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Published: 12 Oct 2018

TIA PhD candidate Harriet Walker is developing a technique to instantaneously assess how much nitrogen is contained in the canopies of grapevines.

“The goal is to develop a method to assess nitrogen levels using hand-held remote sensors that is fast, simple and cost-effective,” Ms Walker said.

“The sensors we are trialling measure leaf greenness, which is an indicator of how much nitrogen the plant needs.

“These sensors are used in other agricultural industries, however not currently in wine production, and I’m hoping my research will change this,” she said.

Ms Walker is trialling sensors on vines at Tasmanian vineyard Jansz Parish and working closely with Jansz viticulturalist James Aubrey.

“Healthy vines need the right amount of nitrogen to produce high quality grapes,” Mr Aubrey said.

“The current method of testing – petiole sampling – is time consuming. We need to cut leaves and send off samples to be analysed and all of this takes time.

“It would be useful to have a quick and easy tool that allow us to take multiple snapshots of nitrogen levels throughout the growing season so our decisions can be even more well-informed,” he said.

Earlier this year, Ms Walker, with help from TIA agricultural science student and summer intern Lauren Rowlands, trialed three different sensors on Jansz vines.

“We took leaf samples from Pinot Noir and Chardonnay vines with low, medium and high nitrogen levels and used the sensors to measure greenness. We were then able to assess the total nitrogen content of the leaves over one season,” Ms Walker said.

“Our results so far show that some of the sensors have potential to accurately estimate nitrogen levels in grapevine leaves,” she said.

Ms Walker said the Greenseeker demonstrated the best results among the hand-held sensors, however a ‘benchtop’ near-infrared (NIR) spectrometer model showed greatest potential overall.

“The Bruker benchtop NIR spectrometer provided consistently accurate data and showed the greatest potential for predicting nitrogen levels in the vine canopy.

“Hand-held portable NIR sensors have since become commercially available, and the next step is to test these and compare the results with other hand-held instruments,” she said.

Ms Walker is currently working with fellow researchers at the University of Tasmania to create an algorithm to predict nitrogen levels.

“We are developing a mathematical model which will calculate the nitrogen needed based on data provided by the sensor,” she said.

Last month Ms Walker and five other TIA researchers presented their viticulture research at Crush, a grape and wine science symposium hosted by the University of Adelaide’s Waite Campus.

“The symposium gave me the chance to reflect on the similarities and differences between the Tasmanian wine industry and other regions in Australia,” Ms Walker said.

“The room was full of fellow wine and grape researchers, so it was a great opportunity to network and get feedback on my research.”

Ms Walker’s PhD research is funded by the University of Tasmania and Wine Australia with in-kind support from Jansz Parish Vineyard and TIA.

Picture (L-R): PhD candidate Harriet Walker and agricultural science student Lauren Rowlands measure canopy greenness.

This article appeared in Tasmanian Country on 12 October 2018.