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.

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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.

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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.

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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.

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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:

This episode is not about calling people out—it’s about slowing down, adding context, and explaining how we know what we know in turfgrass science. Whether you’re a golf course superintendent, lawn care operator, researcher, or homeowner trying to make better management decisions, this discussion is designed to help you separate evidence from noise.

If you’ve emailed me, commented on YouTube, or left a TikTok comment in 2025, there’s a good chance your question—or one just like it—is addressed here.

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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 compounds, and how phosphite applications can reduce algal crusting without relying solely on traditional fungicides 

This discussion covers:

If you manage putting greens, work in turfgrass research, or want an evidence-based explanation of phosphite products that cuts through anecdote and advertising, this episode provides critical context straight from the study’s lead author.

📄 Research discussed:

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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

💡 Why this matters:

👇 Join the conversation:

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🎓 Turfgrass Epistemology — How do we know what we know?

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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 later.

🔬 Topics I cover in the review:

The study design and why the researchers chose fairway- and rough-height mowing

💡 Why this article matters today:

👇 Join the discussion:

Do you agree with how the authors interpreted their data?

Share your thoughts in the comments. Critical evaluation of research—new and old—is how we advance turfgrass science and avoid assumptions that fail in the field.

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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 agronomic claims using critical thinking and epistemology.

In turfgrass, agriculture, and lawn care, new products appear constantly—each claiming to increase yields, improve nitrogen efficiency, reduce inputs, or boost plant health. Without strong critical thinking skills, it’s easy to be misled. Epistemology—the study of how we know what we know—helps protect you when you’re confronted with products, technologies, or scientific claims you’ve never heard of.

By the end of this video, you’ll understand:

If you’re a turfgrass manager, agronomist, sports field manager, lawn care professional, or scientifically curious homeowner, this channel will help you make smarter, evidence-driven decisions.

Subscribe to Turfgrass Epistemology for more videos on turfgrass science, nitrogen management, soil fertility, agronomy, and the critical thinking skills needed to navigate misinformation in the industry.

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