California faces an unprecedented drought and governing bodies have already declared a state of emergency. The greater demand of water for urban and agricultural use necessitates an adapted management of this resource. Vine production is largely concerned by this issue as the incorrect assessment of water deficits might strongly alter yield and fruit quality. Several irrigation strategies have been developed for the sustainability of water resources. itk Company, specialized in the development of decision support tool, carries out a comparative study (over 20 years) between irrigation recommendations applied in California and those from the Vintel software. As an example, a representative vineyard from the Monterrey County was investigated.
The Vintel software developed within a collaborative project involving INRA, CIRAD, IRSTEA, Languedoc wine-growers’ cooperatives, the regional department of agriculture (chambre d’agriculture) and the climate association of Hérault. This software defines the daily optimal irrigation need through the modeling of vine water deficit. The corresponding irrigation recommendations were compared to those of Regulated Deficit Irrigation (RDI) as defined by the UC Davis method. According to the California Wine Community, this last approach would concern nearly 50% of vineyards in California. It is aimed at controlling the grapevine canopy and improving grape quality through the adoption of low irrigation at specific growth stages (60% of potential evapotranspiration in this study). Note that a full irrigation strategy has been also considered in the study. To do this, vine potential evapotranspiration was assessing from the crop coefficient and the reference evapotranspiration. The present study reveals a general decrease in annual rainfall in California over the past twenty years, as evidenced by an increase in the vine water deficit along with a decrease in optimal conditions that compromised the production objectives (Figure.1). In a context of water scarcity, there is clearly a need to adopt optimized irrigation practices as RDI. itk aims to increase the water economy through the implementation of mechanistic models. In this domain, Vintel has decisive advantages as may lead to substantial water economy (Table.1). Results suggest that the best window of opportunity for water savings is the flowering – veraison period. Water deficit however is typically uncommon in California during bud-break and post-harvest, as water demand is being met by winter rainfall. Nonetheless, the climate change expected during the next decades could considerably affect the winter water supply and ultimately irrigation requirements.
These results already show that Vintel is a relevant tool to quantify the vineyard water status. In this domain, mechanistic models have decisive advantages as they deliver a continuous follow up of base water potential.
Marek DUPUTEL & Philippe STOOP
Predict and Decide