The 40pc nitrogen hack: how faba beans are slicing 'colossal' fertiliser bills

Riverina growers are increasingly turning to nitrogen-fixing legumes like faba beans to help rein in "colossal" fertiliser bills.

Berrigan grower Tom Arnold, Carawatha, said residual nitrogen left in the soil by faba beans allowed him to cut urea inputs by up to 40 per cent in the following irrigated canola crop.

"We're using 100 to 150 kilograms per hectare less of urea for the same yield as what we were getting putting 400kg/ha out," Mr Arnold said.

"Given the current prices, that's pretty beneficial."

Mr Arnold said he was quoted upwards of $1400 a tonne for urea delivered on-farm in June. This time last year on-farm urea prices were sitting closer to $800/t.

"It's just colossal...our inputs are getting so much dearer and we seem to be getting paid less for what we grow," he said.

The Arnolds crop around 2100 hectares between Berrigan and Jerilderie, with more than half of that area set up for irrigation across both summer and winter.

Mr Arnold said they introduced faba beans four years ago, initially planting 90ha.

This year, the program has expanded to around 250ha, to be sown in the next couple of weeks, with plans to reach up to 350-400ha from next year.

The Arnolds started growing faba beans to improve the sustainability of their rotations and to reduce their reliance on synthetic nitrogen.

Mr Arnold said continuous cropping of canola and wheat had taken its toll on the soil and had begun to impact yields.

"We realised that our N [nitrogen] was not efficient anymore," he said.

"Our dirt had hit a wall and we couldn't get through that wall, so we decided to bring in legumes."

Mr Arnold's agronomist Greg Sefton, Sefton Agronomics, Barooga, said faba beans also provide a more effective form of nitrogen, compared to urea.

"It's there when the plant needs it and natural N becomes available from the bean stubble even two to three years later. It's just a healthier system," Mr Sefton said.

He said legume hectares within his clients' rotations had increased from one per cent seven years ago to 10-12.5pc this year.

Faba beans were by far the most popular choice of legume for solely cropping operations in the southern Riverina.

"They're the most tolerant legume to water-logging and they go well on our irrigation, on our heavy clay soils, whereas chickpeas and lentils don't like that," Mr Sefton said.

Although faba beans' nitrogen-fixing qualities are becoming more valuable, they are a notoriously fickle crop to grow.

Mr Arnold said they were trialling different sowing strategies to improve plant population and maximise yields.

"That's the trickiest thing with beans, one year we had them do 6t/ha and last year we had them do 2t/ha," Mr Arnold said.

However, he said the crop itself had low inputs, with only 80kg/ha of MAP added at sowing and no urea required.

Tightening profit margins mean many Riverina irrigators will reduce both their water and fertiliser applications this year.

Mr Arnold said they would apply urea and MAP at dryland rates and would not prewater before sowing.

"There's a lot of things this year that we're having to think about that we'd normally just say yes to," he said.

"As far as fertiliser and irrigation is concerned, this year we're running basically as a dryland operation.

"It makes it more difficult because in irrigation you have a lot of area not planted because of rows and channels."

Mr Sefton said irrigators would be questioning whether to spend more than $300 per megalitre to establish a winter cereal crop given current grain prices.

But in positive news, much of the southern Riverina had received a good autumn break, with around 50-100mm of rainfall recorded in March.

Mr Sefton said another client had already seen canola emerge that was planted in early-April

"We've got 50pc of the crop up, which is fantastic...and purely on subsoil moisture from that March rain" Mr Sefton said.

When it came to fertiliser, Mr Sefton said most of his clients had enough urea secured to put on the minimum 100kg/hectare required in continuous cropping systems.

"Those guys who can't get urea secured, we'd be sitting down looking at their program and looking at what we leave out of crop and fallow," he said.

Mr Sefton said current fertiliser and grain prices had also led to some growers favouring barley over wheat this year.

While wheat typically attracts a premium, prices are currently similar, potentially making barley a more economic crop to grow due to its lower urea requirements.

"An irrigated barley crop's probably going to get 250kg/ha of urea whereas wheat, fully irrigated, will get 400kg so there's 150kg of urea difference there," Mr Sefton said.