Quantifying Turfgrass Cover with Digital Image Analysis Using Imagej.

Visual % ground cover ratings have been criticized for being subjective and difficult to reproduce, and line-intersect methods can be more accurate than visual ratings, but are time and labor intensive. Digital image analysis using the commercially available software, Sigma Scan, has been shown to be an accurate and reproducible method for determining turfgrass cover. While it is a useful tool, this software is quite expensive and requires its users to renew a license annually. The objective of this study was to determine if the free open-source software ImageJ could accurately quantify % ground cover in a turfgrass system. Digital photographs were taken with a Canon Powershot A1300 camera in a 90 cm by 90 cm by 90 cm light box. Turfgrass plugs were 15 cm diameter and randomly arranged in bare-soil plots (1.5 m by 1.5 m). Each plot contained a specific number of plugs, ranging from 1 to 16.  Digital image analysis was performed on photographs using Sigma Scan and ImageJ. Ground cover measurements by sigma scan and ImageJ were compared with known ground cover percentages. Photographs were taken of turfgrass plots in varying stages of establishment to determine % ground cover. Five independent observers performed visual % ground cover ratings and line-intersect analysis in the field. Digital image analysis was performed on three photographs from each plot using Sigma Scan and ImageJ. Results from digital image analysis, independent analysis and line intersect methods were compared.