Assessment of Visual Evaluation Techniques¹

Abstract

Visual evaluation parameters are routinely used to assess performance characteristics of turfgrass cultivars in field plantings. Rating systems are commonly employed to evaluate phenotypic variations in color, density, and uniformity of turfgrass stands during the year. In the present study, visual assessment data for quality and density ratings of cultivars of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) from 10 turfgrass researchers were statistically analyzed to determine data conformity, consistency, and uniformity. Analysis of simultaneous data gathering by 10 investigators indicated the following: 1) Visual assessment scales were significantly different among evaluators, 2) Visual criteria used for data collection allowed a wide latitude of perception in quality and density characteristics, 3) Relative rank performance of cultivars differed among evaluators, and 4) Presently accepted techniques for visually assessing turfgrass quality and density are inadequate. Results of national and regional turfgrass cultivar evaluation trials should be considered with caution as most performance variables are based on the use of conventional evaluation schemes. This study emphasizes the need for a coordinated development of qualitative evaluation techniques based on substantiated, biologically definable, growth responses rather than visual perception.

Evaluation of Key Methodology for Digital Image Analysis of Turfgrass Color Using Open‐Source Software

“…However, a common criticism of the visual rating method is its subjectivity. Although standard guidelines for rating turfgrass attributes have been established (Morris, 2002; Carson, 2007), interpretation of rating criteria is often inconsistent (Horst et al, 1984; Skogley and Sawyer, 1992), and individuals impose varying biases in different parts of the rating scale. The inconsistencies can reduce the effectiveness of large‐scale evaluations and hypothesis testing.…”

Additive Main Effect and Multiplicative Interaction Analysis of National Turfgrass Performance Trials: I. Interpretation of Genotype × Environment Interaction

“…Turfgrass quality is based on a visual rating system (NTEP uses a 1 to 9 scale with 9 indicating the highest quality) assessing the aesthetic appeal (and function) of turf which integrates several quality components such as color, density, uniformity, and texture (Turgeon, 1980). The turfgrass rating system is subjective and evaluators may use different parts of the rating scale (Horst et al, 1984) because of evaluator bias. However, there is general agreement among evaluators in cultivar ranking (Skogley and Sawyer, 1992), therefore evaluator bias cause little interaction.…”

“…231-236; Romagosa et al, 1996;Gauch, 1998 (Gauch and Zobel, 1997 to superior turfgrass performance (Shearman, 1985; one location provided one year of data (Richmond Hill, ON, Youngner, 1985). Turfgrass quality is based on a visual Canada (Horst et al, 1984) because of evaluator bias. Howsponse, summer response to drought, winter color, spring denever, there is general agreement among evaluators in sity and green-up (as well as other data) were used to provide cultivar ranking (Skogley and Sawyer, 1992), therefore information to help explain why genotypes interact with envievaluator bias cause little interaction.…”

Effects of Shade on the Persistence of Cool Season Grasses to Form Turfgrass

“…Cover was determined in the field, as the percentage of soil covered by turfgrass, in accordance with the Point Quadrant method, described by Daget and Poissonet (1971). The visual quality or overall quality was determined using a qualitative scale of 0 to 5, which incorporated: percentage of soil cover, density and color of foliage (Horst et al, 1984), variables that were observed directly in each one of the plots. The scale used was: 0 = bare soils, without cover and/…”