Managing saline soils

Some improvements can be made to some of the damaged areas by establishing good soil drainage and ensuring that the quality of the incoming water is of satisfactory standard. It is important to create a system of irrigation that takes in several factors. These should include adequate soil drainage, including where possible, robust schemes of artificial drainage so that the water does not become trapped in the upper layers of the soil. It is essential that water tables are lowered so that only limited amounts of salt enter the soil layers near enough to the surface to be evaporated.

It is even more difficult to manage sodium rich soils particularly if they are heavy clayey soils because sodium will have degraded much of the soil structure. Revitalising soil structure over the soil depth in which roots operate is difficult and costly. To improve these soils it is first necessary to remove much of the excessive amounts of sodium. The favoured method for this is to add significant quantities of gypsum to the soil, which when it breaks down will exchange much of the sodium by calcium, a much more user-friendly element. The sodium then needs to be leached out of the system, a process that will require large amounts of water. In addition to this the soil structure will need to be improved which will involve deep cultivation but on heavy clayey soils this may be difficult to do successfully.

It is a major problem to reclaim saline soils. The cost of doing so is prohibitive and the economics of any proposed land use will rarely sustain the cost of desalinisation. This somewhat depressing fact is evident at a time when more and more land, particularly that associated with irrigation, has become afflicted by salinity. More attention needs to be paid to establishing well based protocols for any further irrigation to ensure that it is conducted according to a strong code of practice. This is well overdue and the penalties so far have been great. In most countries there is continued ignorance of the dangers of irrigation and it is allowed to continue piecemeal and without adequate advice. Permanent and proper control actions are required. Adequate soil and water conservation practices need to be promoted to prevent further major damage to land and the undesirable economic, ecological and social consequences of poor land management.