Agriculture Reference
In-Depth Information
Needless to say, this was a big surprise to the French, who had heretofore said that the
best premium quality grapes could only be grown in French soils. How wrong they were.
Soil type is important, but it is by no means the most important factor. In fact, studies since
the 1970s have shown that premium wine grapes can be grown in a variety of soils.
Most topsoils are categorized as clay, loam, or sand. In fact, many soils are a mixture
of two of these types. Clay soils are typically heavy, do not drain well, and are nutrient-
rich. This type of soil holds water and is poorly aerated, which limits root depth. Silt is a
fine type of clay soil. Sandy soils drain well and tend not to retain nutrients, but they are
well aerated and allow roots to penetrate deeply and easily. Loam or loamy-textured soils
are mixtures of particles of different sizes, a blend of sand, silt, and clay. Loam soils usu-
ally are rated highest in agriculture because they have the best mix of water, air, minerals,
and nutrients for plant growth. They also contain plenty of organic matter, which supports
biodiversity in the soil and is essential for soil health.
Grapevines are adaptable to most of these soil types, but like all plants, they grow best
when they have healthy and well-developed root systems. Grapevine roots can grow down
as much as 15 feet in deep soils, but the main feeding roots are usually concentrated in the
top 2 or 3 feet of soil. They cannot develop these root systems without soil of adequate
quality. Shallow soils may be limited by boulders, bedrock, hardpan, a high water table, or
some kind of mineral or chemical barrier.
Still, many people worry too much about the kind of soil they have. In general, there
will be a rootstock that will adapt your soil to the grape variety you select to grow. That is
not to say that you can put your vines into the soil without a second thought. Soil amend-
ments, quality of sunlight, drainage, water supply, and other issues can moderate differen-
ces in soils. To have a healthy and well-developed root system, it makes sense to be aware
of the characteristics of good soil and how to deal with poor soil.
Soil Qualities
The best soils:
→ Are least 3 feet deep, although you can grow vines in less depth. If the soil is
rich you can use a rootstock that spreads out laterally rather than growing deeply
down into the soil. This will normally require you to provide wider spacing between
plants and rows. You will also need to choose varieties that can adapt to shallow
rootstocks.
→ Have low mechanical resistance (no big rocks, hard uncultivated layers, or other
such barriers).
