High density plantings, intensive orchards to be tested
15 December 2020
The economics of citrus intensification will be tested as part of a new horticulture industry project.
The research will also have an eye to the future, looking to uncover citrus types or varieties better suited to high density plantings as well as practical tips to improve the profitability of existing intensive orchards.
Dave Monks, research horticulturist with NSW DPI, is leading the project, which will build on established information, on behalf of the citrus industry.
He said this was part of a national drive for orchard intensification, in a bid to capture more sunshine and deliver quicker returns on investment across the horticulture sector.
“The primary reason is to generate more yield, because there’s more capture of sunshine,” he said.
“But there’s a delicate balance because we have to determine if it is profitable to simply try and capture all of the incoming solar radiation.
“Our current understanding of managing citrus orchards won’t simply overlay on a higher density planting. There is a financial cost to planting more trees and a gap in our understanding of managing high intensity plantings.”
Dr Monks said some growers had already invested in higher density plantings with mixed results.
Value will be determined by revaluating blocks established during the past 20 years with the dwarfing viroid, as well as planting a new block of navel oranges and inoculating them with newly isolated viroids which haven’t been available to the public.
Cost reductions and efficiency gains are expected due to the smaller size of the tree.
Some of these gains, such as a decreased occupational health and safety risk and simpler pruning, are harder to quantify than others such as decreased fertigation costs, according to Dr Monks.
“It is very reasonable to keep in the back of our minds, that citrus already converts a lot of sunshine into profit,” he said.
“If we, in any way, reduce the tonnage off a hectare, we need to have an equal or even slightly higher decrease in the cost of inputs because you have to recover the cost of planting the trees.”
This information will be conveyed via a financial tool available to growers. Dr Monks said it would be ideal for those considering planting an orchard.
For growers wanting best practice advice on an established high-density planting, the project will also research the most efficient and cost-effective way to prune these blocks to return them to productivity.
This information will be conveyed via case studies and field days at demonstration trials on growers’ properties.
The final part of the project will involve examining the shape and regrowth habit of 400 different citrus varieties to find those best suited to high density plantings; research that may be used by plant breeders.
“For example, the ability to flower in a low-light environment or conversion of minimal sunshine into fruit or return bearing on the same part of the tree year on year,” Dr Monks said.
Brett Hullah is part owner and farm manager of Grandview Orchards at Coomealla, NSW and one of the businesses involved in the project.
His orchard includes 2.5 ha of high-density plantings, with trees including a viroid to limit their size.
Brett’s keen to learn how to better manage the tree size and regrowth after pruning.
“They are a bit of an interesting tree because when you prune, they can regenerate in some areas the same as a normal tree, but it seems to be a little delayed,” he said.
“Pruning the tree, we try and regenerate it but, for the ones with the viroid, we are just not sure if we are pruning the best way to get the best result.”
The project is funded by Hort Innovation, will take five years, and includes up to five grower collaborating properties and five NSW DPI staff.
Barnfield Navels injected with a dwarf virus on Brett Hullah’s orchard.