Maintaining Soil Health Under Irrigation

Many farmers have a deep knowledge and understanding of their property’s potential and susceptibilities and its capacity to support various agricultural enterprises. In recent years however, there has been a considerable expansion of irrigation schemes in Tasmania, and farmers have been presented with opportunities to convert areas of their operations from dryland production to irrigated.  With the new opportunities for production comes different challenges in managing a range of vulnerable soils.  

Successful irrigated agriculture is not simply a matter of investing in irrigation and turning on the water. If not properly designed for the soil type on which it is operating, carefully maintained and managed, farm irrigation systems can be costly to run and damaging to the soil resource, far outweighing the benefits of any increased production that may result. 

Managing soils under irrigation requires careful consideration of soil properties like salinity, sodicity, structure, and drainage.  

This project has developed a series of factsheets to help increase farmers knowledge about the risks of salinity, sodicity, and waterlogging in irrigated landscapes.  

Irrigation Salinity

Irrigation salinity refers to the accumulation of soluble salts within the soil profile of irrigated land. Irrigation can change the natural hydrology of a landscape through the application of large volumes of water to a specific area outside the usual rainfall pattern of the region (i.e. irrigation over summer in a 
climate with winter dominant rainfall).

For more information, download the Irrigation Salinity factsheet below

Soil Sodicity

Soil sodicity occurs when sodium (Na) ions attach to clay particles in the soil profile. A soil is considered ‘sodic’ when these sodium ions are present at an increased level (typically >6%) which begins to affect the soil structure, weakening the soil when it gets wet.

For more information, download the Soil Sodicity factsheet below

The risks associated with waterlogging and drainage as a potential solution

Agricultural soils work best with the right balance of solid particles, moisture and air, along with organic matter. When 
water replaces most of the air in the soil this balance is upset, and agricultural productivity will be impacted. We call these 
soils that are too wet “saturated” or “waterlogged”.

Waterlogging can cause:
• Poor plant health, reducing growth and yield, increasing 
disease risk and even causing plant death
• Nutrient loss through denitrification or leaching
• Softer soils that then become pugged, compacted and 
eroded

For more information, download the Land Drainage - Why, How and Who factsheet below

Drainage design options for maintaining waterlogging

Drainage planning involves several steps to ensure your installation gives you the most benefit, without creating 
problems for your neighbours or the environment. The first questions you will need to answer are:
• What type of drainage is most appropriate to fix my 
problem? 
• Where will the water go when it leaves the drained area?
• How do I decide what type of drainage is most appropriate 
to fix my problem? 

For more information, download the Drainage decision-making support factsheet