Use of vegetation indices for irrigation management in commercial vineyards

Water availability in vineyards plays an integral role in the sustainability of high-quality grapes and prevention of devastating crop loses. Stem water potential (Ψstem) reflects consistently vineyard water status, serving as an aid in irrigation management. However, some drawbacks make the Ψstem little used in commercial vineyards. It requires a pressure chamber, contracting a gas supplier, the need for one or two technicians to carry out the measurement, and the small size of the sample obtained limits the use to control large areas that normally present high intra-field variability.

The objective of this work was to establish a relationship between the Ψstem and the hyperspectral vegetation indices. Four irrigation doses were imposed in a commercial vineyard. Ψstem was measured five days during three-time intervals a day in 2019. The data for the calculation of vegetation indices can be taken quickly by means of a multispectral camera mounted on a UAV, be recorded and processed later. Two different indexes were calculated: NDVI and TCARI/OSAVI.

A total of 12 flights have been made, in addition to 320 measured data for the Ψstem, on 5 different dates at three different time intervals (morning, noon and afternoon) during 2019.There was a significant linear correlation (R² = 0.69, P <0.001) between the TCARI / OSAVI and the Ψstem. Despite the fact that the most widely used is the NDVI, in this study, the TCARI/OSAVI has obtained a tighter adjustment in all cases than NDVI.

The relationship allows estimating the Ψstem from the index (TCARI/OSAVI), which allows the knowledge of the vineyard water status of a larger area, improving the irrigation management in a more functional way for commercial plantations.

ACKNOWLEDGEMENTS

Grant AGL2016-77282-C3-2R funded by MCIN/AEI/ 10.13039/501100011033 and, as appropriate, by “ERDF A way of making Europe”, by the “European Union NextGenerationEU/PRTR”.

This work has been possible thanks to Licinia Wines (Morata de Tajuña, Madrid).

REFERENCES

Cancela, J.J.; Fandiño, M.; Rey, B.J.; Dafonte, J.; González, X.P. (2017). Discrimination of irrigation water management effects in pergola trellis system vineyards using a vegetation and soil index. Agricultural Water Management 183, 70-77. https://doi.org/ 10.1016/j.agwat.2016.11.003

Espinoza, C.Z., Khot, L.R., Sankaran, S., Jacoby, P.W. (2017). High resolution multispectral and thermal remote sensing based water stress assessment in surface irrigated grapevines. Remote Sensing, 9 (9). https://doi.org/10.3390/rs9090961