Grape vines are not tomatoes.
Grape vines prefer a healthy struggle for survival, at least when it comes to the soil they inhabit.
In fact, the best grapes come from vines that actually have to work for a living, not those that live a posh life atop a mound of organic manure, compost, and fishmeal.
Unless your site has an excessive amount of clay (correctable with sand) or a pH outside of the 6.0 – 8.0 relatively neutral zone (correctable with ground limestone under 6.0 and gypsum over 8.0), your vines will do just fine in the soil as is.
That said, backyard vineyard soil preparation is essential to your infant vines’ ability to develop the strong, deep root systems needed for a productive life of winemaking. Mature vine roots, after all, are known to achieve depths of 6ft or more.
So what does “backyard vineyard soil preparation” actually mean?
Preparing the soil means breaking up and cultivating the soil layers well beyond your standard vegetable garden practices. Similar to the way a mason jar of mixed up water and oil will eventually settle into distinct layers over time, your soil will be compacted into layers of clay, sand, or silt, and these need to be broken up, loosened, and mixed.
In practical terms, it means that your rows should be thoroughly tilled to a depth and width of three feet. This can be achieved mechanically with a backhoe or cultivator, by hand, or a combination of the two.
In our case, we followed the below sequence of events:
1) We did some basic measurements and math to determine a quality backyard vineyard layout based on our backyard vineyard site selection.
2) Using stakes, string, some tape measure and spray paint, we marked the rows for the tiller to follow. The key here is to mark the end points and 3ft width very clearly, as the tiller will shred it all up. Though I doubt anyone will notice if you till the rows a few inches to the left or right.
3) Depending if you do this the fall prior to planting, or just a month or two prior to planting (we shamefully followed the latter timeline), you can also measure and spray paint the locations of all the posts. More on this in the “Constructing a Trellis” post.
In our case, we used a gas-powered tiller/cultivator along with some quality manual labor involving a standard garden hoe. We exposed large chunks of clay with the garden hoe, and ran the cultivator over the rows 2-3 times per row, increasing the depth to its maximum after each run.
You’ll know you’ve done your job when the soil, up to a width and depth of three feet, crumbles easily in your fingers like fresh chocolate cake.
And if you are dealing with hard-pack clay, one ton of sand can loosen 100ft of 3ft-wide row as an additive. This, along with any gypsum or limestone you may need to balance pH irregularities, can be added when tilling the trench/row.
When the job is complete, protect what you’ve earned – never step on the cultivated soil, never allow anyone else to do so, and keep out those weeds.
The next phase in your project will be deciding on, and constructing, your trellis.