Coastal Viticultural Consultants, Inc. logo




1575 Deer Park Rd.
CA, 94508
United States
Bryan Rahn

Experienced, Certified Professionals are our Strength!

The principals of COASTAL VITICULTURAL CONSULTANTS (CVC) have been professional VINEYARD consultants for over 25 years and have been CERTIFIED as Professional Soil Scientists and Agronomists for over 20 years. Our professional certifications, breadth of experience and a proven track record places CVC as a leader in the viticulture industry. CVC is proud of the long term relationships that we have developed with our clientele.

CVC’s strength is consistent quality of work and our experienced staff. CVC provides vineyard consulting throughout California and Oregon to growers and wineries that encompasses all aspects Vineyard Soil Testing, Vineyard Soil Mapping, Vineyard Nutrition, Vineyard Design and Vineyard Irrigation Management. We also consult with vineyards throughout the United States and internationally on a project basis. CVC staff consists of A.R.P.A.C.S. Certified Professional Agronomists and Soil Scientists with extensive consulting experience. All of CVC's management and field technical personnel have degrees in viticulture, agriculture and/or soils from major universities. For consistent, high quality work, use a Certified A.R.P.A.C.S. professional.

CVC’s vineyard consulting is custom designed for the specific conditions within each vineyard to maximize quality for both the grower and winery. Our clientele consists of wineries, growers, investors, engineers, financial lenders, and real estate professionals. CVC can design a custom ULTRA-PREMIUM STRATEGY for your vineyard too! The following services are available from CVC:


  • Grape Quality Enhancement Programs
  • Irrigation Management Advice, Soil Moisture and Pressure Chamber Services
  • Vineyard Evaluation & Problem Diagnosis
  • Vineyard Feasibility Studies
  • Vineyard Soil Testing
  • TerroirView® Soil Evaluations
  • Soil Resistivity Mapping
  • Aerial Imagery
  • Complete GIS/GPS Services
  • Vineyard Design & Layout
  • Soil Health/Enrichment Programs
  • Grapevine Nutrition & Fertilizer Programs
  • Soil Reclamation Plans
  • Regulatory Permitting & Compliance
  • Expert Witness/Litigation Support

News Archive

Precision Agriculture – An Essential Tool for Effective Management Strategies
10 April, 2018

Can We Agree

During my tenure as a Soils Scientists at Coastal Viticultural Consultants (CVC), I have observed in recent years that the concept of precision agriculture (PA) has gained coverage in the press and agricultural industry technical meetings, and has increased in its implementation. Precision agriculture seems to have a breath of definitions, beliefs and aspects within the agricultural community. Precision agriculture can be perceived as anything from global positioning systems (GPS) for computer guided field equipment, to automation of irrigation controls, to using geo-referenced aircraft and satellites to collect and review aerial imagery of a particular site or area. For the purposes of this article, let’s subscribe that precision agriculture is, in part, about collecting appropriate information, via observations or from some type of senor(s) or sampling mechanism, and using that information for management decisions that are based upon reliable data. Furthermore, and very importantly, let’s agree that PA is site-specific, meaning managing ‘larger’ fields as a group of ‘smaller’ fields.

Several colleges and government agencies offer courses and grower technical meetings, and many articles (research – based and anecdotal) have been published on the merits of PA and its implementation. As a scientist, I appreciate the value and use of empirical, reliable data to engage sound decision and actions for clientele. Kudos to universities (University of California at Davis, Fresno State, Oregon State, Cornell, etc.) government agencies (USDA, NRCS, Resource Conservation Districts, university agricultural extension services, etc.) as well as private researchers and industries for their hard work in scientifically vetting, developing and providing reasonably reliable, efficacious studies and results that provide a foundation for effective precision agriculture practices. Thanks to the aforementioned entities and their research, as well as advances in technologies, agriculturalists have suitable tools to obtain credible and reliable information to increase the opportunity to reap benefits from precision agriculture practices. It is likely most agriculturalists agree that an important goal of PA is to implement data – based management decisions to achieve more effective use of resources (a mainstay in ‘sustainable agriculture’), increasing opportunities for profits and, in some areas, comply with local regulations.

Ending Long Held Beliefs – New Management Strategies with Precision Agriculture

Having grown up on a farming operation, my first exposure to some likeness of precision agriculture occurred in the late 1960s / early 1970s. Back then farm management decisions were mostly anecdotal; typically based upon ‘that’s the way it’s always been done’ or ‘that’s what my neighbor is doing’, or ‘based upon the date of the calendar, it’s time to do such and such’, to cite a few ‘traditional’ beliefs used to justify and employ farming actions. At that time the notion of precision agriculture primarily consisted of collecting random soil samples for chemical analysis and using the results to better understand fertilizer or soil amendment needs. Collecting samples for data and using that data was mostly perceived as untraditional, ‘expensive’, and met with some resistance from farming communities. Fortunately, since the 1980s / 1990s, precision agriculture, as defined above for this narrative, has become more than a buzz phase, and is become more trusted and mainstream in agricultural management decision processes. As resources, profit margins and regulatory compliance become more challenging to obtain in agriculture, it seems that implementing PA to make management decisions has been replacing habitual actions or using anecdotal experiences in farming operations. This is not to diminish the importance of a grower’s personal observations and knowledge of their particular farming operation. However, the tools within the PA processes can help quantify, enhance and better quantify personal experiences to enable better foresight and predictabilities for more effective resources use and / or improve yield goals, for better economies.

Sound Data Collection – An Essential Path for Precision Agriculture

Any tool can be misused and misapplied, which can produce harmful results. Precision agriculture falls in this realm. And, there can be many tools used within PA that are critical components, which, too, can be misapplied or misused, resulting in data that is counterproductive. Precision agriculture can be a very useful tool in management decision processes to deploy more effective actions in the field and / or to comply with local regulations. Successful PA depends upon collecting data that is applicable to specific areas and accordingly taking appropriate actions based upon the data. So, implementing proper data collection to obtain suitable, representative samples is important for successful PA.

Any management tool can be misused that can produce unintended consequences. In effort to avoid misusing PA as a management tool, critical underpinnings of PA include a) proper collection of data, b) proper interpretation of the data, and c) defining areas (of a site) data represents. Misunderstanding these underpinnings has the potential to produce ill-fated management decisions that can produce results that are inadvertent, costly and detrimental. These aforementioned topics will be elaborated upon in subsequent articles, and will include discussions on technologies used for sound data collection and defining areas data represents. So stay tuned for articles on electronically mapping soils for better clarification of characteristics and boundaries and aerial imagery to monitor and map plant performance, to name but a few topics.

Drought and Irrigation Management
23 June, 2016

Our everyday lives are peppered with reminders of the drought. Bumper stickers decrying the tunnels, I-5 billboards blaming congress for post-apocalyptic scenes of desiccated orchards, the giddy excitement over the radio correlated with major rain events, are all telltale symptoms of the pressure that California’s watersheds are facing, and that I spend too much time driving.

The surly truth is on the horizon. The Sustainable Groundwater Management Act has given local agencies a greater ability to curtail water use, in many cases ending the seemingly unbreakable conviction that the water that flows under a given piece of land belongs to the landowner. Any grower should be aware that water is gaining value. Depending on whom you ask, the price of water for agricultural use can hover between $700 and $2500 per acre-foot.

As a soil scientist, I work in orchards and vineyards. Almond growers have been demonized in the wake of the drought, prompting a smorgasbord of reactions ranging from educational radio soundbites to more billboards, but many have begun to dig deep in finding ways to master their irrigation.

The most basic principle is making sure that you’re not wasting it. Blake Sanden (Kern county UCCE farm advisor) explained at a recent young orchard workshop that tracking soil moisture at multiple depths would give growers an idea of where water is being used and where it’s being wasted. Knowing how deep your feeder roots are located as well as the soil types in question is critical to designing irrigation layouts. Essentially, putting moisture sensors at several depths, or using a neutron probe to measure at foot-by-foot increments, growers should be able to see where moisture levels stay constant and where they are being depleted by roots. Likewise, if you know that your rootzone extends to 3 or 4 feet, but you see moisture that increases with irrigation sets or otherwise stays constant (once at field capacity) at 5 or 6 feet, you are likely overwatering, risking unnecessary leaching.

The anecdote to illustrate Blake’s point on the importance of knowing your soils was the story of a grower who irrigated his orchards on a 48 hour set once every two weeks. The trees in the fine sandy loam on one end of the orchard were fantastic. Walking the line between insufficient and excessive, the trees thrived all the while avoiding problems with root rot. The other end completely collapsed. The soil under the struggling trees was acoarse sandy loam. With a dearth of clay particles to hold onto, water was essentially falling out the bottom and by the time the next irrigation was due, the trees were already under intense stress.

The relationships between soil and irrigation strategies are the same in vines. Soil maps are critical in their ability to provide key information on water holding capacity and when to irrigate. In the midst of the drought, this seems like something worth looking into. But it’s not entirely good enough. Finite differences in soil textures can lead to relatively different outcomes in terms of available water capacity. The process of monitoring your soil moisture status should thus be seen as something that is ongoing.

Most growers are probably better at reading their vineyard’s water status than anyone else standing above the soil line, but ET measurements aren’t nuanced, they’re numerical. By taking advantage of neutron probe readings or real-time capacitance probes, growers can quantify their resources and plan ahead accordingly. The old-school pressure bomb and other stress-monitoring devices are invaluable tools when better understanding what a moisture reading in the soil means for the plant above ground. Unfortunately, that’s only one half of the equation.

The undeniable irony that comes with increased water use efficiency is that groundwater salinity and boron/ chloride toxicity (particularly in stream or groundwater flow from the Coast Range) are becoming more of an issue. Not only are salt and mineral concentrations changing in the soil as irrigated water is transpired, but certain aquifers are becoming more saline or concentrated over time. Understanding how much water would be required to leach accumulated salts or potentially toxic materials in the soil profile requires more than a hunch that it’ll be a good El Niño year, it requires that growers know the moisture status of their soil going into winter and also compels growers to fully understand their water report.

Granted, any step toward better management is positive and growers throughout California cannot be classified into any single tier of water management, but if the drought is a harbinger of change, rather than an anomaly, the wine industry may be involuntarily compelled to evolve, albeit faster than some of my verdantly zealous neighbors. If nothing else, the economic argument for maintaining solid profit margins will compel growers to meet the challenges presented by ongoing drought conditions.

by Konrad Mathesius

Konrad Mathesius is a soil scientist, agronomist, and PCA for Coastal Viticultural Consultants (aka CVC Ag Services). He was born in Australia and raised in Utah.He is based in Sacramento and holds a dual MS from UC Davis in Soils and Biogeochemistry/ International Agricultural Development. Website:

Soil Mapping Technology & Irrigation Management Strategies
16 June, 2014

We believe that wine quality starts in the vineyard. CVC's water management program has a proven track record of maximizing fruit quality, reducing pumping costs and conserving resources for many premium growers and wineries. CVC uses a combination of techniques to accomplish our water management objectives. CVC’s vineyard consulting is custom designed for the specific conditions within each vineyard to maximize quality for both the grower and winery. Click on this  link to view one of our in-depth report presentations to get a better idea of what we can provide.

Title Name Email Phone
President Bryan Rahn 707-965-3700
Soil Scientist Michael Princevalle 925-462-6206
Viticulturist Seth Schwebs 707-479-7718
Viticulture Tech Tom Diaz 707-337-9914

Irrigation Management is one of the keys to wine quality. CVC's irrigation management program is designed to optimize wine quality...

We believe that wine quality starts in the vineyard. CVC's water management program has a proven track record of maximizing fruit quality, reducing pumping costs and conserving resources for many premium growers and wineries. CVC uses a combination of techniques to accomplish our water management objectives. We measure soil moisture with the most accurate technology available throughout the growing season. Our trained viticulture staff also uses pressure chamber readings, visual observations, plant measurements, canopy temperatures and physiological conditions to make a comprehensive assessment of the vineyards. This data is used to produce CVC's Stress Index Curves ® presented on our unique Viticulture Chart. A Stress Index Curve is CVC's proprietary Soil-Water-Plant relations rating system, which we have used successfully for over 20 years. As a component of our Irrigation Monitoring Program, Stress Index Curves accurately depict how vineyard growing conditions impact wine quality. An experienced Certified Professional Agronomist reviews each chart and provides irrigation recommendations.



CVC's Irrigation Management Service provides:

  • Graphed accurate soil moisture readings with the recommended irrigation amounts.
  • Weekly Vineyard observations by trained viticulture staff including phenological stage, periodic pressure chamber readings, shoot length measurements and stress index rating in a Soil-Water-Plant Relations graphed format.
  • Site visits and irrigation recommendations by a Certified Professional Agronomist and Soil Scientist.

TerroirView ®

TerroirView ® is CVC's unique, trademarked, comprehensive soil evaluation that describes your vineyard's distinctive Terroir. TerroirView employs GPS and GIS technology, complete laboratory chemical analysis, soil profile descriptions and photographs to produce soil amendment, soil enhancement and rootstock recommendations, site specific soil maps, waterholding capacity ratings and vineyard design and layout maps.

 Sample TerroirView Report

Soil Resistivity Mapping

CVC uses the most accurate technology and methods for measuring soil resistivity. This cutting edge soil resisitivity technology is combined with a Global Positioning System (GPS) to produce CVC's geo-referenced Soil Resistivity Maps. Soil Resistivity Maps precisely locate changes in soil conditions. These changes in the soil conditions are then described, evaluated and quantified by an experienced, Certified Professional Soils Scientist in the TerroirView phase of the soil study.


Slope and Aspect Maps

CVC uses contour data to develop maps with percent slope, aspect and approximate acreage to spatially define the soil resources of a project. The slope maps will classify specific slope categories and approximate acreage within each category.

Soil Resistivity and Slope / Aspect Maps combined with TerroirView ®provide an extensive evaluation of the vineyard soils and resources that is a powerful tool for vineyard management, planning and optimizing wine quality. CVC utilizes the soil, slope and climate data to design vineyard blocks, irrigation layout, row orientation, rootstock and variety, vine and row spacing and trellis systems.

Aerial Imagery

Coastal Viticultural Consultants, Inc. (CVC) provides geo-referenced, calibrated, 1.0 meter or 0.5 meter resolution, Green Biomass Index (GBI), multispectral imagery to our clientele. Our imagery partner has developed the industry’s strongest range of proprietary technology processes and products that are unrivaled for their calibration (for atmospherics), accuracy and consistency. This geo-referenced, multispectral imagery integrates their proprietary vegetation measurement technology.

Calibrated aerial imagery can be used to evaluate changes in vine vigor from season to season. Geo-referencing aerial imagery allows our clients to use the imagery as background maps for GPS data collected in the field by CVC, their own field personnel, consultants, wineries or grape buyers. The maps generated with the aerial imagery can be used as base maps or data layers in GIS software like ESRI’s ArcMap.

Green Biomass Index (GBI) technology is similar to a Normalized Difference Vegetation Index (NDVI), however, GBI has a greater resolution at the upper end (full canopy) of the spectrum and NDVI is more prone to background interference (soil color, cover crops, etc.) at the lower end of the vegetative scales. A calibrated Green Biomass Index (GBI) is processed to remove the background noise caused by variation is soil brightness and to enhance sensitivity in biomass estimates. The result is a nearly linear vegetation index from a non-vegetative condition to a full canopy. These processes make GBI imagery more repeatable and a better tool for comparing vineyards from season to season.

Aerial Imagery applications in viticulture:

  • Identifying, locating and quantifying variability in vineyard growth.
  • Monitoring changes in vineyard growth patterns.
  • Direction of soil, plant tissue and fruit sampling programs.
  • Identifying and locating growth or vigor patterns that produce optimal fruit quality.
  • Delineating fruit quality variability for more precise, directed fruit harvesting.
  • Implementation of Precision Farming techniques and equipment.
  • Improving efficiency by directing fertilizer and other inputs to specific areas within each vineyard.
  • Direction of field crews or contractors to specific areas within the vineyard.