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

Grape Powdery Mildew Spore Trap and Fungicide Resistance Testing
18 February, 2019

CVC Real Time Canopy Temperature –provides real time, 24/7, water stress data for your vineyard.

  • Know if you have Powdery Mildew present BEFORE an infection occurs!
  • A weekly service with the actual number of spores detected.
  • Next day graphed lab reports sent to you via email.
  • Optimize your grape powdery mildew spray program.
  • The greenest spray is the one you don’t need to apply!

CVC’s patent pending technology is like having pressure chamber or porometer reading 24 hours a day every 20 minutes. Know how much water stress your vineyard is under and how long each day your vineyard is under water stress. Know how long it takes for your vineyard to recover after irrigations are applied. Know how long irrigations last before the water stress returns without using evapotranspiration data (ET).

CVC’s real time canopy temperature data is more accurate than Surface Renewal technology for measuring plant stress. Measure only the vineyard not the cover crop and weeds like other technologies do. Ask us how it works!

Coastal Viticultural Consultants, Inc. (CVC) offers professional technical services to help our clientele efficiently manage their vineyards and grow premium wine grapes. Our services are custom designed to address the specific requirements and conditions of each project. Our vineyard services maximize efficiency and quality for both the grower and winery. CVC’s extensive clientele consists of wineries, growers, investors, engineers, financial lenders, and real estate professionals. CVC can design solutions for your next project.

Precision Agriculture – Mapping a Path to Success
31 July, 2018

My previous editorial in this publicationpresented some background and perspectives on the subject of precision agriculture (PA); particularly pertaining to the use of data to a) improve effective use of resources, b) bolster yields and / or product quality, and c) ultimately increase profits. Additionally, the use of PA is an essential tool in sustainable farming practices and, in some instances, a valuable tool to achieve compliance with local or regional governmental regulations. The previous editorial also discussed the importance of collecting sound, reliable data as critical elements to successfully use PA in farming management. Data that is incomplete, misaligned or misused will likely derail both PA practices and the desirable goals it is intended to achieve.

This article will discuss the importance in spatially identifying where soils change or transition within a field or area, and methodologies commonly used to perform for this identification task. Future articles will discuss investigating and defining soil characteristics, and PA strategies to best use soil characteristics for maximum benefits.

Where to Begin Collecting, Vetting and Applying Data. . . Let’s Start with the Soils

Soils are the foundation for most of agriculture. As expressed by UN Secretary General Ban Ki-moon, “Without healthy soils, life on Earth would be unsustainable”. Identifying and considering boundaries of soil types are major components in successfully maintaining soil health, and the successful use and outcome of precision agriculture. Astute agriculturalists are aware that a given area or field can have different soil types, and that these differences can be appreciable.

In viticulture it is especially important to obtain an awareness of where soil types change as these (soil) differences can appreciably impact the outcome of management decisions and desired effects. For now, the discussion of plotting (or mapping) soil changes will pertain to its significance in obtaining consistent, reliable and meaningful data, and meaningful applications of that data for management. Parenthetically, defining and mapping soil variability can appreciably enhance the application of data obtained from aerial imagery; another commonly used tool in management decisions and PA. Discussions pertaining to aerial imagery will be discussed in future articles.

Ground Zero; Finding Soil’s Hidden Treasures

To iterate, soil variability can significantly impact PA. In particular, soil variability impacts a) data collection (sampling) strategies, b) effectual understanding and application of the data, and c) implementing the most appropriate management strategies to account for variable soil characteristics. In other words, management actions based on data acquired from one soil type may not be appropriate, or maybe detrimental, if the same actions are used on different soil type. Perceptive farmers, especially vineyard managers, are aware of this.

Soils types typically do not reliably show their transitions or variability through topical, visual inspection, or even aerial imagery. Investigating and delineating the boundaries of soil variabilities will necessitate using methodology(ies) that are effectual and practical for time or financial resources. And, probably most importantly, the method(s) must provide consistent, reliable data.

Methods Used to Delineate Soil Boundaries

Various methods have been tried to delineate soil types within a particular site in effort to select sample points and, in turn, to provide management advice on various soil–related topics to clientele for their farming operations. The key is to employ methods that can delineate soil variability with sufficient accuracy for use in precision agriculture, and at a competitive cost.

Various methods have been used to vet and delineate soil changes. For example, remote aerial sensing (infra-red, NDVI, LIDAR, Gamma-ray spectrometry, or other imagery techniques) delineate differences in soil topography, or soil surface colors, or differences in vegetation types, populations or vigor. In turn, the observed imagery from these methods are assumed to delineate (and map) changes in soils. However, it can be very misleading (even disadvantageous) to assume that the displayed variability in surficial soil colors, topography or vegetation can correctly or effectively delineate boundaries of soil variability. Variability in aerial imagery features can be due to a number of factors not necessarily related to changes in soil types. “Accurate soil maps cannot be produced solely by interpretation of aerial photographs. Time and place influence the clues visible on the photographs. Human activities have changed patterns of vegetation and confounded their relationships to soil patterns. The clues must be correlated with soil attributes and verified in the field”. Soil Mapping Concepts, Soil Science Division Staff, Kenneth Scheffe and Shawn McVey, USDA-NRCS.

Figure 1. Towing an array of soil resistivity sensors through an existing vineyard.

Another method to identify soil variability includes using soil surveys by the USDA and / or Natural Resources Conservation Service (NRCS). These soil surveys are generally easily accessible and can provide some broad information on soil boundaries as well as soil chemistry, physical characteristics, etc. on the soils with in the survey area. Soil surveys can provide preliminary information for government agencies and others on regional land use planning matters, and can be a guide to develop more specific soil investigations. However, in general, the soil variability demarcations mapped in the surveys are too broad to support for an effective PA program.

A third method used to delineate soil variability is ‘grid’ pattern sampling, which consists of field sampling soils in a systematic pattern of equally spaced lines or cells. However, this method requires numerous samples points within an area, and is generally labor intensive, time consuming and may not provide adequate soil boundary definition to produce sound data for effective PA or management decisions.

Fortunately, through several years of research and development, field data verification, and use in a myriad of field conditions, Coastal Viticulture Consultants (CVC) has developed high confidence in a soil delineation methodology using soil resistivity. Soil resistivity is a measure of the soil’s resistance to carrying an electrical current. Resistivity is the inverse of conductance; the ability to carry an electrical current. The equipment used in the mapping consists of a GPS receiver, data logger, and an array of sensors. The sensor array has direct contact with the soil’s surface and is towed by an ATV back and forth in a pattern of mostly parallel lines across the study area, or down the ‘tractor row’ of an existing vineyard, or orchard. (See Figure 1.)

The recorded GPS and sensor data is filtered and processed using software programs. The result is a geo-referenced soil resistivity map (See Figure 2) that both identifies and locates soil variability within the study area, to a depth of approximately 1.9 meters (or 6 feet) and laterally within a couple of meters. Particularly note, in Figure 2, the soil variabilities within just a few acres and within the soil unit boundaries (colored with purple lines) mapped by the NRCS.

Figure 2: Soil Resistivity Map. Note the occurrence of soil variations within these fields and the NRCS mapped soil units.

In general, the lowest soil resistivity readings (reddish colors) reflect clay loam or clay-textured soils and/or wetter soil conditions. The more moderate resistivity readings (yellows / orange colors) typically represent loam-textured soils. The highest readings (blue in color; most resistive) are usually sandier or rocky soil conditions. Note that soil resistivity maps do not thoroughly evaluate soil properties (textures, compaction, total salts, fertility status, etc.). The maps show where the soil variability is located that is very important to identify sampling / data collection points in evaluating the soils. Again, understanding soils, which will be further discussed in future articles, is an integral part of PA and effectual management decisions. Parenthetically, particularly in wine grape vineyards, soil resistivity will also delineate soils derived from different parent materials (sandstone, shale, metamorphic rock, etc.), which can have a profound impact on vineyard performance, management decisions, and the flavors imparted to the fruit and wine.

As a side note, electromagnetic technologies (different from resistivity technologies) which are also used for soil mapping, are prone to significant interference issues (from metallic infrastructure) in existing vineyards with a tractor row that is 3 meters (+/-10 feet) wide or less. This can be a serious limitation when soil mapping in existing vineyards. In these situations using soil resistivity typically provides more reliable data.

Taking It Further – The Best Is Yet to Come

Once you have reasonably defined the soil changes within your site, the next steps are to procure a better understanding of the soil’s characteristics (i.e., chemistry and physical) with the (soil) boundaries you have delineated. This information is critical to PA and better provides better implementation of PA and other management actions. These matters will be discussed in subsequent articles.

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.