THE RAIN HAS STOPPED.  WOO HOO!  BUT LOOK AT ALL THOSE WEEDS IN THE VINEYARD.  OR ARE THEY  WEEDS?   TOM JOINS US IN A LITTLE Q & A.

Q:  Tom, it’s mid March. What’s that we see growing between the vineyard rows? Weeds? Flowers?

Tom:   The vineyards were seeded with cover crops. These will benefit the soils foremost and the grapevines indirectly.

Q: How will they benefit the soil?

Tom: They act as an amendment to improve soil quality, reduce compaction and increase water percolation.    They also reduce wind and water erosion on all soil types while attracting beneficial insects to the vineyard.

Q: The yellow mustard one sees between the vines, is this a cover crop?

Tom: Yes, a long time ago mustard was seeded in the Napa Valley and now you see it everywhere. Once a cover crop gets established it can take years to change.

Q: Besides mustard, what else is used as a cover crop?

Tom: There are many types but the best for fixing nitrogen and making it available to the grapes are usually clovers, soybeans, fava, vetch and alfalfa. My favorite is Tom Cat clover (laughter).

Q: Is there one cover crop that’s better than another?

Tom: While certain legumes add important nitrogen to the soil, non-legume types such as rye and oats use excess nitrogen to make phosphorus and potassium available to the vines. It’s best to plant both types to cover the vine’s nutritional needs.

Q: Now I see workers mowing the rows. Why is that?

Tom: Cover crops can eventually steal essential moisture and nutrients needed for long term health of the vines. So you’ll see either mowing or disking at this time to control growth.

Q:  What about using sheep instead?

Tom: Sheep are best used on fallow ground, before grape planting. When used otherwise, attention to manure issues and the possible damage to new shoots is of definite concern.

Q: After mowing, what will be done with the cuttings?

Tom: Most winemakers use cover crops as fertilizer, or ‘green manure’. If they’re not disked, the mowed plants remain in the rows to suppress weeds while providing a haven for beneficial organisms attracted to the decomposing plant material.

Q: Are there any negatives about cover crops?

Tom: They can produce dangerous situations in the event of frost by keeping the cold moist air at ground level and preventing the radiant heat from the otherwise exposed soil from protecting the vine. That’s why the timing of the cutting or mowing is crucial.

Posted by Kerry