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Farmers break new ground on fertiliser

PRACTICAL SOLUTION: Tony and Bonnie Walker have grown the legume pintoi on their Tuckombil avocado farm for the past 15 years, cutting their use of fertiliser by 70%.
PRACTICAL SOLUTION: Tony and Bonnie Walker have grown the legume pintoi on their Tuckombil avocado farm for the past 15 years, cutting their use of fertiliser by 70%. Mireille Merlet-Shaw

NITROGEN is a magic ingredient in healthy crops, fruit, and vegetables, but its overuse is contributing to global warming and environmental damage.

Excess nitrogen transforms into nitrous oxide, a greenhouse gas with 300 times the potency of CO2.

Now scientists from Southern Cross University and the Wollongbar Department of Primary Industries have joined farmers and industry groups across the Northern Rivers to trial some cutting-edge methods to reduce fertiliser use.

It's part of a $2.6 million project funded until 2017 by the Federal Government to introduce practical strategies to reduce agricultural carbon emissions.

At Tony and Bonnie Walker's Tuckombil avocado farm, the team will study the use of a groundcover plant known as a "nitrogen fixer".

The Walkers have been growing the pretty legume, pintoi or forage peanut, almost as long as they've been avocado farming.

"Since we've been using the pintoi we've probably been using 70% less nitrogen," Bonnie Walker estimated.

The legume study will also be extended to local coffee and tea tree plantations.

"We want to quantify exactly how much nitrogen these legumes are putting into the soil," SCU professor Lukas Van Zwieten said.

"What you want is just a little trickle of nitrogen going into the soil so it's available to the plant the whole season, rather than most systems where you chuck on a whole heap of nitrogen at once."

The team is also trialling ultra-high-pressure nitrogen injection at sugarcane plantations, and slow-release fertiliser using a mix of compost and biochar on local blueberry and banana farms.

"Essentially, what we're trying to do is get more of the added nitrogen into the crop.

"Right now most systems will be lucky to get 30-40% nitrogen efficiency."

With nitrogen retailing about $2000 a tonne, it's also a way of saving farmers money while minimising the impact on the environment.

 

Agriculture and Global Warming

The agricultural sector contributes 16.3% of Australia's greenhouse gas emissions, more than double most other countries.

80% of this is in the form of nitrous oxide.

Nitrous oxide is a particularly potent greenhouse gas, 300 times as strong as CO2.

Topics:  agriculture department of primary industries farming global warming