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Movement of water in restructured saline and sodic clay topsoils under a rainfall simulator

Movement of water in restructured saline and sodic clay topsoils under a rainfall simulator
Movement of water in restructured saline and sodic clay topsoils under a rainfall simulator
The nature of water movement through freely draining saturated and field moist aggregates of saline sodic clay topsoil was studied using 200 mm long columns filled with soil aggregates. Water containing tritium as a tracer was supplied either by means of rainfall simulator or directly to the surface of the soil under a negative pressure head of 500 Pa.

The proportion of macropore and micropore flow was elucidated. The micropores of the aggregates were shown to convey very little water (0.013 mm h?) and hence, even at low rainfall intensities water was expected to move down through the macropores. In practice, at a low water application rate of 0.6 mm h? drainage did not begin from the base of the column until the aggregates had become fully saturated due to mobile water in the macropores being continuously absorbed into the micropores. The results, however, indicated that extensive rapid bypassing does occur at medium and high rainfall intensities ( > 2.3 mm ?) , with the result that a large proportion of the water falling on the unsaturated plough layers of clay soils is drained before the topsoil becomes saturated.

The soil absorbed water continuously during the application of the equivalent of a wetter than average winter's rain (400 mm), the rate of absorption being directly proportional to the amount of salt leached.Tritium, used as a tracer, was found to be preferentially absorbed by the clay during the leaching process, the concentration in the soil water rising to 1.8 times that of the applied tritiated water.

drainage, leaching, saline, sodic, clay
0378-3774
255-265
Tanton, T.W.
0f6a361e-394f-4cfc-94a6-5311442ae366
Rycroft, D.W.
52d0fc1b-8b87-41e6-be63-dd3477448d2f
Armstrong, A.S.B.
265c0b35-9c7c-4f95-b62c-7aafc011da85
Tanton, T.W.
0f6a361e-394f-4cfc-94a6-5311442ae366
Rycroft, D.W.
52d0fc1b-8b87-41e6-be63-dd3477448d2f
Armstrong, A.S.B.
265c0b35-9c7c-4f95-b62c-7aafc011da85

Tanton, T.W., Rycroft, D.W. and Armstrong, A.S.B. (1996) Movement of water in restructured saline and sodic clay topsoils under a rainfall simulator. Agricultural Water Management, 29 (3), 255-265. (doi:10.1016/0378-3774(95)01208-7).

Record type: Article

Abstract

The nature of water movement through freely draining saturated and field moist aggregates of saline sodic clay topsoil was studied using 200 mm long columns filled with soil aggregates. Water containing tritium as a tracer was supplied either by means of rainfall simulator or directly to the surface of the soil under a negative pressure head of 500 Pa.

The proportion of macropore and micropore flow was elucidated. The micropores of the aggregates were shown to convey very little water (0.013 mm h?) and hence, even at low rainfall intensities water was expected to move down through the macropores. In practice, at a low water application rate of 0.6 mm h? drainage did not begin from the base of the column until the aggregates had become fully saturated due to mobile water in the macropores being continuously absorbed into the micropores. The results, however, indicated that extensive rapid bypassing does occur at medium and high rainfall intensities ( > 2.3 mm ?) , with the result that a large proportion of the water falling on the unsaturated plough layers of clay soils is drained before the topsoil becomes saturated.

The soil absorbed water continuously during the application of the equivalent of a wetter than average winter's rain (400 mm), the rate of absorption being directly proportional to the amount of salt leached.Tritium, used as a tracer, was found to be preferentially absorbed by the clay during the leaching process, the concentration in the soil water rising to 1.8 times that of the applied tritiated water.

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More information

Published date: February 1996
Keywords: drainage, leaching, saline, sodic, clay

Identifiers

Local EPrints ID: 73998
URI: http://eprints.soton.ac.uk/id/eprint/73998
ISSN: 0378-3774
PURE UUID: 107143c0-5749-48b9-a8e4-23e0f2acff80

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Date deposited: 11 Mar 2010
Last modified: 13 Mar 2024 22:24

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Contributors

Author: T.W. Tanton
Author: D.W. Rycroft
Author: A.S.B. Armstrong

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