Soil salinization

The Savu Islands are dry for large parts of the year, due to hot winds blowing from the Australian continent. Most rain falls during the months from November to March, with little or no rain falling for the months of August to October. The main crop is corn, which is planted in late November, December or early January. Rice and mung beans are usually planted in January, when the soil is well saturated by rain. However, when conditions are drier than usual, planting has to be delayed. Often, farmers are misled by initial rains that offer promise but then cease.

However, rain alone may not be enough, because dry weather often leads to soil becoming contaminated by salt. This occurs because farmers trap water in their fields, allowing it to evaporate instead of flowing downstream. Although the water supply is considered fresh, it does contain very small amounts of salt, which it collected from the land it drained through, before reaching the farm. When the water evaporates from the farm, the salt is left behind in the soil. If this continues for long periods, without a solid rain to flush the salt further downstream, the salt slowly builds in concentration. Eventually, the soil becomes so contaminated by salt that plants cannot thrive, even if it does rain.

This article explains what salinization is, how to recognize it and how to deal with it. Part 1 describes the signs that indicate that there is too much salt in the soil and why salt affects plants in this way. It also suggests what can be done in the short term to remove salt from the soil. Part 2 presents a case study involving an ecological farming system that helps to prevent salinization occurring. The appendix includes a list of plants grouped according to their sensitivity to salt in the soil.

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Copyright © 2006 Ina Tali/Francesca Von Reinhaart

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