Early Mild Phase
Water Salinity Level
Low to Medium Salinity
These areas are often showing very high production even in very dry years due to the plants access to water in the rootzone. If left unmanaged they can quickly grow into large scalded areas, particularly with a medium salinity water table, as salt can rapidly find its way to the surface over the summer/autumn if no cover is established. However, if swift, targeted action is taken, then production losses and significant land degradation can be avoided altogether.
Discharge Zone Management
Often these areas begin as waterlogged zones after wet periods that retain emit moisture throughout the growing season and beyond. Letting these wet areas bare out and bake over summer can rapidly bring salt to the surface and rapid degradation. One strategy is to sow summer crops on these patches – even straight after winter crop harvest – such as sorghum and millet, to maintain cover and use water over the summer/autumn period and stop salt wicking to the surface. These crops can be cut prior to the following winter crop seeding, and will tend to regenerate or reshoot in the following seasons right where they are needed above the perched water table while it still exists. This can stop seep scalds forming, with minimal disruption to your normal cropping program.
Sow lucerne over and just around affected area to lower water table and prevent lateral spread of water table and seep. If small, scalded areas are forming then spread 10-15cm sand over these patches before sowing the lucerne. This will help it establish and keep the surface from accumulating salt. Maintain lucerne and crop through it with the paddock crop each year.
Interception Zone Management
Sow lucerne in a targeted strip of about 20m wide around the discharge zones as close as possible to the affected area. This will both intercept lateral water flows into the perched water table as well as directly lower it. Maintain lucerne and crop through it if required. While you may question the hassle of establishing lucerne, you must also consider the amount of highly productive land that is under threat, often much larger than first thought. Lucerne can be sown through and is quite adaptable to do its vital role within existing farming systems.
Recharge Zone Management
Any deep sand amelioration with ripping, spading, delving, claying and the mixing in of manures or other organic matter etc, resulting in higher water retention and plant water utilisation will have a positive impact on reducing recharge, but will not have as dramatic affect as the water interception achieved with deep rooted perennials.
If it works for your farming system and paddock and you get a season with favorable conditions, then establishing lucerne over a larger portion of the recharge zone will significantly increase the rate at which the perched water table dries up and ceases to be affected by high rainfall periods and events.