Amy Richards
Amy Richards from Phantom Creek Estates, takes a hands - on approach to examining the vineyard soil.
If a random person said the best way to assess vineyard issues was to dig a pit right next to the vines, then hop into it and look around, grape growers would likely laugh and say they were crazy.
After all, don’t growers spend much of their time ensuring roots are protected and left alone to do their thing?
But what if digging a pit could tell all the stories of the vines? Experts are uncovering the benefits of soil pits, which are ideal for learning more about what vine roots deal with, soil qualities and what might be causing localized issues.
At a May BC Grapegrowers’ Association event, Amy Richards, director of farming with Phantom Creek Estates, spoke about the value in digging soil pits to better understand the soil and therefore what roots deal with. Taking a soil sample from a foot down can be helpful, but when vines reach much further into the earth, knowing what they come into contact with can explain why some blocks thrive and others struggle.
“Growers have been excavating pits to examine their soil as long as there have been growers,” Richards says. “I started digging holes in vineyards as part of my PhD research into understanding soil salinity in drip irrigation back in South Australia, my home state.”
The purpose of those study pits was to sample and measure the three-dimensional pattern of water and solute movement under Cabernet sauvignon grapes that had minimal drip-irrigation.
But, digging down isn’t just about water interactions. There are many things soil samples can disclose. The difference between a single soil sample and a soil pit is much like the difference between a single bee and a bee hive. Richards has used pits as a diagnostic tool in commercial vineyards ever since her early exploration.
The BCGA meeting “provided an opportunity for local growers to come together to talk about soil,” she says. “It was a fantastic opportunity to share experiences and knowledge.”
Pits are generally about the width of the excavator bucket and a meter or more in depth, right next to the vines. The length is usually about six feet, but this is intuitive as the digging process begins, says Chris Mark, president and CEO with Vintality Tech.
“A vineyard, it’s an above-ground structure. Most of what’s happening in the vineyard is happening beneath your feet,” he says. “There’s actually an entire structure below the ground, a system that essentially goes down to the bedrock. We’re trying to open up and view – much like you would with a canopy – the structure below. That’s where we get the ‘aha’. All of a sudden it makes sense.”
Amy Richards at BCGA event
Amy Richards in the soil pit.
The soil is a world of its own and the visual of a vineyard above and below ground is somewhat like an iceberg both above and below water. Digging down a foot or two simply can’t reveal the whole story.
“You think you have one thing, then you dig down and it’s such a different world,” says Mark. “This subsurface information, it’s the most critical thing we can do with you for your vineyard.”
In an existing vineyard, use physical observation of the vines and their health to determine digging locations. As Mark explains, once the excavator is on site, the biggest expense has already been incurred. Digging an extra hole (or two or three) is easy to justify.
“In existing vineyards with visible issues (stunted growth, nutrient deficiencies and/or toxicities, for example) soil pits allow the grower to see the growth pattern of the roots,” Richards explains. “Are there any impediments such as a compacted layer or high-water table? Characterize the soil type, sample the soil for chemical analysis (pH, organic content, macro and micro nutrients) and identify limitations.”
Existing vineyards benefit from soil pits to help diagnose issues, she says, but they are also beneficial in assessing the soil and other subsurface factors when renovating or starting a new vineyard.
“Vine growth and productivity are completely dependent upon healthy soil,” she notes. “Digging holes and looking at the dirt is something that we do – or should be doing – regularly.”
This is the same underground view Mark holds. He feels that new sites benefit from 10, or even 15, pits to examine soil characteristics.
“It doesn’t cost that much,” he says. “You want to dig close to, right up to, the vines. You don’t want to do it in the middle, you want to do it right next to the vines.”
This seems counter-intuitive to those who have lived by the adage of not disturbing roots, but Mark assures the benefits far outweigh any short-term issues that may be caused.
The soil pits are small and only disturb a few plants rather than the row or area that will gain specific care due to the deep-down information that comes back from soil testing. Knowing the soil characteristics can also help determine which varietals to plant, where.
“How does it feel? Is it sand or is it clay?” he says of scraping at the soil in the pit at different layers and handling it. “You want to get in there and see what is happening. We recommend bringing a measuring tape with you.”
A measuring tape and notepad allow for making notes of where samples are taken from within the pit as well as visual observations.
“Look at the changes in the layers and the structure,” he says. “Take lots of soil samples. You don’t have to run them right away. You’ve opened up the pit, so take a ton of samples. You might as well take advantage.”
Seal each sample in a bag, label and store them to have them analyzed whenever makes sense. He suggests taking samples from each layer to provide a complete view and adjust management practices based on the full picture.
“You can see how the roots are interacting with the soil itself,” he notes.
Ultimately, knowing soil characteristics will improve fruit quality and help with decisions that lead to better wine or even greater yield. Appreciating what the soil is contributing can inform all management aspects of the vineyard. It’s a small effort for a big impact. ■