2013 Annual Report
1a.Objectives (from AD-416):
Our recently developed improvements in the Surface Renewal (SR) technique will be used to measure vineyard scale evapotranspiration (ET) to complete the following objectives:.
1)Determine the impact of water stress on vineyard ET measured directly with the improved SR technique throughout the growing season; and.
2)Evaluate the influence of water stress on the relationship between real vineyard evapotranspiration and vine water status indicators (i.e., midday leaf water potential and stomatal conductance). By accomplishing these objectives, we will begin to establish base line data needed to evaluate SR as a stand-alone technique for both quantitative and qualitative (i.e., how much plant stress) assessment on vineyard irrigation requirements subjected to different irrigation amounts.
1b.Approach (from AD-416):
Each treatment will be established in one of three contiguous 2-hectare blocks. Daily water use (ETC) throughout the growing season (budburst to leaf-fall) will be determined using the improved surface renewal technique. A SR bio-meteorological station will be established in each irrigation block following the Shapland et al., (2012) procedure, and daily ETC values will be measured and collected. Daily reference evapotranspiration data (ET0) from the nearest CIMIS weather station to the experimental site. Potential ETC/ET0 ratios as “theoretical” wet controls will be estimated every two weeks in two different ways:.
1)Using the relationship between the percent of shaded area beneath the canopy at solar noon, as previously described by Williams and Ayars, (2005). Percent of shaded area beneath the vines will be estimated using the iPhone application developed by Dr. Lampinen;.
2)Using the Landsat satellite images to create NDVI maps. Block NDVI values will be transformed into LAI values, and Pierce’s equation will be used to calculate the potential ETC/ET0 ratio. Midday values of leaf water potential and stomatal conductance will be measured weekly in two sun-exposed leaves from the same vines where iPhone pictures were taken in each block. Applied water quantity and irrigation frequency will be measured by water meters installed at the beginning of each irrigation line.
This agreement was established in support of parent project objective #3 of the in-house project, which is to develop sustainable water management practices for vineyards.
We are utilizing our new adaptation of the Surface Renewal (SR) technique to determine whether it can detect water stress events within a study of commercial vineyard. In recent years, we have worked to refine the method to effectively measure vineyard water use. Base on recent work developed by University of California (UC), Davis, researchers, we are currently testing whether SR can be used to track stress events by documenting when potential water use diverges significantly from actual water use measured with SR. We have established the replicated experiment in a commercial Chardonnay vineyard owned by Constellation Brands, Inc. in Esparto, California. We have been tracking vine water and growth status (stomatal conductance, water potential, canopy growth and development) in these plots that contain SR stations. Irrigation levels were similar in the three plots for the first portion of the growing season, and differential irrigation treatments were initiated at veraison. The experiment is on track to complete the project and publish the work by January 2014.