Abstract
Assessing water status and optimizing irrigation is of utmost importance in most winegrowing countries, as the grapevine vegetative growth, yield, and grape quality can be impaired under certain water stress situations. Conventional plant-based methods for water status monitoring are either destructive or time and labor demanding, therefore unsuited to detect the spatial variation of moisten content within a vineyard plot. In this context, this work aims at the development and comprehensive validation of a novel, non-destructive methodology to assess the vineyard water status distribution using on-the-go, contactless, near infrared (NIR) spectroscopy. Likewise, plant water status prediction models were built and intensely validated using the stem water potential (ψs) as gold standard. Predictive models were developed making use of a vast number of measurements, acquired on 15 dates with diverse environmental conditions, at two different spatial scales, on both sides of vertical shoot positioned canopies, over two consecutive seasons. Different cross-validation strategies were also tested and compared. Predictive models built from east-acquired spectra yielded the best performance indicators in both seasons, with determination coefficient of prediction () ranging from 0.68 to 0.85, and sensitivity (expressed as prediction root mean square error) between 0.131 and 0.190 MPa, regardless the spatial scale. These predictive models were implemented to map the spatial variability of the vineyard water status at two different dates, and provided useful, practical information to help delineating specific irrigation schedules. The performance and the large amount of data that this on-the-go spectral solution provides, facilitates the exploitation of this non-destructive technology to monitor and map the vineyard water status variability with high spatial and temporal resolution, in the context of precision and sustainable viticulture.
Highlights
There is a great potential both for monitoring water stress and scheduling irrigation in commercial orchards (Fernández and Cuevas, 2010)
A novel, non-destructive methodology based on near infrared (NIR) spectroscopy acquired on-the-go, to assess the vineyard water status has been developed and validated over two seasons
The presented results evidence the capability of on-the-go proximal NIR spectroscopy to successfully determine the grapevine water status in a commercial vineyard, using robust and reliable prediction models for the quantification of midday stem water potential (Ψs), which is a widely-used plant water status indicator (Choné et al, 2001)
Summary
There is a great potential both for monitoring water stress and scheduling irrigation in commercial orchards (Fernández and Cuevas, 2010). Conventional plant-based methods to monitor water stress, such as those based on the use of Scholander-type chambers, are destructive as well as time and labor consuming (Fernández, 2014). New methods for monitoring vineyard water status are needed in sustainable water management (Fernández, 2014; Jones and Grant, 2016). In this context, novel tools have been developed for non-destructive, automated, and continuous measurements (Rodriguez-Dominguez et al, 2012; Ballester et al, 2014). Very reliable and informative, many of these tools monitor only a single plant in the field they are unsuited to detecting spatial variation in water status within a vineyard (Baluja et al, 2012)
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