Making The Most Of Saline Irrigation Water

Saline irrigation water can make crop production completely unviable, yet some South African farmers are overcoming this challenge to achieve results that go far beyond expectations. Glenneis Kriel reports.

- Glenneis Kriel

FAST FACTS

High soil and water salinity negatively affects production and the soil.

In deep soil, salts can be leached to lower concentrations with water.

Drip irrigation can help reduce the effect of saline water on production.

High water salinity is one of the greatest constraints in crop production. It causes a build-up of salts in the root zone which, in turn, can reduce yield and even result in crop failure, depending on the plants’ sensitivity.

Chris Malan, agronomy manager at Netafim, explains that excess salinity in the root zone negatively affects water uptake of a plant by increasing the osmotic strength of the soil solution. Plants, in effect, have to work harder to absorb water, leaving them with less energy to grow and produce fruit.

Sodium and chlorine are two elements commonly associated with salinity. A high chloride level may cause toxicity, scorching the roots and leaves, whereas excessive sodium damages the soil structure by binding with clay particles. Sodium not only inhibits uptake of other nutrients, but also results in poor water infiltration, surface crusting and reduced hydraulic conductivity, according to Malan.

MANAGING SALINITY AND IRRIGATION

To manage salinity, a farmer first needs to have his or her soil and water analysed to identify the cause of the salinity and the extent of the problem. High sodium and chloride levels are the biggest concerns in South Africa.