Friday, December 5, 2014

Deconstructing the Masseto (Bolgheri, Tuscany) vineyard: Nutrient monitoring

Masseto is one of the the world's leading Merlot wines and its 6.63 ha vineyard is ensconced within the confines of the larger Ornellaia vineyard in Bolgheri, Tuscany. It has been difficult obtaining information on the details of the vineyard so I have undertaken the task of deconstructing it using data from publicly available sources as well as reasoned assumptions. In this post I cover nutrient monitoring practices.

Adequate amounts of the appropriate nutrients are required to support proper growth of the grape vine, fruit development, and fruit maturity and those nutrients are obtained from the soil.  The table below shows the mineral requirements of the vine plant, the role of each mineral, acceptable ranges of each mineral in the soil, and the impact of mineral deficiency on the vine. 

Toxicity is just as important to the vine as is deficiency as a surfeit of a particular mineral in the environment can also have adverse effects on the vine plant and/or fruit. For example, high levels of magnesium in the soil can inhibit the plant’s uptake of potassium, potentially leading to a potassium deficiency. The viticulturist must have a program in place to monitor the levels of nutrients available to the plant and a plan of action to address deficiencies or toxicity.

Prior to vineyard planting, the only recourse for assessing the availability of nutrients to the grapevine is an analysis of soil samples to determine soil texture, cation exchange capacity, soil organic matter, and pH (Skinkis and Schreiner). Staben et al., (Monitoring Soil Nutrients Using a Management Unit Approach, PNW 570E, October 2003, describe three methods of soil sampling and those are summarized in the table below. 

                                                    Soil-Sampling Methods

Whole-Field Sampling
Grid Sampling
Management-Unit Sampling
Soil cores collected from entire field, mixed together, and single compoite sample sent to lab
  • Field systematically divided into areas of uniform size and shape (cells)
  • Samples taken from each cell and analyzed (composites of 10 or more cores)
  • Patterns of estimated nutrient availability can be determined and a nutrient application map developed
  • Divide field into management units based on soil features and grower’s needs and priorities
  • Collect soil samples throughout each management unit or for a smaller reference area within a management unit
  • Select one of the two above approaches and use it consistently
  • Treats the entire field the same regardless of landscape or cropping history
  • Conclusions drawn from the test may not be appropriate for all parts of the field
  • Basing fertilizer application on these findings will have some areas over-fertilized and others under-fertilized
- More accurate data than provided by whole-field sampling
- Expensive given the labor, equipment, and lab fee costs
  • Save time and money compared to grid sampling
  • Obtain more accurate data than provided by whole-field sampling
  • Provide many of the benefits of grid sampling while overcoming the costs

Once the soil analysis is complete, decisions regarding needed additions can be made. The suggested frequency of soil testing is shown in the table below.

Nutrient-Driven Soil Testing Frequency 

Soil texture
Initial soil assessment
Cation exchange capacity
Organic matter
Bray or Olsen P
K, Ca, Mg, Na, Zn, Mn, Cu, Fe
Electrical Conductivity
Nitrate-N, NO(3)-N
As needed

Source: M. L. Staben, et al.

Once the vineyard is up and running, soil samples alone will not suffice. Soil samples may show adequate amounts of nutrients available in the soil, but nutrient presence in the soil does not translate on a one-to-one basis to nutrients in the plant. Issues such as  mycorrhizae population, rootstock type, presence of manganese, etc., may inhibit the takeup of nutrients into the vine. A much more fitting approach is the sampling and testing of plant tissue. Tissue for this type of analysis is generally taken from the (basal) petiole or blade at bloom (US) or veraison (Europe). According to Skinkis and Schreiner, tissue analysis gives an “idea of sufficiency, deficiency, and toxicity of mineral nutrients" in the vine. According to the authors, petiole samples provide information on chlorine, potassium, and sodium levels while leaf blade samples provide better nitrogen indicators than does petiole analysis and also indicates levels of magnesium, boron, calcium, copper, and manganese.

An effective nutrient management program for vineyards must contain the following elements (Schreiner and Kinkis):
  • Good records of fertilizer and irrigation inputs
  • Vigor assessment
  • Yield
  • Interpretation of soil and plant tissue results.
I am assuming that Masseto conducted an initial soil analysis using the management unit sampling approach and conducts concurrent soil and tissue analysis at veraison on an ongoing basis. I am assuming that the vibrancy of the clay soils obviates the need for nutrient additions. The Bolgheri zonation study failed to identify any toxicities in the soil so my assumption is that no additives to address this issue are required.

©Wine -- Mise en abyme

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