Objective assessment and visual perception of Poa pratensis cultivars under close mowing

Visual appeal and discoloration of 30 closely mown Poa pratensis cultivars were scored by 4 assessors in Jan. 1990. There were significant cultivar × assessor interactions for both of these parameters. Correlation coefficients were calculated to compare scores of each assessor with ground cover deduced from point quadrat, shoot density, leaf width, reflectance ratio (near infrared:red), leaf spot symptoms and colorimeter values of "L" (light-dark), "a" (green-red) and "b" (yellow-blue) data. The significant correlations between visual and objective assessments varied with different individuals. Stepwise regression revealed that average visual merit and discoloration could both best be described by formulae combining just reflectance ratio and shoot density. For visual merit, shoot density was the most important factor whilst for discoloration reflectance ratio was most closely associated. The contributions of ground cover and colour to reflectance ratio were quantified with a formula combining point quadrat and colorimeter "a" values.