Review
Achieving a salt balance—Should it be a management
objective?
T. Thayalakumaran
a,
*
, M.G. Bethune
a
, T.A. McMahon
b
a
Primary Industries Research Victoria, Department of Primary Industries, Tatura, Victoria, Australia
b
Department of Civil and Environmental Engineering, University of Melbourne, Australia
Contents
1. Introduction. . . . . ............................................................................... 2
2. Salt balance concept . . . . . ........................................................................ 2
3. Application of the salt balance . . . . ................................................................. 3
3.1. Representative hydrological volume . . . . . . ...................................................... 3
3.1.1. Root-zone RHV . . . . . ................................................................. 3
3.1.2. Farm and sub-surface drainage system RHV ............................................... 3
3.1.3. Irrigation region RHV ................................................................. 4
agricultural water management 92 (2007) 1–12
article info
Article history:
Accepted 3 May 2007
Keywords:
Salt balance
Drainage disposal
Salinisation
Downstream impacts
abstract
The long-term sustainability of irrigated agriculture depends on protecting land and water
resources from salinity. Generally, a favourable salt balance (mass out ! mass in) is con-
sidered necessary for sustainable irrigated agriculture. This concept has been used in
irrigated agricultural systems to satisfy varying objectives. In this paper we discuss the
application of the salt balance concept at various spatial scales including root-zone, farm,
irrigation-region and catchment scales. The relationship between the spatial scales, the
governing processes and the time to reach salt equilibrium is discussed. Recognised
management options for achieving a favourable salt balance are questioned with regard
to (a) the uncertainties in salt balance estimation caused by a mismatch of surface and sub-
surface hydrological boundaries, (b) the large subsoil salt store, (c) impacts on downstream
water quality and (d) the implications of achieving a favourable salt balance. It is argued that
aiming for a favourable salt balance is critical and achievable at a root-zone scale for
maintaining production. For scales larger than the root-zone, managing for a favourable salt
balance is often not practical nor necessarily beneficial. Management of the water balance is
more important at the larger scale to prevent the formation of a shallow watertable and the
remobilising of salt stored in the subsoil. The management of the water balance is likely to
be more effective in managing productivity and the off-site impacts of irrigation than
managing a farm or regional salt balance.
Crown Copyright # 2007 Published by Elsevier B.V. All rights
reserved.
* Corresponding author at: Department of Primary Industries, Ferguson Road, Tatura, Victoria 3616, Australia. Tel.: +61 3583355268;
fax: +61 358335299.
E-mail address: Thabo.kumaran@dpi.vic.gov.au (T. Thayalakumaran).
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/agwat
0378-3774/$ – see front matter. Crown Copyright # 2007 Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.agwat.2007.05.004