A BRIEF OVERVIEW OF TWO IMPORTANT SOIL MEASUREMENTS
Understanding key interrelated components in vineyard soils in the Mid-Atlantic wine-growing regions
If you’ve ever sunk your hands into the soil of an East Coast vineyard, you know that beneath the surface lies a world of complexity. Your soil is the foundation of your estate—they set the stage for everything that can and should be done. Soils are incredibly complicated parts of our ecosystem and many have spent lifetimes unveiling their secrets. Even when these secrets are uncovered it still may be difficult to understand how everything works together. However, we can’t begin to think about growing grapes without thinking about soil! When you strike up a conversation with any wine-nerd then the conversation of vineyard soils and growing conditions doesn’t take long to follow.
In this article I’ll talk about pH and Cation Exchange Capacity, both being very important and interrelated soil attributes that we measure when evaluating a farm. I’ll break down the numbers for East Coast wine growers so when you get your soil results back you’ll be able to read and understand them like a professional. To say the soils on the East Coast vary widely is a hilarious understatement, so I won’t make any recommendations on dealing with issues here, but I hope to lay the foundation of understanding for these key components.
So grab a glass of your favorite wine and let’s dig in!
Soil pH: A Balancing Act for Vineyard Success
One of the first things you’ll encounter when diving into the world of vineyard soils is pH—the measure of acidity or alkalinity. This is shown as the negative log of Hydrogen ions (pH= -log(H+)) in the soil. Since this is a negative logarithm it means that the lower the pH, the higher amount of Hydrogen ions are present in the soil (a little confusing I know). The pH scale we use is from 0 to 14 with any number over 7 being alkaline, and any number under 7 being classified as acidic, and 7 being referred to as neutral. Vineyard soils on the East Coast can vary widely in pH, from acidic sandy soils on our shores to alkaline clay soils on our rolling hills. Most East Coast soils are acidic due to the leaching of cations under a wooded forest or from previous tillage where the top soil eroded leaving behind more acidic soils closer to the unweathered bedrock material. Understanding and managing pH levels is crucial for ensuring optimal nutrient availability and vine health.
Vinifera grapevines like soils that are neutral (6.5 – 7) or slightly acidic (5.5 – 6.5) while native East Coast grapevines like Aestevalis and Labrusca prefer soils that are slightly acidic (5 – 6.5). When the soils are either higher or lower from this range then we start running into problems.
When the soils have high levels of Hydrogen ions in the soil then they replace other cations essential to vine growth, like Calcium and Magnesium, and are replaced with cations like Aluminum. Since these cations essential to plant growth are not bound in the soil then they are leached from the soil by rainfall. Low levels of Hydrogen Ions in the soil result in alkaline soils, where the soil doesn’t contain enough cations in the soil to exchange for nutrients by the plant roots. These soils do not often occur in the Mid-Atlantic region.
Soil Cation Exchange Capacity (CEC): What Makes the World Go Round
A lesser recognized but equally important factor in vineyard success and longevity is the Cation Exchange Capacity of the soil. This is the measure of negatively charged sites in the soil. Knowing how many negatively charged sites are in the soil is important because many of the essential macro and micro nutrients are cations, meaning positively charged. When there are many negatively charged sites, then the positively charged nutrients (and positively charged water) are able to be held there, available to the plant.
Now why do we care about positively and negatively charged sites? Because the vine does! The vine needs nutrients, and the vine needs to struggle. Understanding the CEC helps us to understand larger functions of the vine and growth patterns throughout the season. The more you get to know about nature then the more you will see how it’s all related… truly amazing. So, grapevine roots produce positively charged Hydrogen cations, which through the fine root hairs interact with the cations that are currently attached to the negatively charged sites in the soil, and exchange the Hydrogen cations with the other nutrient cations that the vine needs, like Calcium, Magnesium, Sodium and Potassium being the major four. The Hydrogen cation is the weakest of all cations and extremely exchangeable, which is why it’s so useful to the plant.
The ideal range of CEC is between 5 and 15 meq/100g. That is, milli-equivalent per 100 grams.
We have all heard that a struggling vine produces high quality fruit, and that a vine with too much fertility produces lower yields and low quality fruit. While this is true, it is also important to balance the vines struggle with it’s ability to grow and protect itself naturally. The vine produces higher yields and ripens fruit better on poor fertility soils because it essentially thinks it’s dying. The vine thinks, ‘If this is the last growing season, then I better get this fruit ripe so birds and animals can eat it and spread my seeds’ on those low fertility sites. Or, ‘I’m happy and living well, no need to produce fruit and worry about the future because content’ says the vine on high fertility sites. Now, there are many hormonal systems that speak to why the vine says that, but thats just paraphrasing. When looking at the CEC value in vineyard soils, we need to be mindful of too high or too low values because what we really desire for the vine is balance. Balancing your vineyard will require a specialized plan, because your vineyard is unique! And it’s requirements will be as unique as the wines you craft.
Conclusion:
And there you have it — our first dive into the world of vineyard soils on the East Coast of America. We’ve explored two very important factors of a complex and nuanced ecosystem that shape the terroir of our vineyards. So the next time you’re out in the vineyard, remember that beneath your feet lies a world of silent activity — and if you ever need a helping hand in navigating the intricacies of vineyard soils, don’t hesitate to reach out. Cheers to the soil beneath our vines and the wines it helps us produce!
Ready to unlock the full potential of your East Coast vineyard soils? Contact me today for expert consultation and personalized guidance tailored to your vineyard’s unique needs
