Liquid fertiliser study finds less harmful nitrogen run-off to Great Barrier Reef

ABC Rural: by Tom Major and Lara Webster / Posted Thursday 19th April, 2018Efforts to keep nitrogen fertilisers on farm and away from the fragile Great Barrier Reef can be boosted by use of liquid fertilisers, a study has found.

Research conducted in the north Queensland town of Ingham has proven the use of molasses, a sugar milling by-product, can slow the rate at which nitrogen leaches from soil.

Pam Pittaway from the National Centre for Engineering in Agriculture at the University of Southern Queensland said the blended fertiliser considerably reduces nitrogen run-off from paddocks.

“Our results show that molasses-amended liquid fertiliser should be considered an enhanced efficiency fertiliser, as it significantly reduces the risk of fertiliser nitrogen leaching,” Dr Pittaway said.

About 37 per cent of the nitrogen from the molasses-blended liquid fertiliser was still in the soil four months after application, compared to just 27 per cent with granular fertiliser.

“This is a major finding for the sugar cane industry as we can confidently say that liquid fertiliser as a whole improves the retention of nitrogen in soil,” Dr Pittaway said.

Microbes activated

Dr Pittaway said soil microbes were the key to understanding how the liquid fertiliser worked.

“The soil microbes are stimulated by the molasses, and they grab luxury amounts of the urea fertiliser, and they turn it into slow-release organic nitrogen,” she said.

“If you think that for ratoon, you put the fertiliser on … you want it to be there for summer storm season — that’s when you really want your nitrogen in the soil.

“It is a win for growers and a win for the reef.”

Reef benefit

Mackay Conservation Group co-ordinator Peter McCallum welcomed the research, but said there was still too much nutrient run-off hurting the Great Barrier Reef.

“It is really good to find out exactly what is happening but I think the results show that when cane farmers purchase fertiliser, two-thirds of their money is ending up in the ocean,” he said.

“There is a stack more work that needs to be done.”

He would like to see more systems such as sediment ponds or artificial wetlands being constructed on farmland to capture nutrient runoff.

Ingham cane grower Johnathon Biasi said, with an eye on future potential reef regulations, anything that reduced leaching was a bonus for his business.

“Down the track if [environmental regulators] say we have to use a slow-release fertiliser, we can say ‘we are’,” he said.

Long-term use

Mackay agronomist Tony Crowley, from agronomic solutions provider Farmacist, said many farmers had been using molasses to retain nitrogen in the soil for longer periods, but to have research proving it meant a lot.

“There has never been proper research completed on it … and their findings are quite significant,” Mr Crowley said.

“The problem we have got with liquid fertilisers is that over the years it was just ‘throw a compound into a drum, mix it up and spray it on’.

“[Now] we are getting smarter with that as we go further, so we are putting the right compounds in the right spots.”

Grower take-up

While granular products still rule the market, transition is taking place across the state.

Mr Biasi said, five years on from his first application of liquid, he was a convert to the product.

“The ease of it, to put it out, no more bag lifters, no more trucks running around, yeah it’s a lot safer to use,” he said.

In addition, the potential to retain more expensive fertiliser on farm was a big plus.

“Because it probably won’t leach as much as a granular product in a wet year there’s a very big bonus, where you put it is where it stays.”

Cost is one issue for many growers, however, with infrastructure such as tanks and equipment like subsurface applicators turning some farmers off.

“It’s probably the same cost to build an applicator as buying a fertiliser box,” Mr Biasi said.

“That cost there is probably persuading people not to shift to that way but there are contractors, there are other ways to get around it.”

Expansion on

Manufacturer of liquid fertilisers Cameron Liddle from Liquaforce in Ingham funded the research through an Australian Commonwealth Innovation Connections grant.

He said demand for the liquid fertiliser product was growing year-on-year.

“We do about 15 million litres [annually] … the last two years we’ve seen 20 per cent growth,” he said.

“Farmers are starting to understand the value aspect we give them … they’re looking at the comparative nitrogen use efficiency.”

Want to listen to the full radio report? Click here to listen to the Country Hour with Charlie McKillop from Thursday 19th April, 2018. The LiquaForce Research yarn features from the 38mins 15 second mark.

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