Reducing fertiliser use on cane farms in North Queensland

A THIRD-GENERATION cane grower who is transitioning his farm to be less reliant on artificial fertilisers says soil health is key.

Ingham cane grower Robert Bonassi has focused on fallow crops and using mill by-products to slash his fertiliser rates without affecting yield.

Mr Bonassi cut his fertiliser rates by up to 20 per cent over four years – moving from 160kg of nitrogen per hectare to 120-130kg for plant cane and 145kg for ratoons.

He said maintaining healthy soils was essential.

“We’d always taken soil samples but now we target every block we fallow on a yearly basis,” Mr Bonassi said.

“You’ve got to keep the soil healthy when you’re reducing nitrogen and phosphorous.”

The Bonassi family grows cane on 180ha over four parcels of land, with 25ha under fallow crops at any given time. They moved to mounded rows and zonal tillage to solve waterlogging issues, manufactured a zonal ripper and mounder, and bought a bean planter last year.

They are also sold on mill mud and mill ash for its nutrient and soil conditioner properties.

“We apply sub-surface mill mud and ash in the fallows. Slowly, it is building our soils up and helping us with reducing our fertilisers,” Mr Bonassi said.

“We spread zonally at the end of every year, using about 80 tonnes to a hectare.

“Within five years we’ll have gone across the whole farm with 80 to 100 tonnes per hectare of mud and ash and we should start seeing results. Then we’ll look at halving that and see if we can still meet the nitrogen levels.”

His farm is 6km from the ocean as the crow flies. Two of the parcels of land have three creeks running through them and one shares a boundary with national park.

“It’s all about getting a good balance – good returns on the soil while minimising run-off to the very best of our ability,” he said.

Mr Bonassi is one of 39 growers to take advantage of the Australian government’s Reef Trust IV program, delivered through the Wet Tropics Sugar Industry Partnership.

Ban on toxic mercury looms in sugar cane farming, but Australia still has a way to go

This month, federal authorities finally announced an upcoming ban on mercury-containing pesticide in Australia. We are one of the last countries in the world to do so, despite overwhelming evidence over more than 60 years that mercury use as fungicide in agriculture is dangerous.

Mercury is a toxic element that damages human health and the environment, even in low concentrations. In humans, mercury exposure is associated with problems such as kidney damage, neurological impairment and delayed cognitive development in children.

The ban will prevent about 5,280 kilograms of mercury entering the Australian environment each year.

But Australia is yet to ratify an international treaty to reduce mercury emissions from other sources, such as the dental industry and coal-fired power stations. This is our next challenge.

Prime Minister Scott Morrison visiting a sugar cane farm in 2019. Mercury-containing pesticides will be banned. Cameron Laird/AAP

A mercury disaster

Mercury became a popular pesticide ingredient for agriculture in the early 1900s, and a number of poisoning events ensued throughout the world.

They include the Iraq grain disaster in 1971-72, when grain seed treated with mercury was imported from Mexico and the United States. The seed was not meant for human consumption, but rural communities used it to make bread, and 459 people died.

In the decades since, most countries have banned the production and/or use of mercury-based pesticides on crops. In 1995 Australia discontinued their use in most applications, such as turf farming.

Despite this, authorities exempted a fungicide containing mercury known as Shirtan. They restricted its use to sugar cane farming in Queensland, New South Wales, Western Australia and the Northern Territory.

According to the sugar cane industry, about 80% of growers use Shirtan to treat pineapple sett rot disease.

But this month, the Australian Pesticides and Veterinary Medicines Authority cancelled the approval of the mercury-containing active ingredient in Shirtan, methoxyethylmercuric chloride. The decision was made at the request of the ingredient’s manufacturer, Alpha Chemicals.

Shirtan’s registration was cancelled last week. It will no longer be produced in Australia, but existing supplies can be sold to, and used by, sugar cane farmers for the next year until it is fully banned.

Workers and nature at risk

Over the past 25 years, Australia’s continued use of Shirtan allowed about 50,000 kilograms of mercury into the environment. The effect on river and reef ecosystems is largely unknown.

What is known is that mercury can be toxic even at very low concentrations, and research is needed to understand its ecological impacts.

The use of mercury-based pesticide has also created a high risk of exposure for sugar cane workers. At most risk are those not familiar with safety procedures for handling toxic materials, and who may have been poorly supervised. This risk has been exacerbated by the use itinerant workers, particularly those from a non-English speaking background.

Further, in the hot and humid conditions of Northern Australia, it has been reported that workers may have removed protective gloves to avoid sweating. Again, research is needed to determine the implication of these practices for human health.

To this end, Mercury Australia, a multi-disciplinary network of researchers, has formed to address the environmental, health and other issues surrounding mercury use, both contemporary and historical.

Australia is yet to ratify

The Minamata Convention on Mercury is a global treaty to control mercury use and release into the environment. Australia signed onto the convention in 2013 but is yet to ratify it.

Until the treaty is ratified, Australia is not legally bound to its obligations. It also places us at odds with more than 100 countries that have ratified it, including many of Australia’s developed-nation counterparts.

Australia’s outlier status in this area is shown in the below table:

Accession, acceptance or ratification have the same legal effect, where parties follow legal obligations under international law.

Mercury-based pesticide use was one of Australia’s largest sources of mercury emissions. But if Australia ratifies the convention, it would be required to control other sources of mercury emissions, such as dental amalgam and the burning of coal in power stations.

The three active power stations in the Latrobe Valley, for example, together emit about 1,200 kilograms of mercury each year.

Time to look at coal

If Australia ratified the Minamata Convention, it would provide impetus for a timely review and, if necessary, update of mercury regulations across Australia.

Emissions from coal-fired power stations in Australia are regulated by the states through pollution control licences. Some states would likely have to amend these licences if Australia ratified the convention. For example, Victorian licences for coal-fired power stations currently do not include limits on mercury emissions.

Pollution control technologies were introduced at Australian coal plants in the early 1990s. But they do not match state-of-the-art technologies applied to coal plants in North America and Europe.

Australian environment authorities have been examining the implications of ratifying the convention. But progress is slow.

The issue of mercury emissions does not attract significant public or political attention. But there is a global scientific consensus that coordinated international action is needed.

The pesticide phase-out and ban is an important step. But Australia still has a way to go.

Farmers change practices to improve Great Barrier Reef health

AN Innisfail sugar cane farmer has reduced his fertiliser use by 20 per cent, without affecting yield.

Third-generation cane farmer Sam Spina, who farms alongside brother Michael, said implementing simple changes had both increased profitability, while providing beneficial environmental outcomes.

Mr Spina started making changes two years ago, planting bean fallow crops and varying fertiliser application rates across his paddocks.

The results have been pleasing, with the brothers reducing fertiliser use from 160kg per hectare to 120kg per hectare – a reduction of 20 per cent.

Mr Spina said he had started planting bean fallow crops two years ago with the help of a new tractor partly financed through the Reef Trust IV program.

He said as a small farm, they would not have been able to do so without the program delivered by the Wet Tropics Sugar Industry Partnership.

“As a small farm we couldn’t have afforded it otherwise,” he said. “We re-plant cane on

four to five hectares and plant beans on the same number of hectares each season to

increase the nitrogen in our soil in a more natural way.”

He then accessed an all-of-farm nutrient management program, also developed by WTSIP officers last year as part of a free service to growers.

“We had a really good look at the soil tests and matched the fertiliser blend to those tests,” Mr Spina said.

“We changed fertiliser and reduced it, and experienced no productivity losses.

“We’re still up around 90 tonnes (of cane) per hectare, depending on the weather and the season.

“We saw in the soil tests that some paddocks needed more super phosphate in the ratoons so we also changed that.

“Our fertiliser box is on GPS now so we can automatically adjust the rate as we go.”

The family’s farm is about 1.5km from the Johnstone River and 8km from the ocean, and Mr Spina said they had also laser levelled their land and reshaped drains to help improve water quality.

“Laser levelling helps to produce a more even crop and it’s also helping with water quality,” he said.

“With the grassed headlands and drains as well, when the water runs off the paddock it moves slowly and goes into the spoon drains first so any sediment can settle.”

Mr Spina said changes that began as cost-saving initiatives had become much more as growers became more environmentally aware.

“Over the years cane growers have become a lot more aware environmentally – we’re grassing our headlands, trash-blanketing, applying fertiliser underground, getting water samples.

“If there is fertiliser coming off our paddocks, we want to know about it so we can fix it.”

The Spinas are one of 39 Wet Tropics growers to receive tenders to reduce fertiliser use on their farms.

WTSIP chair Joe Marano said one the main benefits of the system was that growers could choose the practice changes they believed would be most effective on their farm.

“They’ve been trialling a range of different ways to reduce nitrogen – from using controlled-release fertilisers or applying mill mud to growing legumes as a source of nitrogen and buying specialised equipment,” Mr Marano said.

“These growers have been able to reduce their use of nitrogen fertiliser without affecting their yields – a good result for profitability and for water quality.”