Sunday, July 5, 2020

The white wines of Piemonte: Roero Arneis DOCG

Roero is a small DOCG (DOC 1985, DOCG 2004) located on the north bank of the Tanaro River and running along said bank for approximately 24.1 km (15 miles) between Bra and Govone. The zone is approximately 878 ha (2169 acres) in size with 2014 production of approximately 436,000 cases. The relative positioning of Roero DOCG is illustrated in the map below.

The climate of Roero is described as cold temperate and manifests as harsh, cold winters; hot, humid summers; and unpredictable springs and autumns. Climatic effects are moderated by (i) the warm Mediterranean winds meeting and mitigating the cold winds flowing down from the north and (ii) the Apennines providing a barrier to the winds from the sea.

The soil is primarily sand, a result of the area being an ancient seabed, with clay and/or limestone intermixed in specific areas. Unlike the Langhe, formed 15 million years ago during the Miocene, the soils of the Roero are only 5 million years old, laid down, as they were, during the Pliocene period of the Tertiary era. The proliferation of sea fossils in the sand is a testament to its sub-sea past. According to Antonio Galloni (Exploring Roero, Vinous, May 2015), the soil characteristics give the Roero wine much of its mid-weight, perfumed personalities. In the places where the sand is intermixed with silty soils rich in clay and marine deposits, the grapes grown thereon confer a greater depth and structure to the resulting wines (Galloni).

Roero DOCG governs the production of white and red wines within the zone. The white wines are produced from Arneis, maybe the most important white grape in Piedmont. The reds are made from Nebbiolo and Barbera and, according to Michael Skurnik, the young reds from the region have a "particularly fresh and vibrant character." Galloni sees Roero excelling with Arneis and expressed pleasure with both the top-end and entry-level Nebbiolos and Barberas. He does see some challenges for the region though:
  • The most famous Roero wines are made by producers who are based outside the region (Giacosa and Sandrone, for example)
  • The region lacks a visible, reference point producer who might be able to elevate the standing of the entire area
  • The region continues to live in the shadow of Barolo and Barbaresco.
Arneis is currently one of Piemonte's most important white varieties; but that was not always the case. Tom Hyland, writing in Forbes, tells the tale of this variety -- called Nebbia Bianca at the time -- being planted between Nebbiolo rows to serve as a (diversionary) food source for the birds and, as a result, protecting the more valuable fruit from the marauders.

Hyland also tells of the variety being acquired from Roero farmers by Luca Currado's (Vietti) father for the purpose of crafting a sweet wine and him accidentally fermenting it to dryness. That turned out to be a fortuitous mistake, based on the more than 7 million bottles of Arneis that is produced today.

Below I describe some of the Roero Arneis wines I have tasted.

My first formal Arneis tasting was during a visit to the Vietti estate in Piemonte.

The first wine tasted in that session was the Vietti Roero Arneis 2015. The grapes for this wine were sourced from vineyards planted in 1967 in Santo Stefano Roero on calcareous clay soils. The training system is guyot and the planting density is between 4500 and 5000 vines/ha. The wine wss fermented in stainless steel tanks and remained on the lees for 25 days.

Walnut and creamy richness. Lime and lime rind. Minerality. Attention-grabbing acidity. Elena thought that this wine should be put aside for maybe 1 year.

I first had the Bruno Giacosa Roero Arneis at  a 2018 Wine Watch dinner held in Giacosa's honor. I enjoyed it immensely. The Giacosa Arneis that I tasted recently was from the 2014 vintage. It had a golden yellow color and was perfumed, with notes of green herbs, pepper and straw. Tropical notes on the palate with juicy, ripe fruit sweetness. Lemon-lime and spicy. Lengthy finish with a metallic/cupric aftertaste.

Monchiero Carbone has a history in Roero that stretches back over a century. Its ReCit ("little King" in the Piedmontese dialect) Roero Arneis is an assemblage from a number of different Roero vineyards, fermented in stainless steel tanks. The 2017 version of the wine was aromatic with notes of hay and unripe melon. Weighty on the palate and perfumed fruit. Almost sweet. Not as refreshing as the Giacosa. Slightly overbearing. Tangerine and napthalene ball finish. This was not my favorite Arneis.

The Rocca Felice Roero Arneis appears to be a Total-Wine-Direct label. I was impressed. The 2018 version was a much better wine than the ReCit. Floral on the nose with notes of peaches and pears. Balanced minerality and spice with a clean finish. This wine is a good representation of what I would call a classic Roero Arneis.

©Wine -- Mise en abyme

Friday, July 3, 2020

Asti DOCG: Key aspects of the appellation

The most widely recognized Italian sparkling wines are Prosecco, Franciacorta, and Asti. With that in mind, it was a major oversight on my part to omit detailed information on Asti, and its, wines, in my recently concluded survey of Italian sparkling wines. I correct that oversight in this post.

The key details of Asti DOCG is presented in the chart immediately following.

©Wine -- Mise en abyme

Tuesday, June 30, 2020

Mapping the sparkling wines of Italy

A little over seven months ago, I set out on a journey to develop a map of the sparkling wines of Italy. Fairly early in the process I realized that I would have to undertake the task on a region-by-region basis due to the wealth and diversity of available data. I have completed that effort and thumbnails of each region's map is included in the chart below, with the detailed maps presented at the end of this post.

The data show 137 DOC-level sparkling wines and 16 at the DOCG level. Within each of the appellations, one or more labels are allowed and the wines can be specified Metodo Classico, Charmat, or either. International varieties are the most broadly distributed across the regions with Chardonnay, Pinot Bianco, Pinot Nero, and Pinot Grigio each being used liberally. This highlights the fact that producers largely utilize regional indigenous varieties in making sparkling wines in their individual regions.Wines are specified either as blends or varietals.

Of the large number of allowed wines, a few are more widely recognized than the large majority. I provide a more detailed view of these noteworthy wines in the text below.

Prosecco DOCG 
There are two separate Prosecco DOCG zones, both falling within the borders of the province of Treviso. The first, and having the greatest repute, is Prosecco di Conegliano-Valdobbiadene. This zone is approximately 50 km from Venice and 100 km from the Dolomites. It runs east to west from the plains to the foot of the Alps and incorporates the 15 hill communities that lie between Conegliano and Valdiobbadene. Approximately 6100 ha of vineyards are deployed on south-facing slopes that range between 50- and 500-meters high.

An area within the municipality of Valdiobbadene called Cartizze is considered the region's cru. This 106-ha area has a mild microclimate and a varied soil to include moraine, sandstone, and clay components. The vineyards are positioned on south-facing slopes and have excellent drainage.


The second DOCG zone is Colli Asolani/Asolo and is located in the Montello e Colli Asolani wine region. It encompasses a 5-mile-long ridge of gently rolling hills running between the towns of Cornuda and Asolo. The best vineyards are found on south-facing slopes where the gentle gradients and loose soil combine for excellent drainage and optimal sunlight exposure.


Prosecco DOC
The Prosecco DOC was first awarded in 1969 and was restricted to wines produced in the Conegliano-Valdiobbadene region.  Growers felt that the brand was under attack by "imitators" using just the grape variety and moved to isolate those competitors by changing both the rules and the venue of the game.  Prosecco growers agitated for, and gained regulatory acceptance of: (i) extension of the Prosecco DOC to cover all of Friuli-Venezia-Giulia and approximately two-thirds of Veneto; (ii) promotion of the original Prosecco DOC to DOCG status; (iii) changing the name of the source grape from Prosecco to Glera; and (iv) restricting the use of the name Prosecco only to Glera sparkling wines produced within the delimited zones.  The growers felt that these actions would serve to protect their territory, the brand, and the quality of Prosecco.  The regulations authorizing these actions came into law in 2009.

The Grape(s)
Prosecco is primarily made from the Glera (formerly Prosecco; also known as Prosecco Bianco and Proseko Sciprina) grape variety, a native of northeast Italy which has been used to produce wines since Roman times.  This late-ripening, thick-skinned variety has greenish-yellow berries which evolve to a yellow-gold color as the grapes ripen.  The grapes are high in acid and have a white peach aromatic profile, qualities which render them eminently suitable for the production of sparkling wines.

Glera is primarily used in the production of fizzy and sparkling wines but there are a few examples of still Glera wines around.  In addition to Glera, Prosecco wines can contain as much as 15% of other grape varieties.  The most oft-used supplements are Verdiso, Branchetta, Perera, Glera Lunga, Pinot Bianco, Pinot Noir, Pinot Grigio, and Chardonnay.

Prosecco DOC Production Area
Prosecco DOC wines are authorized for production in Friuli-Venezia-Giulia and Veneto (provinces of Treviso, Belluna, Padova, Venezia, and Vicenzia).  Within the broader Prosecco DOC, there are two sub-zones: DOC Treviso Prosecco and Prosecco di Trieste. These sub-zones cover Prosecco made within these two provinces and wines made therein can so indicate on their labels.  Prosecco wines made in other provinces cannot carry the province name on the labels.


Prosecco Rosé
This is a new addition to the lineup and is viewed as having the potential to provide a significant sales boost to the Consorzio members who have been suffering the effects of the Coronavirus pandemic. The requirements for the new entrant are as follows:
  • Glera base blended with 10 - 15% Pinot Nero
  • Max yields 18 tons/ha for Glera and 13.5 tons/ha for Pinot Nero
  • from Brut Nature to Extra Dry
  • Prise de mousse must happen in vat according to the Charmat Method for a minimum of 60 days
  • Commercialization allowed fro January 1st following harvest
  • Labels must be vintage-dated (millesimato) with a minimum of 85% of the fruit coming form the stated vintage.
Asti DOCG is by far the largest sparkling wine appellation in Piemonte with 9700 ha under vine in 52 municipalities stretching across the provinces of Alessandria, Asti, and Cuneo. Most Asti production is via the Charmat method but, as the region's sparkling-wine map shows, there is a designation for Asti Metodo Classico. The Moscato Bianco grape is used as the raw material for the Asti wine.

Alta Langa DOCG
Alta Langa -- DOC in 2002, DOCG in 2011 -- is the new kid on the sparkling-wine block but the combination of its terroir, traditional Champagne varieties, traditional production method, skilled growers, and savvy producers bode well for the future.

The Alta Langa DOCG is spread over 142 communes in the provinces of Alessandria, Asti, and Cuneo. Given the geographic scope of the region, one encounters a variety of climates, exposures, elevations and soil types. In general, the soil is a mildly fertile calcareous clay marl.

Vineyards are required to be planted at 250 m and above on the region's steep, terraced hillsides. Allowed varieties are Pinot Noir and Chardonnay and other non-aromatic grapes. Planting density is a minimum of 4000 vines/ha with the vines trained using the low espalier system and pruned traditional Guyot and spurred cordon. The maximum allowed yield is 11,000 kg/ha.

The Alta Langa producers -- 27 currently -- do not grow enough fruit to meet their needs but that gap is bridged with fruit from 80 growers who own their land and are guaranteed producer-payment for their grapes and labor.

Franciacorta DOCG
Franciacorta (the name means either "little France" or "tax-free zone," depending on the publication consulted) is located in the "gentle" hills in the area of Brescia and is bounded thusly: to the east by rocky hills; to the west by the Oglio River; to the north by Lake Iseo and the foothills of Alpi Retiche; and to the south by the Brescia-Bergamo Highway.  The region lies in an amphitheater which was carved out by a falling glacier and encompasses all or part of 19 Brescian municipalities.   The zone is approximately 18,000 hectares in size with 2665 hectares under vine.


Franciacorta is mild in the winter and hot in the summer.  The climate is moderated by winds blowing in off Lakes Iseo and Garde which protect the region from the autumnal and hibernial fogs that threaten from the Brescian plains.  Rainfall in the region is concentrated in the spring and fall.

Thanks to exhaustive zoning studies conducted in the region in the late 1990s by the University of Milan, a very clear picture of soil differentials -- and the differing contributions of each type to the finished product -- has been established.  The figure below shows that the combination of landscape units (formations by geologic era) and soil types results in six distinct regional terroirs.  The figure illustrates that the soil, vegetative productive, qualitative, and organoleptic characteristics of each terroir has also been identified.  The details of those characteristics are contained in the table following.

Formulation of Terroirs  Derived from Franciacorta: un vino, una terra, p. 28-33

Characteristics of Franciacorta Terroirs. Derived from Franciacorta: un vino, una terra, p. 28-33

The sparkling wine is produced under the DOCG classification from Chardonnay, Pinot Noir, and Pinot Bianco grapes. The wines are produced using the classic method and, depending on the terroir in which it was grown, or the blend of terroirs, will exhibit some subset of the organoleptic qualities indicated in the last column of the table above. Wines are labeled in terms of sweetness much the same as is the practice for Champagne.

A fourth variety -- Erbamat -- is emerging as potential aide in the battle against the ripeness and climate effects of the region. Erbamat is a high-acid, late-ripening white grape that is native to the region and with a history that stretches back to circa 1500. The cultivar had slipped into obscurity until a recent study by a university professor highlighted its characteristics. Its primary characteristics are as follows (Aldo Fiordelli, Decanter, 3/21/17):
  • Pale straw color with greenish tinge
  • Thin skin
  • Compact bunches
  • Late ripening (20 - 30 days after other varieties)
  • Higher levels of malic acid (produces lean-bodied, high-acid wines)
  • Low sugar production (low alcohol wines).
The thin skin and tight bunches render the grapes subject to disease pressure but that risk is more than offset by the freshness, white florality, and chalky minerality which this wine brings to the blend. The variety is allowed in all of the Franciacorta styles with the exception of Satén.

The most respected producers in the region are Bellavista, Berlucchi, Ca' del Bosco, Cavalleri, Facoli, and Monte Rossa.

Oltrepò Pavese Metodo Classico DOCG
Oltrepò Pavese's 13,500 ha of vineyards makes it one of Italy's largest appellations while its 3000 ha of Pinot Noir vines is easily the largest planting of that variety in Italy. The appellation covers 42 municipalities in the Apennine foothills on the south bank of the Po River across from Pavia; foothills comprised of marine sedimentary rock with significant clay content.

Winters are dry and temperature fluctuation is significant due to ascending air current on the slopes.

Pinor Noir is the dominant variety for sparkling wine production. The first sparkling wine from this variety was made by Count Augusto Giorgi di Vistarino in 1865 and the family still produces some of the best spumante in the region today.

Trento DOC
Trento DOC is the specific appellation for sparkling wine produced in the Trento portion of Trento-Alto Adige. As is the case in Alto Adige, the wine is made using the Metodo Classico.

Trentino terroir is similar to that of Alto Adige even though it is 150 m lower down the valley. The DOC stretches for 800 ha over 74 municipalities with elevations ranging between 100 and 800 m.

Its climate is modified by the peaks and ridges which protect the region from the elements. A cool breeze from the mountains minimizes the exposure to rot and fungal diseases. Two winds blow on the area north of Lake Garda from March to September: a north-to-south morning wind and a south-to-north afternoon wind.

The two major growing areas are Val di Cembra and Valle dei Laghi with the former being narrower, with more volcanic soil, and showing greater effects of elevation. The latter is closer to Lake Garda and shows more of a Mediterranean climate. The soil is a stony limestone in the upper reaches with moraine deposits lower down.

Chardonnay and Pinot Noir  dominate the vineyards. Chardonnay does better at higher altitudes with sun exposure (provides the backbone) while Pinot Noir enjoys lower, less sunny altitudes (imparts body). Producers source grapes from multiple areas and will blend wines from warmer and cooler sites.

According to Kerin O'Keefe, the sparkling wines of this region show "pronounced aromatics, elegance, and bright acidity." Two producers that she recommends are Ferrari (2010 Perlé Nero Extra Brut Riserva) and Rotari (2011 Flavio Brut Riserva).

Approximately 7,500,000 bottles of sparkling wine are produced in this region annually.

Lissini Durello DOC
This sparkling-wine-only appellation covers the high valleys of the Lissini Mountains between the provinces of Verona and Vicenza. The volcanic slopes provide the high hillside vineyards exposure, ventilation, and diurnal temperature variation, all of which contribute freshness and aromatic qualities to the sparkling wine.

The variety is Durella, indigenous to these mountains since the Middle Ages. The grapes are golden-hued with thick skins and acidulous flavor. Because of its high acidity the Durella destined for sparkling wine is picked at full maturity.

Writing in Wine Enthusiast (Metodo Classico, Your Next Italian Sparkling Wine (That Isn't Prosecco)), Kerin O'Keefe describes these sparkling wines as boasting "... tension, energy, and finesse." O'Keefe also points out that an upcoming regulatory modification will have the name Lessini Durello used exclusively for Charmat sparklers while the Metodo Classico versions will be called Monte Lessini. Her wine recommendations are:
  • Coret Moschina 2012 Riserva 60 Mesi
  • Sandro de Bruno NV 36 Mesi
  • Fattori 2012 Ronca Non Dosato 60 Mesi Metodo Classico.
Vigneti della Serenissima DOC
This appellation covers the hilly and foothill areas of the provinces of Belluno, Treviso, Padua, Vicenza, and Verona between the Alps in the north and the Po Valley in the south. The climate is conducive to gradual ripening of grapes. Sparkling wines are produced using the classical method.

Abissi Sparkling Wine
Bisson Winery in Liguria has been aging its Metodo Classico wines in 60 meters of water off the coast of Portofino since 2005. The wines -- there are three of them: Spumante Classico, Spumante Riserva, and Spumante Rosé -- are fermented traditionally to produce the base wines and are then bottled and lowered into the sea in July so that the second fermentation can be completed in the anaerobic conditions below the surface of the water.

The Spumante Classico and Riserva are blends of Bianchetto Genovese, Vermentino, and a third cultivar called Cimixià. The Rosé is a blend of Granaccia and Ciliegiolo.

The innovative method of aging is the brainchild of Pierluigi Lugano, the enterprise's winemaker. "When the wine bottles are picked up, they are enriched with incrustations (sic), seaweeds (and sometimes shellfishes, too) ... For health and sanitary reasons, bottles are then dried and wrapped under a protective, clear film, which also serves the purpose of preserving the natural ornament made by the sea,"


"The main Emilia wine is undoubtedly Lambrusco, the fizzy and sometimes sparkling, jovial red wine from grapes grown on high trellised vines in five DOC zones in Modena and Reggio Emilio." The map below shows the Lambrusco production area within Emilia-Romagna.

Lambrusco production area 

Lambrusco first came to prominence as "cheap, cheerful and fizzy plonk served with ice cubes ... cloyingly sweet versions that flooded U.S. shelves in the 1970s and '80s" (O'Keefe). In an article asking readers to take a second look at the wine, Karen O'Keefe sees that "a number of producers now make distinct, slightly sparkling Lambruscos that belong on every wine lover's radar."

As shown in the sparkling wines maps, there are three specific Lambrusco DOCs (Sorbara, Grasparossa di Castelvetro, and Salamino di Santa Croce) and two other DOCs (Modena and Reggiano) which also produce Lambrusco sparkling wines.

Lambrusco di Sorbara is generally lightly colored, fragrant, and in possession of vibrant acidity. The grapes are thin-skinned, with very little pigment, and the bunches have berries of varying sizes. Grapes for this wine excel in the sandy, fertile plains between the Secchia and Panarao rivers. O'Keefe sees this wine as the most-refined of the Lambrusco category.

Lambrusco Grasparossa di Castelvetro is made from a "thick-skinned, late-ripening, darkly hued" grape that is definitively more tannic than the Sorbara variety. This variety does well in clay and silt soils.

Lambrusco Salamino di Santa Croce is the most planted of the Lambrusco grapes and is often blended with other Lambrusco wines to take advantage of its color and and acidity. The soils in the growing area are similar to the soils in the Sorbara region but some grapes are also grown in the clay and rocky soils close to the Reggio Emilia foothills.

Sparkling wine production in the province of Romagna peaked at the beginning of the 20th Century and then declined somewhat. In order to recapture this past glory the Romagna Consorzio has introduced a new trademark of Romagna Spumante DOC that every producer in the region can utilize if specified conditions are followed. The name of the new wine is Novebolle (nine bubbles) with Nove (nine) referring both the the nine hills of Romagna as well as the period (1900s) in which sparkling wine had flourished in the region.

The wine can be white or Rosé and can be made by either the Charmat or Traditional method. The composition of both wines are included in the second of the two sparkling wine maps above.

The first expression this new trademark has been captured in Bolé, a joint venture between two of the region's Coops: Caviro (the largest winery in Italy) and Terre Cevico.


This Bianco is a mix of Trebbiano and Famosa (5%) made using the classic method. Plans call for increasing production from today's 45,000 bottles to 100,000 bottles and the production of a Rosé that adheres to the Consorzio's restrictions.

Vernaccia di Serrapetrona DOCG
This wine has been described as an "idiosyncratic sparkling red wine produced from the local Vernaccia Nera." This territory was granted DOC status in 1971 and elevated to DOCG in 2003. It is one of the smallest classified zones in Italy with only 20 ha of vineyards and 5000 cases produced. Vineyards must be sited between 450 and 600 m elevation.

Other than the fact that it is a sparkling red wine, Vernaccia di Serrapetrona is also unique in its production method: three fermentations. The first fermentation involves up to 60% of the handpicked grapes. The remaining 40% is dried on straw mats and added to the wine in the following January for the second fermentation. After resting for a few months, the wine is placed into pressurized containers where it is fermented using the Charmat method.

The result of this process is "an intensely aromatic wine displaying a raspberry red color, aromas of strawberries and cranberries, a hint of spice, firm tannins and bright acidity,"

Verdicchio dei Castelli di Jesi DOC and Verdecchio di Matelica DOC
These are the two DOCs that are the temples to Verdicchio, with the former being more revered than the latter. The sparkling wines from both regions require a minimum of 85% of the Verdicchio grape and can be made using either the Metodo Classico or Charmat methods.

The grapes for Verdicchio dei Castelli di Jesi are grown in the hilly areas around the town of Jesi, an area endowed with calcareous clay and limestone-rich soils. The area is blessed with a relatively dry maritime climate with persistent gentle onshore (morning) and offshore (afternoon) winds providing defenses against fungal diseases such as grey rot and mildew.

The Verdicchio di Matelica vineyards are located further inland in more of a continental climate but with soils akin to its compatriot. Vineyard orientation in Matelica is east-to-west, a situation unique to that DOC. A total of 740 ha of vineyards are planted at 400m - 500m elevation.

In his Forbes article on Italian sparkling wines, Tom Hyland identified the Colonnara Tradition Brut as one of the best examples of Verdicchio sparkling wine that he has tasted. The wine, he says, "... offers subdued herbal notes in the finish, along with bright pear and melon fruit."

In that same article, Hyland spoke favorably of a number of Verdicchio/Chardonnay cuvées:
  • Poderi Mattioli Dosaggio Zero -- vintage-dated blend that is aged 48 months on its lees
  • Umani-Ronchi Extra Brut millesimato -- 65% Verdicchio, 35% Chardonnay
  • Umani-Ronchi La Hoz -- 80% Verdicchio, 20% Chardonnay. The Verdicchio is aged in steel while the Chardonnay is aged in mid-sized oak barrels. The wines are aged on lees for 48 months.
Greco di Tufo DOCG
The sparkling wines in Greco di Tufo DOCG are made in the traditional manner and stay on the lees for at least 3 years. According to, "These straw yellow wines are intense, herbaceous, floral, and fruity with typical notes of apples, jasmine, thyme, or sage. They are best paired with rich seafood dishes and could go well with lobster or cod ... they are also an excellent aperitif and would be a great match to various appetizers."

Feudi di San Gregorio, one of the leading independent wine producers in Campania, has established a separate label -- DUBL -- under which to market its Spumante wines. This project began in 2004 and was aimed at bringing the classic sparkling wine method to the grapes of the Campanian tradition: Greco, Aglianico, and Falanghina.

Feudi San Gregorio felt that they had the high-quality fruit for such an initiative. The internal areas of the region are ideal for growth of grapes destined for sparkling wines:
  • Diurnal temperature differences would allow grape ripening with acid-retention
  • The ventilation and exposure of the vineyards are ideal
  • Rugged terroir 
  • Volcanic soils.
They did not, however, have the requisite skill. To fill that gap they sought the advice and assistance of Anselme Selosse -- of Jacques Selosse grower-Champagne fame. The wines that resulted were a 100% Greco sparkling wine, a 100% Aglianico sparkling Rosata, and a 100% Falanghina as a Double Brut.

In April 2016, DUBL extended its product portfolio with DUBL Esse, a Dossagio Zero line, with a white sparkling made from the best grapes from the most exciting vineyards in the Tufo area and a Rosata which comes from grapes from the most exciting vineyards in the Taurasi area.

Etna Spumante DOC
In a May 22, 2019, Forbes article on Italian sparkling wines, Tom Hyland stated thusly:
Given that the climate of Sicily is warm, you wouldn't expect sparkling wine to be produced here, but there are some very fine examples. A few producers in the Etna zone are crafting some beautifully rendered metodo classico cuvées, including Planeta, Terraze dell'Etna and Murgo. The wines vary from Planeta's 100% Carricante version to several offerings each from the latter two producers. Terraze dell'Etna produces two offerings of Brut made entirely from Chardonnay, with one being aged on its lees for 50 months, and they also produce two different Rosé Brut, again with one being aged for 50 months on the lees; the rosés are made from 90% Pinot Nero and 10% Nerello Mascalese. ... The finest sparkling wines from Sicily in my estimation.

©Wine -- Mise en abyme

Regenerative Agriculture: Soil health and carbon sequestration

The Regenerative Organic Alliance recently announced details of its certification program. This will be of interest to viticulturists the world over so I have begun a series detailing the program, the underlying schema, and the practices. To date, I have written posts on the certification program, Regenerative Agriculture as a farming approach, and a soils-composition primer. The Regenerative Certification proposes practices in both soil health and carbon sequestration; I provide background on the convergence of both topics in this post.

Carbon is found in the soil in both inorganic and organic forms. The makeup and storage of carbon in soils (from traditional sources) are detailed in the figure below.

Soil carbon, which comprises 60% of soil organic matter, causes the soil to retain more water and results in better crop yields during droughts, a reduction in soil erosion, increased plant nutrient retention, and increased biological diversity. Higher soil carbon levels also hold soil particles together so that less erosion occurs (Pimentel and Burgess, Maintaining sustainable and environmentally friendly fresh produce production in the context of climate change, Global Safety of Fresh Produce, 2014).

The charts below show how atmospheric carbon makes its way into the soils and how it is used as currency by soil microorganisms.

Source: USDA

Microbial decomposition releases carbon dioxide so the ability of the soil to shelter some carbon from decomposition is important (Cho):
  • Soil aggregates shelter carbon particles within their structures
    • Aggregation happens when tiny particles of soil clump together
    • Mycorrhizal fungi produce sticky compounds that facilitate soil aggregation
      • They are able to transfer 15% more carbon into the soil than other microbes
    • These aggregates give soil its structure
      • Essential for healthy plant growth
  • Soils with high clay content are also able to form chemical bonds that protect carbon from microbes
Soil Health Imperative for Increased Soil Carbon Levels
As the world's population has increased, so has the pressure on its farmers to produce the food necessary to meet this growth. But, conversely (see chart below), the world has seen a 60% loss in the topsoil over the last 150 years.  And the topsoil that remains has been severely degraded by pesticides and fertilizers.

Pesticides can harm beneficial soil organisms as well as pollute waterways with runoffs. Fertilizers harm in that they feed the plants directly, to the long-term detriment of the plant, the soils, and the microorganisms that inhabit those soils.

According to Mark Bradford, et al. (Soil carbon, source for policy and practice, Nature Sustainability), there is a "scientific consensus on the need to rebuild soil organic carbon for sustainable land stewardship."

Climate Mitigation Imperative for Increased Soil Carbon Levels
According to a Slate article, Napa grape growers are embracing "carbon farming" -- "a suite of practices designed to maximize carbon storage in the soil." According to the article, the most optimistic calculations suggest that, if implemented worldwide, carbon farming would sequester 100% of global CO₂ emissions. The Napa County Resource Conservation District is currently creating free customized plans for interested vineyard managers. Let's take a deeper look at the thinking behind carbon farming.

The earth's soils store three times the amount of carbon in the atmosphere and four times the amount stored in all living plants and animals. Human action introduces an enormous amount of carbon dioxide into the atmosphere and about 25% of that amount is returned to the soil through the photosynthetic activity of plants.

Programs like California's Healthy Soils Initiative and France's 4 per 1000 Initiative (detailed below) promote land management practices designed to build soil organic matter in order to increase carbon sequestration and reduce overall greenhouse gas emissions.

Strategies for Increased Soil Carbon Retention/Capture
Reducing the amount of carbon that is released from the soil -- plus storing additional carbon in the soil -- is seen as key to both improved soil health and the battle against climate change.

Table 1. How soils can sequester greater amounts of carbon.
Regenerative Practices Outcomes
Cover crops (like clover and legumes)
  • Can compensate for carbon loss from tillage by putting more carbon into the soil
Leaving crop residue in the ground
  • Can compensate for carbon loss from tillage by putting more carbon into the soil
Crop rotation/diverse crops Adds more varied biomass to the soil, and, hence, more carbon
Conservation tillage
  • Soil carbon not exposed to O and soil aggregates remain intact, sheltering their carbon
Rotational grazing
  • Helps keep carbon in the soil by moving herds to new pastures after grazing, allowing old ones to renew
  • Carbon, in the form of manure, gets spread around
Manure and compost Increase soil productivity and the formation of stable carbon that cam remain in the soil for decades

More carbon in the soil translates to more fertile soils which:
  • produce more food
  • promotes biodiversity
  • holds moisture more effectively
  • is less vulnerable to erosion, floods, nutrient loss
There are a number of dissenting voices around the use of carbon sequestration as a tool in the battle against climate change. Bradford says that the conflation of arguments relating to climate mitigation and soil health is not surprising because many of the initiatives share carbon acquisition and soil restoration goals. But, he says further, "we submit that rebuilding soil carbon in agricultural soils should be treated as a distinct objective that is well supported by soil scientific knowledge." I note here that The Regenerative Organic Alliance Certification does have separate channels for Soil Health and Carbon Sequestration practices.

Janet Ranganortham, et al. (Regenerative Agriculture: Good for Soil Health, but limited potential to Mitigate Climate Change, World Resources Institute, 8/12/20), states that "Practices grouped as regenerative agriculture can improve soil health and yield some valuable environmental benefits, but are unlikely to achieve large-scale emissions reductions."

According to Cho, scientists at UC Irvine think that models might have overestimated -- by 40% -- the potential of soils to sequester carbon. Cho says that these studies say that there is no silver bullet and that, ultimately, the best way to combat climate change is to reduce fossil fuel use and move to renewables as quickly as possible. And the latter is the fundamental point that Bradford was making. He did not want carbon initiatives to divert attention from the real large-scale opportunities in the climate change fight.

©Wine -- Mise en abyme

Thursday, June 25, 2020

Regenerative Agriculture: A soils-composition primer

Soil health, according to the USDA, is "... the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans." Agriculture Victoria defines soil health as "... the condition of the soil in relation to its inherent (or potential) capability, to sustain biological productivity, maintain environmental quality, and promote plant and animal health."

Photo credit: USDA

Soil health is one of the key pillars of the Regenerative Organic Certification and a key objective of Regenerative Agriculture as a discipline. In order to fully understand the principles guiding the soil health requirement of Regenerative Agriculture, we need an understanding of soils. I present a soils primer in this post.

The essential functions of soils are (
  • Regulating water -- soil helps control where rain, snowmelt, and irrigation water go. Water and dissolved solutes flow over the land or into and through the soil
  • Sustaining plant and animal life -- the diversity and productivity of living things depend on soil
  • Filtering and buffering potential pollutants -- the minerals and microbes in soil are responsible for filtering, buffering, degrading, immobilizing, and detoxifying organic and inorganic materials, including industrial and municipal by-products and atmospheric deposits
  • Cycling nutrients -- carbon, nitrogen, phosphorous, and many other nutrients are stored, transferred, and cycled in the soil
  • Physical stability and support -- provides a medium for plant roots.
The major soil components are illustrated in the chart below and then detailed in the text following.

Approximate composition of soil

Soil Components
Soil is comprised of air, water, mineral particles (a mix of clay, silt, and sand), organic matter (decomposing plant material), and organisms (bacteria, algae, fungi, earthworms, insects, etc.).

Soil Minerals
The earth is made up of varying proportions of the 90 or so naturally occurring elements but, according to Alex Maltman (Vineyards, Rocks, & Soils), four of these -- oxygen at 48%, silicon at 28%, aluminum at 8%, and iron at 6% -- are responsible for 88% of its composition. In most geological materials, these elements combine to form minerals -- "a naturally occurring combination of specific elements that are arranged in a particular repeating three-dimensional structure or lattice" (, Minerals and Rocks).

In nature, minerals are found in rocks "and the vast majority of rocks are composed of at least a few different minerals." The picture below shows a piece of granite and its constituent minerals.

A close-up view of the rock granite and associated minerals

Jackson (Wine Science: Principles and Applications) stipulates that (p. 245) "... the mineral content of soil is primarily derived from the parental rock substrate." Soil minerals play a vital role in soil fertility in that (i) mineral surfaces serve as potential sites for nutrient storage and (ii) the weathering of primary minerals yields smaller particles that we call soil as well as releasing nutrients into the soil. The figures below show the weathering of rocks into minerals.


Soil Organic Matter (SOM)
What is SOM? "The organic fraction of the soil that includes plant, animal and microbial residues in various stages of decomposition, biomass of soil microorganisms and substances produced by plant roots and other soil organisms."

The soil components chart above shows organic matter comprising approximately 5% of the total soil but it plays an outsize role in the health of the soil and the crops raised therein. The distribution of SOM components are shown in the chart below.

Approximate distribution of organic matter in healthy soils

SOM makes up a small portion of the overall soil but has an outsize influence on soil functions (see Table 1 below).

Table 1: SOM influences on soil functions
Soil Function SOM Influences
Water management
  • Helps soil create large pore spaces and channels that allow water to infiltrate and drain and small pore spaces that hold on to water
  • Residues on the surface protects the soil surface from atmospheric elements 
Soil structure
  • Plant exudates and microbial byproducts can be sticky substances that help soil particles held together to form and stabilize aggregates
  • Physical benefits of increased aggregation
    - Better aeration
    - Better friability (crumbly): ideal rooting medium for plants
    - Less crusting
       - Crusting prevents water and air movement into the soil
       - Can prevent seedlings from emerging
       - Promotes water runoff
  • Biological benefits of increased aggregation 
    - A home for soil microbes, worms, and insects
    - Food storage — organic matter incorporated into aggregates and slow-released 
Nutrient cycling and retention As soil organisms break down and decompose soil organic matter will be consumed by soil organisms and released into the soil solution
Cation exchange capacity (CEC)
  • CEC measures the soils ability to temporarily hold on to many cations
  • SOM provides between 20 and 80% of the CEC in mineral soils
Microbial diversity and resiliency
  • Organic matter is the main food source for many organisms in the soil
  • Organic matter helps to create a mix of conditions and variety of homes to support the diversity that we rely on 

Living Organisms
The soil food web is the community living all or part of their lives in the soil. The food web diagram below shows a series of conversions of energy and nutrients as one organism eats another.


"As organisms decompose complex materials, or consume other organisms, nutrients are converted from one form to another, and are made available to plants and to other soil organisms. All plants -- grass, trees, shrubs, agricultural crops -- depend on the food web for their nutrition ... By-products from growing roots and plant residue feed soil organisms. In turn, soil organisms support plant health as they decompose organic matter, cycle nutrients, enhance soil structure, and control the population of soil organisms, including crop pests" (NRCS.USDA).

The fuel for the food web is the SOM discussed above.

Soil Water
Half of the overall soil content is pore space, a 50-50 mix of air and water.

Through the process of transpiration, water serves as a vehicle for moving material into, within, and out of the vine plant.  Water enters a vineyard through precipitation or irrigation and that water either runs off, flows to levels beyond which it can be accessed by the vine plant, or remains in the rooting zone where it is available for the plant's use. The plant uses water as an internal distribution vehicle (in addition to other functions) and facilitates this by expelling water through pores (stomata) in the leaves.  As water is transpired from the leaves, replacement water is drawn in at the roots.


Water attracted to the vine root by transpiration moves undiluted nutrients to the root surface (bulk flow) but also carries dissolved nutrients into the roots as a part of its transit. Nitrogen is the nutrient most frequently acquired by the roots in this manner.  Nutrients are moved up from the roots to needed areas through the phloem by transpiration.

Soil Air
Half of the overall soil content is pore space, a 50-50 mix of air and water.  balance must be maintained as water can displace the air in the soil. Soil air differs from surface air in that it is heavily influenced by the soil's carbon content.

Soil Types
Please follow this link for an elaboration of soil types.

©Wine -- Mise en abyme