Airborne Thermal Imagery to Detect the Seasonal Evolution of Crop Water Status in Peach, Nectarine and Saturn Peach Orchards

Joaquim Bellvert,Joan Girona,Elías Fereres,Pablo Zarco-Tejada,Jordi Marsal,Victoria Gonzalez-Dugo,Susan Ustin

doi:10.3390/rs8010039

Abstract

In the current scenario of worldwide limited water supplies, conserving water is a major concern in agricultural areas. Characterizing within-orchard spatial heterogeneity in water requirements would assist in improving irrigation water use efficiency and conserve water. The crop water stress index (CWSI) has been successfully used as a crop water status indicator in several fruit tree species. In this study, the CWSI was developed in three Prunus persica L. cultivars at different phenological stages of the 2012 to 2014 growing seasons, using canopy temperature measurements of well-watered trees. The CWSI was then remotely estimated using high-resolution thermal imagery acquired from an airborne platform and related to leaf water potential (ѰL) throughout the season. The feasibility of mapping within-orchard spatial variability of ѰL from thermal imagery was also explored. Results indicated that CWSI can be calculated using a common non-water-stressed baseline (NWSB), upper and lower limits for the entire growing season and for the three studied cultivars. Nevertheless, a phenological effect was detected in the CWSI vs. ѰL relationships. For a specific given CWSI value, ѰL was more negative as the crop developed. This different seasonal response followed the same trend for the three studied cultivars. The approach presented in this study demonstrated that CWSI is a feasible method to assess the spatial variability of tree water status in heterogeneous orchards, and to derive ѰL maps throughout a complete growing season. A sensitivity analysis of varying pixel size showed that a pixel size of 0.8 m or less was needed for precise ѰL mapping of peach and nectarine orchards with a tree crown area between 3.0 to 5.0 m2.

Highlights

Water scarcity is a major concern in many irrigated agricultural areas of the world
The relationship between difference of canopy and air temperature (Tc -Ta ) with vapor pressure deficit (VPD) for well-watered peach trees was significant for the two years of study (Figure 2)
It was concluded that crop water stress index (CWSI) derived from remotely sensed thermal imagery is a suitable indicator for water stress monitoring in peach species

Summary

Introduction

Irrigation water management needs to be carried out more efficiently, aiming at saving water and maximizing its productivity [1]. The adoption of regulated deficit irrigation (RDI) techniques, using water stress indicators, has been used in many fruit trees in order to optimize water use without affecting crop yields. In peach trees (Prunus persica L.), the benefit is well-known for applying RDI during stage II of fruit development. RDI has the potential to reduce excessive. The difficulty in identifying spatial variability of the crop water status across orchards limits its practical implementation in commercial fields. The success of RDI techniques strongly depends on the appropriate use of on-farm irrigation system and on the capacity to use new tools to detect crop water status across orchards

Methods

Results

Discussion

Conclusion