Understanding Vineyard Soils – Robert E. White (2015)

Title	Understanding Vineyard Soils
Author	Robert E. White
Publisher	Oxford University Press
Date	2015
ISBN	9780199342068
Pages	264
Summary	The first edition of Understanding Vineyard Soils, published in 2009, has been praised for its comprehensive coverage of soil topics relevant to viticulture, and is a major resource for professionals in the industry. However, the subject is not static—new developments are occurring in the field all the time. For example, the ‘organic movement’ in viticulture continues to grow in importance and the emphasis on wine quality relevant to quantity is changing in an increasingly competitive world market. The promotion of organic and biodynamic practices has raised a general awareness about ‘soil health’ and methods to assess it, which is often associated primarily with the biological status of the soil. Many commercial laboratories offer an extensive range of tests for soil (biological) health, the relevance of which is not clear to many growers. However, the development of new tools for characterizing soil microorganisms and identifying the specific functions of taxonomic groups is an exciting area of research that may offer answers to some of these questions in the future. This second edition of White’s influential book presents the latest updates and developments in vineyard and soil management practices. Just like the first edition, Understanding Vineyard Soils introduces readers from all backgrounds to the principles of viticulture.
Excerpt	Understanding Vineyard Soils

About the Book

Understanding Vineyard Soils by Peter White presents a science-based framework for managing soil as the foundation of quality viticulture. The book demonstrates that there is no single “ideal soil” for wine grapes; instead, soil performance emerges from the complex interaction of inherent factors (geology, climate, topography, and time) that cannot be changed, and dynamic factors (organic matter, pH, nutrient availability, structure, water supply) that growers can manipulate through management. The first half of the book explains how soils form, how to assess site suitability through climate and soil surveys, and how to prepare vineyard land through deep ripping, amelioration, and irrigation design. The second half addresses the practical management of soil chemistry (balancing macronutrients like nitrogen and potassium with micronutrients), water dynamics (understanding field capacity, plant-available water, and regulated deficit irrigation), soil biology (earthworms, microorganisms, carbon cycling, and pest management through rootstock resistance), and integration of these elements into sustainable vineyard systems.

Throughout, White emphasizes that optimal vineyard management is not dogmatic but evidence-based and site-specific. Whether a grower pursues organic viticulture or conventional, whether aiming to express a wine’s sense of place or achieve a consistent house style, the underlying principle remains constant: understand the soil’s physical, chemical, and biological properties through systematic measurement and monitoring; recognize the constraints and opportunities these properties present; and adjust management—including irrigation strategy, nutrient inputs, cover crops, and rootstock selection—to match the site’s potential and the grower’s objectives. For wine professionals seeking to deepen their understanding of how soil shapes vine performance and ultimately wine quality, this book provides both the conceptual frameworks and practical tools necessary to transform vineyard soils from overlooked background into a sophisticated, managed resource central to sustainable, high-quality wine production.

About the Author

Robert White is Emeritus Professor of Soil Science at the University of Melbourne, Australia. He consults to the wine industry and provides technical advice on soil matters to the AWRI. His book Principles and Practice of Soil Science is a standard textbook for soil science. He has also written Soils for Fine Wines, Understanding Vineyard Soils, and Healthy Soils for Healthy Vines (with Mark Krstic) and co-edited the four volumes of Earthscan’s Soil Science.

Robert Edwin White | Google Scholar

White authored several soil-related entries in the Oxford Companion to Wine.

Soil (OCW)
soil and wine quality (OCW)

Book Reviews

Understanding Vineyard Soils by Susan S. Hubbard – 2010

Bonus

Book Notes

Understanding Vineyard Soils: A Complete Framework for Growing Quality Wine Grapes

Soil is far more than inert dirt beneath the vines—it is a living, dynamic system that shapes every aspect of viticulture from vine establishment through wine quality. Understanding Vineyard Soils provides a comprehensive, science-based framework for managing this complex medium, grounded in the realization that there is no single “ideal soil,” only appropriate combinations of biophysical properties matched to climate, grape variety, and winemaking objectives.

The Foundation: Soil Formation and Terroir

Soils develop through the interaction of five inherent factors—parent rock (geology), climate, organisms, topography, and time—that operate largely beyond human control but profoundly shape vine potential. Granitic soils produce coarse, well-drained, naturally low-fertility profiles suited to vigorous varieties on shallow slopes; basaltic soils develop into fine-textured, often fertile red loams that require careful vigor management in cool climates. Limestone soils are typically shallow but, when fractured, allow deep rooting and water regulation that produces distinctive, intensely flavored wines in regions from Burgundy to Coonawarra to Saint-Émilion. These inherent factors anchor the concept of terroir—the distinctive character of wines from a place—yet terroir’s precise mechanisms remain elusive. What is clear is that soil variability, operating at scales of meters to kilometers, is a practical resource for quality-focused growers.

Site Selection and Soil Preparation: Data-Driven Decisions

Establishing a vineyard requires gathering and integrating climate data, soil surveys, water availability assessments, and pest risk screening. Climate operates at three scales: macroclimate (regional, shaped by latitude and sea proximity), mesoclimate (local topography and slope), and microclimate (within-canopy conditions). Quantitative bioclimatic indices such as heat degree days help match cultivars to regions, though climate change introduces uncertainty. Soil surveys using electromagnetic induction (EM38) and ground-truthing can map spatial variability at high resolution, revealing zones suited to different management strategies. Deep ripping, executed when soil moisture is optimal (50–100 mm deficit), shatters compacted layers and opens fractured rock for root exploration—critical for otherwise constrained sites. The investment in systematic site assessment pays dividends through targeted amelioration, optimized irrigation design, and informed variety and rootstock selection.

Nutrient Management: Balancing Supply and Demand

Grapevines require 16 essential elements, most sourced from soil through root uptake from the soil solution. Nitrogen, phosphorus, and sulfur exist predominantly in organic forms and must be mineralized by soil microorganisms to become available; the carbon-to-nitrogen ratio of organic matter determines whether decomposition releases nitrogen (ratio <25) or immobilizes it (ratio >25). Nitrogen timing matters: early-season supply supports shoot growth, while post-flowering nitrogen uptake drives berry nitrogen concentration critical for yeast fermentation (200–480 mg N/L). Phosphorus, strongly adsorbed to clay and iron/aluminum oxides, is immobile; calcium, magnesium, and potassium bind to exchangeable cation sites; micronutrients like iron precipitate as insoluble hydroxides at higher pH, often necessitating foliar sprays. Plant tissue analysis (particularly petioles sampled at flowering) reveals nutrient imbalances more reliably than soil testing and guides corrective fertilizer applications. The principle is balanced nutrition—adequate supply without excess that triggers vigor, shading, and reduced wine quality.

Soil Water: Structure, Storage, and Regulated Stress

Soil structure—the arrangement of particles into aggregates with networked pores—determines whether a soil can support deep rooting and adequate water storage. Macropores (>500 μm) drain rapidly, allowing aeration; medium pores (30–500 μm) hold plant-available water; small pores (<0.2 μm) hold water so tightly that vines cannot extract it. At field capacity (two days after thorough wetting), a well-structured soil retains 10–15% air-filled porosity and 20–25% available water capacity—the balance required for aeration and water storage. Soil strength (measured with a penetrometer) should remain 1–2 megapascals at field capacity to allow root penetration without creating compacted, low-water-availability zones. The concept of “non-limiting water range”—the band of soil water content where aeration is adequate and strength permits root function—shrinks as structure deteriorates, effectively reducing water availability even if total water present is adequate.

Regulated deficit irrigation (RDI), practiced in most regions outside France’s AOC zones, withholds water strategically to balance yield and fruit quality. Moderate water stress from fruit set through veraison enhances flavor concentration and phenolic compounds in red varieties while reducing yield; stress severity and timing vary by cultivar (Cabernet Sauvignon should reach 22–23° Brix before peak stress, Syrah 18–20° Brix). Water stress management requires monitoring soil water deficit using tensiometers or water-budget calculations and understanding variety-specific sensitivity. Salt and sodium accumulation under irrigation demand winter leaching and gypsum amendment to maintain soil structure and vine health long-term.

The Living Soil: Organisms, Carbon Cycling, and Biological Health

Soil is fundamentally alive. The carbon cycle—the cascade of growth, death, and decay—nourishes decomposers (bacteria, fungi, actinomycetes) and reducers (earthworms, arthropods, mites) that mineralize nutrients and build soil structure through organic matter turnover. The rate of carbon turnover (expressed as turnover time: 1/k, where k is the annual decomposition fraction) indicates biological activity; turnover times of 20 years or less suggest active soils. Soil organic matter accumulates when inputs (cover crops, mulches, manure, compost) exceed losses through decomposition and erosion. Earthworms—when abundant (>250/m² or 2.5 million/ha in cool climates)—create biopores up to 5 mm diameter, dramatically improving drainage and structure. Building soil organic matter through legume-based cover crops (which fix atmospheric nitrogen via Rhizobium symbiosis at 50–100 kg N/ha/year when occupying the entire mid-row) and compost is feasible but depends on climate (faster in cool, humid regions) and soil texture (easier in clays than sands).

Phylloxera and root-knot nematodes—devastating pests—necessitate resistant rootstock selection (American species like V. riparia, V. berlandieri, and their crosses confer phylloxera and nematode resistance). Contemporary viticulture cannot operate as a purely “closed input system”: nutrient export in harvested grapes must be balanced by external inputs or long-term fertility declines. Organic viticulture benefits the soil biota through higher organic matter inputs and reduced synthetic chemicals, yet claims that organic wines are inherently superior remain subjective and unsupported by consistent sensory evidence.

Integration: Precision, Sustainability, and Winemaking Objectives

High-resolution soil and climate mapping, integrated into geographic information systems, enables creation of “digital terroirs”—spatially defined management zones optimized for variety, rootstock, irrigation, and harvest strategy. Precision viticulture’s main commercial application is differential harvesting by zone or timing to capture fruit quality variation, though adoption requires technical expertise, multi-year data, and willing buyers. A pragmatic approach integrates organic and conventional best practices: permanent cover crops and mulches build soil health; soil and plant tissue testing guide fertilizer applications; regulated irrigation and targeted amendments (lime, gypsum) address chemical constraints; and rootstock selection manages pests and salinity tolerance.

Climate change presents both uncertainty and opportunity. Growing season temperatures have risen 0.6–0.8°C since mid-20th century, with regional variation (Bordeaux +1.8°C, Rhine Valley +0.7°C); quality wine production is limited to 13–21°C average. Earlier-season water deficits, increased frost variability, and potential poleward shifts of wine regions pose challenges. Yet Australia and California have benefited from warming, achieving riper fruit and more consistent quality.

Ultimately, managing vineyard soils is about understanding the interaction of inherent and dynamic factors—the former fixed by geology and climate, the latter adjustable through cultivation, water management, nutrition, and biological stewardship. There is no “ideal” soil; there are only informed choices about how to work with a site’s constraints and opportunities to express its sense of place while achieving the grower’s economic and quality objectives. For those willing to invest time in understanding their soil, measure its properties systematically, and adapt management to match site potential, the result is not just better wine but vineyards that become more resilient and fertile over time—a legacy of stewardship rather than depletion.

Key Takeaways by Chapter

Chapter 1: What Makes a Healthy Soil?

Soil health integrates chemical, physical, and biological attributes that determine ecosystem functions—nutrient cycling, water storage, biodiversity support, and resilience.
Inherent factors (geology, climate, organisms, topography, time) create a site’s “sense of place” and cannot be changed; dynamic factors (organic matter, pH, nutrients, structure, water) can be managed by growers.
Soil formation varies dramatically by parent material: granite produces coarse, low-fertility, well-drained soils; limestone forms shallow but distinctive soils; volcanic basalts develop fertile, fine-textured profiles.
Terroir—the distinctive character of wines from a place—results from centuries of empirical knowledge linking soil variability to grape variety performance, not from scientifically demonstrated causal links between specific soil properties and wine typicity.
Modern soil survey using electromagnetic induction (EM38) and GPS-linked geographic information systems reveals fine-scale soil variation (meters) that traditional mapping misses, enabling precision management.

Chapter 2: Site Selection and Soil Preparation

Successful site selection integrates climate (using heat degree days or homoclime analysis), soil properties (depth, texture, drainage, strength), water availability, and pest risk into a local site index weighted by regional priorities.
Deep ripping performed in late summer/autumn when soil has 50–100 mm water deficit shatters compacted layers and opens fractured rock for root exploration without the structural damage caused by plowing.
Phylloxera and nematode testing of soil samples is essential before planting; all Vitis vinifera must be grafted onto resistant rootstocks if pests are detected, as fumigants provide only temporary control.
Irrigation water quality (electrical conductivity <0.8 dS/m, low sodium adsorption ratio) is critical; even low-EC water accumulates salts over repeated irrigation cycles, necessitating winter leaching or soil amendments.
Topography affects solar radiation, frost risk, and water drainage; slope aspect and altitude create mesoclimatic variation within vineyards that can be mapped and managed with precision viticulture.

Chapter 3: The Nutrition of Grapevines

Sixteen essential elements are required; nitrogen, phosphorus, and sulfur must be mineralized from organic matter by soil microorganisms before vine roots can absorb them.
Nitrogen timing shapes fermentation success: early-season supply supports growth; post-flowering nitrogen uptake drives yeast assimilable nitrogen (YAN) in juice (target 250–480 mg N/L for optimal fermentation).
The carbon-to-nitrogen ratio of organic matter (C:N) determines whether decomposition releases nitrogen (C:N <25, net mineralization) or locks it up (C:N >25, net immobilization); legume residues mineralize readily, straw does not.
Plant tissue analysis (petioles at flowering) detects nutrient imbalances earlier and more reliably than soil testing; critical values for macronutrients and micronutrients have been established by variety and region.
Micronutrient availability is pH-dependent: iron, zinc, manganese, and copper decrease in solubility as pH rises; molybdenum and boron (to pH 8) increase; acid soils (pH <4) risk aluminium toxicity but may produce distinctive wine character.

Chapter 4: Where the Vine Roots Live—Soil Structure and Water Management

Soil structure—how particles organize into aggregates with pore networks—determines porosity (typically 50–60% in A horizons), aeration, drainage, water storage, and root penetration.
At field capacity, ideal vineyard soil has 10–15% air-filled porosity and 20–25% available water capacity (200–250 mm per meter depth); this balance allows oxygen diffusion while storing readily available water.
The “non-limiting water range” (NLWR)—the soil water content band where aeration is adequate and strength permits root function—shrinks as structure deteriorates; compacted soils can reduce NLWR to millimeters despite adequate total water present.
Regulated deficit irrigation (RDI) manipulates water stress strategically: adequate supply bud burst to fruit set (to avoid yield loss), moderate stress fruit set to veraison (enhances flavor and phenolics in reds), and variety-dependent stress thereafter (Cabernet/Merlot: 22–23° Brix; Syrah: 18–20° Brix).
Salinity and sodicity under irrigation require winter leaching (preferably via rainfall) and gypsum amendment; high sodium content (>6% of cation exchange capacity) destabilizes soil structure and impairs drainage.

Chapter 5: The Living Soil—Carbon Cycling, Organisms, and Pest Management

Soil organic matter turns over at varying rates: fresh residues decompose in weeks, while humified organic matter persists for decades; turnover time of 20 years or less indicates biologically active soil.
Earthworms—the most important soil reducers in vineyards—can reach 2.5 million per hectare under permanent grass cover in cool climates, creating biopores up to 5 mm diameter that dramatically improve drainage and aeration.
Soil organic matter accumulates when inputs (cover crops adding 1–12 t dry matter/ha/year, manure, compost) exceed losses; accumulation is slower in hot, sandy soils than in cool, clay soils.
Legume-based cover crops fix atmospheric nitrogen through Rhizobium symbiosis (50–100 kg N/ha/year when occupying the entire mid-row) but require adequate pH, calcium, phosphorus, and effective bacterial strains for success.
Phylloxera and root-knot nematodes demand resistant rootstocks (V. riparia, V. berlandieri, V. champanii crosses); organic viticulture offers no advantage in pest control; modern viticulture cannot operate as a truly “closed input system” due to nutrient export and losses.

Chapter 6: Putting It All Together—Integration and Sustainable Viticulture

There is no ideal soil; soil performance depends on matching inherent properties (depth, parent material, natural fertility) to climate, variety, and management objectives; deep soils suit low-nutrient sites but risk excess vigor in fertile regions.
Precision viticulture using high-resolution soil and climate mapping creates “digital terroirs”—management zones for differential variety selection, irrigation design, and harvest timing; adoption depends on technical expertise and willingness to harvest zones separately.
Nitrogen supply must balance vigorous growth with fruit quality: red varieties risk excessive shading at high N (compromising color and phenolics); white varieties like Sauvignon Blanc need good N and water for aromatic development.
Organic viticulture improves soil biological measures and reduces synthetic chemical inputs but shows no consistent sensory quality advantage over well-managed conventional viticulture; both approaches require external nutrient inputs for long-term sustainability.
Climate change has warmed growing seasons 0.6–0.8°C since mid-20th century with regional variation; quality wine production remains limited to 13–21°C average; future challenges include earlier water deficits, increased frost variability, and potential poleward region shifts.
Sustainable viticulture balances environmental soundness, social equity, and economic feasibility through nutrient budgeting, systematic soil monitoring, targeted amendments, irrigation management, and pest control via rootstocks and biological methods.