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July 2015 P R A C T I C A L W I N E R Y & V I N E YA R D 71 B O O K E X C E R P T • Managing natural soil variability in a vineyard, • Managing soil water, • Organic, biodynami, and conventional viticulture, • Climate change and possible consequences, • Benchmarking for soil quality, • Integrated produc- tion systems (IPS) and sustainability. Managing natural soil variability in a vineyard Natural soil variability is an important contributor to over- all variability in vine perfor- mance. Precision viticulture (PV) provides a range of tools for a winegrower to manage variability and make informed m a n a g e m e n t d e c i s i o n s , thereby gaining better control over the production system. Chapter 1, What makes a healthy soil? discusses the causes of soil variability. Chapter 2, Site selection and soil preparation, describes methods based on remote and/or proximal sensing to delineate the spatial structure of this variability. By making such measurements at a high spatial resolution and incor- porating the data into a geo- graphic information system, a winegrower can identify zones within a vineyard that can be managed separately, from planting through to pro- ducing fruit and ultimately harvesting. When key soil and climate variables are combined into a model, similar to the local site index described in chap- ter 2, which is linked to a geographic information sys- tem, the resulting map can be interpreted as defining digital terroirs for the site. Figure 6.8 shows the map output of such a model that has been devel- oped for the Cowra region, New South Wales, Australia. Proffitt et al. (2006) give more examples of digital maps of variability in soil properties and vine vigor in their book Precision Viticulture. Chapters 3, The nutrition of grapevines, Chapter 4, Where the vine roots live, and Chap- ter 5, The living soil, describe how the expression of soil variability through nutrient supply, soil structure, aera- tion, drainage, soil strength, water supply, salinity, sodic- ity and soil biology can be rec- ognized. Actions to remedy any onsite constraints and offsite effects of winegrowing are recommended. Possible applications of PV include differential soil amelioration, through the use of lime or gypsum (see box 3.6, Chapter 3), installing under drainage in parts prone to waterlogging (see "How to Improve Soil Drainage," Chapter 4), and planning the design and layout of an irri- gation system to supplement soil water. For example, through the choice of dripper placement and delivery rate, combined with flow control valves, water can be differentially applied to parts of a vineyard according to the available water and drainage proper- ties of the soils. A map of vineyard soil variation show- ing soil textures and depths allows "readily available water" (RAW), "deficit avail- able water" (DAW) and "plant available water" (PAW) val- ues to be estimated, as shown in Table 4.4 in Chapter 4. None of these applications of PV will convince a wine- grower of the need to act unless they result in a bet- ter product and making more profit, with minimal environ- mental impact. Hence, the main interest shown by wine- growers in PV is in mapping yields, vine vigor and indices of fruit ripeness, and using this information to plan dif- ferential harvesting in time or space. To this end, the book Preci- sion Viticulture gives examples of where zones of different vine vigor within blocks were