The role of lateral stresses on soil water relations in swelling clays

Soil Research ◽  
1986 ◽  
Vol 24 (4) ◽  
pp. 457 ◽  
Author(s):  
BG Richards
Keyword(s):  
Soil Water ◽  
Water Relations ◽  
Soil Water Potential ◽  
Three Dimensional ◽  
Soil Physics ◽  
Swelling Soils ◽  
Simple Theories ◽  
Swelling Clays ◽  
Swelling Soil ◽  
Stress States

The moisture characteristic of a swelling soil is the result of complex interaction between the soil water potential and imposed mechanical stresses. This can give rise to soil water profiles which cannot be interpreted by soil water theories for non-swelling soils. Agricultural soil physics has been concerned primarily with highly structured surface soils, and has developed simple theories for the effects of stress on soil water relations in swelling soils. These simple theories ignore the effect of lateral stress in the soil. Civil engineers, on the other hand, dealing mainly with less complex soils at depth, have developed more complex theories for the effect of three-dimensional stress states on soil water relations. This paper shows how the effect of three-dimensional stress can and should be included in soil water studies of swelling soils, and gives examples to demonstrate the possible magnitude of such effects.

scholarly journals Stem girth changes in response to soil water potential in lowland dipterocarp forest in Borneo: a time-series analysis

2020 ◽  
Author(s):  
D. M. Newbery ◽  
M. Lingenfelder
Keyword(s):  
Time Series ◽  
Soil Water ◽  
Water Relations ◽  
Time Series Data ◽  
Soil Water Potential ◽  
Series Data ◽  
Relative Depth ◽  
Ecological Processes ◽  
Flux Dynamics ◽  
Negative Relationships

AbstractTime series data offer a way of investigating the causes driving ecological processes. To test for possible differences in water relations between species of different forest structural guilds, daily stem girth increments (gthi), of 18 trees across six species were regressed individually on soil moisture potential (SMP) and temperature (TEMP), accounting for temporal autocorrelation (in GLS-arima models), and compared between a wet and a dry period. Coefficients were estimates of response in gthi to increasing SMP or TEMP. The best-fitting significant variables were SMP the day before and TEMP the same day. The first resulted in a mix of positive and negative coefficients, the second largely positive ones. Negative relationships for large canopy trees can be interpreted in a reversed causal sense: fast transporting stems depleted soil water and lowered SMP. Positive relationships for understorey trees meant they took up most water at high SMP. The unexpected negative relationships for these understorey trees may have been due to their roots accessing deeper water supplies (SMP being inversely related to that of the surface layer), this influenced by competition with larger neighbour trees. A tree-soil flux dynamics manifold may have been operating. Patterns of mean diurnal girth variation were more consistent among species than, but weakly related to, time-series coefficients, suggesting no simple trait-based differentiation of responses. Expected differences in response to SMP in the wet and dry periods did not support a previous hypothesis for drought and non-drought tolerant understorey guilds. Trees within species showed highly individual responses. Time-series gthi-SMP regressions might be applied as indicators of relative depth of access to water for small trees. Obtaining detailed information on individual tree’s root systems and recording SMP at many depths and locations are needed to get closer to the mechanisms that underlie complex tree-soil water relations in tropical forests.

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.

Water relations of winter wheat: 2. Soil water relations

1978 ◽  
Vol 91 (1) ◽  
pp. 103-116 ◽  
Author(s):  
P. J. Gregory ◽  
M. McGowan ◽  
P. V. Biscoe
Keyword(s):  
Winter Wheat ◽  
Water Potential ◽  
Soil Water ◽  
Water Relations ◽  
Unit Length ◽  
Soil Water Potential ◽  
Rooting Depth ◽  
Wheat Crop ◽  
Deep Roots ◽  
Volumetric Soil Water Content

SummaryVolumetric soil water content and soil water potential were measured beneath a winter wheat crop during the 1975 growing season. Almost no rain fell between mid-May and mid-July and the soil dried continuously until the potential was less than – 20 bars to a depth of 80 cm. Evaporation was separated from drainage by denning an ‘effective rooting depth’ at which the hydraulic gradient was zero.Rates of water uptake per unit length of root (inflow) were calculated for the whole soil profile and for individual soil layers. Generally, inflow decreased throughout the period of measurement from a maximum of 2·5 × 10–3 to a minimum of 0·66 × 10–3 ml water/cm root/day. Values in individual layers were frequently higher than the mean inflow and the importance of a few deep roots in taking up water during a dry season is emphasized. A similar correlation between inflow and soil water potential was found to apply for the 0–30 cm and 30–60 cm layers during the period of continual soil drying. This relationship represents the maximum inflow measured at a given soil water potential; actual inflow at any particular time depends upon the interrelationship of atmospheric demand, soil water potential and the distribution of root length in the soil.

scholarly journals Eucalyptus sp. seedling response to potassium fertilization and soil water.

2008 ◽  
Vol 18 (1) ◽  
pp. 47 ◽  
Author(s):  
Paulo César Teixeira ◽  
José Leonardo Moraes Gonçalves ◽  
José Carlos Arthur Junior ◽  
Cleci Dezordi
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Leaf Area ◽  
Water Deficit ◽  
Water Relations ◽  
Transpiration Rate ◽  
Dry Matter ◽  
Soil Water Potential ◽  
Eucalyptus Grandis ◽  
Eucalyptus Urophylla

A considerable portion of Brazil‘s commercial eucalypt plantations is located in areas subjected to periods of water deficit and grown in soils with low natural fertility, particularly poor in potassium. Potassium is influential in controlling water relations of plants. The objective of this study was to verify the influence of potassium fertilization and soil water potential (Ψw) on the dry matter production and on water relations of eucalypt seedlings grown under greenhouse conditions. The experimental units were arranged in 4x4x2 randomized blocks factorial design, as follow: four species of Eucalyptus (Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus camaldulensis and hybrid Eucalyptus grandis x Eucalyptus urophylla), four dosages of K (0, 50, 100 and 200 mg dm-3) and two soil water potentials (-0.01MPa and -0.1 MPa). Plastic containers with 15 cm diameter and 18 cm height, with Styrofoam base, containing 3.0 dm3 of soil and two plants per container were used. Soil water potential was kept at -0.01MPa for 40 days after seeding. Afterward, the experimental units were divided into two groups: in one group the potential was kept at -0.01MPa, and in the other one, at -0.10 MPa. Soil water potential was controlled gravimetrically twice a day with water replacement until the desired potential was reestablished. A week before harvesting, the leaf water potential (Ψ), the photosynthetic rate (A), the stomatal conductance (gs) and the transpiration rate were evaluated. The last week before harvesting, the mass of the containers was recorded daily before watering to determine the consumption of water by the plants. After harvesting, total dry matter and leaf area were evaluated. The data were submitted to analysis of variance, to Tukey's tests and regression analyses. The application of K influenced A, gs and the transpiration rate. Plants deficient in K showed lower A and higher gs and transpiration rates. There were no statistical differences in A, gs and transpiration rates in plants with and without water deficit. The addition of K reduced the consumption of water per unit of leaf area and, in general, plants submitted to water deficit presented a lower consumption of water.

Relative sensitivity of leaf elongation and stomatal conductance of cucumber plants to changes in leaf and soil water potentials

1995 ◽  
Vol 75 (4) ◽  
pp. 909-915 ◽  
Author(s):  
Jeffrey Melkonian ◽  
David W. Wolfe
Keyword(s):  
Stomatal Conductance ◽  
Root System ◽  
Soil Water ◽  
Water Relations ◽  
Osmotic Adjustment ◽  
Soil Water Potential ◽  
Irrigation Scheduling ◽  
Leaf Water ◽  
Leaf Elongation ◽  
Split Root

Identification of drought-resistant cucumber genotypes and optimization of irrigation scheduling require an improved understanding of cucumber plant water relations. Stomatal conductance (ks), relative leaf elongation rate (RLER), and leaf water relations were examined on greenhouse-grown cucumber (Cucumis sativus L. 'Marketmore 80') over two drought cycles. Water was withheld from the entire root system of cucumber plants and ks, leaf length, leaf water (ΨL) and osmotic potential, and soil matric potential were measured periodically. In both drought cycles, ks decreased before, and RLER decreased after predawn ΨL began to decline. No osmotic adjustment was found after one drought cycle and slight osmotic adjustment (−0.14 MPa) was observed in expanding leaves after a second drought cycle. Evidence for a nonhydraulic root signal in cucumber was examined in split-root experiments. ΨL was similar in plants which received water to one (stress treatment) or to both halves (control treatment) of the root system. Stomatal conductance and RLER remained at control levels as soil water potential (Ψ soil) around half the root system declined to −0.25 to −0.30 MPa. No convincing evidence for effects of root signals on ks and RLER at lower Ψ soil was observed. Key words:Cucumis sativus L., leaf elongation, osmotic adjustment, split root, stomatal conductance, water stress

scholarly journals Water Relations and Abscisic Acid in Pot-grown Strawberry Plants under Limited Irrigation

2009 ◽  
Vol 134 (5) ◽  
pp. 574-580 ◽  
Author(s):  
Nauja Lisa Jensen ◽  
Christian R. Jensen ◽  
Fulai Liu ◽  
Karen K. Petersen
Keyword(s):  
Abscisic Acid ◽  
Water Potential ◽  
Soil Water ◽  
Water Relations ◽  
Root Zone ◽  
Water Vapor Pressure ◽  
Xylem Sap ◽  
Soil Water Potential ◽  
Significant Difference ◽  
Irrigation Treatments

We investigated the effect of full irrigation (FI), deficit irrigation (DI), partial root zone drying (PRD), and nonirrigation (NI) on soil and plant–water relations, leaf stomatal conductance (gs), and abscisic acid (ABA) concentration in the xylem sap ([ABA]xylem) of pot-grown strawberry plants (Fragaria ×ananassa cv. Honeoye) in a greenhouse experiment. The DI and PRD treatments, irrigated with 70% of the volume of FI, reduced soil water content (θ), whereas crown water potential (ψcrown), leaf water potential (ψleaf), and gs were only significantly reduced from 11 to 15 days after initiation of irrigation treatments. Although [ABA]xylem was not significantly affected by the DI and PRD treatments, the NI plants increased [ABA]xylem, which coincided with decreased ψcrown, ψleaf, and gs 3 to 4 days after withholding irrigation. When ψcrown dropped below a critical value of −0.4 MPa, [ABA]xylem was linearly correlated with ψcrown. The gs tended to decrease as a function of [ABA]xylem, but gs was also affected by the water vapor pressure deficit (VPD) of the air. It is concluded that we did not observe a significant difference between strawberry plants grown in PRD and DI because ψcrown had to be below −0.4 MPa and soil water potential (ψsoil) had to be below −0.25 MPa before [ABA]xylem increased, these values were only reached toward the end of the experimental period (11–15 days after initiation of irrigation treatments).

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.

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