Deconstructing the Masseto vineyard: The soils

Masseto is one of the world's leading wines and one of my personal favorites. As part of a class assignment, I had to select a vineyard for further analysis and I chose the Masseto vineyard. In order to complete the assignment I needed some specific data which I attempted to obtain directly from the estate. They were unresponsive to my request so I will attempt to model the vineyard based on publicly available data and reasoned guesses. I will begin this "adventure" with a look at the soils.

Source: masseto.com

According to masseto.com, this 6.63 ha vineyard lies on soil comprised of thin silty clay and broken rock fragments and is sub-divided into three distinct sections based on soil characteristics.  The lowest section of the vineyard has soils that are a clay-sand mix. The middle portion of the vineyard has the highest levels of Pliocene clays. The top portion of the vineyard is located 120 meters above sea level and the soil here consists of loose clays and sand along with pebbles.  The soil here is the shallowest in the overall vineyard. 

Soils Assessment

I was able to identify a list of soil analytical elements (Vineyard Soil Technologies, Soil Assessment for Vineyard Design, www.vineyardsoil.com/evaluation-soil-design.html) and will attempt to assess the Masseto soils within this framework.  The elements and metrics (where available, sourced from Masseto.com and Bolgheridoc.com; otherwise, my assessment) -- are as follows :

Physical attributes:

• Soil color --taupe to light brown
• Soil texture -- heavy soils with clumping clays requiring extensive work to make/keep plant-ready
• Rock (abundance, size, type) -- abundance of pebbles in the upper portion of the vineyard
• Soil structure and particle aggregation -- Loose clays and sand with many pebbles in the upper portion of the vineyard; high proportion of clays -- as much as 40%, according to Masseto -- in the middle portion of the slope; less clay on the lower slopes
• Soil hardness -- clays can be very hard in the middle portions of the vineyard
• Soil porosity -- clay retains moisture, especially in the spring
• Root density -- N/A
• Color and quantity of mottling -- N/A
• Approximate moisture content -- N/A
• Irrigation quality - N/A

Chemical attributes:

• Plant nutrients -- No data available. Assumed to be adequate given the high clay content of the soils
• pH -- not available for the vineyard. For the region (according to bolgheridoc.com), the soils range from sub-alkaline to alkaline (with a pH which ranges from 6.93 to 8.55)
• toxic elements -- according to the Consorzio, the zonation study revealed no toxic elements in the soil
• Cation exchange capability -- N/A but expected to be high given the soil type.

Pests and diseases:

• Phylloxera -- assumed
• nematode analysis -- N/A

Additional Observations

Soil Composition

The soil in the subject vineyard is primarily clay and while it has some beneficial qualities (moisture retention and high mineral content) it also has some disadvantages (WSET):

• It takes longer to heat up in spring
• Swells when it absorbs water and shrinks as it dries. This can cause cracking through which water is lost and can also damage the root system
• Does not drain well
• Becomes sticky when wet and structure deteriorates if worked in that condition.

Clay soils can be made more suitable by the addition of organic matter and sand and working of the soil to ensure that the particles are conducive to the growing of quality grapes.

Soil Depth

According to winegrapes.tamu.edu (Vineyard Soils), “Soil depth for vineyards is commonly recommended to be a minimum of 30 to 40 inches before reaching an impermeable layer. Shallow soils limit development of the root system, resulting in smaller vines and greater sensitivity to changes in soil moisture levels. Irrigation must be managed with extreme care on shallow soils ... Deeper soils are preferable; grape roots will penetrate very deeply if the soil is permeable. A larger root system can support a bigger vine and is less sensitive to short-term changes in soil moisture.”

Given that clay soils tend to form impermeable layers closer to the surface than do sandier soils, Masseto will have to have taken that into consideration in vineyard design, vine spacing, and rootstock selection  This situation can be mitigated by building effective soil depth through addition of material at the surface or terracing.

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