Farming Ahead October, 2008 No. 201

Urea ammonium nitrate (UAN) has provided central Queensland farmer, Andrew Bate, with a way to combine nitrogen application with sowing. For many years, Andrew had been thinking about how he could apply nitrogen at the same time as sowing wheat. The season of 2004 was the catalyst for change. “We pre-fertilised 800 hectares with urea, in anticipation of sowing a wheat crop,” Andrew said. “This was carried out with a zero-tillage planter fitted with spear points. “We left another 400ha fallow for chickpea, which we deep-planted during the third week of April. “We tried to continue planting chickpea into the re-fertilised country, but the fertilising operation had dried the soil.” The Bates harvested 0.8 tonnes/hectare of chickpea, despite a lack of in-crop rain, and forewent the opportunity to plant the paddocks that had been pre-fertilised. “By pre-fertilising, we missed the opportunity to deep-plant chickpea and spent a lot of money on urea and running a planter across the country — all in a low income year,” Andrew said.

Spotlight on UAN
UAN, in a liquid form, is a popular fertiliser on the sandy soils in Western Australia and the southern states of eastern Australia. It is pre-sprayed onto fallow country, sprayed on as a foliar spray in crop, banded in crop with streaming nozzles or deep banded with the seed. UAN is compatible with glyphosate and several other herbicides and fungicides and these are often added to do two jobs with one pass. UAN also has the added benefit of being slightly less toxic to seedlings and is safer to use in side- and deep-banding situations. “Because the product is a liquid, it is also easy to direct,” he said. “The grower can simply use a six-millimetre tube to
squirt the liquid to where it is required.”

The nitrogen content of 42.5 per cent weight-for-volume comprises 50% urea, 25% nitrate and 25% ammonia. It contains 57% more nitrogen per litre than any other liquid form of nitrogen. Because half of the nitrogen content is present as urea, this fertiliser is still susceptible to volatilisation losses.

The cost break-down
“The obvious disadvantage with UAN is that it costs much more than urea,” Andrew said. “However, with increased uptake by WA growers, prices have reportedly dropped to within 5% of urea. “Queensland farmers are unlikely to see a similar price reduction until significant volumes are used.” UAN is available for delivery in single, B-double and roadtrain quantities. Two manufacturers supply UAN to central Queensland: Incitec Pivot and Nipro.

Adapting to the north
“We expected that deep-banding points would not work on our heavy black central Queensland soils and would cause excess smearing in the bottom of the seed trench, as well as requiring increased draft to pull the planter,” Andrew said. “Side-banding, using a small knife (or delta wing) attached to the side of a planting point, with fertiliser applied in a separate band beside the seed, seemed more practical for our soils. “Unfortunately, there did not appear to be a side-banding liquid opener available in Australia, so we developed our own.”

The trial results
“We have trialled the use of UAN on our farm for the past three years. “We started during 2005 by applying UAN in strips at sowing to determine how much we could apply before seedling burn occurred.” The homemade side-banding boots separated the seed from the UAN by 2.50 centimetres with application rates equivalent to 60 kilograms a hectare of urea. As a result, seedling emergence was reduced. At this stage, Andrew had a front-mounted spray tank on the tractor. “We were encouraged enough to continue and, during 2006, we built better sidebanding boots that separated the UAN from the seed by 50mm. “We built a tow-behind liquid cart that held 3000 litres and set up a chain-driven pump to deliver the UAN. “The entire planter was set up with sidebanding boots and we took a leap of faith and planted 800ha with UAN. “We conducted strip trials to check plant establishment, yield and protein, eventually increasing rates up to the equivalent of 100kg/ha of urea,” Andrew said. There was no seed burn at these application rates and the yield and protein from the trial strips showed good results. But, the homemade side-banding points did not perform and fell apart after about 1200ha.

Updating pays off
During 2007, Andrew replaced his planter and air cart. The new airseeder has a 4000L stainless steel tank and a spray-rate controller to set the application rate. “We adapted side-banding boots that were originally made to apply gas,” Andrew said. During 2007, the trials were designed to compare a traditional application of pre-applied urea, the side-banded UAN and urea dissolved in water (a cheaper alternative to UAN). The results showed there was no significant difference between sidebanded UAN, pre-applied urea or sidebanded liquid urea. “During the trial, we used a budget rate of nitrogen based on soil tests and also a higher optimistic rate, targeting a higher yield,” Andrew said.

“During this season there was an economic benefit in applying the higher rate as a higher yield resulted. “Interestingly, even the higher rate still only achieved 11% protein, indicating that more fertiliser would have resulted in an even higher yield. “The 5cm separation between the seed and fertiliser seemed to be ideal, as there was no seed burn,” he said.

Innovation beats tradition
The cost comparison shows a significant saving by using side-banded liquid products at planting compared with traditional urea. The extra product cost is offset by the removal of the pre-plant fertiliser from the programme. Since this trial was completed fertiliser has increased significantly and ensures the economic benefits remain. The cost comparison does not take into account setting up the planter to side-band or the cost of storage tanks and pumps. Some farmers could modify their planter themselves, while others would spend money buying professionally made equipment. Set-up costs to side-band UAN would generally range from $10,000 to $35,000, according to Andrew. In comparison, liquid urea generally loses its cost competitiveness once it has to be freighted more than 150km from a mixing plant, due to its weak concentration and resultant high freight cost. Urea can be converted to a liquid form on-farm by mixing with water, but the labour and set-up costs may outweigh the cost savings. “To make liquid urea a viable option in central Queensland, a fertiliser manufacturer would need to build a local mixing plant,” Andrew said. “When using a low-concentration product such as liquid urea, extra time is required to fill liquid tanks on the planter. “A farmer would need to stop sowing to fill up nearly twice as often, compared with using the higher concentration UAN.” “This is important, as two days of extra time to plant a crop can make a big difference, especially in dry years.”