“To Fly or Not to Fly”: Airborne Remote Sensing for Determination of Vine Water and Nitrogen Status at a Regional Scale
Vinay Pagay,* Catherine Kidman, and Allen Jenkins
*University of Adelaide, PMB 1, Glen Osmond, SA 5064, Australia
In the face of a warming climate, the long-term sustainability of Australian vine-yards depends on prudent management of natural resources such as freshwater for irrigation. Likewise, nitrogen (N) fertilizers aid vine growth and improve juice nitrogen levels for healthy fermentations, however, excess N applications in vine-yards can result in excessive vine vigor, leading to increased water use and leaching from vineyards. Recently, remote sensing platforms have emerged to characterize the water and nitrogen status of vineyards at high spatial resolution (<0.35 m), allowing viticulturists to make decisions on water and fertilizer applications at the sub-block level. Remotely-sensed water status is typically based on thermal imagery, or thermography, while nitrogen status is based on multispectral imagery to determine specific vegetation indices that relate to leaf nitrogen concentration. Our objectives were: (i) to validate vine water and nitrogen status data obtained from an airborne remote sensing platform using conventional on-ground measurements across an entire viticultural region; and (ii) to determine whether remotely-sensed vine water status data could be used to make irrigation scheduling decisions. Airborne campaigns were conducted over several timepoints in the 2015 to 2016 and 2016 to 2017 seasons in the Coonawarra region of South Australia. Remote sensing was a powerful tool for large-spatial scale characterization of water and N status of Cabernet Sauvignon and Shiraz grapevines and generally cor-related well with ground-truthed data. Remote sensing also improved irrigation uniformity by delineating zones of non-uniformity in certain blocks. Temperature indices of vine water status varied based on cultivar and phenological stage and, therefore, require calibration over multiple seasons to be useful for irrigation scheduling.
Funding Support: Coonawarra Grape and Wine Inc.