As harvest approaches, we need to accomplish a myriad of jobs in the vineyard to ensure quality, deal with impending problems, and achieve crop requirements. Below are a few examples of our current vineyard tasks:
Bird Control
Now that August has arrived, we are finally reaching the end of our powdery mildew preventative program. When véraison occurs, (the period when berries begin to color and soften), the clusters are no longer susceptible to infestation. With the building of sugars within the grape, comes bird pressure. We do several things to lesson that pressure:
1. We distribute a metallic tape, known as flash tape, throughout the vineyard. The breeze and the bright sun light, create a light show in the vineyard that is disturbing to birds.
2. Secondly we deploy Avalarms throughout the blocks that we traditionally have trouble in. These devices are solar or battery powered and give off amplified distress calls of the birds that habitually feed on the grapes.
3. We also deploy propane powered cannons in areas of highest pressure. These devices are mounted on a rotating platform and are propelled by the concussion of the device and fire bursts of up to three shots per set.
4. We also have some metallic magnetic birds, that we suspend above the canopy. The theory behind this measure is that the magnetic field given off by the birds promotes an uncomfortable feeling in the feeding animals causing them to move on to different venues.
5. One of the final measures to prevent hungry birds from pecking grapes is the use of netting. Bird netting is our maximum deterrent, and it is not deployed until we have observed a substantial amount of bird pecking. Over the years, we have discovered that certain locations and varietals are more susceptible to pecking, such as Zinfandel and Tempranillo. The Zinfandel block is located near cherry orchards and tends to attract lots of Magpies. Tempranillo is a thin-skinned, early ripening grape, and it attracts Robins, Magpies, and Starlings.
All of these measures should be in place before bird feeding begins near the end of August. Protecting the fruit from birds is critical for wine quality. Bird-pecked grapes and berries can harbor bacterial and fungal pathogens that alter the flavor of wine or juice.
Extenday®
Many of you are aware of our use of Extenday, a material that we use to amplify the intensity of sun light in the vineyard. It is a white tarp that is deployed on the floor of the vineyard, running between the rows of vines. This material is stored in the vineyard and is deployed at véraison. At the conclusion of harvest we role it up and attach it to the drip wire. The timing on the deployment is critical and needs to happen when véraison is occurring.
Crop Estimates
Another job that we take on at this time of year is crop estimates. When we start the season we have certain crop loads in mind for each variety. As the season unfolds, we may need to adjust the crop to a lower level of production. Because we fear over thinning, we usually approach the need incrementally. In the springtime, we use a process called Shoot Positioning to reduce the crop and better position the location of the fruit. Those targets may not have been attained. So now we go to the vineyard, count and weigh clusters, and really try to hone in to actual yields. Further crop reductions usually occur after véraison with the removal of whole clusters or portions of the cluster that may not ripen as early. Uniformity is always the key to the best wines. Crop reduction is a real science, and to elaborate beyond this point might be overkill.
Harvester Maintenance
One of our winter jobs is to go through all our harvest equipment and make repairs on wear items, so that during harvest the process goes as smoothly as possible. When spring arrives, some of that work might have gotten shoved to the back burner. So now is the time when we need to finish the process, as harvest is just around the corner.
I am sure I omitted a number of annual requirements, however we will discuss them later. Until then… cheers!
CELLAR TASKS
Harvest is anticipated to commence in mid to late September (a few weeks behind the average starting date). Nevertheless, there is plenty of prep work to do in the cellar. Below is a glimpse at our Winemaker’s Pre-Harvest Check List:
Many of our wine club members have asked questions related to cover crops, so I would like to elaborate on the issue based on my personal experience…
A cover crop is a crop grown to cover the soil – serving as a protective layer. Sometimes, it is tilled into the soil as a “green manure.” Other times, it is a living or dead mulch located on the surface of the soil. Basically, a cover crop can be any type of plant. The most common types are grasses, legumes, or grass/legume mixtures.
Cover crops play an essential role for vineyards, especially here in Eastern Washington. Without them, the topsoil would blow away & the weeds would take over. Depending on the type of cover crop used, they can also be beneficial by decreasing water runoff, enhancing infiltration, conserving soil moisture, supplying nitrogen, increasing nutrients & organic matter, improving the structure & overall quality of the soil, suppressing soil born diseases, attracting beneficial insects, & encouraging a diverse ecosystem.
Finding the right cover crop to grow can be quite challenging in the Yakima Valley because of the dry, arid climate & sandy soil conditions. Over the years, we‘ve learned a lot about specific cover crops & their interactions with vineyard sites.
In the past, we’ve tried many permutations. We’ve used Sudan grass, Vetch, & Austrian winter peas. All of these crops are annuals, meaning they grow from seed & do not grow over winter. They all increase the tilth of the soil through the introduction of organic material at the end of the season. (Good tilth refers to soil that has the proper structure & nutrients to grow healthy crops.)
The downfall with these cover crops is that they also increase the total available level of nitrogen in the soil, and wine grapes tend to be low users of nitrogen. Increasing the amount of nitrogen above certain levels can actually cause the vine to produce excess vegetative growth, which in turn, can adversely affect wine quality.
After discovering this issue, we decided to use a cover crop that incorporates perennial grasses. The product that we had the most success with was a blend of several perennial grasses named Companion. Because it was a blended product, it could adapt to a multitude of vineyard conditions, resulting in a highly adaptable cover crop that performed well in a multitude of vineyard environments.
Nevertheless, we found one major obstacle with Companion – rodent control. Eventually the floor of the vineyard became so undulating due to the incessant borrowing of the rodent and coyote populations, that it was difficult to transport equipment, such as mechanical harvesters or sprayers, at the optimal speed.
In 1997, we installed our first drip irrigation system. With this method of irrigation, a drip line was suspended beneath the cordon wire, and it delivered water to each vine via individual emitters. Before conversion to drip, we were using furrow irrigation, which delivered water with ditches. We also used sprinklers, which delivered water over the top of the vine, wetting the entire surface of the vineyard. With the conversion to drip, we lost the ability to irrigate the area between the rows, where we plant cover crops. With the change, we needed to rethink our strategies.
Our new strategy is to use rye, which is an annual grass similar to wheat. Rye grass can often be grown under conditions where other cover crops fail because it establishes quickly and grows throughout the winter. Rye is an excellent choice for soil protection and weed suppression.
At Airfield Estates, we plant the cover immediately after harvest. We utilize winter precipitation to germinate and nourish the cover crop. Once we have established a healthy stand between the rows and before the plants become overly dry, we kill the cover crop. The mulch left by the dead cover crop can be used to help prevent weed germination in that area for the rest of the grape growing season. Control is not always stellar, so from time to time it may be necessary to run a mower through the middles to keep weeds at bay.
This dialog basically exhausts Airfield’s experience with cover crops. In other regions, with other climatic and topographical influences at play, the discussion could be much different. In general, the cover crop must match the site and vine vigor. Growers need to be aware of cover crop and vine interactions, and they must realize how these interactions may change as the vine matures.
Written By Mike Miller
Airfield Estates Grape Grower
