Generally, to describe a soil, you take a core sample with an auger or you dig a pit or trench. You then identify over the entire depth studied the homogeneous soil strata, called “horizons”. Each horizon is defined, amongst other things, by its colour, and by its composition in solid elements, i.e. the proportion and nature of the coarse elements (gravel, stones, etc.) and the texture of the soil (clay and sand content, etc.) As an initial estimate, by direct observation in the field, you can evaluate the proportion of more or less coarse elements. Then you can analyse soil texture.
- Coarse fragments: This includes all soil particles with a diameter greater than 2 mm. Various terms are used, depending on size.
- Fine soil particles: This refers to all the fine particles in the soil. They are classified in 3 main groups, or soil textural classes: clay, silt and sand.
Take a soil sample from a specific area. Determine the proportion of coarse elements, their nature and the texture of the soil.
- Coarse elements: Look at the sample you collected and estimate the proportion of coarse elements (as a percentage). Based on their diameter, indicate which coarse elements are present.
- Type and proportion of fine soil particles: With the following tests, you can determine whether the soil contains a higher proportion of sand or silt and estimate its clay content.
- Conclusion: Once you have determined the fraction of each of the types of fine particles in your soil, using the previous information, find the type of soil and its textural class.
For describing a soil texture of a vineyard, I took my soil sample from Chateau Kalpak Vineyards in Thrace area in Turkey. I dug a small pit next to a vine and the depth of the pit for taking my sample was about 15-20 cm.
First step was to estimate the proportion of coarse elements; Fine to medium gravel: %70, Coarse Gravel: 30%, Stones: 0%, Large Stones: 0%, Boulders: 0%. With the following tests, I determined whether the soil contains a higher proportion of sand or silt and estimated its clay content. When I listen the sound of the dry soil while I rub it between my fingers it made a scratchy sound and that means was my soil was sandy. Then I took a little piece of soil in my hand, moistened it and rolled it into a ball. I pressed my thumb to it, and there was almost no thumbprint. That’s why I cannot categorize my soil as a silty or loamy soil. Next step was making a soil sausage to determine the clay content. I picked up a handful of damp earth and kneaded it between my fingers and then gave a shape of a sausage. It was very easy to make a soil sausage with my soil; I could say that the clay content of my soil was higher than 10%. It was not easy to make a ring of soil as much as making a sausage of soil. It cracked in the ring before it closes. My clay content was higher than 10% but at the same time it was lower than 20%.
In conclusion, when I collect all the results from the steps that helped to determine the soil texture, I found the textural class of this vineyard’s soil Sandy Clay. Elegant wines with high aromatics, pale color and low tannin are coming from the sandy soils and muscular wines with high extract and color are coming from the clay soils. This vineyard has the combination of both soils for producing wines with a wide range.