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Water is a key resource in commercial wine production and both large excesses and deficits have undesirable effects upon the amount and quality of the wine produced. A balance between the water requirements of a fully developed canopy and the induced stress necessary for the commercial quality of the wine must be reached. Thus we need a physiological indicator that integrates both soil and climatic conditions to use as a management tool. An experimental field was established in the eastern part of the Demarcated Region of Douro -Portugal, to study the effect of water supply on the quality of the musts produced and we need a physiological indicator that relates to the water use and stress of the grapevines (Vitis vinifera L.) and to the later evaluation of the effect of irrigation practices upon the quality of the musts. We chose as indicators sap flow, leaf water potential at pre-dawn (0600 h), mid-morning (1000 h), solar noon (1400 h) and sunset (1900 h), stomatal conductance and leaf transpiration both measured at mid-morning and at solar noon, and related them to our experimental treatments that induce differences in soil water content, evaluated with time-domain reflectometry probes, with the objective of selecting the indicator that best describes the plant water status under different amounts of available water. Sap flow, leaf water potential and leaf transpiration rate measured at solar noon had highly significant correlations with soil water content and their regression on soil water content was also highly significant. Each of these parameters has shortcomings and none has a clear advantage over the other two as an integrator of the environmental conditions under these experimental conditions. Further studies of the parameters and their relationship with the quality characteristics of the produced musts are needed to achieve the ultimate objective of manipulating the soil water content.

Spatial information on vineyard soil properties can be useful in precision viticulture. In this paper a combination of high resolution soil spatial information of soil electrical resistivity (ER) and ancillary topographic attributes, such as elevation and slope, were integrated to assess the spatial variability patterns of vegetative growth and yield of a commercial vineyard (Vitis vinifera L. cv. Tempranillo) located in the wine-producing region of La Rioja, Spain. High resolution continuous geoelectrical mapping was accomplished by an Automatic Resistivity Profiler (ARP) on-the-go sensor with an on-board GPS system; rolling electrodes enabled ER to be measured for a depth of investigation approximately up to 0.5, 1 and 2 m. Regression analysis and cluster analysis algorithm were used to jointly process soil resistivity data, landscape attributes and grapevine variables. ER showed a structured variability that matched well with trunk circumference spatial pattern and yield. Based on resistivity and a simple terrain attribute uniform management units were delineated. Once a spatial relationship to target variables is found, the integration of point measurement with continuous soil resistivity mapping is a useful technique to identify within-plots areas of vineyard with similar status.

<p style="text-align: justify;"><strong>Aim</strong>: To test the hypothesis that shading of the fruiting zone of the plants might reduce yield losses caused by excessive exposure to sun while avoiding the most damaging effects associated with reduced radiation.</p><p style="text-align: justify;"><strong>Methods and results</strong>: A number of grapevine rows were shaded with a double layered white plastic netting on their south-facing side, from the ground to about 20 cm above the cluster zone. Data on meteorological conditions, plant growth, plant water availability, yield components and must characteristics were recorded during three growing seasons. Shading significantly increased yield but did not alter significantly the must characteristics.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Partial shading of the grapevine canopy reduced yield losses attributable to excessive radiation. The must obtained from shaded berries had a lower concentration of anthocyanins, and the wines made from these musts had a lighter colour which may be detrimental to their quality.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The study highlights the effects of solar radiation on the composition of grape musts and suggests a potentially cost-effective method to control excessive radiation in vineyards.</p>

In regions with Mediterranean climate, water is the major environmental resource that limits growth and production of plants, experiencing a long period of water scarcity during summer. Despite the fact that most plants developed morphological, anatomical, physiological, and biochemical mechanisms that allow to cope with such environments, these harsh summer conditions reduce growth, yield, and fruit quality. Irrigation is implemented to overcome such effects. Conditions of mild water deficit imposed by deficit irrigation strategies, with minimal effects on yield, are particularly suitable for such regions. Efficient irrigation strategies and scheduling techniques require the quantification of crop water requirements but also the identification of pertinent water stress indicators and their threshold. This chapter reviews the scientific information about deficit irrigation recommendations and thresholds concerning water stress indicators on peach trees, olive trees, and grapevines, as case studies.