Don't Call It Dirt
Soil is more than just dirt. Soil is the interface between our beloved Vinifera vines and the earth. Minerals and nutrients are pulled from the soil by tiny root hairs, carried by water, giving the vine its structure. Vines take carbon dioxide from the air to respire/breathe, and combined with water and sunlight, make sugars; carried throughout the vine, sometimes to the fruit, and eventually into your glass as alcohol and “winey” stuff.
As knowledge grew about these mechanics, we forgot what our ancestors intuited – soil is more than just the physical composition of dirt; it’s a balance, a biome. The same worms and millipedes and grubs that eventually may consume our bodies, transform and create soil. The organic matter they produce and consume can create a wonderful, spongy substrate to create vigorous life in the vine and ultimately, beautiful wine. More than the sum of its parts, that is for sure.
To apply this to viticulture, you have to look at the macro level – how the continents formed and drifted over eons, where you are in those strata, and how the vine touches the soil. There are some fun spots in California with crazy soils – hard granite in the Sierras, volcanic red soils in Lake County, silt in the Delta. But if you’re thinking of growing good cool-climate grapes, you’re thinking coastal regions, which means sandstone, or some decomposed form of it. I won’t go into the millions of years containing the dinosaurs and the ages after. In Anderson Valley we are dealing with just what are called “Quaternary” soils, formed over the last 2.5 million years. Previous seabed and sandy shores were solidified and lifted, eroded and weathered. There were trees and deposits of organics, washed away and mixed depending on the intensity of the weather and flooding. Eventually this dirt settled and formed layers. Some riverbanks have cobbles, the lowest spots tend to be more silty. The USDA has a great visual aid called the Soil Matrix triangle . Each point – clay, sand, silt – overlap and form other basic soil types.
Fast forward to modern times and you are planting a vineyard. First, dig a pit and see what your soil layers are. Go to a web geology site (such as Soil Web or Geological Map of California) and see what lies beneath your feet. On our property we have Boontling loam which is a nice clay loam on the soil matrix. In some spots, perhaps this loam is a bit “heavy” with too much clay, holding moisture like a hard-to-wring rag; a soil that is sandy enough to drain, but with enough silt to bind it all together. Pick a rootstock that matches the soil. Some rootstocks go deep for water, others stay shallow. How much water do you want to promise to these vines? Deep roots sometimes make too much crop, now you’re hacking the canopy back, risking imbalance. Find the middle path, find the right match. Yes, your farming practices play a role. Choose wisely. So much depends on just this choice. Now wait, and think, and wait some more. Want to find out how these grapes taste? Me too.
