In this episode of Vineyard Underground, Fritz welcomes Dr. R. Paul Schreiner, recently retired research plant physiologist from the USDA, for a deep dive into the fascinating world of mycorrhizal fungi and their impact on vineyard health. With over two decades of research experience in grapevine physiology and root biology, Dr. Schreiner shares the critical roles these fungi play in nutrient uptake, root efficiency, drought tolerance, and overall soil structure.

Fritz and Dr. Schreiner explore what arbuscular mycorrhizal fungi (AMF) are, how they form symbiotic relationships with grapevine roots, and why grapes are considered “super hosts.” They discuss how AMF enhances phosphorus acquisition, especially in low-P soils, and how they support the uptake of other nutrients like potassium, zinc, and copper. They also talk about factors that suppress or encourage fungal colonization, such as excessive fertilization, cultivation, cover cropping, and herbicide use.

Dr. Schreiner also previews ongoing research from the High-Resolution Vineyard Nutrition Project, which is helping redefine best practices for tissue sampling and nutrient timing. Whether you’re planting a new vineyard or managing an established one, this episode offers an essential look at how understanding underground biology can elevate your vineyard management decisions.

In this episode, you will hear:

• How grapevines form symbiotic relationships with mycorrhizal fungi

• Why phosphorus is the most important nutrient supported by AMF

• The effects of nitrogen and phosphorus fertilization on fungal colonization

• Whether commercial AMF inoculants are worth the investment

• Practices that promote healthy fungal populations in vineyard soil

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Resources:

If you are starting a vineyard or thinking about starting a vineyard, apply to be on the podcast for Fritz’s help planning your vineyard – VineyardUndergroundPodcast.com/Contact/ 

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Today’s Guest:

Dr. R. Paul Schreiner is a research plant physiologist specializing in research on grapevine physiology with a focus on plant nutrition and the functioning of roots and arbuscular mycorrhizal fungi. He is currently working with the High Resolution Vineyard Nutrient Management Project as a co-director, leading the plant nutrition and product quality group.

Connect with Paul through the High Resolution Vineyard Nutrient Management Project: https://highresvineyardnutrition.com/. 

Episode Sponsor:

Today’s episode was brought to you by the Inside Winemaking podcast.

Thank you to the Inside Winemaking podcast for sponsoring today’s episode. To learn more about the art & science of winemaking with Jim Duane, visit www.insidewinemaking.com/ and listen to the Inside Winemaking podcast on your favorite podcast app with new episodes releasing every other Tuesday.

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.