[Information based on DipWSET D1 material]
Six ways growers can manage the health of vineyard soil.
In our last exciting episode of WSET studying, we discovered the world of soil and left off acknowledging that there are loads of tests that growers can conduct before a vineyard is established to understand the composition and overall health of his/her/their potential vineyard. Just as important are regularly scheduled tests—think of it as your vineyard’s annual checkup. Soil health tests can indicate what, if anything, needs to be improved—be it the structure, nutrient level, water availability, or pest management.
As I discussed in Needed Nutrients most of the nutrients needed for healthy vine and grape growth, as well as good wine quality, are found in the soil. During the growing season, it’s up to the grower to monitor and control, if needed, the level of nutrients and their accessibility to the vine. This includes everything from direct application of nutrients to managing weeds and cover crops.
Key ways growers can manage the health of vineyard soil include:
1. FERTILIZERS
Fertilizers can be added to the soil before vineyard establishment (to help the growth of young vines) as well as to established vineyards to assist with any nutrient deficiencies. Growers must be aware of what kind and how much soil nutrients are being used, as excess fertilization can lead to excess vine vigor, resulting in unbalanced vine growth, grape development, and—eventually—wine.
There are two types of fertilizers that can be used.
Organic fertilizers are fertilizers that are in organic, that is carbon-based, form. They come from things like fresh or composted plant or animal material—like manure. FUN FACT: Or more like, HILARIOUS FACT: Cover crops can be mown into the soil to decompose and provide nutrients—this is called Green Manure. (Bahahaha…)
An important note is that for a vine to actually uptake nutrients, they need to be in an inorganic form. Good news is that organic fertilizers also provide nutrition for soil organisms (remember Earthworm Jim?), so these guys can help out with that breakdown. But it’s noted that for this to happen, the organic fertilizer needs to be incorporated into the soil (you can’t just throw it on top and hope the magic will happen), which will require some manual labor on the part of the vineyard crew. This also means that the nutrients will become available slowly over time, which can actually be an advantage. (Like, you don’t want to eat the whole cake at one sitting, do you? Or maybe you do…I don’t know…depends on the cake…anyway…) One more benefit: many organic fertilizers are high in humus which can help improve soil structure, increasing nutrient and water-holding capacity. (Remember our soil types?)
This is a kind of funny footnote and something I never thought about, but organic fertilizers “can be bulky and therefore expensive to transport and spread.” Big cow, big…
Anyway…
Mineral fertilizers are either extracted from the ground or are chemically manufactured. They can provide either a single nutrient or a whole host of nutrients. So, an upside is that you can tailor pick your fertilizer to suit your specific needs. (You know, you can’t just tell your cow to poop a bunch of Nitrogen, can you?) Another upside is that mineral fertilizers are already…mineralized! As in, you don’t have to wait for them to break down further, they’re already in their inorganic form and can be taken in and utilized by the the vine immediately.
Bad news is that they don’t help out your Earthworm Jims or other organisms and do nothing to improve soil structure. They can also be expensive, but they’re more condensed so cheaper to transport and distribute.
2. CULTIVATION
Cultivation refers to ploughing the soil in order to disturb weed root systems as a method of weed control.
The good news: No need for chemicals here—so organic and biodynamic vineyards, you are good to go. Furthermore, this helps create that Green Manure (Bahahahah….)
The bad news:
- Cultivating on a regular basis can damage soil structure, not to mention the biodiversity within the soil system. (You just mowed over Earthworm Jim!)
- It requires investment in both machinery and labor.
- You end up ploughing IN the weed seeds, so they’ll probably grow back at some point.
- Getting rid of weeds completely can decrease the vines’ competition for water and nutrients, thus increasing vigor—this is more of a disadvantage for those sites with particularly fertile soils and lots of water availability.
3. HERBICIDES
Herbicides—a fancy word for chemicals that kill weeds. There are three types of herbicides:
- Pre-emergent: Herbicides that are sprayed before a weed is established. They persist in the soil surface layer but end up being absorbed the weed’s root system, inhibiting germination.
- Contact: These guys are sprayed onto weeds that are already established and kill the green parts of the plant that the herbicide came into contact with
- Systemic: These are sprayed onto established weeds but are taken in by leaves, thus traveling within the weed’s veins via the sap and killing the whole plant.
Why we Like Herbicides:
- They’re cheap in regards to labor and machinery.
- They’re highly effective, especially in the hard-to-reach under-row areas.
- They are less damaging to the soil structure than cultivation
Why we Hate Herbicides:
- Poison. Yeah, they can poison the operator, the environment, the vineyard ecosystem, and, yes, even the consumer. Capital “G”-ross.
- Weeds can actually become herbicide-tolerant. So, like any bad drug, you’ll need to spray more and more or find new chemicals in order to be effective.
- As with cultivation, the removal of weeds can create excess vine vigor due to reduced water and nutrient competition.
- Organic and biodynamic—not allowed.
4. ANIMAL GRAZING
It’s sort of like Animal Crossing but…
No, it’s just another method of weed control utilizing animals’ natural tendency for grazing. Sheep, pigs, goats, among others are all used.
Why We Love Our Animals:
- No chemicals—organic and biodynamic approved!
- Free manure!
- I can’t believe my book added this but, “The animals can be a source of meat for humans.” *Sigh*
Why Animal Love isn’t for Everyone:
- Animals will also eat leaves and berries. So, vines need to be trained fairly high. If you’ve got bush vines, or need to keep your trellis low to the ground, this is a no-go.
- If you own the animals, you must take care of the animals—which will cost. If you don’t own the animals, you have to pay for their time.
- If you’re using animals, cool it on the pesticides.
5. COVER CROPS
Cover crops are either specifically planted or allowed to grow in a vineyard because they have specific beneficial effects on the vineyard in which they grow, including
- improving soil structure
- competing with vines for water availability and nutrients (thus moderating vine vigor)
- impeding soil erosion
- enhancing biodiversity
- and—this is kind of amusing—”providing a surface to drive on.”
It’s noted that cover crops that are quick to establish and are adapted to the pre-existing soil and climactic conditions are your best bet. This is also why it’s possible, and often times beneficial, to leave some natural vegetative growth pre-existing on a potential vineyard site prior to vine establishment.
NOTE: Cover crops of all kind do need to be monitored so as not to provide *too much* competition for water and nutrients at key times in the vine growth cycle.
As mentioned above, these extra plant materials can be plowed into the soil, providing organic fertilizer, aka Green Manure (Bhahahaha…..)
Why We Love Cover-Croppin’:
- No chemicals—organic and biodynamic vineyards rejoice!
- Increases biological activity and biodiversity in the vineyard.
- Can moderate vine vigor by competing for water and nutrients
- “Provides surface to drive on,” actually that is kind of important, especially in places where theirs loads of rain.
When Cover-Croppin’ is Crappy:
- Reducing that vine vigor in areas where there’s already poor soils and an overall dry climate is no bueno.
- It’s harder to mow cover crops located in the under-row area, which means vineyard crew will have to work over time.
- Slippery when wet. Although they “provide a surface to drive on,” it doesn’t work so well on vineyards located on steep slopes.
6. MULCHING
Mulching refers to spreading matter—usually stuff made of biodegradable material like straw or bark—that provides nutrients to the vine.
Why we Love Munching on Mulch:
- No chemicals! “Yay!” said all the biodynamic and organic vineyards.
- They help reduce water evaporation from the soil. Awesome if you’re in a particularly dry and sunny climate.
- Promotes soil biological activity and aids soil structure, as mulch is ultimately a source of nutrients and humus.
When Mulch is just Too Mulch:
- It’s only really effective when applied in a thick layer over the soil, so you need a lot and…
- Because it’s bulky, it’s expensive to transport and spread
- It reduces vine competition for water and nutrients, so can potentially increase vine vigor too much. Not cool in areas with super fertile soils.
Thanks again for studying with me!
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