The first year of the fertigation trial running at McInnes Brothers farm at Harrisville has finished with some interesting findings. These were presented and discussed at a fertigation field day held in January.
About the Trial
The trial was run under a centre pivot in the 2017 autumn/winter months, under Aston ryegrass. One half of the centre pivot area was used for the trial, with one quarter (Q3) fertilised after grazing with Easy N liquid fertiliser, and the other quarter (Q4) fertilised with broadcast urea as a comparison. An Ecodose fertigation pump was purchased, at a cost of $2,900 (excl. GST) and installed at the pivot site, and the Easy N liquid fertiliser was purchased in 1,000L shuttles for this trial. Soil moisture monitoring equipment was installed with an Enviropro SDI 12 unit with tipping bucket installed in each quarter to monitor soil moisture content and in-crop rainfall for precision irrigation scheduling. Pasture dry matter yield was measured pre and post grazing using a C-Dax pasture meter to compare the two systems. Fertiliser and irrigation events were recorded.
Results from the Trial
Results of the on-farm trial demonstrated a production response in the pivot quarter that was fertigated compared to the quarter that was traditionally fertilised with broadcast granular urea*. The trial highlighted that even greater cost-benefits can be derived when the Easy N is purchased in bulk. For this trial, it was decided to purchase Easy N liquid fertiliser in 1,000 litre Intermediate Bulk Containers (IBC’s or ‘shuttles’) instead of going to the expense of bulk liquid storage in the early stages of the project. However, cost-benefit analysis has revealed that the cheaper price per litre of bulk Easy N will recover the extra cost of bulk storage set-up in the first ryegrass season, making it a wise investment choice.
Over the ryegrass season, bulk Easy N liquid fertiliser cost an extra 1 cent per kilogram dry matter utilised compared to granulated urea but yielded an extra 751 kg DM /ha. This translated to an extra fertiliser cost of $2,991.60 over the 18 hectare pivot area. However, when you consider that it would cost 35-47 cents per kilogram dry matter to purchase lucerne hay for the equivalent extra yield (i.e. $4,731 to $6,353), the extra cost of the liquid fertiliser is more than justified (see following table).
The fertigation system also resulted in a labour saving of approximately 18 hours (costed at approximately $500) over the ryegrass season. This takes into consideration that traditional broadcast application required getting a tractor, hooking on a spreader, filling the spreader and then 2 hours of tractor driving over the pivot area as opposed to merely pushing a button. Reduced tractor useage also derived further benefits of reduced fuel consumption, reduced repairs and maintenance, as well as reduced soil compaction and pasture damage. By spending less time on the tractor, human resources can be saved or directed towards alternate activities for even greater efficiencies such as improved grazing management.
The trial highlighted the importance of obtaining specialist advice prior to installing a fertigation system in order to maximise the benefits derived from improved nitrogen use efficiency. Precision is paramount and it is important that the irrigation system is operating at optimum water use efficiency. Initial setting up of dosing systems requires somewhat complex calculations but once established, the system is very easy to use.
The key benefits of fertigation were found to include:
• Reduced labour requirements
• Decreased R&M on machinery
• Fuel savings, less tractor work
• Could fertilise immediately following grazing, instead of days later
• Better timing of fertiliser, less volatilisation
• Reduced soil compaction with less traffic on pasture/crop
There are, however, some considerations to keep in mind before purchase of a fertigation system. These include an upfront setup cost (fertigation pump, bulk storage tank). The uniformity of application is only as good as the DU of the irrigation system, therefore it is vital to have a low pressure irrigation system with good DU. In times of extended wet weather, some fertiliser applications may be missed due to unnecessary irrigation applications. It may be still important to have a spreader for this reason, and to apply other nutrient requirements.
The trial will commence again in autumn this year for a second year, to try to improve upon some of the findings from year 1. Some grazing management changes will be implemented, in addition to an improved focus on irrigation scheduling and fertiliser applications.
Year 1 of the project was funded through the Australian Government’s National Landcare Programme, and was delivered by the Dairying Better ‘n Better program, a joint initiative of Queensland Dairyfarmers’ Organisation and Subtropical Dairy; and the Dairy and Fodder Water for Profit program.
* Please note an extra 54 kg N / ha was applied via fertigation compared to broadcast.
Fertigation and Irrigation Scheduling Factsheets