A study of within-vineyard variability with conventional and remote sensing technology

[摘要] ENGLISH ABSTRACT:In the past it was very difficult to visualise the extent and distribution of variability in growthvigour within vineyards. The advancement of remote sensing technology has changed thishowever, establishing new methods to assess and manage variability. Even though thecauses and effects of within-vineyard variability in growth vigour are complex, newtechnologies offer better ways of monitoring, researching and managing these factors. Inaddition to the possible benefits of aerial or satellite remote sensing, new methods ofmapping soil spatial variability as well as advances in georeferencing technologies supplyprecision tools to both researchers and producers. The scientific advancement of thetechnology, however, is currently the most important aspect needed. This is crucial toanswer and explore fundamental questions regarding the use of the technology and theinterpretation of results within the framework of the plant's observed reaction. Only thencan the possible applications in vineyard management be optimised to address themanagement problems of extensive within-vineyard variation in growth vigour. The choicewill always be to use the technology to manage the observed variability in order to limit thenegative impacts of a heterogeneous harvest, or to identify the variability and its causesfor the implementation of management practices aimed at a more homogenous vineyardand harvest. Whatever the case, extensive research is needed to provide tight correlationsbetween information gathered with new technologies to assess variability and plant status,such as multi- and hyperspectral analysis, and ground-truthed results in the vineyard. Onlythen will it become evident which methods and analyses would be useful in the drivetowards in-depth analysis and management of vineyards within the concept of precisionviticulture and its derived advantages.With this in mind, the aim of this study was to establish an experimental model to useremote sensing technologies to identify and classify within vineyard variability with asubsequent analysis of the causes of variability and the effects on the plants. The targetedexperimental model was a vineyard with highly heterogeneous above-ground growth. Anaerial photograph of the vineyard was studied and manipulated to yield image pixel valuesused to quantify the degree of variability for different plots, which were chosen accordingto different plot layouts. Soil conditions were assessed on both a global and plot level, withextremely high pH and low resistance values in the soil in combination with erratic soilpreparation practices found to be the main cause of variability. Soil physicochemicalcondition was also assessed during a soil profile pit study. Significant differences werefound between several soil-related parameters measured for the higher and lower vigourlevels and a strong correlation was also found between the resistance of a saturated soilpaste and the image pixel values.Vegetative measurements also yielded highly significant differences between thevigour levels and confirmed the suitability of the vineyard to study within-vineyard variability. Some of these measurements were also strongly correlated with soil conditionsas well as image pixel values. Trunk circumference proved to be an excellent measure forthe level of variability, being linked strongly to canopy characteristics, soil conditions aswell as the image pixel values. Leaf water potential measurements also yielded significantdifferences between the vigour levels.Harvest data and wine analyses showed the effect that vigour differences can have ongrape composition and wine quality, even though the differences found here were muchless than expected. Even though no clear preference was shown between the wines madefrom the different vigour levels, the lower vigour wine was considered fruitier. The overallquality of both experimental wines was however very high, considering that experimentalwinemaking techniques has been used.Hyperspectral measurements also confirmed differences between the vigour levelsthrough a narrow-band NOVI (normalised difference vegetation index). It was also possibleto show differences in certain biochemical compounds between the vigour levels on both aleaf and canopy level. Wavelength regions corresponding to carotenoid, chlorophyll a andchlorophyll b showed different spectral reactions in the leaves of more stressed (lowervigour) canopies, indicating possibilities for further studies.This study and its results is the first of its kind in the South African wine industry andpaves the way for more focussed and in-depth analyses of the use of specifically multiandhyperspectral data to accurately assess within-vineyard vigour variability and themanagement thereof to yield optimum quality grapes for a specific wine target. Moreover,the approach adopted in this study is also echoed in other international research programsin prominent wine countries. The availability of scientific research regarding the optimaluse and limitations of these technologies has the potential to revolutionise productionmanagement practices in the next few years in the viticultural industry.

[发布机构] Stellenbosch University