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Rehabilitation of saline environments

Under natural conditions, saline soils can carry salt-tolerant vegetation including trees, shrubs and grasses. The vegetation provides forage for sheep, goats and camelidae while the shrubs also provide fuelwood. Overgrazing and excessive removal of fuelwood have denuded numerous saline areas.

In other cases hydrological changes induced by mismanaged irrigation and drainage may cause the destruction of vegetation. In some cases, poor irrigation practices have produced excessive soil salinization and the consequent disappearance of the original non salt-tolerant vegetation. In all cases action is required to "revegetate" the denuded saline areas.

Salt-tolerant shrubs (halphytes)

Three major groups of halophytic shrubs can be used:

- Samphires which include the Salicornia, Athrocnemum, Halocnemum, Halosarcia and Allenrolfea genera - found on very saline and often water logged ground;

- Chenopods which include the Atriplex, Chenopodium, Rhagodia and Halimione genera. These leafy shrubs are highly salt-tolerant but are found in less waterlogged areas than samphires;

- Prickly Saltworts and Bluebushes which include the Salsola, Kochia, Maireana, Sarcobatus, Suaeda and Euchylaena genera. Their tolerance to salt and waterlogging varies from levels similar to samphires and chenopods to much lower levels.

The selection of plants to be used is therefore essential for the successful rehabilitation of saline environments. This selection needs to be made on the basis of the environmental parameters of climate, salinity and site hydrology (depth of water table and water flow).

Land preparation

The land needs to be prepared with two objectives in mind. The first is to control the groundwater where this leads to salt accumulation on the soil surface. This can either be done by drainage or by tracing deep furrows and ridges. The second objective is to force the salt down the soil instead of having it accumulate on the surface. This can be clone by selecting niches where the salt is naturally leached or by establishing man-made niches on which to plant seedlings or sow seeds.

The diagram below illustrates the niche technique developed in Australia for the planting of salt-tolerant shrubs in saline areas. The technique consists of tracing a furrow and a ridge and of establishing a niche on the ridge. niche covered with straw land level ridge.

Figure 2. Land preparation

The best method of preparing the land a given saline environment needs to be based on a careful examination of soil conditions. The following principles need to be observed:

- Minimization of the risk of surface water saturation, flooding and erosion by protecting the area under treatment with appropriate soil conservation works;

- Reduction of salt in the topsoil by breaking this up to facilitate leaching by rainwater;

- Prevention of wind erosion.

The rehabilitation of the plant cover on denuded saline soils by using shrubs helps to produce forage and fuelwood, to reduce runoff and erosion, to raise the groundwater level, to improve the landscape and to restore the wildlife habitat of a region.

April 1993

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