Tasmanian Institute of Agriculture researchers have cut down 16 healthy cherry trees with the blessing of a commercial orchard, as part of the More Profit from Nitrogen Program.
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The project is led by institute tree physiologist Dr Nigel Swarts, and involves close collaboration with commercial growers and industry advisors to find out how to improve the efficiency of fertiliser use in cherry orchards.
“Nitrogen is essential for cherry tree development and fruit production,” Dr Swarts said.
“We need to know more about soil processes that affect nitrogen, the total nitrogen loss from current management practices, and how much nitrogen cherry trees actually need.”
James Clements of Wandin Valley Farms in the Derwent Valley manages the commercial orchard hosting this research and grew the ‘Sacrificial Sixteen’.
“As orchardists, we want to ensure our cherry trees receive adequate nutrition from nitrogen to produce premium quality fruit with minimal waste,” Mr Clements said.
Since last year, the cherry trees were given fertiliser containing a form of nitrogen that can be traced through the tree and the soil to see how much nitrogen the tree actually takes up, and when is the best time to apply fertiliser.
To do this research, the whole tree must be cut down and separated into its main parts, including the branches, main trunk and the excavated roots.
Each part will be weighed and chemically analysed to find out how much of the fertiliser has ended up in each part of the tree.
Dr Peter Quin, a postdoctoral research fellow at the institute, said that this experiment would help track the fate of fertiliser once it was applied.
“By following the nitrogen through the tree, soil and emissions to the atmosphere, we can better understand fertiliser use efficiency,” he said.
Two other key parts of the project will look at processes in the soil that release nitrogen: decomposition of leaf litter and pruning material, and the application of different types of fertilisers.
“It is possible that decomposing plant material may provide an important source of nitrogen for tree crops,” Dr Quin said.
“However, we need to better understand the availability of nitrogen that comes from the decomposition process to the tree, and whether we can include it our overall nitrogen budget.”
He said that soil mineralisation – where soil organic matter is converted by microbes into forms of nitrogen that are available to plants – was often unaccounted for as a source of nitrogen in fruit tree orchards.
“With the information we gain from the soil and trees, we’ll be better able to advise cherry growers on when and how much nitrogen it is advisable to apply,” Dr Quin said.
In the same orchard, conventional synthetic fertilisers (such as calcium nitrate) are being compared with alternative biological fertilisers (such as manure).
University of Tasmania PhD student Nadine Macha set up the trial to find out how different sources of nitrogen can influence cherry tree yield and fruit quality outcomes.
“I’m investigating how different types of fertiliser influence the qualities of cherries such as colour, firmness, size, shelf life, and their ability to withstand storage. All these are critical for export grade fruit,” Ms Macha said.
Dr Swarts said the work in Tasmania would lead to the development of advice about best management practices for nitrogen fertiliser use that would be distributed to the cherry industry around Australia.
More Profit from Nitrogen research is supported by funding from the federal Agriculture and Water Resources department as part of its Rural R&D for Profit program, Hort Innovation and the Tasmanian Institute of Agriculture.