Correlating remote and terrestrial water status indices in a nectarine orchard

M.R. Conesa, W. Conejero, J. Vera, M.C. Ruiz-Sánchez
Accurate measurements of the plant water status are becoming essential for precise irrigated agriculture, especially in semi-arid regions where water resources are limited. This work aimed to study the feasibility of precise irrigation scheduling based on real-time soil water content (SWC), assessed by traditional discrete plant water status indicators, and compared with others based on multispectral and thermal indices taken from unmanned airborne vehicles (UAVs). The experiment was conducted in a nectarine tree orchard applying two irrigation treatments: Control (CTL), irrigated to ensure non-limiting water conditions (100% of crop evapotranspiration; ETc) and automated irrigation (AUTO) based on threshold SWC values, using capacitance probes, allowing a slight water deficit during the postharvest period. Plant water status was determined from stem water potential (Ψstem) and gas exchange measurements. Two flights were conducted on a typical summer day, using VIS-NIR multispectral and thermal cameras installed in a UAV. From the information obtained, the normalized difference vegetation index (NDVI) and canopy temperature were calculated. At soil level, the AUTO treatment registered a mean soil water deficit of 15% with respect to the CTL treatment. A significant mean reduction of 0.25 MPa in the Ψstem values was observed in the AUTO treatment in respect to the CTL treatment, corresponding to a situation of moderate water stress. Gas exchange parameters were slightly lower in the AUTO treatment. However, no significant differences were detected in the UAV indicators between irrigation treatments. The results showed that care should be taken when using UAV indicators to assess moderate water deficit in deciduous fruit trees.
Conesa, M.R., Conejero, W., Vera, J. and Ruiz-Sánchez, M.C. (2022). Correlating remote and terrestrial water status indices in a nectarine orchard. Acta Hortic. 1335, 363-370
DOI: 10.17660/ActaHortic.2022.1335.45
normalized difference vegetation index (NDVI), plant water status, precise irrigation, Prunus persica sp., soil water content

Acta Horticulturae