If you live in close proximity to a vineyard or travel to a wine region this time of year, you’ve likely asked yourself “what is all that stuff growing between the vines”? They are called cover crops, which are crops planted in between the vines to achieve a variety of beneficial things like slow erosion, improve soil health, enhance water availability, smother weeds, help control pests and diseases, increase biodiversity and bring a host of other benefits to your farm.
We use several different cover crops, depending on our goals for each vineyard block. These include soil-building legume and grass mixes that add just enough nitrogen and organic matter to keep the vines healthy; insectary plantings to increase beneficial insects; grasses and clovers for erosion control; deep-rooted perennial grasses to control vigor in excessively fertile soils. The primary combination here on our estate vineyards is an organic mix of 50% triticale (cross between wheat and rye), 25% magnum peas, and 25% bell beans.
This mix allows us to reenergize the soil with organic matter and natural sources of nitrogen. They’ll grow for about 3-4 months before we incorporate them. The peas and beans are the nitrogen fixers, while the triticale is for organic matter. Using legumes to increase nitrogen is a long term investment. Where we’ve sown cover crops we will till (or incorporate) them into the ground. Time permitting, we’ll mow them before incorporation, as it helps things break down faster. However, each year is unique – some years the cover crops grow better than others, and our management decisions change depending on how the winter plays out. We till the cover crops using a “Spader”, which has a series of flat “shovels” opposing along a shaft, similar to pistons rotating along a crankshaft in an engine. These shovels are enclosed and only penetrate the soil several inches. The spader incorporates the cover crop, keeping the soil in place and not totally destroy soil structure, while evening out the ground in the middle rows.
At our Sonoma County vineyards, we usually get the cover crops incorporated by the end of February in case we encounter frost. A high cover crop (or native grasses) can effectively “raise” the height of the ground, increasing the vineyard’s risk for frost damage. The cold air sinks and it gets held up by the cover crop three feet or so off the ground, which is the same height as the buds are on the grapevines. Also, the cover crop row always stays the same, year after year. It is common for some in the industry to alternate the rows after each vintage, but we have seen that’s it’s better to leave one side of the row undisturbed to maintain its soil structure.
We also have some mow-only areas (The hills at Lytton Springs East, and a few blocks at East Bench) where we don’t sow the mix and will only mow. We keep the Lytton hills mow-only because of erosion concerns, while leaving East Bench on “native cover” to slow the development down and help keep the vine in balance. In addition to cover cropping, we also amend our soil with compost and organic gypsum when needed. Utilizing cover crops is just one practice we employ in our overall approach to sustainable agriculture.