Crop Water Stress Index of an irrigated vineyard in the Central Valley of California

Abstract

Water-limiting conditions in many California vineyards necessitate assessment of vine water stress to aid irrigation management strategies and decisions. This study was designed to evaluate the utility of a Crop Water Stress Index (CWSI) using multiple canopy temperature sensors and to study the diurnal signature in the stress index of an irrigated vineyard. A detailed instrumentation package comprised of eddy covariance instrumentation, ancillary surface energy balance components, soil water content sensors and a unique multi-canopy temperature sensor array were deployed in a production vineyard near Lodi, CA. The instrument package was designed to measure and monitor hourly growing season turbulent fluxes of heat and water vapor, radiation, air temperature, soil water content directly beneath a vine canopy, and vine canopy temperatures. April 30-May 02, June 10-12 and July 27-28, 2016 were selected for analysis as these periods represented key vine growth and production phases. Considerable variation in computed CWSI was observed between each of the hourly average individual canopy temperature sensors throughout the study; however, the diurnal trends remained similar: highest CWSI values in morning and lowest in the late afternoon. While meteorological conditions were favorable for plant stress to develop, soil water content near field capacity due to frequent irrigation allowed high evapotranspiration rates resulting in downward trending CWSI values during peak evaporative demand. While the CWSI is typically used to evaluate plant stress under the conditions of our study, the trend of the CWSI suggested a lowering of plant water stress as long as there was adequate soil water available to meet atmospheric demand.

State-of-the-art of tools and methods to assess vine water status

“…The need to fuse direct plant-based methods with indirect methods has been highlighted in recent literature, such as Kustas et al (2018) who showed that T/ET 0 estimates obtained by merging atmospheric measurements with remote sensing imagery require independent measurements such as vine transpiration using sap flow gauges to determine vine water use and stress level, which directly impact yield and fruit composition. From there, new analytical methods combining data fusion processing package and machine learning algorithms with direct and indirect measurements of vineyard ET are yielding successful results (Alfieri et al, 2018;Andújar et al, 2019;Helman et al, 2018;Prueger et al, 2018;Romero et al, 2018;Semmens et al, 2016) and could be promising tools for wine water status assessment and irrigation monitoring in the future.…”

Review of water deficit mediated changes in vine and berry physiology; Consequences for the optimization of irrigation strategies

“…Various approaches seeking to assess vine water stress via canopy and atmospheric temperatures are under evaluation Prueger et al, 2018). Their already promising results reveal however, that more efforts are needed to address fundamental questions on how to measure vine canopy temperature and how to account for vineyard leaf area architecture (trellising, pruning practices, for example) via airborne thermal sensors to derive an index of vine water status.…”

Characterizing Crop Water Use Dynamics in the Central Valley of California Using Landsat-Derived Evapotranspiration

“…The Central Valley, as shown in Figure 1a, is a large flat valley that covers over 52,000 km 2 and dominates the central portion of California extending nearly 720 km along a northwest-southeast axis [15,16]. The Central Valley is composed of the Sacramento Valley in the north, the San Joaquin Valley in the center, and the semi-arid Tulare Basin at the southernmost end [16].…”