Trials test ‘sweet spot’ for fertiliser

FINDING THE ‘SWEET SPOT’ FOR FERTILISER

Thirty-eight growers from Mareeba to Ingham have trialled changes to their cane-growing practices across 10,000 hectares of land to find the ‘sweet spot’ for productivity and sustainable agriculture.

Changes have ranged from using enhanced efficiency nitrogen fertiliser and applying fertiliser at variable rates to improving soil health through compost production, mill mud application and planting legumes fallow crops. They have also included upgrading soil and yield mapping to better understand each cane block.

The Wet Tropics Reef Trust IV Repeated Tender program is funded by the Australian Government and delivered by Terrain NRM in partnership with Cairns Canegrowers, Herbert Cane Productivity Services and Tully Canegrowers.

Hear from Tully grower Mario Quagliata:

Mario Quagliata – Tully

The old days of “six bags to the acre” are gone on Mario’s cane farm in the Tully region. Ask him how he’s successfully dropped his rates from 187 to 140kg of inorganic nitrogen per hectare and he’ll tell you he’s been using “witches brews”.

Mario has trialled bio-stimulants among a range of other changes, and he credits that with the reversal of an initial drop in yield when the Wet Tropics Reef Trust IV Repeated Tender program began on his land.

“In the first two years it felt like we were going backwards. But last year we saw yield increase that looks to be a combination of very favourable growing conditions and, we’re thinking, a liquid product that supposedly unlocks phosphate in the ground. I’m applying it at the same time as fertiliser and it looks to be giving the cane something to balance out the lower nitrogen input.”

Mario has also tried seaweed and worm juice as supplements in recent years, with varying results.

Extending bio-stimulant trial

He’s now looking at extending the current bio-stimulant trial to other parts of the farm. He has 400 hectares under cane with owned and leased land. He’s also adopted semi zonal tillage and legume systems.

The home farm has a bioreactor which was constructed as part of the Wet Tropics Major Integrated Project – a 10-metre trench between sugarcane paddocks and a nearby drain that is trapping paddock run-off. Water is slowly filtered through woodchips, where bacteria strips it of nitrates.

“We keep trying. The funding and assistance helps. We need a few more years to see the results given all the variables, and to see if other products come on board.”

Helping to reduce financial risks 

Terrain NRM’s Trevor Parker says the Repeated Tenders program has helped growers to reduce the financial risk of determining optimal inorganic nitrogen application rates and, as a result, many farmers have made permanent changes.

“In the tropics, with our variable rainfall from season to season, timing fertiliser application and improving fertiliser efficiency to minimise nitrogen losses is a big challenge for the industry,’’ he said.

“Financial support provided through the Repeated Tenders program gave growers the confidence to work out their sweet spot for nitrogen application and this has resulted in a collective reduction of 1000 tonnes, which is a good cost saving.

“Some found they’d gone down too far in terms of its effect on yield, but then they readjusted to rates that were still below their old rates. Others experienced no yield changes. And some growers are now reporting yield increases.

Matching fertiliser use more closely with crop needs

“This has been all about working with cane growers to match fertiliser use more closely with crop requirements, leading to the same or better yield and profitability results. A good thing about the program was that growers could choose what actions to take. They also had support from extension officers beyond their cane blocks – in things like improving record-keeping, becoming a BMP-accredited grower if they weren’t already and developing a customised nutrient management plan.”

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