Grains Research and Development

Date: 01.09.1999

Can growers coax nitrogen

Estimates of the amount of ammonium nitrogen under the north's brigalow-belah cropping lands vary from 100 to 250 kg/ha down to 3 metres depth.

'Blue sky' research, supported by growers through the GRDC, aims to crack the secrets of huge deposits of ammonium nitrogen beneath two million hectares of brigalow-belah cropping soils in Queensland and northern NSW.

Success in the project — allowing graingrowers to use this underground nitrogen bonanza to grow their crops — could be worth anything from $100-$250 million to the grains industry.

But it could mean new farming systems or new, deep-rooted crops — agroforestry perhaps — to draw ammonium nitrogen from up to 3 metres in the subsoil to replace chemical fertilisers.

Queensland's Departments of Natural Resources and Primary Industries and the University of Queensland are collaborating on the project, led by Ram Dalai.

Brigalows fixed some nitrogen but...

Dr Dalai says scientists knew from earlier research that brigalow-belah subsoils became acidic and were likely to hold nitrogen. Later, tracking lucerne roots, they found quantities of nitrogen 3 metres deep.

Most brigalow-fixed nitrogen is in the top metre of the soil, and most leaching is nitrate-N rather than ammonium. "Estimates of the amount of ammonium nitrogen under the north's brigalow-belah cropping lands vary from 100 to 250 kg/ha down to 3 metres depth," Dr Dalai says.

"That's a potential total of 200-500 million kg N, and provided farming systems can be devised to use even half of it over time, it will mean savings of more than $100 million in fertiliser N."

Dr Dalai says the team plans first to confirm the actual amount of the ammonium N, and then develop an understanding of why it occurs and the processes affecting its levels, transformations and movement.

Then the research team will set out to identify possible cropping systems and management practices to use the N. This is expected to be the most difficult challenge.

"On top of the more direct benefits to graingrowers on brigalow-belah country, other positive results from our research may reduce the risk of unforeseen adverse environmental impacts through N build-up and movement to groundwater," Dr Dalai says.

"It's certainly what you call 'blue sky' research but, if it succeeds, it will have large benefits for graingrowers and also reduce environmental degradation across the brigalow-belah cropping belt of northern Australia."

Program 3.4.1

Contact: Dr Ram Dalai 07 3896 9895

Region North