Soil Texture
Soil texture ranges from fine clay, to silt to coarser sand. Loam is a relatively even combination of these three.
Gravel is technically too big to be considered soil, but I have included it because it is very common in vineyards throughout California. Each soil texture has different physical and chemical properties that affect grape production.
Clay
Clay has a very fine texture and sticks together. It is unporous and very water retentive. Although some clay helps to nourish the vine, too much is not considered suitable for high-quality grape growing.
Silt
Silt is coarser than clay, but has finer particles than sand. It is made up of physically weathered minerals and is very common in flood plains or along streams and rivers.
Sand
Sand is made up of particles between .0625 and 2 mm in diameter. It is made primarily of chemically inert quartz that weathers very slowly. Sand is coarse compared to silt’s powdery texture.
Loam
Loam is a mixture of sand, silt and clay. Because loam is a mix of the other 3 soil types, it has beneficial qualities from each. Deep and well-drained loamy soils produce very high quality grapes.
Gravel
Gravel is made up of particles between 2 and 64 mm in diameter. It is technically to large to be a soil type and is the smallest rock size. It drains very well, is heat retentive and is very porous.
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