Technical


Figure 1: Part of the middle section of the perennial ryegrass evaluations for sports showing data for 15 of the 105 cultivars presented. From Turfgrass Seed 2016 “


Considering the data has been collected year upon year, the accumulated data on turfgrass cultivar development and performance must be truly enormous


even perhaps to derive more general information pertaining, for example, to climate change. What I am concerned with here, however, is how the booklet could be made to provide practical information on cultivar performance that is more easily drawn out by the lay person, and I would like to describe a way in which this can be done. I have chosen for this explanation the data


presented in Tables S1 and L1 in the Turfgrass Seed 2016 booklet. These refer to cultivars of perennial ryegrass for Sports (25mm) and Lawn (10-15mm) use respectively and, in addition to the varying mowing heights, these groups of cultivars are also subject to differing degrees of wear. This is to simulate the circumstances of their intended use more closely. It is necessary only to use those measures that are common to both sets of data, hence not all of the columns of information in the tables have been used for this example anaylysis. The equivalent analysis could be undertaken for the cultivars in just one table but, for this exercise, I have chosen to combine the two tables. If you plot the values of, for example, ‘visual


merit’ against those of, say, ‘fineness of leaf’ you get what is called a scattergram. That


particular scattergram, for all of the sports ryegrass cultivars, is shown in Figure 2 below. In the close-up section, on the right you will


see that the cultivars Cadix, Calico, Eugenius and Barorlando are close together. This indicates that they are similar to one another in relation to their visual merit and fineness of leaf. The cultivar Monroe is further away and is, therefore, that bit different in both these terms, but none of those in the right hand close-up are as different from one another as they all are from those in the left hand close- up. So Stravinsky, Platinum, Limonica etc, being much further away, are all very different indeed from Barorlando, Monroe and Eugenius. Now we could plot similar scattergrams for all of the possible pairs of measured criteria. ‘Live ground cover’ against ‘shoot density’, for example, or ‘cleanness of cut’ against ‘resistance to red thread’ and all sorts of interesting comparisons could be made. Because most of the measurements are in some way related to one another (greater visual merit is generally associated with higher shoot density, for example), it is possible, using a clever statistical technique, to present most of the variability in the data in just one


Figure 2: Scattergram of Visual Merit against Fineness of Leaf from Table S1 in Turfgrass Seed 2016. The insets show more clearly the names of the individual cultivars in the marked areas


98 I PC FEBRUARY/MARCH 2017


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