Upscaling evapotranspiration with parsimonious models in a North Carolina vineyard

Authors: DOLD, CHRISTIAN - Orise Fellow; HEITMAN, J - North Carolina State University; GIESE, G - New Mexico State University; HOWARD, A - North Carolina State University; HAVLIN, J - North Carolina State University; Sauer, Thomas

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2019
Publication Date: 3/23/2019
Citation: Dold, C., Heitman, J., Giese, G., Howard, A., Havlin, J., Sauer, T.J. 2019. Upscaling evapotranspiration with parsimonious models in a North Carolina vineyard. Agronomy. 9(152):1-15. https://doi.org/10.3390/agronomy9030152.
DOI: https://doi.org/10.3390/agronomy9030152

Interpretive Summary: Water stress can positively or negatively impact grape yield and yield quality, and there is a need for wine growers to accurately regulate water use. In a four-year study (2010-2013), water dynamics were measured with an eddy-covariance (EC) weather station in a North Carolina vineyard (Vitis vinifera cv. Chardonnay), and the amount of water transpired by plants and evaporated from the soil was calculated (that is, water loss or water use). In addition, the severity of water stress was evaluated using the Crop Water Stress Index (CWSI), which signals water stress on a scale between 0 (no stress) and 1 (high water stress). In addition, satellite images were used to estimate the “greenness” of the vineyard using the Enhanced Vegetation Index (EVI). The EVI shows how vigorous plants are, and together with air temperature is a good predictor of the amount of water used, as more vigorous plants transpire more water and higher temperatures increase transpiration and soil evaporation. Water loss as measured with the EC weather station was between 0.10 and 5.36 mm per day, or 765 mm per year. Mid-growing season CWSI was between 0.51 – 0.77, which indicates moderate water stress levels. Vineyard EVI was between 0.36 and 0.65, and EVI range within the vineyard was +0.19. There was a good relationship between water loss, air temperature and EVI, which allowed us to estimate water loss with a 58% variation. The calculated daily water loss for the whole vineyard ranged between 1.14 and 4.76 mm. This study presents easily applicable approaches to analyze water dynamics and stress for extension workers and scientists. It may also help wine growers to cost-effectively quantify water use in vineyards.

Technical Abstract: Water stress can positively or negatively impact grape yield and yield quality, and there is a need for wine growers to accurately regulate water use. In a four-year study (2010-2013), energy balance fluxes were measured with an eddy-covariance (EC) system in a North Carolina vineyard (Vitis vinifera cv. Chardonnay), and ET and the Crop Water Stress Index (CWSI) calculated. A multiple linear regression model was developed to upscale ET using air temperature (Ta) and Enhanced Vegetation Index (EVI) determined from 29 Landsat scenes. Daily ET was between 0.10 and 5.36 mm, and annual ET was 765 ± 90 mm, as measured with the EC system. Mid-growing season CWSI was between 0.51 – 0.77, which indicates moderate water stress levels. Median vineyard EVI was between 0.36 and 0.65, and EVI range within the vineyard was +0.19. The empirical model explained 58% of the variation in ET, and Ta and EVI were linearly related to ET. Modeled vineyard ET ranged between 1.14 and 4.76 mm d-1. This study presents easily applicable approaches to analyze water dynamics and stress. This may help wine growers to cost-effectively quantify water use in vineyards.