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What comes after harvest?

In the world of California’s wine grape growers, harvest is both an end and a beginning. The grapes have been picked, signaling the end of the growing season, but as the vines recover from the hard work of producing a grape crop and prepare to go dormant, growers are already looking ahead to the next year, ensuring vineyards and soils are healthy and vibrant before the growth cycle begins once again.

“From budbreak to harvest, it’s all about the crop,” says Ryan Metzler, owner of Fruita del Sol, which farms 75 vine acres in the Fresno area. “But in late fall and winter, we’re concerned about the overall health of the vineyard.”

For many growers, the assessment of vine health begins in the spring when they analyze young leaves to see what nutrients might be deficient in the plant. After harvest they’ll conduct a similar analysis with soil samples, and then come up with a battle plan to address the needs of each individual vineyard. Nutrients vital to healthy soils include calcium, potassium, phosphorous and/or nitrogen, and if any of these are depleted, late fall is the best time to add them back so that vines can absorb them prior to going dormant.

Once the grower determines what amendments are needed, he/she also has to decide the best way to deliver them. Sometimes nutrients are delivered via the vineyard’s irrigation system, mixed with water; in other cases they’re spread across the soil in the form of manure (rich in nitrogen) or powdered gypsum (rich in calcium). If a vineyard is in relatively good balance nutritionally, a grower might decide to use an all-purpose compost – one that doesn’t “specialize” in any particular nutrient. Some growers even spread wine grape pomace (skins and seeds left over after the grapes have been crushed and pressed) in their vineyards.

“Every vineyard is different, and figuring out what each block needs can be like a complex math equation,” says Metzler. “A ranch with sandy soils can more readily soak up the nitrogen from manure, while one with heavier soils may do better with a liquid application, but trial and error is the only way to figure out what’s best. It pays to have experience.”

Late fall is also the time California wine grape growers start planting cover crops – the crops between the vine rows that help build organic matter, control erosion, suppress weeds, improve soil structure and reduce nutrient loss. The timing of this is tricky: if the grower plants too early and there’s no rain, the seeds won’t germinate. But if he/she waits too long and there have been a few hard rains, the soil will be soggy making it hard to get into the vineyard. Once the rainy season starts, growers avoid bringing heavy equipment into the vineyards because the soils can get compacted – which can negatively affect vine health.

Other post-harvest activities include basic maintenance like adjusting and/or replacing trellises and stakes, but this usually occurs after the vines have dropped their leaves so that growers can see what needs to be fixed. Again, it’s all about getting ready for the next vintage. “The most important thing a grower can do once the grapes have been picked is take a good look at the overall health of the vines and soils,” says Metzler. “The cyclical nature of wine grape growing means there’s never really any down time.”

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Although many winegrape growers should be enjoying a much needed break after a busy harvest, the post harvest season is essential for monitoring and improving overall vine and soil health.


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