(Another) Year in the Vineyard, Week #7
April 23-30, 2010
Irrigation, Fertilization and Pinot Petioles
According to my desk calendar, last week was supposed to be pretty mellow. On more than one day the calendar read ‘GOLF?’, but I am sad to say the question mark won out and I haven’t moved the clubs from the back of my truck for more than three weeks. The plan is to charge into today with all the alacrity and purpose I can muster, and then cross out the question mark on tomorrow’s calendar. Sisyphus WILL get the rock to the top of the hill today, come hell or high water. I will travel north with a number of golf pilgrims tomorrow and play a new course. And before you think something like: ‘Well you have the whole weekend to do that…’, realize that the weekend is generally the busiest time for tours, tastings, sales, dinners and the like. The wine business is the hospitality business, and that means we make money when everyone else is playing and relaxing. And this weekend is busy enough that I had to use a very thin pen to get all of the appointments and must-do’s to fit on the brand new page on the calendar.
Is it May already? Well, that’s a hell of a thing because it signals the beginning of the end of Frost Season. Mother’s Day is the traditional day that we relax a bit, as Jack Frost is supposed to have been thwarted, but then some Old Timer had to tell me this week of a freak July frost that happened back in the 70’s. I’m hoping he was just messing with my head, as I used to when I taught High School back in the day. I called teaching ‘being paid by the State to subvert young minds’. That grizzled old farmer was probably doing the same damn thing. Except he probably wasn’t subsidized by the State…but nevermind.
In a world of GPS technology, soil sensors, pressure bombs that measure water status, etc., sometimes I like to go back to Bronze Age technology in the vineyard. This week I dug a few holes to see how moist the soil is down to a few feet. It appears that there is still a good deal of soil moisture from our bout with the wrathful Christ Child (aka El Nino), and even though he is supposed to rise and disappear miraculously on Easter Sunday, it appears that the El Nino will continue on until May, and I even read this morning that the ocean temperature oscillation that causes the wet weather in California, may even be predicted to last all the way into next year. As I mentioned in a previous blog, an inch of rain saves us thousands of dollars in electricity (from pumping ground water for irrigation), so while we don’t like to see a lot of rainfall during the growing season (it spreads disease and makes for more sprays and stuck tractors), the thought of getting two winters in a row of 15”+ rainfall actually makes me a touch giddy. That means the salts will be completely leached out of the soil and we can expect solid yields for a few years to come (which makes steve and cathy giddy)—as long as we aren’t hit with more frosts, swarms of locusts, or angry Babylonians or Hittite raiders. Fortunately we don’t have to worry much with the Christ Child swirling in the Pacific. Rumor has it El Nino rains burn the skin of the unbelievers. And Hittites don’t do umbrellas.
But back to the holes in the ground (talk about an A.D.D. fit!), ths oil moisture appears ample for at least a few more weeks of holding off from supplemental irrigation. The weather here in the Santa Rita Hills is supposed to warm soon, though, and with that warming trend the vines will have an increased capacity to take up nutrients that can’t exchange when the soil is still chilled from Winter. The collection of organic fertilizers waiting in the barn cost us about $5000 this year, and pouring them into the cold soil (pushed through the drip system, which is also called fertigation), would be like making Sangria with 18 year old single malt Scotch whisky. Well, actually no. That’s a bad analogy, because it would still get you drunk. It would be like making Sangria with First Growth Bordeaux that had been sauteed over a stove until all the alcohol (and flavor) had been removed. A $5000 punch that would taste horrible and do nothing to assuage your ennui or sobriety? Not a good idea! So as I see the temperatures warming, and the soils following suit and gaining more microbial activity and ability to transport nutrients into the vine, I will start to drip fertilizer to the vines in a 5-10 gallon per plant portion. I also imagine that the moist soil will allow the fertilizer to spread through the soil profile easily, getting to all the areas in the dirt where vine roots exist.
So how are decisions on fertilization made at Clos Pepe? Well, for the first few years we didn’t fertilize. I thought the ‘terroir’ would be affected, but the vines were so small and the shoots so short, that we didn’t get much of a crop. Of course the wines were delicious (in very small quantities), and as I continued my studies through periodic visits to the campus of UC Davis, I learned that getting a balanced vine on poor, sandy soils does require some supplemental nutrition.
How do we know what the vine needs? When the vine blooms, dropping its caps and allowing the tiny flowers to surround each and every grape berry for pollination, we also take samples of the leaf stems (called petioles) for analysis. Using petioles adjacent to the forming berries gives us an exact snapshot of the nutritional availability exactly at the point where those nutrients are needed by the clusters. The petioles are ground up and tested, and the reports come back in a slick format that shows a short red bar for deficiency, a yellow bar for slight deficiency, a green bar for ample supply, and perhaps a very long green bar for an over abundance. Too much nitrogen, for example, may actually be worse for wine quality than not enough. After getting our petiole samples, we sit on them and use them next year for fine tuning the nutrient status in the vine. In a serious deficiency situation, we may try a bit of fertilization immediately, but by the time the vine is flowering, fertilization should have been completed for the year, at least in a mature vineyard.
But what does a vine need? Let’s focus on what we call the macronutrients, or NPK: Nitrogen, Phosphorous, and Potassium. I know there’s not a ‘K’ in Potassium, but I think it has something to do with that big chart in my high school AP Chemistry class that I never quite memorized. (I was too busy pilfering anhydrous caffeine, which is a story for another blog.)
Nitrogen (N): naturally occurs in most soils from decomposition of dead plants and soil organisms. This is why equatorial societies are involved in massive amounts of ritual sacrifice. Put a dead body in the jungle, and stuff grows out of it—one main reason is the production of nitrogen, the main ‘food’ for the vegetative growth of plants. Nitrogen compounds are oxidized by soil organisms into nitrates, which is the form most readily available to the vines. So it’s not just dumping a bunch of nitrogen on the plant. Keeping a healthy and active soil (teeming with microbes, decomposers, worms and the like) makes the nitrogen we do add extremely effective. Nitrogen is a major component of both chlorophyll and plant tissue, so it is required not only as the ‘building blocks’ of new plant growth, but also to form the compound by which plants use sunlight energy to produce sugars from water and carbon dioxide.
Phosphorous: Phosphorous (P) is the gear box of a plant. It is used by the plant to transfer energy from one reaction to drive another reaction within the plant’s cells. In ample amounts it allows the vine to grow vigorously early in the growing season and also will hasten maturity of fruit late in the season. I could also go into how soil pH impacts Phosphorous uptake, but let’s keep it simple. Phosphorous helps drive cell-based plant reactions, is essential for plant growth, but has to be added to soils carefully, because you do not want phosphorous or phosphates running off into water sources.
Potassium: Potassium (K) is commonly present in large amounts in soil (20,000 parts per million), but plants can only use the exchangeable potassium on the outside of soil particles, and that which has been dissolved in water. After those factors are taken into account, the normal amount of exchangeable K in the soil plummets 200 fold to less than 100 parts per million. Potassium, if it could speak, would call itself the ‘Regulator!’ <
Grapevines are fertilized to a point of health, but not overt vigor. The proper balance is much like that used in raising a child. Keep them healthy but not spoiled, growing but not fat, fruitful but not knocked up as a teen.
Next week: A short and sweet blog coming to you ‘live’ (I hope) from the Riverside International Wine Competition, where I will be judging over 300 wines over three long days. Expect some slurring.