Turfgrass Epistemology

In this episode of Turfgrass Epistemology, I break down the classic Crop Science paper “Assessing Irrigation Management for Its Effects on Disease and Weed Levels in Perennial Ryegrass” by Jiang, Fry, and Tisserat (1998).

This study directly examines how irrigation scheduling (daily vs. ET-based irrigation) influences brown patch, dollar spot, weed pressure, pesticide use, and turf quality on perennial ryegrass fairways. I explain how ET-based irrigation reduced water use by nearly 200%, how daily irrigation suppressed brown patch but increased dollar spot, and why irrigation strategy did not significantly influence crabgrass or dandelion populations.

If you manage golf course fairways or make decisions about irrigation management, turfgrass disease control, and water conservation, this video connects classic research to modern turf management and integrated pest management strategies.

Subscribe for more turfgrass science, irrigation research, and evidence-based golf course management discussions focused on how we know what we know.

#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:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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

In this episode of Turfgrass Epistemology – Comments & Emails Part 2, I continue responding to viewer questions and email discussions about turfgrass management, soil testing, fertilizer programs, dollar spot control, and common lawn care myths.

This follow-up video addresses new comments from golf course superintendents, lawn care operators, and homeowners who are trying to separate evidence-based turfgrass science from marketing claims and social media advice. I clarify misunderstandings about nutrient ratios, iron applications, nitrogen programs, and disease suppression while explaining how to interpret research correctly.

If you’re interested in soil fertility, turfgrass disease management, golf course agronomy, or lawn care best practices, this episode provides practical, research-driven answers to real questions from the field.

Subscribe for more turfgrass science, critical thinking in lawn care, and evidence-based golf course management discussions that go deeper than quick tips and product hype.

Become a member of Turfgrass Epistemology and support turfgrass research:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

In this episode of Turfgrass Epistemology, I respond to viewer comments and emails covering some of the most common questions and misconceptions I see about turfgrass science, soil fertility, nutrient management, and disease control.

I address recurring themes from golf course superintendents, lawn care professionals, and homeowners, explain where confusion often arises, and clarify how peer-reviewed research should be interpreted instead of relying on anecdotes, marketing claims, or social media shortcuts.

This video focuses on critical thinking in turfgrass management, explaining how to evaluate advice, understand soil and tissue test results, and avoid common reasoning errors when making fertility and pest management decisions.

If you’ve commented on a video, sent an email, or wondered whether advice you see online is actually supported by science, this episode is for you.

Subscribe for evidence-based turfgrass content, long-form explanations, and practical discussions that go beyond soundbites and fertilizer folklore.

🔔 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:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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

In this episode of Turfgrass Epistemology, I discuss the peer-reviewed article “Dollar Spot and Gray Leaf Spot Severity as Influenced by Irrigation, Chlorothalonil, Paclobutrazol, and a Wetting Agent” by McDonald, Dernoeden, and Bigelow (2006), published in Crop Science.

This landmark study examines how irrigation regime, soil moisture, and common management inputs influence dollar spot and gray leaf spot development on creeping bentgrass and perennial ryegrass fairways. I explain why dollar spot was consistently more severe under dry, infrequently irrigated conditions, how soil moisture strongly influenced disease severity late in the season, and what this means for cultural disease management strategies on golf courses.

The discussion also covers how chlorothalonil performance varied with irrigation regime, why paclobutrazol provided partial dollar spot suppression, and why wetting agents alone were unreliable for disease control. Most importantly, I explain how this paper reshapes the way we should think about water management as a disease driver, rather than viewing irrigation only through the lens of turf stress or playability.

If you manage creeping bentgrass fairways, battle chronic dollar spot, or want an evidence-based explanation of how irrigation practices interact with fungicides and plant growth regulators, this video walks through what the data actually show—and how to apply it responsibly in modern turfgrass management.

Subscribe for more turfgrass science discussions, classic paper reviews, and evidence-based explanations focused on how we know what we know in turf management.

Don’t forget to like, share, and subscribe to stay updated on more science-driven insights!

Become a member of Turfgrass Epistemology and support turfgrass research:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

In this episode of Turfgrass Epistemology, I discuss and interpret the peer-reviewed article “Optimizing Liquid-Applied Iron Sulfate Rate and Application Interval for Dollar Spot Suppression on Golf Course Fairways” by Soldat et al. (2024), published in Crop Science.

This paper builds on earlier iron sulfate research and focuses on practical optimization—how rate, application interval, and spray volume influence dollar spot suppression on creeping bentgrass and annual bluegrass fairways. I explain the dose-dependent response observed across multiple locations, why 7-day reapplication intervals consistently outperformed 14-day intervals, and why spray water volume and tank-mixing with fertilizer had minimal impact on disease control.

The discussion emphasizes what this research means for golf course superintendents looking to reduce fungicide reliance while avoiding phytotoxicity and unnecessary applications. Rather than treating iron sulfate as a cure-all, I place these results in the context of integrated dollar spot management, fungicide resistance concerns, and realistic expectations for non-fungicidal suppression strategies.

If you manage fairways, evaluate iron programs, or want an evidence-based explanation of how liquid iron sulfate actually performs against dollar spot, this video breaks down what the data show—and how to apply it responsibly.

Subscribe for more turfgrass science, peer-reviewed paper discussions, and evidence-based explanations focused on how we know what we know in turf 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:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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

In this episode of Turfgrass Epistemology, I discuss and interpret the peer-reviewed article “Influence of Ferrous Sulfate and Its Elemental Components on Dollar Spot Suppression” by McCall et al. (2016), published in Crop Science. This paper is foundational to many modern discussions about using iron—specifically ferrous sulfate—as a tool for managing dollar spot on creeping bentgrass putting greens.

The study evaluates whether ferrous sulfate itself, or its individual components iron and sulfur, are responsible for observed dollar spot suppression. Using both field trials on USGA-spec creeping bentgrass greens and controlled in-vitro assays, the authors show that ferrous sulfate consistently reduced dollar spot severity, while elemental sulfur had no effect and chelated iron produced inconsistent results across years.

In this video, I walk through the experimental design, disease response data, and turf quality results, with particular emphasis on what actually drives suppression. The findings demonstrate that ferrous sulfate behaves differently than iron chelates and sulfur, and that the disease response cannot be explained simply by nutrient sufficiency, sulfur acidification, or color response. Instead, the evidence points toward a direct fungistatic or fungitoxic effect of ferrous sulfate on the dollar spot pathogen at sufficiently high concentrations.

I also explain why the in-vitro results matter for interpreting field performance. The paper shows that low iron concentrations can actually stimulate fungal growth, while very high concentrations suppress mycelial development across a range of pH levels. This nuance is critical, because it explains why iron programs can sometimes appear inconsistent or even counterproductive when rates, formulations, or application frequency are poorly understood.

Throughout the discussion, I place this study in the broader context of dollar spot management, fungicide resistance, and integrated pest management. Ferrous sulfate is not presented as a replacement for fungicides, nor as a fertility shortcut, but as a biologically active compound that can partially suppress disease under specific conditions—while also carrying real risks if misused.

This episode is especially relevant for golf course superintendents, turfgrass researchers, and advanced turf managers who are considering iron-based programs for dollar spot suppression and want to understand what the science actually supports, what it does not, and why oversimplified interpretations can lead to poor decisions.

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

Don’t forget to like, share, and subscribe to stay updated on more science-driven insights!

Become a member of Turfgrass Epistemology and support turfgrass research:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

In this episode of Turfgrass Epistemology, I discuss and critically interpret the peer-reviewed article “Impact of Ferrous Sulfate Concentration on Clarireedia Isolate Growth and Dollar Spot Development” by Shelton et al. (2021), published in Crop Science. This paper is frequently cited in conversations about using iron—specifically ferrous sulfate—as a non-fungicidal tool for dollar spot suppression on golf course turf.

The study combines multi-site field trials with controlled in-vitro experiments to examine how ferrous sulfate rate influences dollar spot severity on creeping bentgrass fairways and putting greens, as well as how different Clarireedia isolates respond to increasing iron concentrations in culture. I walk through both components of the research, explaining what the data show about rate response, diminishing returns, and why previously recommended rates may be higher than necessary for meaningful disease suppression.

A major focus of the discussion is the nonlinear nature of the response. The results demonstrate that approximately 25–26 kg ha⁻¹ of ferrous sulfate was sufficient to achieve about 50% dollar spot suppression, with much smaller gains at higher rates and increased risk of turf injury under stress conditions. I explain why this matters for real-world management and how these findings challenge the tendency to assume that “more is better” when it comes to iron applications.

I also discuss the in-vitro portion of the study, which shows that ferrous sulfate has a direct fungitoxic effect on Clarireedia, but that the concentration required to suppress mycelial growth varies by isolate and by host type. This section is important for understanding why field performance can be inconsistent and why pathogen biology, management history, and turf system context all influence outcomes.

Throughout the video, I place this paper within the broader dollar spot literature and explain what it does—and does not—justify in practice. Ferrous sulfate is not a replacement for fungicides, nor is it a magic bullet, but it can function as a partial suppression tool within an integrated disease management program when its limitations are understood.

This episode is especially relevant for golf course superintendents, turfgrass researchers, and advanced turf managers who are evaluating iron-based programs for dollar spot control and want to separate evidence-based conclusions from oversimplified recommendations.

Subscribe for more long-form turfgrass science discussions, peer-reviewed paper breakdowns, and clear 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:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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

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.

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

Don’t forget to like, share, and subscribe to stay updated on more science-driven insights!

Become a member of Turfgrass Epistemology and support turfgrass research:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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 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:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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:

Voicemail:

Apple Podcast

Spotify Podcast

iHeart Radio Podcast

Podbean

Online consulting

Twitter

Email

Turfgrass Programs and Extension Service Information:

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