By Levi Glenn
The falling leaves mark the commencement of the “slow time” of the year in the vineyard. Harvest is in the rear-view mirror. All the grapes have been fermented and the wines are resting comfortably in their respective vessels, yet one last series of tasks needs to be completed. We have come to call this winterization, and it has nothing to do with new wiper blades or antifreeze. Our tasks include ripping the soil, discing, applying compost, seeding cover-crop, and spreading straw bales. In a normal year it’s a race against the clock. The rain usually arrives at some point in November (we’ve only received 0.59 inches so far), after which it becomes a lot harder to get our tractors into the vineyard. With the tractors darting around the property, it can almost look choreographed. One tractor will broadcasting compost, a second closely behind with a disc to incorporate the compost and aerate the soil, and a third tractor bringing up the rear with seed drill to sow our cover-crop. It takes us close to a month to finish it all up, and that’s when we can really sit down and take a breather.
On a good portion of our vineyard we use our Yeomans Plow. This consists of a three-shank ripper and a roller behind it. There seems to be no end to benefits of this tool. We use it to break-up soil compaction, which is caused mostly by our long, dry summers, but contributed to by our tractorsand even the winter rainfall, depending on the physical composition of the soil. It simultaneously aerates the root zone allowing the roots to breathe and spread more easily, and it trims surface roots forcing the roots to grow downwards instead of into the row middles (allowing us to dry-farm more effectively). On our steepest head trained, dry-farmed blocks we also use it for erosion control. By ripping across the hill, any run-off that may occur sinks down the trenches left by the shanks, allowing us to retain water rather than having it run off down hill. The only drawback to this tool is the amount of rock that it pulls out of the soil, that we then have to remove by hand. The Yeomans has become an invaluable tool in the vineyard.
Organic compost is at the very center of our nutritional program at Tablas Creek Vineyard. For many blocks this is the only fertilization they receive for the entire year. Our application rates vary from 2-5 tons/acre. This may sound like a huge amount, but an acre is a big area, and as you walk behind the spreader you can see only a scattering of compost on the ground. We make around 100 tons of compost each year from own property. We collect all the vine prunings from the vineyard and run them through a wood chipper, then throw in all the pomace from the winemaking process, and lastly add green waste from tree trimming. All of these ingredients are put into a pile and turned every couple months. Microbes in the raw materials break down all this organic matter into compost, which takes close to a year to finish. We can’t make enough compost ourselves, so we purchase another 250 tons from organic sources to supplement our own. The compost gives the plants a little boost of nitrogen, which helps their growth, but just as importantly introduces an immense quantity of microbes. Even better, compost has a time-release effect, and not all the nutrition will be used up right away. This year’s compost will feed the vines for 3 years, and since we apply every year, the vines receive a compounding effect.
Throughout the whole estate vineyard we seed cover-crop. We use a seed drill, which creates a small furrow in the soil and drops a selected amount of the seed a couple inches below the soil surface. The seed mixes we use are mostly made up of legumes, but also have some barley and other grasses. Legumes have the unique ability to pull nitrogen from the atmosphere and process it and actually put it back into the soil. The grasses are mostly for erosion control. As the seeds start to germinate, their roots penetrate into the soil and help hold onto the little topsoil that we have. Perhaps the most beneficial aspect of cover cropping is harnessing the immense amount of greenery that grows between the vine rows. Once we till this cover crop back into the soil in the spring we increase the percentage of organic matter in our soil. Organic matter improves soil nutrition, water holding capacity, microbial activity and soil structure. Increasing organic matter in soil is what farmers refer to as “building soil”. With different seed mixes we get different flowers that bloom and attract good bugs, and the more species of plants the more diversity of microbes we have in our soil. A side-benefit is that a cover-crop allows us to choose the plants that grow in the winter, and cut down on invasive and troublesome species of weeds such as yellow starthistle.
We only have one last thing to do before we are fully buttoned-down for winter. On the steeper dirt access roads between vineyard blocks, winter rainfall can cause serious erosion problems, but plowing across the slope or planting with cover crops aren't really feasible. So we spread straw in a thin layer across these areas. The straw slows down the water, and helps distribute the force of the heavy rainfall. Only the steepest of spots are in jeopardy. Once it rains a couple times, grass germinates and grows up through the straw, further reinforcing these sensitive areas.
Just a week ago we finished up with all of our various winterization tasks. The winter slumber can now begin. It's on to building more rock walls and waiting for the rain. Even with average rainfall from here on out, we will most likely still suffer some drought conditions in 2014. As of today we are at just 16% of normal rainfall. This is making most growers quite axious right now, in a time that would usually be the more restful. It wont be until February that our next big task of pruning begins. Hopefully between now and then all of our erosion control efforts actully get put to use. In any case, the rest will be much appreciated.