094: Vineyard Nutrition Essentials - Magnesium Fundamentals with Dr. Jaclyn Fiola
Release Date: 03/31/2026
096: Do Plant Growth Regulators Have a Place in Winegrapes with Dr. Matthew Fidelibus
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Plant growth regulators (PGRs) are powerful tools that can dramatically influence vine performance, but they also come with complexity and risk. In this episode, Fritz welcomes back Dr. Matthew W. Fidelibus of UC Davis to explore how these compounds are used across table, raisin, and wine grape production. Dr. Fidelibus explains that PGRs include both naturally occurring plant hormones and synthetic compounds that mimic hormonal effects. While they’ve long been foundational in table grape production, their use in winegrapes is far less common and more nuanced. The conversation highlights how...
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095: Transitioning from Conventional to Organic Grape Farming with Rob Warren
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Organic grape production is gaining momentum, but making the transition from conventional farming requires careful planning, patience, and a willingness to adapt. In this episode of Vineyard Underground, Fritz welcomes Rob Warren, owner and operator of Desert Willow Vineyard and Warren Farms in Seminole, Texas, to share his experience converting his vineyard to certified organic production. Rob explains how his agricultural background in organic row crops gave him experience with organic systems long before he applied those principles to grape growing. As consumer demand began to shift toward...
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094: Vineyard Nutrition Essentials - Magnesium Fundamentals with Dr. Jaclyn Fiola
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In this final installment of the Vineyard Nutrition Essentials series, Fritz is joined by Dr. Jaclyn Fiola, Assistant Professor of Soil and Environmental Science at Delaware Valley University, to unpack the critical role magnesium plays in vineyard health and productivity. Building on prior discussions around potassium, the conversation explores how magnesium functions as a key macronutrient, particularly as the central component of chlorophyll and a driver of photosynthesis and energy transfer in grapevines. Dr. Fiola explains that magnesium primarily originates from soil minerals, especially...
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093: Vineyard Nutrition Essentials - Phosphorus Fundamentals with Dr. Terry Bates
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Phosphorus may not grab attention like nitrogen or potassium, but it plays a foundational role in vine growth, fruit set, and overall vineyard performance. In this episode of Vineyard Underground, Fritz welcomes Dr. Terry Bates, Senior Research Associate at Cornell University and Director of the Cornell Lake Erie Research and Extension Lab for Cornell AgriTech, for a deep dive into phosphorus fundamentals. Drawing on decades of research in plant nutrition and root biology, Dr. Bates explains what phosphorus is, where it comes from, and why it is essential for grapevines at the cellular level....
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092: Vineyard Nutrition Essentials - Nitrogen Fundamentals with Dr. Markus Keller
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In this first installment of a three-part vineyard nutrition series, Dr. Markus Keller joins us to break down one of the most influential nutrients in vineyard management: nitrogen. We explore from the ground up. Dr. Keller explains what nitrogen is, where it comes from in vineyard soils, and why it plays such a critical role in vine growth, fruit set, and overall vine performance. While nitrogen makes up 78% of the atmosphere, vines rely on soil processes to convert it into plant-available forms like nitrate. Dr. Keller details how nitrogen influences vigor, canopy density, fruit set,...
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091: Rare Grape Varieties & Their Wines with Jolie-Laide Wines
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090: Old Vines and Argentina's Ungrafted Massale Selection with Dr. Laura Catena
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Some of the world’s most valuable vineyard lessons are rooted in vines that predate modern viticulture. In this conversation, we are joined by Dr. Laura Catena to explore Argentina’s remarkable legacy of old, ungrafted vines and what they reveal about vine genetics, site expression, and long-term resilience. Drawing on her experience, Dr. Catena explains why phylloxera never devastated many Argentine vineyards and how this unique history allowed ancient vine material to survive. The discussion dives into massale selection from old vines, highlighting why genetic diversity matters —...
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089: Red Flags for Planting a Vineyard with Dr. Mark Greenspan
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Planting a vineyard is a major investment, and the decisions made before the first vine goes into the ground can determine long-term success or costly failure. In this episode, Fritz sits down with renowned viticulture expert Dr. Mark Greenspan to unpack the most common red flags vineyard owners and operators should watch for when planning a new planting. Drawing on more than three decades of scientific research and hands-on field experience, Dr. Greenspan explains why many vineyard problems originate long before planting day. Fritz and Dr. Greenspan also discuss the dangers of relying on...
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088: Pruning Q&A with Fritz Westover
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Pruning is one of the most influential decisions vineyard owners and operators make each season, and in this solo Q&A episode, Fritz tackles the most common — and most misunderstood — questions he hears in the field. Drawing on hands-on experience, Fritz walks listeners through the practical realities of dormant pruning, why it matters far beyond vine appearance, and how pruning choices directly impact vine balance, yield, and long-term vineyard health. Throughout the episode, Fritz addresses real-world concerns from growers, including how aggressive pruning should be, what mistakes...
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087: Mothballing a Vineyard - What Growers Need to Know with Dr. Christopher Chen
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A topic that many growers consider but few understand is mothballing a vineyard. In this episode, Fritz covers it all with Dr. Christopher Chen, Integrated Vineyard Systems Advisor with the University of California Cooperative Extension. With economic pressures, market shifts, and operational challenges affecting vineyard owners across the industry, temporarily idling a vineyard can feel like a practical option — but it comes with important agronomic, legal, and financial considerations. Dr. Chen brings a research-based, boots-on-the-ground perspective to the conversation, helping listeners...
info_outlineIn this final installment of the Vineyard Nutrition Essentials series, Fritz is joined by Dr. Jaclyn Fiola, Assistant Professor of Soil and Environmental Science at Delaware Valley University, to unpack the critical role magnesium plays in vineyard health and productivity. Building on prior discussions around potassium, the conversation explores how magnesium functions as a key macronutrient, particularly as the central component of chlorophyll and a driver of photosynthesis and energy transfer in grapevines.
Dr. Fiola explains that magnesium primarily originates from soil minerals, especially in darker, magnesium-rich parent materials, and that soil characteristics such as pH, texture, moisture, and cation exchange capacity influence its availability. There is a delicate balance between magnesium, potassium, and calcium, and nutrient competition can lead to deficiencies even when soil levels appear adequate.
Listeners will learn how to identify magnesium deficiency symptoms, including interveinal chlorosis in older leaves, and why these symptoms typically emerge later in the growing season. The episode also underscores the importance of accurate diagnosis through soil and tissue testing to avoid mismanagement.
Listen now to learn the important role of magnesium in your vineyard.
In this episode, you will hear:
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Magnesium as a core component of chlorophyll and photosynthesis
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Soil pH, texture, and moisture driving nutrient availability
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Competition between magnesium, potassium, and calcium
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Late-season deficiency symptoms and how to recognize them
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Importance of tissue testing for accurate diagnosis
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Pre-plant and in-season magnesium correction strategies
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Resources:
Visit www.virtualviticultureacademy.com/sampling to access Fritz’s how-to guides and videos for proper sampling and target nutrient values.
Listen to Dr. Jaclyn Fiola’s previous podcast episode (episode 73) to learn about the role of potassium in vineyards.
Have a vineyard question? Go to VineyardUndergroundPodcast.com and click the Ask Fritz button.
Come grow with Fritz through https://www.virtualviticultureacademy.com! Save $75 off your first year of membership with the code Underground at checkout.
Today’s Guest:
Dr. Jaclyn Fiola is a soil scientist who specializes in vineyard soils and soil science pedagogy. She works as an Assistant Professor of Soil and Environmental Science at Delaware Valley University.
Connect with Jaclyn, follow her, and view her research.
Episode Sponsor:
Today’s episode was brought to you by Vigneron Toy Store and Shellt Grow Tubes.
Thank you to Vigneron Toy Store for sponsoring today’s episode. Vigneron Toy Store specializes in Harvesters, Sprayers, Frost Mitigation Equipment, Canopy Management Trimmers, and more. As grape growers themselves, they can expertly help you determine the best equipment for your specific vineyard needs. And, as a special offer for our podcast listeners, you can save 5% off in-stock machines by entering the promo code Underground on the contact form at vignerontoystore.com.
Thank you to Shellt Grow Tubes for sponsoring today’s episode. Shellt makes the ultimate grow tubes for grape vines and orchard trees. Their grow tubes are reusable, recyclable, and designed to grow with your vineyard by clicking together for taller or wider coverage. I exclusively recommend Shellt Grow Tubes to the growers I work with. Visit https://www.shellt.us/ and order with the code UNDERGROUND to save 15% off all online orders, plus free shipping within the continental United States.
Episode Credits
If you like this podcast and are thinking of creating your own, consider talking to my producer, Emerald City Productions. They helped me grow and produce the podcast you are listening to right now. Find out more at https://emeraldcitypro.com. Let them know we sent you.