In Search of Wine Quality: Soil and Water---Part 3

I'm back to blogging about Wine Quality. Winter is the time for recapitulation---reviewing the first things I learned in the U.C. Davis online course. I started in December, 2017 with the following two blogposts:
In Search of Wine Quality: Vineyard Location
Following by:
In Search of Wine Quality: Soil and Water---Part 2
Today's blog is about:
Part 3. Soil Drainage
Another way to think about the water holding capacity of the soil is to look at the drainage of the different soil textures. The following chart shows soil drainage as it relates to the type of soil texture. Soil Drainage is expressed in the NRCS soil databases as: "Natural drainage class refers to the frequency and duration of wet periods under conditions similar to those under which the soil developed."

The Cornell Site also provides the following descriptions of soil drainage. I reversed the order of the drainage types to be consistent with the color coded chart above beginning with the clays and silty clays that are very poorly drained and not suitable for growing grapes.

Description	Relevance to Grapes
Very poorly drained. Water is removed from the soil so slowly that free water remains at or very near the ground surface during much of the growing season. The occurrence of internal free water is very shallow and persistent or permanent.	Not acceptable for grapes
Poorly drained. Water is removed so slowly that the soil is wet at shallow depths periodically during the growing season or remains wet for long periods. The occurrence of internal free water is shallow or very shallow and common or persistent. Free water is commonly at or near the surface long enough during the growing season so that most mesophytic crops cannot be grown, unless the soil is artificially drained. Not acceptable for grapes except possibly with extensive tile drainage, but not recommended.	Not acceptable for grapes
Somewhat poorly drained. Water is removed slowly so that the soil is wet at a shallow depth for significant periods during the growing season. The occurrence of internal free water commonly is shallow to moderately deep and transitory to permanent. Wetness markedly restricts the growth of mesophytic crops, unless artificial drainage is provided.	Not recommended except with tile drainage at close spacing. Not recommended due to general soil limitations and cost of drainage.
Moderately well drained. Water is removed from the soil somewhat slowly during some periods of the year. Internal free water occurrence commonly is moderately deep and transitory through permanent. The soils are wet for only a short time within the rooting depth during the growing season.	Generally acceptable, but may have poor soil aeration during wet periods. Tile drainage is likely needed.
Well drained. Water is removed from the soil readily but not rapidly. Internal free water occurrence commonly is deep or very deep. Water is available to plants throughout most of the growing season in humid regions. Wetness does not inhibit growth of roots for significant periods during most growing seasons.	Good soil for grapes as it has a good balance of drainage for good aeration for root growth with adequate water and nutrient-holding capacity. Due to water holding capacity they provide plenty of water and tend to be better for white varieties.
Somewhat excessively drained. Water is removed from the soil rapidly. Internal free water occurrence commonly is very rare or very deep. The soils are commonly coarse-textured and have high saturated hydraulic conductivity or are very shallow.	Generally excellent for grapes although may be droughty and/or low in nutrients. Excellent, if irrigation is available. Such soils tend to be preferred for red varieties that do best with some water stress.
Excessively drained. Water is removed very rapidly. The occurrence of internal free water commonly is very rare or very deep. The soils are commonly coarse-textured and have very high hydraulic conductivity or are very shallow.	Excellent soil aeration for root growth. If too light, such soil may hold too little water unless the soil is very deep. Irrigation may be needed. The course texture (gravel or sand) soils may also have low fertility.

Our soil texture is sandy loam so our soil falls into the "well drained, somewhat excessively drained to excessively drained" categories. Nevertheless, we chose to put tiling to ensure that we have good drainage in the vineyard. Next up, how to tile a vineyard.
References:
1. Alan N. Lakso and Tim E. Martinson , The Basics of Vineyard Site Evaluation and Selection, Department of Horticulture, Cornell-Geneva.
2. Terry Pritchard, Winegrape Irrigation Scheduling Using Deficit Irrigation Techniques.