Ground-Based Thermal Imaging for Assessing Crop Water Status in Grapevines over a Growing Season

Abstract

The quality of wine grapes in dry climates greatly depends on utilizing optimal amounts of irrigation water during the growing season. Robust and accurate techniques are essential for assessing crop water status in grapevines so that both over-irrigation and excessive water deficits can be avoided. This study proposes a robust strategy to assess crop water status in grapevines. Experiments were performed on Riesling grapevines (Vitis vinfera L.) planted in rows oriented north–south and subjected to three irrigation regimes in a vineyard maintained at an experimental farm in southeastern Washington, USA. Thermal and red–green–blue (RGB) images were acquired during the growing season, using a thermal imaging sensor and digital camera installed on a ground-based platform such that both cameras were oriented orthogonally to the crop canopy. A custom-developed algorithm was created to automatically derive canopy temperature (Tc) and calculate crop water stress index (CWSI) from the acquired thermal-RGB images. The relationship between leaf water potential (Ψleaf) and CWSI was investigated. The results revealed that the proposed algorithm combining thermal and RGB images to determine CWSI can be used for assessing crop water status of grapevines. There was a correlation between CWSI and Ψleaf with an R-squared value of 0.67 for the measurements in the growing season. It was also found that CWSI from the shaded (east) side of the canopy achieved a better correlation with Ψleaf compared to that from the sunlit (west) side around solar noon. The created algorithm allowed real-time assessment of crop water status in commercial vineyards and may be used in decision support systems for grapevine irrigation management.

How can proximal sensors help decision-making in grape production?

“…This can be a good tool for handling spatial and temporal differences; therefore, it contributes to optimizing irrigation. Zhou et al [ 68 ] installed a thermal imaging sensor and a digital camera to collect data on the canopy. Furthermore, an AgWeatherNet station was used to obtain weather-related data, while a thermal sensor provided data on canopy temperatures.…”

Technologies and Innovative Methods for Precision Viticulture: A Comprehensive Review

“…Furthermore, the CWSI index evaluated by the handheld thermal camera correlates well with the index values measured by the UAV (R 2 = 0.58), however, proximal measurements have the limitation of not allowing spatialisation of the data [113]. Thus, thermography offers many advantages, however, there are currently sensors that including microchips embedded in the vine trunk that allow continuous monitoring of the stem water potential [132]. These instruments present some criticalities such as maintaining intimate contact with the xylem over long periods of time and, finally, its single measurements, which makes it difficult to apply them in large areas.…”

A Smart Crop Water Stress Index-Based IoT Solution for Precision Irrigation of Wine Grape

“…Ground-based thermal imaging has also assessed crop water status across different growth stages [57]. -Geospatial analysis tools: Tools such as QGIS have been highlighted for their ability to interpret and visualize data, providing a greater understanding of spatial patterns within vineyards.…”