Influence of "terroir" factors and vineyard management (organic, biodynamic) on plant performance and fruit quality of grapevines

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DoeringJohanna_2019_05_29.pdf (35.12 MB)

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2018

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DOI:
http://dx.doi.org/10.22029/jlupub-16766

Abstract

Plant performance and fruit quality of grapevines are influenced by a wide range of terroir factors. These factors, namely climate, soil as well as agricultural practices often called the human factor in terroir all determine final wine quality to a high extend. Agricultural management is an important tool to adapt agricultural systems to specific environmental conditions. By comparing different management systems several parameters are usually varied together among treatments, such as soil management, fertilization strategy, pest and disease management, application of compost and crop rotations of annual cropping systems. The most wide-spread viticultural management systems today are integrated, organic and biodynamic viticulture, even though organic and biodynamic viticulture are gaining more and more importance and attention among consumers and producers in the last decades. The aim of this thesis was to establish a method for fast and accurate LAI measurements in the vineyard on one hand and to describe the influence of terroir factors and vineyard management systems on plant performance and fruit quality of grapevines on the other hand by assessing vine water status, physiological activity, standard agronomical parameters as well as LAI. A reliable, fast and accurate method to non-destructively and dynamically assess leaf area was established which can be applied in a small scale in the field. Different protocols for indirect estimation of leaf area index (LAI) by gap fraction analysis in VSP trained grapevines (Vitis vinifera L. cv. Riesling) were tested and correlated to direct leaf area measurements. LAI measurements were carried out using the portable Plant Canopy Analyzer (PCA, LAI-2200, LI-COR, Lincoln, NE, USA). One optimized protocol was chosen, the calibration equation was determined and the protocol was successfully used in the field trial in Geisenheim, Germany, comparing integrated, organic and biodynamic viticulture to assess LAI throughout the growing season as well as for determining leaf area to fruit weight-ratio at harvest.Within the second approach of this doctoral dissertation the influence of the terroir factors soil water-holding capacity and grapevine genotype on plant performance was assessed. For this purpose a greenhouse trial was set up comparing the physiological behavior of two grapevine genotypes (Cabernet Sauvignon and Syrah, near-isohydric and near-anisohydric) on two different soil substrates differing in their capacity to withhold water (water-draining and water-retaining). Stem-water potentials together with stomatal conductance and embolism formation (percent loss of conductivity PLC) were determined to describe physiological response mechanisms of the two different grapevine genotypes on two soil substrates. Considering the different characteristic traits of the two grapevine genotypes and the two types of substrate in relation to soil water potential it can be deduced that there are optimal set-ups of combinations of genotype and water-holding capacity, but interactions between genotype and substrate did not occur. Syrah might have more specific requirements concerning the environmental conditions under which it shows optimal growth. Cabernet Sauvignon, in contrast, might be more universally usable compared to Syrah due to its characteristic near-isohydric behavior under drought. Yet all these observations need further confirmation and approval, since the number of plants included in the trial was low and thus influence of environmental factors in the greenhouse could not be excluded to a satisfactory extent. The main objective of the third study included in the current doctoral dissertation was to determine growth, yield and fruit quality of grapevines under organic and biodynamic management in relation to integrated viticultural practices. Moreover, the mechanisms for the observed changes in growth, yield and fruit quality should be investigated by determining nutrient status, physiological performance of the plants and disease incidence on bunches in three consecutive growing seasons. A field trial (Vitis vinifera L. cv. Riesling) was set up at Hochschule Geisenheim University, Germany, in 2006. The integrated treatment was managed according to the code of good practice. Organic and biodynamic plots were managed according to Regulation (EC) No 834/2007 and Regulation (EC) No 889/2008 and according to ECOVIN- and Demeter-Standards, respectively. Due to the investigation of important parameters that induce changes especially in growth and yield of grapevines under organic and biodynamic management the study can potentially provide guidance for defining more effective farming systems.For a broader evaluation of the effects of organic and biodynamic viticulture compared to integrated or conventional viticulture a review of currently available literature was included into the doctoral dissertation. Effects of conventional, organic and biodynamic viticulture on soil properties, biodiversity, vine growth and yield, disease incidence, grape composition, sensory characteristics and wine quality were assessed and summarized. Only studies with representative field replicates or studies with a representative number of samples were included into the review. Yet studies were partially heterogenic and limited in number and publication bias cannot be excluded. In order to predict the behavior of vines under organic and biodynamic viticulture in different terroirs worldwide parameters mediating between terroir and plant performance and thus fruit quality such as physiological activity and PLC could eventually be used. This would provide the possibility to further adapt the practices of organic and biodynamic viticulture to environmental conditions worldwide.

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