Dry-Farming in California's Drought, Part 2: Looking Forward to the Past
May 15, 2015
In the first part of this 3-part series on farming in California's drought, I looked at how our climate here in California differs in crucial ways from that in the Mediterranean, and what lessons we took from these differences in how we would choose to farm. In this second part, I pick the story back up with how we planted and trained our vines in the early days to allow us to dry-farm them now, and what changes we've made in recent years as we adjust to what is likely to be a drier future. The third part is more historical, looking at how grapevines -- which should be one of the easier crops to dry-farm -- came to be so widely irrigated in California. If you missed Part 1, go read it now. OK, welcome back.
In the Beginning
When we began planting, we used a hybrid of the planting methods of modern California and the traditional Rhone. At Beaucastel, vines are planted head-trained but closely spaced on their relatively flat terrain. They cultivate these vineyards using tall over-the-vines tractors as the spacing (roughly 1.5 meters square) doesn't allow tractors to pass in-between. On our steep hillsides, these tractors wouldn't work, so we matched the overall vine density, but moved the vines into rows, planting more closely within the rows (3 feet) and spacing the rows either 8 feet or 10 feet apart, depending on our terrain. We achieve a similar vine density at around 1600-1800 vines per acre, but can cultivate mechanically, essential for our organic techniques:
Our decision to plant at similar density to Beaucastel was grounded in our initial belief that in our broadly similar environment we should use the techniques that they had developed over the years as a starting point, and then learn from our experiences here and adjust gradually over time.
The first choice we needed to make was what rootstocks to use. Wine grapes need to be grafted onto rootstocks to be resistant to the root parasite phylloxera. These rootstocks are descended from different species of American wild grapes, and have inherited differences in level of vigor, rooting configuration, tolerance for soil chemistry, and affinity for various varietals from their progenitors. [For a good technical overview of rootstock science, see this piece in Wines&Vines.]
Modern fashion in relatively water-rich areas (including Napa Valley, which has a fairly stable water table on the valley floor) suggests the use of low-vigor, shallow-rooting rootstocks, to keep the vines from growing too much canopy and from setting high quantities of low-intensity fruit. But it was clear to us that we should focus instead on higher-vigor, deeper rooting rootstocks because of the high-stress nature of our climate and topography. We chose deep-rooting, relatively high-vigor rootstocks to graft to (principally 110R and 1103P).
Our next decision was if and how to irrigate the blocks we would be planting. After speaking to local growers, it became clear to us that in order to get our young vines through the dry summer months, we would need to be able to irrigate at least in the early years. Grapevine roots grow down fairly rapidly, about a foot and a half per year when the vines are young, slowing as they age. To determine the length of time we'd need to supplement, we did some trench cuts in the vineyard, digging down a dozen feet through the topsoil and the top layers of limestone, to see where the water was by late summer. These showed that even with the water-holding capabilities of our calcium-rich soils, we needed to dig down 6-8 feet to find layers that still had moisture in September. So, we figured we would need to irrigate for the first five or so years, if all went well, and if we were able to encourage the deep root growth that would eventually allow us to get the bulk of the root mass down where water could be found.
Our technique was infrequent but deep irrigation. This should be intuitive. Grapevine roots grow where water is present. If you water frequently but shallowly, roots continue to grow near the surface, where water can be found. If the only water to be found is deep, roots grow deep. Watering infrequently (twice per summer, and eventually only once) but deeply causes the soil to dry out from the top down in between waterings, and encourages root growth in the deeper areas that have moisture.
It didn't work as smoothly as we had originally hoped. We lost so many vines to gopher predation that we had to replant in some cases as much as 25% of our blocks with young vines. These vines needed to be irrigated when they were young, and even longer, as they grew more slowly due to competition from the older vines nearby. It wasn't until the wet years of 2005 and 2006 that we felt able to wean our established blocks entirely from supplemental irrigation, but when we did, we were rewarded by consecutive great vintages.
Now, we feel that our older blocks are able to go not just through a normal rainfall winter without needing to be supplemented, but can go one year into a drought cycle (as in the 2012 vintage) without needing additional water. When we get multiple years into a drought, as we have been since 2013, we are able to supplement, again using the infrequent but deep watering that will discourage the vines from the bad habits of excessive shallow root growth. We supplemented most blocks once in 2013 and twice during the 2014 vintage, and feel that these are going to be two of our greatest vintages ever.
In addition to the continuing work that we've done easing our original plantings toward water self-sufficiency, the last decade has seen us look to even older models to plant vineyard in ways that won't need to be supplemented even in droughts. As early as 2000, we had planted some of our low-lying blocks in relatively deep soils head-trained, dry-farmed. These areas most resembled, to our minds, the terrain at Beaucastel. We also looked at old vineyards in the Paso Robles area, many of which date back to the years before Prohibition. These vines, mostly Zinfandel, were head-trained and widely spaced, and had made it nearly a century still in high quality production. Our first block that we planted in this manner was the small block of Mourvedre near our front entrance, just to the east of where our tasting room is currently located. We spaced the vines 8 feet apart in a square pattern (a density of 680 vines per acre). A recent view of this block (with the vines and their solar panel backdrop) shows how well established they've become in the last 15 years:
The success of these never-irrigated vines encouraged us to plant most of our former rootstock fields in this manner between 2003 and 2005. Though these worked well too, we weren't sure yet whether we could translate these successes to hillside blocks with less topsoil and less water. In the end, it was the logistical challenge of getting well water pumped to our one block on the south (opposite) side of Tablas Creek that pushed us to give it a shot. We planted that thirteen-acre block, which we call Scruffy Hill, head-trained and dry-farmed in 2006 and 2007. Scruffy Hill presented some new challenges. It was (is) one of our most rugged blocks, on a very steep slope, with at the top just a foot or so of topsoil. Cultivation was also going to be a problem, with slopes as steep as 35% making it unsafe to cultivate across the hills, so after speaking with locals we decided on a 12 foot by 12 foot diamond pattern, reducing the vine density to about 340 vines per acre and creating two mostly-vertical avenues we could use to cross-cultivate safely. We weren't comfortable leaving these vines to fend for themselves entirely, so we bought several 5-gallon plastic buckets, drilled a small hole in the bottom of each, and then used our water truck to give each vine a single bucket of water in the late summer in years one and two. Scruffy hill is now thriving:
We've also been experimenting with our rootstocks. The rootstocks that we have used, from the beginning, have needed to be relatively high in vigor and tolerant of Calcium. This has meant that we use predominantly 1103-P and 110-R. In recent years, we've planted a few blocks of Grenache on the famously deep-rooting St. George rootstock, the standard in California before irrigation, though in more recent decades largely replaced by lower-vigor, more shallow-rooted crosses. We are hopeful that these experiments will allow us to develop healthier, more vigorous vineyards without needing supplemental irrigation.
The Upshot: Forward to the Past
All told, in the last decade we've planted over 30 acres head-trained, dry-farmed, in the manner vineyards would have been planted (per force) a century ago. And while it may not be intuitive, in our recent dry years, the vines in these blocks have shown less signs of stress, and the production from these blocks has declined less, than in our trellised blocks. But perhaps it shouldn't be so surprising that 340 vines in a dry-farmed acre can thrive with the roughly 15 inches of rain we've received each of the last four winters, while the 1800 vines planted in a trellised acre really need something closer to the 28 inches that is our average. While a 24-hour irrigation session can keep them going through a dry summer, it's still not making up the difference between a normal rainfall winter and what we've averaged during our drought.
Would we make the same commitment to dry-farming if we needed 4 or more tons per acre off of our vineyard? Perhaps not. Our dry-farmed blocks tend to produce between 2 and 2.5 tons per acre, even in the most productive years. But given that we're only aiming for between 2.5 and 3 tons per acre even from our trellised blocks, we're not sacrificing much production. And given how much less expensive it is to plant, prune, cultivate and thin 340 vines per acre than it is to do the same work on 1800, it may not be costing us more per pound of fruit even with the lower yields.
Even more important, the quality of the wine lots from these dry-farmed vines has been among the best in the cellar both of the last two years. Take into account that these are still among our youngest blocks and you can see why we feel it's a win-win situation for us, and why we're planning to plant our entire new parcel -- all 55 acres -- this way over the next decade.
So, if we're so happy with these old-fashioned techniques, how did the paradigm in California become so dependent on irrigation? I explore the history in part 3.