Cover Crops in Vineyards Mitigate Erosion and Boost Soil Nutrients | Local news
When winter rains hit Napa Valley, soil erosion is a top concern for many winegrowers. Terracing and other structural changes to the terroir are largely a mitigation method of the past, with many wineries planting the grassy areas between their rows with mustards, legumes and grasses as cover crops.
And while the blooming yellows of mustard certainly brighten up the Napa landscape every year, these ubiquitous plants have important ecological benefits as well.
âIt’s all about protecting watersheds,â said Molly Moran Williams, director of industry and community relations for the Napa Valley Grapegrowers. âCover crops on the hillsides prevent erosion, which in turn protects our river and watershed. “
âOn top of that, in vineyards across the valley, cover crops add nutrients to the soil, increase microbiome diversity, and are widely used as a climate smart farming practice. “
So for Brittany Pederson, who studied viticulture and oenology as well as crop science before starting her career in vineyard management, cover crops are the perfect way to deepen her interests.
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âMost winemakers would probably agree with that, but as you move forward in your career and have done it enough you start to really delve into certain topics,â said Pederson, who is currently viticulture director at Renteria Vineyard Management. âCover crops for me were one of those that about three or four years ago really started to interest me. “
Pederson says that after working with one crop all year round, she was intrigued by the different types of cover crops and their impact on the field depending on the soil’s needs.
âI started to think of the cover crop almost as a secondary crop because we use it to create the best kind of balance with the pitch,â she said. âAnd going from somewhere like Carneros to Calistoga are two totally different things because the soil is different and the terrain is different, so once you get to that level of grape cultivation you really have to respond specifically to what you’re doing. for that specific site. “
Here in Napa Valley, winemakers often use a mix of different plants, but overall mustards are the go-to option for most wineries.
âAesthetically people really love it, and it’s subconsciously become kind of a Napa Valley staple, because everyone loves coming during that time because those colors are popping,â Pederson said. “But it’s actually also used as a suppressant of nematodes, which are those tiny, tiny insects in the soil.”
The composition of the mustard plant and its root system suppresses nematodes, pushing them deeper into the soil and thus eliminating the problem of pests. Other types of cover crops are also used to account for nutrient deficiencies or overloads in the soil, nitrogen being the clearest example that is monitored in this way.
âWhen we think of legumes, it definitely adds a lot of nitrogen to the soil and ends up going to the vine,â Pederson said. âFor places that may need more nitrogen because they don’t get it in a different form and we think that might use a boost, we think we can fix it in a more natural way through to cover crops instead of injecting a pile of fertilizer. “
“On the other hand, if a vineyard is too vigorous and it is unbalanced on the other side where it no longer needs nitrogen, then we will use another type of plant cover, whether it is grasses, or ‘we plant every other row as a permanent cover to try to achieve a more natural balance, âsaid Pederson.
The location and orientation of the vineyard is also important when planting cover crops, as Pederson says she will often plant the same type of grasses both deep in the valley and on steep hillsides for reasons totally different.
âDown in the valley you maybe use them to invigorate them and achieve that natural balance, but in the hills you really do it to fight erosion,â she said. âI played around with a lot of different combinations of things to see what worked in different areasâ¦ You can also have hillside properties where you plant a permanent cover crop for erosion control, and that. is awesome and she will reseed naturally. “
Garrett Buckland of Premiere Viticultural Services also uses permanent cover crops to prevent erosion in his vineyards as he says the weather is getting harder to predict, complicating maintenance and the constant need to replant.
âAnd so, therefore, the performance of it is supposed to be pretty passive. Setting up a permanent cover crop system will stabilize the soil and is meant to be a kind of set-up and forgetfulness, âhe said. âMore and more, all of these vineyard designs that we’re doing really take it back to a natural slope and then focus mostly on the herb cover crop which does the heavy lifting to keep the soil on the ground. “
While many wineries use cover crops, Pederson says she encounters situations where she helps develop a property’s plan from scratch. Regardless of the condition of the vineyard, she said, planting usually takes place between August and November depending on when the grapes are ripening that year.
âPast sites, whether it’s chardonnay or sauvignon blanc or something of that nature, we usually always seed them first because we finished harvesting them first,â she said. âIn an ideal world, that would be right after the harvest, that you sow and let go all winter. “
In the spring, the vintners will take care of the cover crop again, mow it and continue a process called cultivation, usually by disc or spade.
âI do both ways every year,â Pederson said. “And basically what it does is you have to have that mulch and drill it into the ground at different depths, and that’s really where you get that aeration.”
âYou repeat it and start over after the harvest. “
You can reach Sam Jones at 707-256-2221 and [email protected]