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.

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