Tully cane farmers are using leaf tests to learn more about their soil.
Alex Lindsay, WTSIP's Extension Officer in the Tully district, has been facilitating a Peer-to-Peer Learning program to help a group of growers to work through some common issues and find new solutions.
“We’ve been working with a small group of growers who are planting cane on farmland they used to have bananas on, and there have been some interesting results,’’ Mr Lindsay said.
“Growers weren’t trusting the soil test results in these paddocks because the correlation between organic carbon and nitrogen that’s usually a reliable indicator of nitrogen levels in cane soils doesn’t apply as well in banana soils, where there can be higher nitrate and ammonia levels.
“Now they are using leaf tests to supplement the soil tests. We’re finding leaf tests, which are not commonly used for cane, can be a really useful indicator in this case.
“The amount of nitrogen in cane leaves reflects what is available to the plant and can be as much as 30 per cent higher on ex-banana land than nearby long-time cane land.”
Murray Upper cane grower Tony Todd said leaf tests in one widely grown variety of cane showed zinc deficiency, where soil tests showed there was adequate zinc. Other varieties grown nearby showed good agreement between the soil and leaf test values.
“If the four of us hadn’t put our heads together through this program it wouldn’t have come to this,’’ he said. “Test results showed all of us had the same problem with our soil.
“After the zinc results, I applied zinc to half a block only and you could see the results in the (leaf) tissue,” he said. "I’m waiting to see whether this makes a difference to production.
“That was the outstanding thing we learnt but getting together as a group has also been very helpful to hear what others are doing fertiliser and variety-wise.”
The project is funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation, and the Queensland Government Reef Water Quality Program. It is delivered by the Wet Tropics Sugar Industry Partnership.
Mr Lindsay said the four Tully district farmers who were part of the project were keen to continue leaf-testing and trials.
“It has been really successful. Once they all started talking about the results it triggered thoughts about other things they had seen on their farms. Because it was growers talking with growers, we could learn from different perspectives and different ways they’d tackled issues in the past.”
He said the growers nominated blocks for testing as a one-off in 2019 and these blocks were re-tested in 2020 to see changes through time.
Mr Todd said he already used less fertiliser on ex-banana land but he expected his fertiliser levels to drop further and application to be more targeted as a result of the leaf tests.