Water footprint, productivity, and wine quality of twenty winegrape cultivars under water deficits

Summary:

Competition for water resources is increasing between urban and agricultural entities. Current restrictions on deliveries for agriculture necessitate more accurate information on water requirements of important crops. Tree and vine crops have more potential for water conservation than field crops. Almost half of the acreage of tree and vine crops consists of vineyards. The water footprint of a crop is the total volume of water needed to produce a commercial unit of product. Knowledge of a crop’s water footprint allows for informed irrigation management decisions. Previous research has shown that grape yields can be maintained under deficit irrigation techniques. This research investigated the drought responses, water footprint, and wine quality through the imposition of water deficits to increase understanding of water use and fruit quality for specific cultivars, therefore allowing growers to apply a minimum amount of irrigation water to sustain profitable production levels.

Investigators:

Larry Williams and Mark Matthews
Department of Viticulture and Enology
UC Davis

Project description:

In recent years, deliveries of water for agricultural use in the San Joaquin Valley (SJV) have been reduced, or in some instances cut all together. Growers in the SJV would have the most potential to conserve water if the amount of irrigation water needed to produce a unit of product could be accurately measured.

Since 1980, the acreage of annual crops has decreased by 40%, while the acreage of perennial crops has increased 77%. Recent research has shown that perennial crops have a higher potential for water conservation. Also, it has been shown that yields do not decrease significantly under some levels of water stress. As trends in California agriculture shift away from traditional field crops, more detailed information is needed on the amount of water required to grow tree and vine crops.

Vineyards now account for nearly half of the total acreage of woody perennial crops. However, there is a lack of data detailing how much water is necessary to produce a ton of grapes. Similar in concept to the carbon footprint, the volume of water required to produce a ton of grapes is deemed the ‘water footprint.’ Knowledge of a vineyard’s water footprint can help growers make better irrigation management decisions, effectively using less water to produce the same amount of fruit.

Our long-term goal is to identify red winegrape cultivars with lower water requirements than currently in production, and to develop irrigation requirements and strategies to minimize water use and maximize yield and quality for those cultivars. The overall objective  for this project was to evaluate cultivar responses to water stress on a physiological level. It was our central hypothesis that cultivars respond differently to the same level and timing of water stress. We further hypothesizde that wine quality to SJV could be improved through cultivar selection and water management.

The specific aims of this project were to:
1. Impose water stress on various red winegrape cultivars and quantify blue water footprints of each cultivar.
2. Measure physiological responses in vegetative and reproductive growth parameters.
3. Make select wines to examine the effect of irrigation treatment and cultivar on wine quality.

This project addressed the need to generate detailed information on the amount of water to produce a specific agricultural product. The outcomes of this research were valuable in increasing knowledge of water use and fruit quality for specific cultivars, therefore allowing growers to apply a minimum amount of irrigation water to sustain profitable production levels.