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 Ingham grower Paul Marbelli:

Paul Marbelli – Ingham

Third-generation cane farmer Paul Marbelli describes the last three years as a ‘learning curve’. But he says they’ve led to cost-savings and a much better understanding of what his soil needs across 200 hectares of diverse cane blocks.

The Ingham grower reduced his inorganic nitrogen use to an average of 135 kilos per hectare over plant and ratoon cane with the “peace of mind” that the Wet Tropics Reef Trust IV Repeated Tenders program was a financial buffer if he’d dropped too far for his land and the seasons.

“I probably reduced it a little too much,’’ he said. “Now I know how low I can go before starting to lose production when conditions are not as favourable, I’m back around the 140 mark and following soil tests and the Six Easy Steps nutrient management program to the letter.”

The project also helped him to move into variable rate fertiliser application. “Getting a rate control system fitted means we know more accurately how much fertiliser we are placing, so we can be more confident in reducing nitrogen.”

In addition, the Marbellis have focused more on their mill mud application.

“Our farms are close to the mill so we’ve used a lot of mill by-products over the years. But previously we haven’t reduced our fertiliser rates where we’re using mill mud. Now we’ve got more confidence to do that. With fertiliser prices doubling, there is plenty of incentive. There are huge cost savings in finding the balance between minimising impacts on the environment and maintaining a productive farming business.”

The Marbelli family’s farms have creeks crossing through them that flow to the Herbert River. There are wetlands and sediment ponds on most of their properties.