Smart irrigation decisions to maximise productivity
As dairy farmers prepare for spring following a challenging drought season in large parts of southern mainland Australia, making informed irrigation decisions is critical to maximising productivity and managing risk.
Dairy Australia’s recent webinar, part of its drought support series, hosted by Dairy Australia’s Soils & Irrigation Lead Cath Lescun, brought together experts to share practical strategies and tools to help farmers navigate irrigation planning with confidence.
Start with system readiness
Before the irrigation season begins, we support and remind farmers to ensure their systems are fully operational and emphasise the importance of pre-season checks, including pumps, sprinklers, hoses, and control units. Uniform water application and correct system pressure are essential for optimal performance. Dairy Australia offers downloadable checklists for various irrigation systems - travelling irrigators, centre pivots, and surface irrigation - through its Smarter Irrigation for Profit 2 project.
Timing is everything
Nick O’Halloran, Irrigation Extension Officer with Agriculture Victoria, highlighted the importance of accurate irrigation scheduling, especially during spring - the most productive season for pasture growth. Delaying irrigation can result in significant dry matter losses, with studies showing up to 60 kg/ha lost per day of delay. Moreover, stressed pastures may take weeks to recover, compounding productivity losses.
To avoid this, Nick encouraged farmers to monitor evapotranspiration (ET) rates – an indication of daily crop water use. Tools like extensionAUS and Agriculture Victoria’s interactive ETo irrigation scheduling tool (also known as the ETo Map) provide location-specific data, including rainfall information, to help farmers estimate water demand and plan irrigation accordingly.
Understand farm soil’s water holding capacity
Effective irrigation scheduling relies on understanding how much water your soil can hold and how much of that water plants can actually use. This usable water is referred to as Readily Available Water (RAW) - it’s the moisture in the soil between when it is full and when it needs watering again. Different soil types have varying RAW levels. For example loamy soils (which are a good mix of sand, silt and clay) typically hold more water than sandy or heavy clays soils. How deep plant roots grow also matters - shallow-rooted pastures may only utilise water from the top 30–50 cm of soil.
By calculating RAW and tracking ET, farmers can maintain a water balance and determine when irrigation is needed. Tools like IrriPasture help automate this process, offering crop-specific recommendations based on soil type, weather data, and crop water use reducing risk and improving outcomes.
Prioritise paddocks and crops
When water is limited, strategic prioritisation is key and important to focus on paddocks with healthy plant populations, minimal weed pressure, and good fertility. Crops like cereals can offer high returns from a single well-timed irrigation. Spring irrigation generally yields the highest water productivity - up to 2.5 tonnes of dry matter per megalitre - making it the best time to invest water resources.
Avoid the green drought trap
Cath Lescun shared a case study from Tasmania where poor scheduling and system performance led to a “green drought” - pastures appeared healthy but were under-irrigated, resulting in a five tonne/ha dry matter loss over five months. At a conservative fodder value of $250/tonne, this equated to a $125,000 opportunity cost across 100 hectares. Ensuring systems can deliver adequate water and starting irrigation on time are crucial to avoiding such losses.
As water prices rise and climate variability increases, making smarter irrigation decisions is not just beneficial - it’s essential. With the right tools, knowledge, and support, dairy farmers can optimise water use, boost productivity, and build resilience for the seasons ahead.