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Getting More from Loess
By Wayne Belding
Dec 16, 2014
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Loess soils are found throughout the world, comprising nearly ten percent of the earth’s soil surface.  These widely distributed soils are of interest to winelovers because they are the underpinning of several famous and highly desired wines.  We find references to loess and wine most commonly in Austria, Germany, Hungary and the western United States.

Loess (Löß in its native German) means “loose” -- a reference to the poorly compacted nature of the soil.  Loess is, in geologic terms, a recent deposit of windblown silt.  Silt particles are very small -- 0.002 to 0.063 millimeters in diameter.  That’s 100 times smaller than your average beach sand grain size, so it’s easy to see how silt particles can be transported by strong winds.

So, how does that much silt become available and airborne?  Some of the answer lies in the effects of the broad glaciations that covered much of the northern hemisphere land mass as little as twenty thousand years ago.  As glaciers advance, albeit slowly -- at a ‘glacial’ pace, they grind up the rocks beneath into a fine “rock flour.”  When we look at lakes at the terminus of a glacier, we note that the waters are milky rather than clear.  That is the visual evidence of this fine rock flour in suspension.  As these waters are borne downstream, they transport those fine sediments and ultimately deposit them as their flow slows.











Milky “rock flour” suspended in glacial lake waters

During periods when streamflows are low, the sediments dry out and can become airborne when strong winds arise.  It is important to note that these are wind-borne deposits.  Even in microscopic form, the silt particles collide in the turbulent winds and develop or maintain an angular form in the transportation process.  Particles that are entirely transported by water often become rounded.  Thus, when deposited, the airborne silt can become a cohesive soil while the water borne particles cannot.  Think of trying to stack marbles as opposed to cubes and you can imagine the same forces at work in loess deposition.

The strong winds and cool, dry climate of the northern hemisphere as the glaciers retreated lifted vast clouds of dust and transported them to sheltered spots or dropped them as wind speeds abated.  It’s also important to note that windblown sediments are naturally sorted by the wind speed.  Heavier sand grains are left behind by winds that can only lift the much smaller silt particles destined to be loess.  The composition of most loess soils is about 60% quartz, with the balance mostly feldspars, micas and carbonates plus trace amounts of many other minerals.  Once deposited, the feldspars and micas can weather to clay minerals, which provide the crucial water-retention properties of loess soils.


 







The Mézes Mály vineyard in Tokaji

The combination of easy workability and an optimal balance of drainage and water retention make loess soils desirable not only for vines, but for many other crops as well.  Loess is stable when it remains dry, but subject to severe erosion if it gets too wet.  Terracing and other erosion control methods are often required to hold the loess in place.

The optimal conditions for deep loess deposition occurred during the glacial advances and retreats of the Pleistocene Period of the last two million years.  The deepest loess deposits are in China, but those noteworthy to wine aficionados are in the central European winegrowing regions.  The Tokaji-Hegyalja of eastern Hungary has long been noted for its luscious, botrytis affected dessert wines.  The loess deposits here form the soils of the legendary Mézes Mály, Teleki, Hétzőlő and Birsalmás vineyards, among others.


 







Loess terrace in the Wagram

The deep loess soils along the Danube River in Austria provide a favorable environment for the Grüner Veltliner vines.  The Wagram region is dominated by loess terraces, and noted for powerful, rich Grüners.  Many famous vineyards of the Kamptal -- Lamm, Spiegel and Hasel -- are planted on loess.  Several producers highlight their terroir with designations such as “loess terrassen” or similar.  There are pockets of loess in Kremstal and the Wachau that influence the styles of wine produced here.  Producers often feel that wines from loess soils are fuller and softer in style than those from other soils -- a characteristic popular with Grüner drinkers.

In Germany, loess is widespread in the Hessische Bergstrasse and Baden, where the famous Kaiserstuhl vineyards are on loess overlying volcanic rock.  Loess deposits are also found in the anbaugebiete of Nahe, Pfalz and Rheinhessen.  Of particular note are the Oberhauser Brücke Vineyard in the Nahe, an alleinbesitz (monopole) of the Hermann Dönnhoff estate, and the noted Krötenpfuhl and Brückes vineyards of Bad Kreuznach.  In the Pfalz, sites with loess soils yield rich and flavorful Rieslings.  The Ruppertsberger Reiterpfad and Gimmeldinger Mandelgarten vineyards are noted for loess soils and rich wines.  The rolling hills of the Rheinhessen also have many vineyards on loess.


 




Seven Hills Vineyard in Walla Walla

The vast wheat fields of the Palouse Hills in Washington and Oregon are planted on loess but this widespread soil provides a habitat for vineyards as well.  The Columbia Valley AVA has many pockets of loess soils, but the most noted are in Walla Walla, where the windblown covering can be quite thick.  The Seven Hills and Les Collines vineyards are noted for loess soils.  Loess is common as well on the Oregon side of the Walla Walla AVA.  In the Willamette Valley, loess is occasionally found, especially on the northern side of the Chehalem Mountains.

In the central US, wineries are taking advantage of the deep loess soils in Missouri and Iowa.  There is even a Western Iowa Wine Route that winds through the Loess Hills of that state.  Missouri vintners are planting Norton grapes on the deep loess soils overlooking the Missouri River.  There is a lot more loess in the world than most wine drinkers realize.  It’s an intriguing exercise to sample different wines from a common soil type.