Leaf nutrient monitoring from space

As Anne (Yue) Wang prepares to complete her “challenging” PhD, she is already looking at further ways to contribute to research on vegetation monitoring using advanced remote sensing techniques.

Anne Wang measures leaf chlorophyll with handheld instrument.

The University of Melbourne student is one of the early career researchers the Mallee Regional Innovation Centre has been supporting to undertake project activities in the region.

Anne’s research has focused on assessing leaf nitrogen content in almond orchards across two growing seasons, using both airborne and spaceborne imagery involving solar-induced fluorescence, radiative transfer models and machine learning algorithms.

At her PhD completion seminar in February, Anne received lots of encouragement and there was great discussion regarding the potential of her work.

“As part of my research, I found a reliable and consistent indicator of nutrient content across imaging scales and growing seasons, which provides growers with an improved indication of nitrogen status for individual trees,” Anne said.

“As a result, growers can apply different fertigation solutions, maximising the value of resources and money whenever possible, to improve the vigor and production of their plants.

“Also, the improvement of nitrogen assessments in discontinuous tree orchards is feasible using spaceborne hyperspectral imagery, such as the newly developed DESIS (DLR Earth Sensing Imaging Spectrometer) onboard the International Space Station, at a 30-metre spatial resolution. These results demonstrate the contribution of hyperspectral spaceborne missions to large-area nitrogen monitoring and precision agriculture.”

Anne Wang's PhD completion seminar.

Anne will present her latest findings at the 43rd International Geoscience and Remote Sensing Symposium (IGARSS) in Pasadena, California in July. It will be the third time she has presented at IGARSS about her PhD research.

“It has been a challenging PhD with such advanced and depth of work, but I have enjoyed seeing how my research has developed step by step,” she said.

“I am very grateful to my supervisors Professor Pablo Zarco-Tejada, Dr Lola Suárez and Professor Dongryeol Ryu for their detailed guidance and support, as well as to the Invergowrie Foundation for the generous financial support. It is certain that this great journey will have a long-lasting impact on my research and my personal life.

I am committed to contributing to the research on vegetation monitoring by using these advanced remote sensing techniques. Future directions may include exploring vegetation status at a fine spatial scale with high-resolution imaging and using new satellite sensors with fine spectral resolution employed for the regional and global investigation.