RESEARCH UPDATE: POTASSIUM FERTILIZATION ENOUGH IS ENOUGH

Science long ago established the necessity of potassium to plants, and this element has always been a standard component of fertilizers. However, because potassium (K) has been reputed to provide a variety of benefits to turf, including better drought, heat, cold and wear tolerance, many turf managers have begun increasing the amount of potassium they apply, sometimes exceeding even the amount of nitrogen (N).

Does this have any proven benefit? To address this question, Drs. George Snyder and John Cisar of the University of Florida examined the effects of various K/N ratios on turfgrass quality.

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The study was conducted on a mature sward of Tifgreen bermudagrass. During the 3-year study, Snyder and Cisar applied K and N in ratios of 0 (no K), 0.5, 1.0 and 2.0 (twice as much K as N) and then evaluated the turf for visual quality, susceptibility to take-all disease, clipping production, tissue levels of N and K, and thatch and root weight.

The researchers found that the K did have significant positive effects on most of the parameters they studied, but this was mainly apparent when plots fertilized with K were compared to those without any K applied at all. By contrast, the rate of K applied had little affect beyond a K/N ratio of 0.5 to 1.0. In other words, it mattered that turf got some K, but for the most part, not how much.

The researchers measured tissue K levels and found similar results — K fertilization resulted in significantly higher tissue levels than no K fertilization, but higher application rates of K increased tissue K levels only slightly.

This is just one study on one type of turfgrass, but it suggests the N and K rates found in most standard turf fertilizers may be adequate to satisfy turf's K needs.

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