Two and a half years of alley-management studies in vineyards have revealed some valuable data.

Oregon State University Extension viticulture specialist Patricia Skinkis is looking at three different scenarios: leaving vegetation, mainly grass, on all year long; cleaning out the vegetation at budbreak; and tilling only every other row.

Skinkis is now in her third year with some small Pinot Noir research plots in the Red Hills of Dundee (Stoller Vineyards, Archery Summit), where all three management options are being evaluated. In all cases, in-row ground is kept vegetation-free.

It took two years before Skinkis started noticing some differences. "We're starting to see some differences in pruning weight" with the year-round cover crop that competes for water and nutrients, reducing biomass production.

During the second year Skinkis also started seeing positive differences in canopies, to include increased anthocyanin (color) and phenolic (grape astringency) development.

In 2009, "We're starting to see marked differences in shoot growth and in nitrogen (levels) as well."

So far Skinkis has found no water stress with permanent grass alleyways, but thinks this year may show some nutritive declines due to competition.

Another concern is decreased levels of yeast-assimilated nitrogen, important during the fermentation process. That is usually not a concern because that form of nitrogen can be supplemented in the wine must.

Skinkis said she's not studying various types of ground covers because that work has already been done elsewhere. "We're using what the growers already (use). They're requesting not what cover crops grow (best), but how to manage them."

What's more, because reducing vine vigor is the goal, using a nitrogen-fixing legume as a cover crop is totally out of the question, she said.

-- John Schmitz