senescence; in fescue, better stomatal control and higher leaf water potentials prolonged its period of active growth. The relationships between soil water content, transpiration rate and pattern of water absorption by both root systems were compared using an existing theory of water uptake. Two parameters for integrating soil water potential and soil conductance down the soil profile gave more consistent relationships with the transpiration rates of fescue than with those of clover. These two parameters may be less able to account for the pattern of soil water absorption by a clover root system and a possible explanation for this effect is discussed. Relative canopy conductance ratios gave similar relationships with the relative transpiration ratios for fescue and clover. Therefore, leaf senescence in clover was apparently important for balancing its rates of transpiration and water uptake. In contrast, fescue was able to rely upon its more extensive root system, effective stomatal control and ability to roll leaves to regulate its water balance.

The role of soil resistance in determining water uptake by plant root systems

Soil Research ◽  
1983 ◽  
Vol 21 (4) ◽  
pp. 571 ◽  
Author(s):  
NR Hulugalle ◽  
ST Willatt
Keyword(s):  
Water Stress ◽  
Hydraulic Conductivity ◽  
Water Uptake ◽  
Plant Root ◽  
Soil Water Potential ◽  
Root Systems ◽  
Plant Roots ◽  
Soil Resistance ◽  
Plant Root Systems

Resistance to water flow in plant roots has been suggested as a significant factor limiting water uptake by plants. The results of previous experiments have been used to show that soil resistance may be more significant than has recently been suggested, particularly in soils of low hydraulic conductivity and where root density is low. As the technique used to determine soil resistance relies on hydraulic conductivity, the latter may be more appropriate as an indicator of water stress than soil water potential.

Water Relations of Winter Wheat: the Root System, Petiolar Resistance and Development of a Root Abstraction Equation

1985 ◽  
Vol 21 (4) ◽  
pp. 377-388 ◽  
Author(s):  
M. McGowan ◽  
E. Tzimas
Keyword(s):  
Winter Wheat ◽  
Root System ◽  
Soil Water ◽  
Water Uptake ◽  
Water Relations ◽  
Field Experiments ◽  
Soil Water Potential ◽  
Root Systems ◽  
Wheat Crop ◽  
Winter Wheat Crop

SUMMARYThe vertical distribution of water potentials within the leaf canopy, along the stem and within the soil profile of a winter wheat crop was analysed and it is concluded the failure by previous workers to recognize the significance of petiolar resistance has probably resulted in over-estimates of the resistance of the soil to water uptake by root systems of field crops.From an analysis of the water relations of several winter wheat crops an equation is developed to describe the extraction of soil water reserves by crop root systems, based upon values of soil water potential, root xylem potential and ‘effective’ resistance to water uptake which can be obtained from field experiments. The equation provides an empirical basis to specify the minimum desirable root system for efficient capture of soil water reserves, to analyse the effects of differing root distributions and thus to help identify situations where it would be profitable to modify rooting either by tillage or by plant breeding.

Water relations of winter wheat. 5. The root system and osmotic adjustment in relation to crop evaporation

1984 ◽  
Vol 102 (2) ◽  
pp. 415-425 ◽  
Author(s):  
M. McGowan ◽  
P. Blanch ◽  
P. J. Gregory ◽  
D. Haycock
Keyword(s):  
Winter Wheat ◽  
Water Potential ◽  
Root System ◽  
Soil Water ◽  
Osmotic Adjustment ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Plant Water ◽  
Potential Evaporation ◽  
Plant Water Potential

SummaryShoot and root growth and associated leaf and soil water potential relations were compared in three consecutive crops of winter wheat grown in the same field. Despite a profuse root system the crop grown in the second drought year (1976) failed to dry the soil as throughly as the crops in 1975 and 1977. Measurements of plant water potential showed that the restricted utilization of soil water reserves by this crop was associated with failure to make any significant osmotic adjustment, leading to premature loss of leaf turgor and stomatal closure. The implications of these results for models to estimate actual crop evaporation from values of potential evaporation are discussed.

scholarly journals Evaluation of DSSAT soil-water balance module under cropped and bare soil conditions

2003 ◽  
Vol 46 (4) ◽  
pp. 489-498 ◽  
Author(s):  
Rogério Teixeira de Faria ◽  
Walter Truman Bowen
Keyword(s):  
Soil Moisture ◽  
Water Balance ◽  
Soil Water ◽  
Water Flux ◽  
Soil Water Potential ◽  
Bare Soil ◽  
Root Water Uptake ◽  
Soil Water Balance ◽  
Soil Conditions ◽  
Soil Water Flux

The performance of the soil water balance module (SWBM) in the models of DSSAT v3.5 was evaluated against soil moisture data measured in bare soil and dry bean plots, in Paraná, southern Brazil. Under bare soil, the SWBM showed a low performance to simulate soil moisture profiles due to inadequacies of the method used to calculate unsaturated soil water flux. Improved estimates were achieved by modifying the SWBM with the use of Darcy's equation to simulate soil water flux as a function of soil water potential gradient between consecutive soil layers. When used to simulate water balance for the bean crop, the modified SWBM improved soil moisture estimation but underpredicted crop yield. Root water uptake data indicated that assumptions on the original method limited plant water extraction for the soil in the study area. This was corrected by replacing empirical coefficients with measured values of soil hydraulic conductivity at different depths.

Soil Physical Methods for Estimating Recharge - Part 3

1998 ◽  
Author(s):  
W Bond
Keyword(s):  
Soil Water ◽  
Root Zone ◽  
Plant Root ◽  
Water Flux ◽  
Soil Physics ◽  
Plane Method ◽  
Physical Methods ◽  
Basic Concepts ◽  
Zero Flux Plane ◽  
Over Time

Measurements in and just below the plant root zone, using principles of soil physics, can be used to estimate recharge. This booklet describes the Zero Flux Plane Method, Methods Based on Darchy's law, and Lysimetry for making such estimates. The work presents the basic concepts of soil water physics that will be referred to in this and other booklets in the series. Another method, the Soil Water Flux Meter, is discussed briefly, but as this is not sufficiently well developed for routine use readers are referred elsewhere for full details. All these methods require that consideration be given to interpolation over time and spatial extrapolation or averaging. A brief discussion of this is given.

Resistance to water movement through wheat root systems

1978 ◽  
Vol 29 (5) ◽  
pp. 913 ◽  
Author(s):  
KA Seaton ◽  
JJ Landsberg
Keyword(s):  
Water Potential ◽  
Flow Rate ◽  
Soil Type ◽  
Water Movement ◽  
Soil Water Potential ◽  
Root Systems ◽  
Experimental Period ◽  
Root Surface Area ◽  
Analogue Model ◽  
Stem Resistance

A three-layer electrical analogue model was used to calculate resistance to water movement through the roots of wheat plants growing in small weighing lysimeters. In one experiment the wheat was grown in two soil types; in a second experiment one soil type was used but different root systems were induced by controlling the water table before the start of the experimental period. Resistance calculations were based on hourly measurements of transpiration rate, leaf water potential and water uptake from three soil layers (qi), calculated from measurements of soil water potential at three depths. The number of main roots per stem (required for the model) and root surface area in each layer (Ai) were obtained from measurements of root lengths and diameters in soil cores taken at the end of each experiment. Estimates of the resistance to flow through stems led to estimates of ψ0), the water potential at the stem base, at any stem flow rate. Axial (main) root resistances (Rxi) were calculated from the Poiseuille equation. Values of the resistance to water movement through the roots in layer i were calculated from the set of equations describing uptake from each layer in terms of flow rates, potential gradients and resistances; these values, inserted in the solution for 1/10 from the set of three equations, yielded total root resistances (RT) and estimates of the effective soil moisture potential (^ψs) for the whole profile. (RT) ranged from 63.9 to 627.3 bar sec mm-3 (cf. stem resistance between 24 and 70 bar sec mm-3) and was inversely related to flow rate through the main roots, which indicated a constant potential drop (^ψs – ψ0) of about 10 bars, irrespective of soil type or root system. Radial root resistances, estimated as At(<ψsi – ψ0)/qi, ranged from 4.6 x 104 to 4.2 x 106 bar sec mm-l and were inversely related to qi. Inaccuracies in estimates of Rxi do not affect the results much and the model used is potentially valuable as a framework for field research.

Resistance to water uptake by irrigated potatoes on a duplex soil

Soil Research ◽  
1990 ◽  
Vol 28 (4) ◽  
pp. 487 ◽  
Author(s):  
MA Rab ◽  
KA Olsson ◽  
ST Willatt
Keyword(s):  
Root System ◽  
Soil Water ◽  
Plant Resistance ◽  
Root Length ◽  
Hydraulic Properties ◽  
Potato Crop ◽  
Soil Resistance ◽  
Soil Hydraulic Properties ◽  
Matric Potential ◽  
Soil Hydraulic

Resistances to water flow were analysed for the soil-root system of a potato crop growing on a duplex soil-where soil hydraulic properties varied with depth-under two irrigation regimes: 'wet' (irrigated weekly) and 'dry' (irrigated twice only during the growing season). The relative magnitudes of the soil and plant resistances controlling root water uptake were evaluated over depth and time using field-measured soil hydraulic properties and root length densities in successive soil layers. Resistance to water flow in the root system is likely to be the dominant resistance in the liquid phase, although soil resistance increased more rapidly than plant resistance with decreasing soil-water matric potential and root length density. Soil resistance reached similar values to plant resistance only when the soil-water matric potential was in the range -900 kPa to -1500 kPa (corresponding soil hydraulic conductivities of 10-7 and 10-8 m day-1 respectively), depending on the root length beneath unit ground area in the soil layer, La. Poor utilization of water from depth of this soil was attributed to resistance in the root system (possibly radial) associated with low La. Practical considerations for improved water management of the potato crop on clay soils are discussed.

Effect of drought on growth and water use of sugar beet

1987 ◽  
Vol 109 (3) ◽  
pp. 421-435 ◽  
Author(s):  
Kay F. Brown ◽  
A. B. Messem ◽  
R. J. Dunham ◽  
P. V. Biscoe
Keyword(s):  
Sugar Beet ◽  
Root System ◽  
Soil Water ◽  
Water Use ◽  
Dry Matter ◽  
Unit Length ◽  
Fibrous Root ◽  
Deep Soil ◽  
Uptake Rates ◽  
Fibrous Roots

SummaryThe growth and water use of sugar beet affected by early (ED) and late (LD) drought was compared with that of irrigated (I) and unirrigated (NI) controls. Mobile shelters were used to exclude rain from ED plots during June and July, and LD plots during August and September, respectively, whereas outside these periods the ED and LD plots were irrigated as necessary.The ED treatment affected the fibrous roots severely. Many of the roots in the top 60 cm of soil died and development of the root system below this depth was slow. Expansion of the leaf canopy slowed, radiation interception was reduced and the rate of water use fell from about 1·2 times to 0·6 times Penman potential transpiration rate. The LD treatment, which was imposed when the fibrous root system was already extensive, had little effect on the fibrous roots except in the top soil. The accessible soil water was quickly depleted and the resulting stress was accompanied by earlier senescence of leaves. The rate of converting intercepted light to crop dry matter was reduced in both treatments. However, the ED treatment was the most detrimental because the amount of light intercepted in the months of highest radiation was greatly reduced owing to the restricted leaf cover. The relative effects on growth are reflected in the final sugar yields which were 8·7, 10·5, 9·9 and 12·0 (±0·30) t/ha in the ED, LD, NI and I treatments respectively.More of the deep soil water was used in the drought-affected plots (particularly LD) than in the irrigated controls. Maximum depths of water extraction were 140–150 cm in ED and I plots and > 170 cm in LD plots. The highest uptake rates per unit length of root (20–40 μl/cm per day) were measured in the deepest part of the root system. At all depths, uptake rates declined as the soil dried. After correcting for overestimated water use where necessary, the ratios of final dry matter and sugar yields respectively to season-long water use (June–October) were close to 1·4 and 0·8 t/ha per 25 mm for all four treatments.

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