Site preparation consists of 5 steps:
Topography & Layout: choosing the site and orienting the vineyard rows for optimal sun and wind exposure.
Ripping & Terracing: loosening up the soils, removing old stumps and terracing the surface if necessary.
Soil Analysis & Amendments: sampling and analyzing the soil to determine what fertilizers need to be added for a healthy vineyard.
Choice of Trellis System: choosing a trellis system which defines the spacing of the vines and the relationship between the rooting area and the crop density.
Irrigation System: Laying out the irrigation pipes, valves and drip lines.
The following paragraphs expand on these 5 steps and explain the differences between the choices made between the Lower and the Upper Fields.
Topography & Layout
The following picture shows the two vineyard layouts projected onto a Google map..
The Lower Field vineyard was planted in 1997 in 14 rows running south-west to north-east adapting to the contours of the land. The direction of the rows was dictated primarily by the topography. The 333 plants are spaced 6 feet with rows 10.5 feet apart. The total area covered is 333*6*10.5 = 20,979 sqft or 0.48 acres.
The Upper Field vineyard was planted in spring of 2015 with 16 rows running approximately north-south. The topography allowed a north-south direction of the rows with minimal terracing. The 256 plants are spaced 6’ with rows 9 feet apart. The total area covered is 256*6*9 = 13,824 sqft or 0.317 acres.
The following picture shows the two vineyards in topographical maps indicating elevations
Ripping & Terracing
Ripping is necessary to loosen up the soil 2 feet deep, remove dead tree stumps and other debris and destroy networks of old gopher tunnels. Terracing is advisable to facilitate easy access with tractors for spraying and mowing between the rows.
The Lower Field was ripped and cleaned by Ron Mosley in 1997. We terraced outside the south-west endposts later to allow easier turning after we introduced tractors for field maintenance in 2000.
We had the Upper Field ripped 2 feet with a big bulldozer by a contractor (Peter Mesa 408-438-1016). Then we terraced it with a box-scaper attached to our tractor to accommodate for the slope, particularly on the east side.
Soil Analysis & Amendments
A good starting point for soil composition in California is the online soil map by UCDavis: http://casoilresource.lawr.ucdavis.edu/gmap/
The first step in site preparation is to take soil samples and send them to a laboratory for analysis which highlights deficiencies in nutrients. Soil analysis is done before ripping and terracing, but the amendments are added after.
For the Upper Field, we followed the excellent instructions for taking soil samples at http://www.growyoursoil.org and then submitted samples of top-soil and sub-soil to A&L Westen Laboratories (http://www.al-labs-west.com/services.php?section=Soil%20Analysis ). We took 2 samples – one a mixture of 12 topsoil locations spread around the site, the other a subsoil sample at 2.5 feet in the middle of the site. We then had the soil analysis reviewed by GrowYourSoil and by our vineyard consultant, Ron Mosley. Their recommendations were consistent and are summarized in the table.
We spread all additions evenly across the vineyard acreage during the winter rains after ripping and terracing the site.
We have no records of the original soil analysis and amendments by Ron Mosley in the Lower Field in 1997. After we ripped out 70 weak plants in autumn of 2014, we did a soil analysis in January of 2015 which indicated a very low pH, or high acidity. Following recommendations by John Beeby, we made the additions suggested during tilling in the cover crop.
We purchased the fertilizers from Sierra Pacific Turf Supply (www.sierrapacificturf.com) in San Jose and the compost from B&D Mushrooms in San Martin (through Gordon Hodges Trucking 1-408-888-9291).
Vines have a complex system of roots below ground and a highly crafted architecture of trunks, arms, cordons and shoots above ground. The picture on the side provides an excellent view of a carefully excavated mature vine. From http://disciplegideon.files.wordpress.com/2012/07/grapvine-roots.jpg
Above ground, the trellises hold up the vines and allow to expose the grape bunches and leaves evenly to sunshine and air movement. We use the following vocabulary (adapted from Fundamentals of Grapevine Pruning by Ed Kwiek, Feb/March 2014 Winemaker Magazine) for describing different parts of the vine:
Trunk: a permanent, vertical stem of the vine (above ground)
Arm: permanent horizontal extensions of the trunk connecting the trunk to the cordons
Cordon: wood that is 2 or more years old, trained along a wire
Cane: a mature shoot after leaf fall
Spur: a cane that has been pruned back to 1, 2 or 3 buds (a compound bud)
Node: location of a compound bud
Bud: an undeveloped embryonic shoot
Shoot: new green growth with leaves, tendrils and flower clusters developing from a bud of a cane or spur. Each shoot produces 2-3 clusters of grapes.
Lateral: a branch of a shoot
Sucker: a shoot growing from old wood on the trunk, arms or cordons (rather than from shoots or canes)
Tendril: a twisting, threadlike part of the shoot which that wraps around wires and other shoots to provide support
There are many different types of trellis systems.
For the Lower Field, Ron Mosley chose a quadrilateral trellis system. The picture below illustrates what this means. The trunk of the vine splits into two arms each of which splits again into two cordons. Endposts delineate the end of the rows and trellises after every third plant support the guide wires. This is a complex system which has the advantage of widely spaced rows for tractors without giving up too much crop density. It only works in soils where a single root system can support a large plant. The disadvantage of quadrilateral trellises is labour intensive pruning, canopy management and netting because you can only access the fruit zone from one side of the cane curtain.
For the Upper Field, we chose a bilateral trellis system. It allows easy access to the canopy and fruit zone from both sides of the vine. This simplifies pruning and canopy management, but it bilateral systems have lower crop density if the rows are spaced widely to allow easy tractor access.
Lower Field Irrigation: The irrigation system has 2 manually switched drip lines for the vineyard, one for the northern half, the other for the southern half. In addition, there are 2 electrically switched lines for the roses at each endpost east and west, and there are two switched lines for irrigating the border plantings south and west. In 2015 we extended the irrigation system for the roses into the vineyard rows with drip tubing, so the roots of the newly planted vines can be irrigated more frequently than the mature vines.
Upper Field Irrigation: Each row has 2 driplines: one is for surface drippers, the other for 3 feet soaker hoses buried under each plant. The root soakers can be regulated individually. The rows are divided into areas for different grape varieties (Merlot, Cabernet Sauvignon, Cabernet Franc and Petit Verdot), and each of these areas has a remote-controlled valve. At each endpost there is drip irrigation for roses; this circuit is also on a remote-controlled valve. Furthermore, there is a live line and a switched line going to the east and west borders for irrigation. The following chart shows the layout as well as the component assemblies for the vine and rose irrigation lines.
Interesting website on irrigation supplies: http://www.urbanfarmerstore.com/wp-content/uploads/2012/12/DripHandbk.pdf