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, berry size, phenolic development, and even wine quality. The episode also dives into how soil type, organic matter, temperature, moisture, and cover crops affect nitrogen availability. For growers across diverse regions, this conversation highlights why vineyard nutrition strategies must be site-specific.

Whether you're managing high-vigor blocks or navigating lean soils, episode one of our three-part series equips vineyard owners and operators with foundational knowledge to make smarter nitrogen decisions.

In this episode, you will hear:

• Nitrogen primarily comes from soil organic matter, not rock minerals

• Microbial activity drives nitrogen availability in vineyards

• Both deficiency and excess nitrogen can reduce vine balance and fruitfulness

• Soil moisture and temperature strongly influence nitrogen mineralization

• Leaf blade tissue sampling offers improved precision for nitrogen analysis

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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.

Have a vineyard question? Go to VineyardUndergroundPodcast.com and click the Ask Fritz button.

Today's Guest:

Dr. Markus Keller is a Distinguished Professor in Viticulture at Washington State University, a renowned viticulture researcher, and the author of The Science of Grapevines – a top reference book in the industry. He is also the Project Director for the seven-institution High Resolution Vineyard Nutrient Management Project.

Connect with Markus:

· Dr. Markus Keller - WSU Research & Publications - https://wine.wsu.edu/faculty/markus-keller/

· High Resolution Vineyard Nutrient Management Project - https://highresvineyardnutrition.com

· Order The Science of Grapevines 4th Edition - https://a.co/d/00UpfN1f

· Listen to the HiRes Vineyard Nutrition Podcast - https://highresvineyardnutrition.com/podcast/

Episode Sponsor:

Today's episode was brought to you by Bahco Tools and Shellt Grow Tubes.

Thank you to Bahco Tools for sponsoring today's episode. As innovators for more than 165 years, Bahco has introduced the most advanced tools in the world, and Bahco products are manufactured in factories across Europe. I exclusively prune with the Bahco ERGO™ Bypass Secateurs with Elastomer Coated Fixed Handle (size medium). Visit www.bahco.com/int_en to find a dealer near you to get the best pruning tools on the market, along with loppers, hedging tools, cutting blades, files, and more.

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.