Reclamation of saline clay soils -
A manual for the Horizontal Leaching Technique
The Horizontal leaching technique, described in the manual, enables excess salt to be removed from clay soils in a relatively short period. It is particularly intended for salt-affected, heavy clay soils of more than 1m depth and with a permeability of less than 0.1m/day. Such soils are commonly found in irrigated plains in arid and semi-arid countries, and suffer from rapid swelling when water is applied to them. The technique has been developed from field studies, carried out on saline lands in Egypt, and Turkey and Jamaica.
Background
Clay soils are potentially very fertile, but the removal of excess salts in them has presented severe technical difficulties, and until now there has been no suitable approach for reclaiming heavy soils. The technique, described in the manual, therefore provides an approach by which land reclamation agencies in arid and semi-arid countries can undertake the reclamation of saline clay soils. The main application of the technique is in the mechanised farming sector since it requires the use of heavy tractors and subsoilers. In common with most irrigation projects, fields need to be relatively large (minimum 0.5 hectare) and fairly flat (less than 1% slope).

The manual
The manual describes the horizontal leaching technique. The procedure is a rapid and practical method that enables land reclamation engineers to restructure clay soils before leaching to remove the soil salts. The applied water and the removed salts are then conveyed away from the area via a drainage network.

What it covers
The manual has been produced to:

  • Assist potential users to assess whether the technique is suitable for their particular salinity problem.
  • Provide sufficient technical information for users to implement the method.

    The guide takes the user through the four main activities required for the practical application of the horizontal leaching technique:

    1) Assessment of site suitability and pilot testing of methodology

    		•  
    2) Site preparation
    3) Water application procedures
    4) Monitoring and assessment

    The manual also contains detailed appendices on relevant issues that must also be considered:

    • Soil salinity
    • Water and salt movement in clay soils
    • Causes of salinity
    • Review of clay soil reclamation techniques
    • Converting laboratory salinity measurements to plot-scale salt balances
    • Estimating soil hydraulic conductivity and machinery specification
    • Saline-sodic soils.

    Contributors
    HR Wallingford Ltd, UK; Institute of Irrigation & Development Studies, University of Southampton UK; The Sugar company of Jamaica Ltd.

    Intended users
    The manual is intended for use by agricultural engineers, agronomists or soil scientists involved in the operation and management of irrigated agriculture on clay soils.

    Armstrong, ASB; Hughes, EJ; Rycroft, DW; Tanton, TW; Pearce, GR and Abbott, CL, 1996. Reclamation of saline clay soils - A manual for the Horizontal Leaching Technique. University of Southampton, UK, in association with HR Wallingford, UK. ISBN: 1 898485 03 8.

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