In this episode of Turfgrass Epistemology, I break down and discuss the peer-reviewed article “Dollar Spot Suppression on Creeping Bentgrass in Response to Repeated Foliar Nitrogen Applications” by Townsend et al. (2021), published in Plant Disease. This paper directly addresses one of the most common and controversial questions in turfgrass management: can nitrogen fertilization meaningfully suppress dollar spot without relying solely on fungicides?

The study evaluated repeated foliar nitrogen applications on creeping bentgrass putting greens across multiple years and locations, using a spoon-feeding approach that mirrors how many golf course superintendents manage fertility today. I walk through the experimental design, nitrogen rates, nitrogen sources, and how dollar spot severity responded over time. A major focus of the discussion is why only the highest nitrogen rate consistently reduced dollar spot severity, while lower, more typical spoon-feeding rates provided little to no disease suppression.

In this video, I explain what the results actually show—and just as importantly, what they do not show. While nitrogen clearly influenced dollar spot development, the rate required to achieve meaningful suppression raises practical, agronomic, and environmental concerns. I also discuss how nitrogen source had minimal and inconsistent effects, why foliar nitrogen concentration may be more informative than application rate alone, and how these findings fit into integrated pest management strategies rather than stand-alone fertility “solutions.”

This episode is especially relevant for golf course superintendents, turfgrass researchers, and advanced turf managers who hear that “more nitrogen reduces dollar spot” without adequate context. The data demonstrate that the relationship between nitrogen and disease is real but non-linear, highly rate-dependent, and constrained by tradeoffs involving growth, thatch accumulation, environmental risk, and secondary disease pressure.

As always, the goal of this discussion is evidence-based interpretation, not fertilizer folklore or oversimplified recommendations. If you are making fertility decisions to manage dollar spot on creeping bentgrass putting greens, this video will help you better understand how nitrogen fits into the bigger disease management picture.

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In this episode of Turfgrass Epistemology, I critically examine and respond to two popular soil fertility videos that promote base saturation theory and a simplified soil pH–nutrient availability diagram, and I explain why both should be treated with extreme skepticism—or ignored entirely—when making turfgrass management decisions.

Much of the base saturation messaging presented in these videos relies on the idea that soils must be managed toward specific “ideal” cation percentage ratios to achieve productivity. In this video, I explain why base saturation is not a causal driver of turfgrass performance, why the concept persists despite decades of contradictory evidence, and how it functions more as a marketing narrative than a scientifically defensible soil fertility framework in turf systems. I also discuss how focusing on cation ratios distracts from the variables that actually matter, such as nutrient sufficiency, cation exchange capacity, soil texture, and plant demand.

I also critique the soil pH diagram used in these videos, which is frequently circulated across agriculture and lawn care media. I explain why this diagram is oversimplified, misleading, and biologically inaccurate, and why it should not be used to diagnose nutrient deficiencies or guide fertilizer decisions. Rather than nutrients abruptly “locking up” outside narrow pH bands, I explain how nutrient availability is continuous, soil-specific, and governed by chemistry, mineralogy, and management history—not cartoon gradients.

Throughout the video, I walk through why these ideas are especially problematic in turfgrass systems, where soils are often sand-based, heavily modified, intensively managed, and fundamentally different from agronomic field soils. I explain how misuse of base saturation theory and pH diagrams leads to unnecessary amendments, wasted money, and false confidence—while offering no predictive power for turf response.

This episode is intended for golf course superintendents, turfgrass scientists, lawn care professionals, and homeowners who want evidence-based soil fertility interpretation rather than tradition, authority, or marketing-driven dogma. The goal is not to argue opinions, but to explain why certain ideas fail scientifically, why they continue to spread, and how to replace them with better reasoning.

If you’ve ever been told your soil is “out of balance,” that your calcium-to-magnesium ratio is wrong, or that nutrients are “locked up” based on a single pH chart, this video will help you understand why those claims persist—and why they don’t hold up under scrutiny.

Subscribe for long-form turfgrass science discussions, critical analysis of common soil fertility claims, and clear explanations focused on how we know what we know in turfgrass management. Subscribe for more long-form turfgrass science discussions, peer-reviewed paper breakdowns, and practical explanations focused on how we know what we know in turfgrass management.

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Turfgrass Programs and Extension Service Information: https://www.usna.usda.gov/assets/images/as_pdf_image/LandGrantColleges.pdf

Diagnostic Criteria for Turfgrass Bullshit Disorder:https://drive.google.com/file/d/1Y_GeVPQ237pzm0ImTP4eVij6I9D0PHPn/view

In this episode of Turfgrass Epistemology, I walk through a recent peer-reviewed study that examines how potassium fertilization influences dollar spot severity on annual bluegrass (Poa annua) and creeping bentgrass (Agrostis stolonifera) putting greens.

The article, Potassium fertilization effects on dollar spot of annual bluegrass and creeping bentgrass, presents multi-year field data showing that increasing potassium rates consistently increased dollar spot severity under the conditions tested. This directly challenges the common assumption that potassium fertilization automatically improves stress tolerance or reduces disease pressure in turfgrass systems.

In the video, I explain the experimental design, including potassium and nitrogen rate treatments, mat layer and leaf tissue measurements, and how disease severity was quantified over time. I also discuss why potassium behaved differently than many turf managers expect, and how disease response depended on antecedent potassium levels in both the mat layer and plant tissue.

This discussion emphasizes the importance of context in fertility management. Potassium is an essential nutrient, but its relationship with turfgrass disease is not linear or universally beneficial. The results highlight why relying on generalized nutrient “rules” without soil and tissue data can lead to unintended consequences in disease management programs.

If you manage golf course putting greens, work in turfgrass research, or make fertility decisions based on soil tests and tissue analysis, this episode provides critical insight into how potassium, nitrogen, and dollar spot interact in real turf systems. The goal is not to discourage potassium use, but to encourage evidence-based decision-making grounded in measured nutrient status rather than assumptions.

Subscribe for more long-form turfgrass science discussions, peer-reviewed paper breakdowns, and practical explanations focused on how we know what we know in turfgrass management.

🔔 Subscribe for more evidence-based turfgrass content, scientific paper discussions, and long-form explanations that go beyond social media soundbites.

#Turfgrass #SoilScience #LawnCare #GolfCourseManagement #TurfgrassScience #SoilFertility #CriticalThinking #TurfTok #TurfgrassEpistemology #EvidenceBased #LawnCareTips

📌 https://www.gofundme.com/f/TurfgrassEpistemology

Thank you for being part of this community and for supporting evidence-based turfgrass science.

Join Turfgrass Epistemology to get access to perks: https://www.youtube.com/channel/UC-UZnHkJhAmARDZ4YoHnc_A/join

Voicemail: 859-444-4234

Apple Podcast https://podcasts.apple.com/us/podcast/turfgrass-epistemology/id1717271379

Spotify Podcast https://open.spotify.com/show/1cTpdrChToeEFAOX9wkXFI

iHeart Radio Podcast https://www.iheart.com/podcast/1323-turfgrass-epistemology-129043524/

Podbean https://turfgrassepistemology.podbean.com/

Online consulting Calendly.com/TravisShaddox

Twitter Twitter.com/TravisShaddox

Email TravisShaddox@gmail.com

Turfgrass Programs and Extension Service Information: https://www.usna.usda.gov/assets/images/as_pdf_image/LandGrantColleges.pdf

Diagnostic Criteria for Turfgrass Bullshit Disorder:https://drive.google.com/file/d/1Y_GeVPQ237pzm0ImTP4eVij6I9D0PHPn/view