+ Site Statistics
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on LinkedInFollow on LinkedIn

+ Translate

The pressure response of the soil water sampler and possibilities for simultaneous soil solution sampling and tensiometry

The pressure response of the soil water sampler and possibilities for simultaneous soil solution sampling and tensiometry

Soil Science 154(3): 171-183

A soil water sample may be viewed as a tensiometer with a relatively slow response time. An expression for the pressure response of a fixed volume soil water sampler is derived. The criterion for determining when the gage pressure within the soil solution sampler may be used to infer the soil water matric potential in the vicinity of the sampler tip depends upon the cup-soil conductance (K*), the sampler's pressure (Po) associated with the vacuum set on the sampler, and the elapsed time since application of the vacuum (t). It was found that the dimensionless time given by [PoK*t] is greater than about 5, the sampler pressure may be used in determinations of matric and/or pressure potentials (.PSI.), or more generally the tensiometer pressure potential which also includes that influence of the soil air pressure potential. The essential difference in the response of tensiometers and soil water samplers arises from differences in the nature of the instrument sensitivities (S*). In the "tensiometer-limited" response, the standard tensiometer approaches an equilibrium reading via an exponential decay of the initial pressure disturbance characterized by a response time .tau. = (K*S*)-1, where K* and S* are, in principle, constant for a particular equilibration. A nonexponential decay response of the soil water sampler on the other hand arises from the time-dependant S* and K*. Only the time-dependent S* effect is considered here. The S* in the case of soil water sampler is equal to P (Vgas)-1, where P and Vgas are the instantaneous sampler gas pressure and gas phase volume, respectively. Under conditions where the ratio P(Vgas)-1 undergoes considerable change during the course of soil water collection, large deviations from the exponential decay response occur. Conversely, when only minor variations in P(Vair)-1 are experienced, soil water sampler pressure response approaches that of the exponential decay. The time-weighting of the collected soil solution is discussed. One particular instrument design suited for simultaneous tensiometry and soil water sampling is described. Field data illustrating cases where soil and water sampler pressures may and may not be used to obtain .PSI. data are provided. The possible use of this type of device for both soil solution sampling and tensiometry in deep (> 10 m) profiles is explained.

(PDF emailed within 0-6 h: $19.90)

Accession: 002526152

Download citation: RISBibTeXText

DOI: 10.1097/00010694-199209000-00001

Related references

Use of a looped hollow fiber sampler as a device for non-destructive soil solution sampling from the heterogeneous root zone. Soil Science and Plant Nutrition 39(4): 737-743, 1993

Possibility of different soil sampling techniques with automated soil sampler. Communications In Soil Science & Plant Analysis. 27(3-4): 211-212, 1996

Possibility of different soil sampling techniques with automatic soil sampler. Communications in Soil Science & Plant Analysis 27(5-8): 1779-1794, 1996

Calibration of a neutron probe: soil sampling and tensiometry. Revista de Ciencias Agroveterinarias 2(1): 58-67, 2003

Monitoring drainage solution concentrations and solute flux in unsaturated soil with a porous cup sampler and soil moisture sensors. Ground Water 32(3): 356-362, 1994

Implementation of automated infiltration soil water sampler; application to unsaturated soil in dune fields. Eos, Transactions, American Geophysical Union 84(46, Suppl, 2003

Effect of soil water content at the time of application on herbicide content in soil solution extracted in a pressure membrane apparatus. Weed Research: 201-206, 1979

Optimizations in the solid phase soil solution plant system i. effect of osmotic pressure of the soil solution on wheat growth. Pochvoznanie Agrokhimiya i Rastitelna Zashtita 22(1): 14-22, 1987

DenNit - experimental analysis and modelling of soil N2O efflux in response on changes of soil water content, soil temperature, soil pH, nutrient availability and the time after rain event. Plant and Soil 272(1/2): 349-363, 2005

The influence of soil water content and soil structure on the chemical composition of the mobile soil solution. Mitteilungen der Deutschen Bodenkundlichen Gesellschaft 59(1): 163-166, 1989

Gradients in soil solution composition between bulk soil and rhizosphere - in situ measurement with changing soil water content. Plant and Soil 258(1/2): 307-317, 2004

Method of soil water sampling under pressure. Landbouwkundig Tijdschrift 86(7): 175-177, 1974

Simultaneous water tensions at different depths in the soil. An evaluation of several annual cycles of water tension readings. discussion of possibilities to forecast starting point for irrigation. Zeitschrift fur Kulturtechnik und Flurbereinigung: 18 (4) 213-222, 1977

Possibilities of potassium concentrate estimate in soil solution from the soil test Mehlich 2 and KVK-UF. Rostlinna Vyroba 43(1): 1-5, 1997

Soil solution of submerged soil. Part I. Methods of sampling and analysis. Journal of the Science of Soil and Manure, Japan 44(7): 241-245, 1973