Frequent Trinexapac‐ethyl Applications Reduce Nitrogen Requirements of Creeping Bentgrass Golf Putting Greens

The plant growth regulator trinexapac‐ethyl (TE) [4‐(cyclopropyl‐a‐hydroxymethylene)‐3,5‐dioxo‐cyclohexanecarboxylic acid ethylester] reduces turfgrass clipping yield and enhances turfgrass color and density. Typically, such responses are achieved through alteration of N application rate, yet few have comprehensively investigated the effect of TE on turfgrass N requirements. We hypothesized that TE reduces putting green N requirements without sacrificing turfgrass quality. A three year study was conducted on a creeping bentgrass ( Agrostis stolonifera L.) putting green with treatments consisting of three N application rates (5, 10, and 20 kg N ha −1 14 d −1 ) with or without TE application. To sustain season‐long growth suppression, TE was applied at 0.10 kg a.i. ha −1 every 200 growing degree days (GDD; base 0°C). Turfgrass yield and color were quantified every other week, and clipping tissue N content was analyzed monthly. Clipping yield, tissue N content, N removal, and color index increased with N rate. All attributes responded linearly to N application rate. Trinexapac‐ethyl enhanced color while suppressing clipping yield and nutrient removal from mowing. As a result, TE reduced creeping bentgrass putting green N requirements by 25% conservatively and on several occasions by greater than 50%.