South-East Queensland’s Fertigation Project Wraps Up

The Dairying Better ‘n Better program’s on-farm fertigation demonstration has finished, following a second year of monitoring.

The project was undertaken in the 2017 and 2018 ryegrass seasons at McInnes Brothers dairy farm at Harrisville, in south east Queensland. Monitoring was undertaken in the two consecutive years under irrigated, grazed, ryegrass to compare fertigation against traditional broadcast methods of applying nitrogen fertiliser on a south-east Queensland dairy farm. A centre pivot irrigation system was used in the project.

One quarter of the pivot area was fertilised after grazing with Easy N liquid fertiliser, and one quarter was fertilised with broadcasted urea as a comparison. The Easy N liquid fertiliser was purchased in 1,000L shuttles for this trial. An EcoDoseTM Fertigation System injector pump was purchased for the trial. Pat Daley, Irrigation Agronomist from Daley’s Water Service Pty Ltd, provided the advice and support for the purchase, installation and use of the fertigation system.

Soil moisture monitoring equipment (EnviroPro SDI 12 unit with a tipping bucket) was installed in each quarter to monitor irrigation and rainfall. Pasture dry matter was measured before and after grazing, and results indicated that the fertigation quarter was slightly ahead on pasture growth. Pasture dry matter yield was measured pre and post grazing to compare the two systems. Soil moisture monitoring equipment was installed to assist with irrigation scheduling, and fertiliser and irrigation events were recorded.

Benefits of the fertigation system included labour and fuel savings, which then lead on to cost savings on repairs and maintenance of machinery.  The liquid fertiliser is immediately available to the plants and can be distributed more evenly (provided the irrigation system has an even distribution uniformity) compared with granular fertilisers. Applying smaller amounts more often enables a more optimum growth rate, and liquid fertilisers aren’t as volatile, reducing potential losses to the atmosphere.

Considerations prior to purchase include upfront setup costs, and uniformity of application is only as good as the DU of the irrigation system, therefore need a low pressure system with good DU. In times of extended wet weather may still need a spreader to avoid unnecessary irrigation applications (and for application of nutrients other than nitrogen)

Observations made during the project included:

  • The EcoDoseTM fertigation pump was relatively inexpensive to purchase.

  • The fertigation quarter was less labour intensive than the broadcasted quarter.

  • Managing the soil moisture profile with the assistance of soil probes was effective. Grazing management is a key factor of a cost effective ryegrass season.

  • Getting the right advice upfront when considering fertigation should ensure that the right size injector unit is purchased.

  • Soil testing prior to planting highlighted potassium deficiencies, if not corrected there may have been an adverse effect on pasture growth.

  • No detrimental effects were observed to applying nitrogen through the pivot, smaller amounts of nitrogen were applied regularly as opposed to one big application.

  • A comparison of the true cost of each option demonstrates that buying in bulk (setting up a bulk storage tank holding 19,000L) will generally be more cost effective than the constant purchase of 1,000L shuttles.

In 2017 the project was funded through the Australian Government’s National Landcare Programme, and in 2018 was funded through the Dairy and Fodder Water for Profit program. The project was delivered by the Dairying Better ‘n Better program, a joint initiative of Queensland Dairyfarmers’ Organisation and Subtropical Dairy, with support from the Dairy and Fodder Water for Profit program.