Correction to “Quantifying golf course nitrogen use efficiency”

Bekken, M. A. H., & Soldat, D. J. (2022). Quantifying golf course nitrogen use efficiency. Grassland Research, 1(3), 174–186. https://doi.org/10.1002/glr2.12024

There was an error in the variance term used in the growth potential (GP) model in this study. Variances of 10 and 12 were used for C₃ and C₄ turfgrasses, respectively. These variances are for Fahrenheit temperatures; however, this study used Celsius temperatures. When using Celsius in the equation, it is best to adjust these variance terms to 5.5 for C₃ grasses and 7 for C₄ grasses. With the updated variances, the definition of a turfgrass growth day also needed to be adjusted. Following the recommendation of Gelernter et al. (2016), we adjusted the definition of a turfgrass growth day to a day in which the growth potential was greater than 20%.

The updated parameters caused small changes to the number of turfgrass growth days calculated at each golf course in the study. This, in turn, changed the N rate normalized by turfgrass growth days, the Nitrogen Efficiency Scores (NES), the N_max normalized NES, and the correlations between the N rate normalized by turfgrass growth days and the economic factors. Figures 3-9 have been updated and Tables 3–9 have been updated. None of the paper's main conclusions have changed, but a description of the updated results from the original manuscript is included below.

With the updated parameters, the ratio of the golf course-wide N application rate to the GP N requirement prediction (termed the NES) was 0.47, indicating that golf courses used 53% less N than predicted by the model.

With the updated parameters, four (US-East Texas, US-Florida, US-Northwest, Norway) of the eight regions had similar N rates on fairways; median fairway N rates normalized by growth days were between 0.61 and 0.65 kg ha⁻¹ day⁻¹ in these regions. The remaining four regions (Denmark, US-Midwest, US-Northeast, UK) were below this range, with the median fairway N rate normalized by turfgrass growth days between 0.34 and 0.19 kg ha⁻¹ day⁻¹.

With the old parameters, tees in Norway were the only golf course components across all regions for which the median NES was greater than 1. With the updated parameters, US-East Texas, US-Florida, US-Northwest, and Norway had median NES values that were greater than 1 on greens. On tees in Norway, the median NES score remained above 1. In the US-Northwest, the median NES score on tees rose above 1. The median NES score in all other regions across all components stayed below 1.

The updated parameters slightly changed the rankings of NES in Table 9. The ranking of the N rate normalized by turfgrass growth days and the NES of the US-Midwest changed from 6th to 5th and the ranking of the US-Northeast changed from 5th to 6th.