Turfgrass Epistemology

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...

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 con...

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 exper...

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 de...

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...

In this episode of Turfgrass Epistemology, I review and respond to comments, emails, and TikTok messages I’ve received throughout 2025 related to turfgrass science, soil fertility, nutrient management, and common turf industry claims.

From thoughtful questions to recurring misconceptions, this video highlights what turf managers, lawn care professionals, golfers, and homeowners are asking—and where confusion often arises when science meets social media. I address trends I’ve seen across platforms, clarify misunderstandings, and explain why certain claims persist despite decades of research.

Topics discussed include:
Common turfgrass myths repeated in social media comments
Mi...

In this episode of Turfgrass Epistemology, I sit down with Dr. John Inguagiato to discuss his peer-reviewed research on phosphite use for suppressing cyanobacteria (blue-green algae) on putting greens. Together, we break down the science behind phosphite chemistry, application rates, turf safety, and what the data actually say—beyond marketing claims.

Dr. Inguagiato’s 2017 Crop Science paper, “Effect of Phosphite Rate and Source on Cyanobacteria Colonization of Putting Green Turf,” is one of the most frequently cited studies on this topic. In this conversation, we explore how phosphite differs from phosphate, why cyanobacteria respond differently to these compound...

In this video I take a close, critical look at "Data-Drive Lawn Care" (https://www.youtube.com/watch?v=pjRXNcIi3Hk) and share my honest thoughts on what works — and what doesn’t. I break down the arguments, highlight where I think the logic falls short, and offer my own perspective on the topic.

🔎 What I cover:

Key claims made by the original creator

Moments where I agree — and moments where I respectfully disagree
Glaring omissions and what I believe should have been addressed
My own take: what’s convincing, what needs more...

In this video, I review and break down one of the most referenced articles in cool-season turfgrass pathology: “Severity of Gray Leaf Spot in Perennial Ryegrass as Influenced by Mowing Height and Nitrogen Level” by Williams, Burrus, and Vincelli (2001).

This study investigated how two major management practices—mowing height and nitrogen rate—affect the intensity of gray leaf spot (Pyricularia grisea) epidemics in perennial ryegrass managed under golf-course conditions.

I walk through the methods, results, and implications of the research, and I discuss how the findings align—or don’t align—with common industry assumptions twenty years l...

In this video, I provide an in-depth, evidence-based critique of the nitrogen-efficiency product RDX-N and the claims made in the promotional video circulating online. If you’ve ever wondered whether biostimulants, nitrogen enhancers, or “metabolic activators” actually work in real-world turfgrass or crop management, this breakdown is for you. I review the product’s marketing claims, examine the data presented in the official RDX-N brochure, and explain what the science really says about nitrogen uptake, nitrogen metabolism, and plant physiology.

But this video is more than a review of one product—it's a lesson in how to evaluate a...

In this episode of Turfgrass Epistemology, I sit down with Dr. Lee Miller of Purdue University, one of the leading experts in turfgrass pathology, to break down everything you need to know about turfgrass disease resistance, fungicide rotations, and accurate turf disease identification. Whether you manage golf course greens, sports fields, or home lawns, this conversation gives you the practical, science-based guidance needed to protect your turf from common and emerging diseases.

We explore what disease resistance in turfgrass truly means, why resistance develops, and how environmental conditions and management practices influence disease pressure. Dr. Miller explains...

In this video, I analyze the 2025 Zhang et al. study on how fungicide scheduling and bentgrass cultivar resistance interact to influence dollar spot control. This research provides some of the strongest evidence to date that curative, damage-threshold-based fungicide programs can dramatically reduce inputs—up to 78 percent in certain cases—when paired with disease-resistant bentgrass cultivars. I explain how the researchers designed the field trials, what the low damage threshold means in practice, how 24-hour and next-application-day schedules performed differently, and why resistant cultivars such as Declaration produced such large savings without sacrificing control. I also discuss how inoculation affected dise...

In this video, I break down one of the most influential papers ever written on turfgrass pathology: Walsh, Ikeda, and Boland’s 1999 review on the biology and management of dollar spot. This paper remains a foundational resource for understanding how the pathogen operates, why the disease is so persistent on cool-season turf, and which management strategies are supported by evidence rather than tradition. I walk through the key sections of the paper, including the pathogen’s life cycle, the environmental conditions that drive epidemics, the role of cultural practices, and the strengths and weaknesses of common fungicide approaches. I also...

In this episode of Turfgrass Epistemology, I review a popular lawn-care website article and an accompanying YouTube video that teach homeowners how to interpret a soil test that is, in reality, scientifically invalid for making nutrient decisions. These resources look polished and authoritative, but the advice they provide is fundamentally flawed — and following it can lead to unnecessary product applications, wasted money, and incorrect assumptions about soil health.

I’ll walk through both the website and the video step-by-step and explain:

Why the soil test they promote is not valid for nutrient recommendations
How cert...

Not all scientific journals are created equal. Some exist to advance knowledge — others exist to collect publishing fees. In this episode of Turfgrass Epistemology, we explore how to tell the difference.

I’ll walk through the refereed process and explain how it differs from standard peer review, why that distinction matters, and how the structure of editorial oversight determines the credibility of the science that reaches the public. We’ll also take a close look at predatory journals — publications that mimic legitimate science while bypassing or corrupting the review process in exchange for author fees.

But the...

In this episode of Turfgrass Epistemology, we take a close look at one of the most frequently cited studies in turfgrass pathology — Golembiewski and Danneberger’s 1998 Agronomy Journal paper exploring how trinexapac-ethyl (TE) and nitrogen fertility influence the severity of dollar spot (Sclerotinia homoeocarpa) in creeping bentgrass.

The researchers found that TE, a popular plant growth regulator, didn’t increase disease as many feared — in fact, it reduced dollar spot when combined with adequate nitrogen. This discovery challenged the prevailing assumptions of the time and suggested that growth regulation and fertility could work together to reduce fungicide reliance...

In this episode, I sit down to talk about a topic that’s been at the heart of American higher education for more than a century — university extension. We’ll explore how extension began, why it was once the lifeblood of land-grant universities, and how the system that connected science to society is now quietly disappearing.

Extension was created so universities could serve the public — not just by publishing papers, but by helping real people solve real problems. For decades, that mission worked. Faculty were rewarded for outreach, and industries like turfgrass, horticulture, and agriculture thrived because science...

Can something as simple as mowing time really stop a turfgrass disease? In this episode of Turfgrass Epistemology, we look back at a landmark 1996 study by Williams, Powell, Vincelli, and Dougherty from the University of Kentucky — a paper that changed how superintendents think about dew, nitrogen, and dollar spot control.

Dollar spot (Sclerotinia homoeocarpa) thrives on leaf moisture. Williams et al. tested what happens when you simply remove that moisture early in the morning. Their data were stunning — mowing or “poling” to knock dew off reduced dollar spot by as much as 81% on fairways and 53% on greens. That’s b...

In this video, I explore the history and current state of university turfgrass programs—from their rise during the post-war boom in golf, parks, and sports fields to their decline in recent decades. I explain how turfgrass faculty positions are created and filled, what factors lead to the loss of those positions, and why many programs are now disappearing altogether. I connect the dots between enrollment trends, industry funding, and the shifting priorities of universities that have left turfgrass science struggling to survive. Most importantly, I discuss what the turfgrass community—educators, managers, and industry leaders—can do to revers...

In this video, I examine the 2021 study by Beckley and Roberts published in the International Turfgrass Society Research Journal titled “Utilizing Organic Amendments for General Suppression of Dollar Spot on Creeping Bentgrass.” The discussion centers on one key question: Does biochar actually reduce dollar spot? I break down the experimental design—how researchers compared biochar, compost, vermicompost, and traditional fertilizers under equal nitrogen rates—and explains what the data really show. Were the reductions in dollar spot due to microbial changes, or simply better nitrogen nutrition? You’ll see how biochar performed across two years, why the results were inconsiste...

In this video, I explore the recent review article “Review of the Biology and Management of Large Patch of Warm-Season Turfgrasses” (Kreinberg et al., Crop Science, 2025). I walk you through what the authors tell us about Rhizoctonia solani AG 2-2 LP — the fungal pathogen behind large patch disease in warm-season turfgrasses — how environmental conditions favor its development, and how it can persist in thatch through seasonal dormancy. Along the way, I highlight the state of current cultural, chemical, and biological control strategies, and I point out the gaps and future directions the turfgrass pathology community still needs to address. If you’r...

In this video, I take you through the state of the science on dollar spot disease in turfgrass, framed by the recent review “New Approaches to an Old Problem: Dollar Spot of Turfgrass.” We explore how this ubiquitous fungal disease (caused by Clarireedia spp.) continues to challenge turf managers, why traditional fungicide programs are increasingly under pressure, and what new genomic tools and breeding strategies may offer as solutions. I’ll break down the authors’ discussion of pathogen genomics, host–pathogen interactions, and quantitative trait loci (QTL) for resistance, while also reflecting on where future research might be headed. Whether yo...

In this video, I dive into the article “Survey of Water Use and Management Practices on US Golf Courses from 2005 to 2024” published in HortTechnology (Shaddox et al., 2025). The study tracks nearly twenty years of changes in how golf courses across the United States use and manage water. I discuss how irrigation volumes and irrigated areas have shifted over time, highlight important regional differences, and explain why some water sources—like recycled water—are declining while others remain steady. I also cover the adoption of new management strategies such as moisture sensors, irrigation audits, and objective scheduling, along with the continui...

In this video, I discuss the YouTube episode “Struggling Turf? Calcium Could Be the Missing …” and examine it through the lens of the strawman fallacy. We’ll look at how someone can present information that is technically true, yet still mislead by reframing the issue or knocking down an argument no one actually made.

This breakdown shows how a conman can be both truthful and deceptive at the same time—a powerful reminder of why critical thinking matters in turfgrass science, lawn care, and beyond.

If you’ve ever learned something useful from this channel, please consi...

In this video, I review the scientific article “Irrigation Frequency Affects Zoysiagrass Rooting and Plant Water Status.” We’ll look at how different irrigation schedules influenced root development and water relations in zoysiagrass, and what these findings mean for turfgrass management. If you’ve ever wondered how often you should water to encourage deeper roots and better turf performance, this study offers valuable evidence-based insights.

Article: https://journals.ashs.org/view/journals/hortsci/31/2/article-p234.xml

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In this episode, I break down the claims made in “Check out These Roots, John Perry! | [LIVE PODCAST] Ep.8 of the Average Joe Lawn Care Show,” where the hosts argue that liquid aeration is an effective solution for lawn health. I dive into the science and present evidence that challenges their assertions. With years of turfgrass science experience, I explain why liquid aeration doesn’t deliver the promised results and why relying on this product could lead to misguided lawn care practices. Don’t fall for the hype – join me as I debunk the myths and set the record straight w...

In this video, I take a look at some of the recent comments and questions from TikTok and YouTube. Your feedback not only shapes the conversations we’re having here but also sparks deeper discussions about turfgrass science and management.

I’m also excited to introduce a new fundraiser supporting turfgrass research. Turfgrass plays a vital role in sports, recreation, and landscapes, yet research in this area often goes underfunded. Your support will help advance studies that improve sustainability, water use efficiency, soil management, and turf quality—work that benefits golf courses, sports fields, parks, and home lawns...

In this video, I explore the findings of the research article “Tall Fescue Rooting as Affected by Deficit Irrigation” (HortScience, Volume 42, Issue 3). The study, conducted by Jinmin Fu, Jack Fry, and Bingru Huang and published June 1, 2007, investigates how reduced irrigation impacts the rooting behavior of 'Falcon II' tall fescue grasses using minirhizotron imaging.

I’ll walk through:

The study’s experimental setup using varying levels of evapotranspiration (20%, 60%, and 100%)
Key findings such as the surprising increase in root length and surface area under severe water stress (20% ET)
Practical implications for turfgrass management and water conservati...

In this video, I examine the research by Cain et al. (2022) that explores how varying irrigation schedules affect the encroachment of annual bluegrass (Poa annua) into perennial ryegrass turf systems in western Oregon. The study reveals that watering once per week significantly reduces annual bluegrass encroachment compared to irrigating four times a week, and that replacing irrigation volumes based on reference evapotranspiration (ETref) had no meaningful impact on that outcome

Throughout the video, I walk viewers through the experimental approach, highlight the implications for turfgrass managers aiming to suppress undesirable bluegrass without altering evapotranspiration-based irrigation schedules, an...

In this video, I discuss the scientific article "Irrigation Rates and Frequency Affect Tall Fescue Color and Weed Encroachment." We’ll examine how adjusting irrigation amounts and timing influences turfgrass aesthetics and weed pressure. From water conservation to maintaining turf quality, this study provides valuable guidance for anyone managing tall fescue under variable moisture conditions.

https://onlinelibrary.wiley.com/doi/full/10.1002/its2.184

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In this video, I review the scientific article "Irrigation Frequency and Amount Effect on Root Extension during Sod Establishment of Warm-season Grasses." We’ll explore how different irrigation strategies influence root growth during establishment, what this means for practical turfgrass management, and how to strike the right balance between watering efficiency and sod performance. If you manage turf or are curious about water-wise establishment practices, this study offers some important insights.

https://journals.ashs.org/view/journals/hortsci/46/8/article-p1202.xml?rskey=SDm3zj&print

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In this video, I offer commentary on the scientific article titled "Water use and performance of Kentucky bluegrass influenced by cultivar, irrigation practices, and soil texture," published in the International Turfgrass Society Research Journal (DOI: 10.1002/its2.200).

The study evaluated two Kentucky bluegrass cultivars, Mallard and Geronimo, grown in lysimeters filled with either loamy sand or silt loam. Each setup was subjected to two irrigation levels: 40% and 80% replacement of reference evapotranspiration. The authors monitored water use and turf coverage throughout the growing season to assess drought resilience.

My commentary covers the key findings from the research...

In this video, I dive into the 2002 study from Crop Science that evaluates how different irrigation schedules, tall fescue cultivars, and mowing heights interact to shape turf performance.

Article: https://acsess.onlinelibrary.wiley.com/doi/full/10.2135/cropsci2002.2011

✅ What you'll discover:

Study design highlights: 2‑year field trial in Riverside, CA, comparing 2–4 irrigation events per week at ~80 % ET₀, two cultivars (a dwarf vs. a turf-type), and two mowing heights (~3.8 cm vs. 6.4 cm)

Key findings: Twice-weekly “deep” watering yielded the highest visual quality. Dwarf cultivars and shorter mowing height boosted turf quality early, but overwatering and m...

In this video, I respond to the Bermuda Grass Central video “The Best Summer Fertilizer for Lawns? Why Yard Mastery 7‑0‑20 is …”. I break down their main arguments, evaluate their fertilizer recommendations, and highlight both strong and weak points.

✅ What you’ll get:

Summary of Claims: A quick overview of the video’s main points—why the creator supports Yard Mastery’s 7‑0‑20 blend for summer turf.

Critical Analysis: Comparing their claims to current turf fertilization research—does a high-potassium, zero-nitrogen mix really benefit warm-season grasses in mid-summer? I'll cite recent studies and best management practices.

Pros and...

In this video, I critique “Found the Best Iron to Apply to Your Lawn For Summer Color” by a former golf course superintendent. While I agree that iron can boost turf color without pushing growth, I question some of the application advice—especially the dosing schedule and lack of soil pH context.

I break down what the original video gets right, what it misses, and share my evidence-based tips for using iron effectively this summer. If you want deep green turf without wasting money or product, this video’s for you.

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In this video, I break down the findings from the scientific article "Optimizing Irrigation Rates and Frequency for Perennial Ryegrass in Western Oregon." We’ll look at how different irrigation strategies affected turf quality and what this means for managing ryegrass under Pacific Northwest conditions. Whether you’re a turf manager or a lawn care enthusiast, this research has practical takeaways you can use.
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On this episode of Turfgrass Epistemology, Dr. Dan Sandor joins me to break down his study that addresses one of the most commonly misunderstood aspects of turf establishment: how much water should you really apply when seeding a new lawn?

Sandor et al. (2021) evaluated daily irrigation at 50%, 75%, 100%, and 125% reference evapotranspiration (ETo) to determine how quickly tall fescue and bermudagrass cultivars reach full coverage. The big takeaway? Applying more than 100% didn’t help, and drought-resistant cultivars didn’t show any special advantage during establishment.

In this video, we discuss:

    💧 Why 100% ETo is the sweet spot for...

In this episode of Turfgrass Epistemology, we dive into a study from Oregon State University that looked at how turfgrass species and mowing height affect water requirements in western Oregon. The results might surprise you—tall fescue and perennial ryegrass significantly outperformed fine fescues when it came to conserving water.

We’ll break down the data on evapotranspiration replacement, irrigation intervals, and how mowing height can influence your watering schedule. Should you mow higher? Should you convert to tall fescue? This video gives you practical, science-backed guidance on how to choose and manage turfgrasses for water conservation.

In this episode, I dive into the comment section and my inbox to respond to the most interesting, insightful, and downright puzzling messages I’ve received from viewers. From soil test questions and fertilizer theories to passionate turf debates and a few questionable product claims—nothing is off limits.

Whether you're here to learn, laugh, or just see if your message made the cut, this video is a behind-the-scenes look at the community that makes Turfgrass Epistemology what it is.

Let’s talk turf, tackle misinformation, and maybe share a few facepalms along the way.

...

In this episode, I dive into the comment section and my inbox to respond to the most interesting, insightful, and downright puzzling messages I’ve received from viewers. From soil test questions and fertilizer theories to passionate turf debates and a few questionable product claims—nothing is off limits.

Whether you're here to learn, laugh, or just see if your message made the cut, this video is a behind-the-scenes look at the community that makes Turfgrass Epistemology what it is.

Let’s talk turf, tackle misinformation, and maybe share a few facepalms along the way.

...